TREATMENT

### TECHNOLOGY BACKGROUND DOCUMENT 

# ?f3 1/-**I~**

# o**S"S~** Larry Rosengrant

Section Chief

Laura Lopez Project Officer U.S. Environmental Protection Agency Office of Solid Waste 401 M Street, SW Washington, DC 20460

January 1991

### TABLE OF CONTENTS Section 

### EXECUTIVE SUMMARY Applicability

......... . Underlying Principles ofOperation

. Description of the Treatment Process

...... . Waste Characteristics Affecting Performance (WCAPs) Design and Operating Parameters

...... . 

### I. TREATMENT TECHNOLOGIES A. DESTRUCTION TECHNOLOGIES 1. 1.1 1.2 1.3 1.4 1.5 1.6 2. 2.1 2.2 2.3 2.4 '2.5 2.6 3. 3.1 3.2 3.3 3.4 3.5 3.6 

### BIOLOGICAL TREATMENT Applicability .•........ Underlying Principles ofOperation

..... Description ofBiological Treatment Processes

... Waste Characteristics Affecting Performance (WCAPs). Design and Operating Parameters

.... Refsrences

. . . • . 

### CHEMICAL OXIDATION

. . . . . . . Applicability

. • . . . . . . . . . Underlying Principles ofOperation

..... Description of Chemical Oxidation Processes

.... Waste Characteristics Affecting Performance (WCAPs). Design and Operating Parameters References

. . . . . 

### CHEMICAL REDUCTIOK

. . . . . . . . Applicability

......... . Underlying Principles ofOperation

... Description of Chemical Reduction Process

..... Waste Characteristics Affecting Performance (WCAPs). Design and Operating Parameters •........ References

. . . . . . . . . . . . . . . . . . . . .

f\docunent\15254031.01.001 

### Page No. viii xi xiii xiv XV 

### xvii

1 1 1 3 8 11 16 17 17 18 21 23 24 28 29 29 29 30 32 33 37 

# ,

### Section
4. 

### 4.1 4.2 4.3 

### 4.4 4.5 4.6 5. 

### 5.1 5.2 5.3 5.4 5.5 5.6 6. 6.1 6.2 6.3 6.4 6.5 6.6 

### TABLE OF CONTENTS (CONTINUED)

ELECTROLYTIC OXIDATION OF CYANIDE Applicability ..........• Underlying Principles ofOperation • . . . . . . Description ofElectrolytic Oxidation of Cyanide Process

. . . . . . . . . . . . . . . . . . . 

## .. Waste Characteristics Affecting Performance (WCAPs). Design and Operating Parameters References

. . 

### INCINERATION

. . . . . . . . . . App1 icability
. . . . . . . . . . . Underlying Principles ofOperation

. Description of Incineration Process

. . . . . . . . Waste Characteristics Affecting Performance {WCAPs). _Design and Operating Parameters References

. . . . 

### WET AIR OXIDATION Applicability .••........... Underlying Principles of Operation

... Description ofWet Air Oxidation Process ••.... Waste Characteristics Affecting Performance {WCAPs). Design and Operating Parameters • . . . . . ... References

. . . . . . . . . . . . . . . . . . . . . 

### B. TECHNOLOGIES THAT REDUCETHE SOLUBILITY ORLEACHABILITY OF METALS 

### Page No.
38 38 38 39 39 40 43 44 44 45 46 54 

### 57 63 64 64 66 66 67 70 73

1. 

### AMALGAMATION

. . . . . . . . . . . 74 1.1 Applicability •....• o . • . 74 1.2 Underlying Principles ofOperation •.. o . . . 74 1.3 Description ofAmalgamation Treatment Processes o . 75 1.4 Waste Characteristics Affecting Performance (WCAPs)o 75 1.5 Design and Operating Parameters o o . o . 77 

### 1.6 References • o o o o o• 0 • 

### o o o o . o• o• o o• 80

f\dacument\15Z54031.01.001 i i

### TABLE OF CONTENTS (CONTINUED) Section ( 2. 

### CHEMICAL PRECIPITATION

. 2.1 

### Applicability

.......... . 2.2 

### Underlying Principles ofOperation

.... . 2.3 

### Description ofChemical Precipitation Process

... 2.4 

### Waste Characteristics Affecting Performance (WCAPs). 2.5 

### Design and Operating Parameters 2.6 

### References

. 3. 

### ENCAPSULATION ......•.. 3.1 3.2 3.3 3.4 3.5 3.6 

### Applicability

.......... . Underlying Principles of Operation

. Description ofEncapsulation Processes

.. Waste Characteristics Affecting Performance Design and Operating Parameters References • . . • • . . . . • • • . 4. 

### STABILIZATION OFMETALS

. . . . 4.1 

### Applicability

.......... . 4.2 

### Underlying Principles of Operation

. 

## .

## . . . (WCAPs).

4.3 

### Description ofStabilization Process •....... 4.4 

### Waste Characteristics Affecting Performance (WCAPs). 4.5 

### Design and Operating Parameters 4.6 

### References • . . ... 5. 

### VITRIFICATION • . • . . . ..• 5.1 Applicability ......•.• 5.2 Underlying Principles ofOperation

. • 5.3 Description ofVitrification Processes ••..... 5.4 Waste Charatteristics Affecting Performance (WCAPs). 5.5 

### Design and Operating Parameters ..•....... 5.6 References

. . . . . . . . . . . . . . . . . . . . .

f\document\15254031.01.001 

### iii Page No.
81 81 82 83 85 89 93 94 94 94 94 96 98 101 .. 102 ' 

## . 102 102 104 104 106 110 111 111 112 113 115 119 124

### TABLE OF CONTENTS (CONTINUED) Section • t. 

### II. REMOVAL TECHNOLOGIES A. RECOVERY, REUSE, AND/OR SEPARATION TECHNOLOGIES FOR ORGANICS 1. 

### CARBON ADSORPTION

. . . . . . . . Page No.

125 

### 1.1 Applicability

. . . . . . . . . . 125 

### 1.2 Underlying Principles of Operation

. . . 125 

### 1.3 Description ofCarbon Adsorption Process

. . . . . . 125 1.4 

### Waste Characteristics Affecting Performance (WCAPs). 129 

### 1.5 Design and Operating Parameters

. . . . 130 1.6 References

. . . . . . . . • 133 2. 2.1 2.2 

### 2.3 2.4 2.5 2.6 3. 

### 3.1 3.2 3.3 3.4 

### 3.5 3.6 4. 4.1 4.2 4.3 4.4 4.5 

### 4.6 

### DISTILLATION TECHNOLOGIES

. . .. Applicability

. . • . . • . . . . . .•. Underlying Principles ofOperation

. . ... Description ofDistillation Processes .....•. Waste Characteristics Affecting Performance (WCAPs). Design and Operating Parameters

. • . • . References • . • . • . • EXTRACTIONTECHNOLOGIES

. . . . . Applicability ..•.......• Underlying Principles ofOperation • Description ofExtraction Processes • . . . •••. Waste Characteristics Affecting Performance (WCAPs). Design and Operating Parameters ..•.. References • • • . • . • • . . FUEL SUBSTITUTION

. . . . . . . . . Applicability • . . . . . . ... . Underlying Principles ofOperation

.. . Description of Fuel Substitution Process .•.... Waste Characteristics Affecting Performance (WCAPs). Design and Operating Parameters .....•.... References • • • . • . . . . . . . . . . . • . . .**f\documant\15Z5~031.01.001** iv 134 134 

### 135 137 146 150 

### 156 157 

### 157 157 

### 158 164 166 

### 170 171 171 174 174 

### 177 179 183 

# ,TABLE OF CONTENTS (CONTINUED) Section ( Page No. 

### B. RECOVERY AND/OR SEPARATION TECHNOLOGIES FOR METALS 1. ACID LEACHING o o o o o o o o o o 184 1.1 Applicability o0o 000o o0o 184 102 Underlying .Principles ofOperation o o 184 1o3 Description of Acid Leaching Process o o .. 000 185 1o4 Waste Characteristics Affecting Performance (WCAPs)o 186 1o5 Design and Operating Parameters 188 1o6 References o o o0o o o o 190 2. FILTRATION TECHNOLOGIES o o o o 191 2o1 App1icabi1ity 00o o o0o o0o 202 Underlying Principles ofOperation 2o3 Description of Filtration Processes o0

.. 0000 2.4 -waste Characteristics Affecting Performance (WCAPs)o 2o5 Design and Operating Parameters 2o6 References 0o . 0o • o o . o o 3. 3o1 3o2 3o3 

### 3.4 3.5 .3.6 4. 4.1 4.2 

### 4.3 4.4 4.5 4.6 

### HIGH TEMPERATURE METALS RECOVERY o Applicability • o o • 0• o o0o Underlying Principles ofOperation 000000 Description of High Temperature Metals Recovery Process

. . . . . . . . . . . . . . . . . . . 

## . . Waste Characteristics Affecting Performance (WCAPs). Design and Operating**Par~ters** References 0o . o• o ION 

### EXCHANGE

. . . o• o o o o o o Applicability • o o •. o o o0o Underlying Principles ofOperation o Description of Ion Exchange Process o o o o o o . o Waste Characteristics Affecting Performance (WCAPs). Design and Operating Parameters o o o o o o o o o• References 0o• 0o• 0000o0

. 000o o o0

.

f\docunent\15254031.01.001 v 191 191 192 194 196 200 201 201 202 202 205 206 210 211 211 211 212 213 217 220 

# 1\



# I 

# I

\ \ I ! 

### TABLE OF CONTENTS (CONTINUED) Section • Page No. (_ 5. 

### RETORTING


## . 

## .. . .

## . . ..

## . . .. 221 5.1 Applicability

. . . . . . . . . . . 221 5.Z Underlying Principles ofOperation

. 221 5.3 Description ofRetorting Process

. . . . . . . . . . 222 5.4 Waste Characteristics Affecting Performance (WCAPs}. 225 5.5 

### Design and Operating Parameters

. . . . . . . . . . 227 5.6 

### References • . . . . . . . . . . • . . . . . . . . 228 

### III. TECHNOLOGIES APPLICABLETO MIXED WASTE (RADIOACTIVE/HAZARDOUS) INTRODUCTION

. . . . . . . 229 

### A. TECHNOLOGIES FORWASTES CONTAINING ORGANICS AND IHOR6AHICS OTHER THAN 

### METALS

. . . . . 1. 2. 3. 

### Carbon Adsorption

.... Distillation Technologies Extraction Technologies

.. 

### B. TECHNOLOGIES FORMIXED WASTES CONTAINING METALS 1. 

### 2. 3. 4. 5·. 6. 

### Acid Leaching

. . . . . . .. . Chemical Precipitation

. . .. . Filtration ••.•....... High Temperature Metals Recovery

. Ion Exchange • • . • . . . . . . . Stabilization ofMetals ....• C. 

### TECHNOLOGIES FOR

### MJXED WASTES IN SPECIALTREATABILITY 231 231 

### 231 232 

### 233 233 233 233 233 234 234 

### GROUPS

. . . . • . • . • . . • 235 1. 2. 3. 

### 4. Amalgamation • Encapsulation Vitrification Incineration • 

### REFER!NCES

. . • . . • . . .

f\document\15254031.01.001 vi 235 235 

### 236 237 238

### TABLE OF CONTENTS {CONTINUED} Section ( 

### Page No. APPENDIX A List of Best Demonstrated Available Technology (BOAT) Background Documents and Associated BDAT(s) A-1 LIST OF FIGURES Figure 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21**~2** 23 24 

### 25 

### Activated Sludge System

.... . Trickling Filter System

..... . Anaerobic Digestion

....... . Continuous Chemical Reduction System Liquid Injection Incineration System Rotary Kiln Incineration System

.. Fluidized Bed Incineration System

. Fixed Hearth Incineration System

.. Continuous Wet Air Oxidation System

... Continuous Chemical Precipitation System •. CircularClarifier Systems Inclined Plate SettlerSystem Carbon Adsorption Systems Plot of Breakthrough Curve

. Batch Distillation System

. Fractionation System •... Steam Stripping System

... Thin Film Evaporation System Screw Flight Dryer •............. Two-Stage Mixer-Settler Solvent Extraction System Packed and Sieve Tray Solvent Extraction Columns

. High Temperature Metals Recovery System

... . Two-Step Cation/Anion Ion Exchange System

..... . Retorting Process (Without a Scrubber and Subsequent Wastewater Discharge) .•........... Retorting Process (With aScrubber and Subsequent Wastewater Discharge)

.............. .

f\document\15254031.01.001 

### vii Page No. 4 7 9 31 49 50 52 53 68 84 86 87 127 128 138 140 142 143 145 160 162 203 214 223 224 ' #

### EXECUTIVE SUMMARY

- This**doc~ent** provides a discussion of the treatment technologies applicable to wastes that are subject to the Land Disposal Restrictions (LOR), which were mandated by Congress as part of the 1984 Hazardous and Solid Waste Amendments (HSWA) to the Resource Conservation and Recovery Act (RCRA). This document does not include every possible technology that may be used to treat wastes subject to the LOR, but discusses those most corrvnonly used. The technologies discussed include those that are demonstrated (commercially available) and have been proven to substantially diminish the toxicity of hazardous constituents and/or to reduce the likelihood of migration of such constituents from the waste of concern. These technologies include those that treat wastewaters* and those that treat nonwastewaters. Treatment performance data from technologies discussed in this**docume~t** were the basis for the detennination of the Best Demonstrated Availabl'e Technology (BOAT), fromwhich theLandDisposal Restrictions treatmentstandarcfs were promulgated (as numerical standards or methods oftreatment). Information supporting the development of these treatment standards may be found in the applicable background documents prepared for EPA's Office of Solid Waste, Waste Treatment Branch. These BOAT background documents contain information on the following: industries affected and**t"ii~tc:** characterization, applicable and demonstrated treatment technologies for the wastes ofconcern, determination of BOAT, and treatment performance data with design and operating conditions.

*For the purpose ofthe Land Disposal Restrictions rule, wastewaters are

defined as wastes containing less than or equal to 1 percent (weight basis) filterable solids and less than or equal to 1 percent (weight basis) total organic carbon (TOC). Wastes not meeting this definition are classified as nonwastewaters.

f:\document\15Z5403l.Ol.OOZ viiiThe methodology EPA used to develop the BOAT treatment standards is described in twa separate documents: Generic QualityAssurance Project Plan for Land Disposal Re-strictions Program ("BOAT") (USEPA 1990) and Methodology for Developing

### BDA~- Treatment Standards (USEPA 1990). The second document also discusses the petition process to be followed in requesting a variance from the BOAT treatment standards. Appendix Alists the background documents developed for the BOAT program, identifying the technologies and the types of constituents treated (e.g., organics, inorganics, metals, etc.) when present in actual treatment performance data.
The treatment performance data and the design and operating data (see Section 5 of this executive sumary for a discussion of design and operating data} contained in these documents may be used to help determine whether a treatment system has been designed and operated properly. The treatment ' performance data from these background documents may be used to compare th'e performance of a treatment system of concern treating the same or similar constituents (provided the waste matrices are not significantly dissimilar). Comparisons can be made ofthe destruction or removal efficiencies, the level of treatment achieved, and the design and operating parameters of a system (for example, feed rate, temperature, and oxygen concentration for incineration systems orconcentrationofnutrients, dissolvedoxygen, residence time, etc. for**biologi~al** treatment systems).
One document that may be particularly helpful is the F039 (Multisource Leachate) background document, Volumes Athrough E(USEPA 1990). This document contains comprehensive treatment performance data covering the complete list of Pand Uwaste code constituents. The nonwastewaterdata, for the mostpart, were derived from 11 incinerationtest burns for the organics and from stabilization treatment for themetals. The wastewaterdata were derived from various sources such as EPA's Office of Water's Industrial Technology Division (lTD), the

f:\document\15254031.01.002 ix 

# ,National Pollutant Discharge Elimination System (NPDES), Water Engineering Research.**Laborat~ry** (WERL), and other data sources available to the Agency. These**above-me~t**ioned data were generally considered to represent 1 eng-term samp1 ing, with many data sets meeting EPA's criteria for qua1 ity assurance/ qua1 ity contra1. Hence, treatment performance data from the F039 background document and other BOAT documents may be used as a basis for comparison when evaluating the performance of other treatment systems. The Agency wishes to point out that additional information on treatment technologies may be obtained through EPA's Alternative Treatment Technology Information Center (ATTIC), operated by the Office ofEnvironmental Engineering andTechnologyDemonstration. TheATTIC isan informationretrieval networkthat provides up-to-date technical information on innovative treatment methods for hazardous wastes. The ATTIC provides information on innovative treatment technologies, cost analysis, and migration and**s~pling** data bases; provides information on experts who can be contacted for assistance; and is asource for locating and ordering documents. Also, the EPA Office ofWaste Programs Enforcement has tapes and manuals for Inspectors of Incinerators (only available to EPA personnel). Information include an introduction to incinerator design, air pollution control, and regulatory guidance. Further information may be obtained by contacting the**Regio~al** RCRA training coordinator. The treatment technologies presented in thisdocument have been organized into three separate groups according to how they treat waste and to what types ofwaste they are applicable: (1) treatment technologiesthatdestroy or reduce the migration of wastes; (2) removal technologies that separate or recover constituents for recycle/reuse or treatment; and (3) technologies that treat mixed waste, i.e., hazardous/radioactive waste. Although some of the technologies can belong to more than one group, each technology has been placed in the group where it is most commonly used.

f:\document\15254031.01.002 X 

# 1The remainder of this introduction describes the purpose and contents of each o( the various e 1 ements presented in each technology section: app1 icability,**~nderl**yingprinciplesofoperation, descriptionofthetechno1 ogy, wastecharacteristicsaffectingperformance, anddesign andoperatingparameters. Specifically explained are what information is provided in each technology subsection, how the Agency uses this information as part of its BOAT program, and, when applicable, haw theAgency intends to modify the treatment technology discussions as more treatment data and information become available. 1. Applicability {a) InformationProvided. Theapplicabilitysectioncontains information on thegeneral**a~plication** ofthe treatment technologytovarious wastes. EPA's analysis of applicability is performed in consideration of the parameters and constituents known to affect treatment selection. That is, in order to ident1_f:Y whetheratreatment technologywas applicableto anyparticularwaste stream, the Agencyconsidered all parameters andcharacteristics associatedwith ahazardous waste that could affect the selection of a treatment technology. EPA uses the acronym PATS (i.e., parameters affecting treatment selection) for these parameters. EPA's list ofPATS, shown inTable 1, identifies all known constituents and parameters thatare needed to select atechnologyor technology train for agiven waste.· It is important to point out that in developing this ltst, EPA's goal was todetermine thedemonstratedtechnologyortreatmenttechnology trainthatwould best treat all of the constituents in the waste (i.e., achieve the lowest concentration in the residual). Accordingly, EPA will add components to the treatment train as long as they are demonstrated and will achieve statistically significant reduction in the concentrations of the constituents. (Note: the statistical analysis that the Agency uses to determine whether a significant**f:\document\1525~031.01.002** xiTable 1 List of Parameters Affecting Treatment Selection

l BOAT listmetals content BOAT list organics content Content ofother BOAT constituents (sulfides and fluorides) Biological oxygen demand (BOD) Btu content Presence ofcomplexed metals Cyanide content Filterable solids content Oil and grease content Oxidation state pH Total organic carbon (TOC) content Total organic halides (TOX) content Viscosity Water content Selectivityvalue Sublimation temperature Ash fusion temperature

f:\document\15254031.01.002 xHreduction in constituents has occurred is referred to as Analysis of Variance (ANOVA). Refer to the Methode1 ogy for Developing BOAT Treatment Standards**document~for** further information.) t {b) EPA's Use ofThis Information. EPA uses the PATS as the basis for making decisions regarding whether aparticulartechnology is "demonstrated" for aparticularwaste. The Agency is performing treatmenttestson specificwastes to NdemonstrateN the treatment of the waste using the technology, to develop treatment standards, and to set the criteria by which other wastes can be regulated using the demonstrated technology. The PATS analysis will sometimes show that several technologies are applicable for treating the waste. EPAwill prioritizethese technologies based on its analysis ofavailable data and information regarding the effectiveness of the various technologies. For organics, EPA's preference will be technologies that recover ordestroy the compounds; for metals, the Agency's preference wi11 be technologies that result in recovery ofthe metals. ; In some instances, analysis ofaparticular**par~eter** affecting treatment selection will not be possible or would be meaningless with regard to selecting atreatment system. For example, the BOO of acontaminated soil is essentially meaningless sincethe soil isnot likelyto be treatedin abiological wastewater treatment system. (c) Use of New Data and Information. As data become available either from industryor through EPA's BOATdata collectionprogram, EPA will modify the PATS analysis to further refine specific concentration ranges for which various technologies can handle various parameters.

f:\document\15254031.01.002 xiii 

# '2. Underlying Principles ofOperation (a) InfDrmationProvided. Foreach treatment technology EPAprovides the fundamental theory ofoperation ofthe technology. This section is not meant to provide a detailed discussion on the specific complex physical, chemical, or biological mechanisms by which treatment occurs. Instead, the discussion describes themechanisms involvedsothatonecanunderstandwhat characteristics can affect the performance of the technology. For example, the underlying principle ofchemical precipitation is that metals in wastewater are removed by adding a treatment chemical to form a metal precipitate that is generally insoluble and therefore settles out of solution. Formation of the precipitate and the settlingmechanismare theprinciplescontrollingtechnologyperformance. (b) Use of Information Provided. The theory ofoperation is necessary as the precursor to analyzing which waste characteristics can affect the

. . .. performance of a gtven treatment technology. That is, the principles cif treatment operation are used as the rationale and basis on which nn: Agendy determineswhatwaste characteristicscan affectperformance. Accordingly, waste characteristics affecting performance (WCAPs), which are discussed below, must be understood from the standpoint of how each waste characteristic inhibits or interferes with the fundamental operation of the treatment technology. 3. Description of the Treatment Process This section provides a briefdescription of the principal components of atreatment technology

.. It is intended to provide abasic understanding ofthe equipment used and the treatment sequence. This presentation relates the discussion onunderlying principles ofoperationwiththe laterdiscussionofthe design and operating parameters important to effective wast2 treatment. Simplified block diagrams are provided in this section. The information presented is general in nature to avoid attempting to show all combinations and permutations that are possible in describing a particular technology.

f:\document\15254031.01.002 xiv4. Waste Characteristics Affecting Performance (WCAPs)



## . (a) Information Provided. The WCAPs are based on the underlying principles of the treatment technology. For example, the underlying principle ofchemical precipitation isformation ofthe insolublemetal precipitateand the settlingofthe precipitateout ofsolution. WCAPs forthistechnology are those parameters that affect the chemical reaction of the metal compound or the solubilityofthe metal precipitate (i.e., formation) and/or affect the ability ofthe precipitated compound to settle. The WCAPs include (a) the concentration and type of metals, (b) the concentration of total dissolved solids, (c) the concentrationofcomplexing agents, and {d) the concentrations ofail and grease. The first three parameters can affect precipitate formation, and the last parameter can affect settling rate. EPA's selection ofWCAPs for the various treatment systems is based on.a literaturereview, as well as information obtained during plant sampling**visi~s** that test the treatment technology. EPA is aware that in same cases analytical methods are not available to measure the specific waste characteristics that affect treatment. In such instances, EPA measures the parameter that most closely approximates the actual parameter of concern. For example, aWCAP for steam stripping is the relative volatility of a component. Because relative volatility cannot be measured, EPA uses boiling point as the best measure of assessing the WCAP ofrelative volatility.
The analysis ofwaste characteristics affecting performance is conducted where EPA already has determined from a PATS analysis that an untested waste could be treated effectively by the same BOAT technology as another waste for which treatment performance data are available. The WCAP analysis is then used to determine whether the treatment standards from the tested waste can be transferred to the untested waste. Simply stated, this analysis compares, for two separate wastes, the characteristics that affectthe level oftreatment that can be achieved. Where this comparison shows that the untested waste can be

f:\doclll•nt\15ZS.C03l.CLCC2 XVtreated as well or better, the Agency will transfer the treatment standards to the untested waste.**~** For example, for wastes that can be treated using chemical precipitation, if the Agency tests awaste containing lead at agiven level, it will transfer the treatment standards developed from the testto asecond lead-containingwaste if the second waste meets the following WCAP-based conditions:

• The lead concentration is similar to that of the tested waste;
• The second waste has alower total dissolved solids level;
• The concentration and type ofother metals are similarto those ofthe tested waste; and
• The untested waste has aconcentration ofoil and grease similar to or less than that of the tested waste. (b) Use of Information Provided. In applying the WCAP analyses, it**~s** important to remember that the technology itself and the associated design and operating conditions are fixed (i.e., they are fixed at the values that existed for the already tested waste). EPA does not assume that, where WCAPs for the untested waste showthat itwouldbe significantlyharder to treat, the addition of another treatment component or a change in design and operating conditions will result fn the untested waste achieving the same performance as that of the previously tested waste. EPA is aware that modifying the treatment system or operating conditions could result in similar treatment. However, the Agency is not certain, without demonstrating through testing, that treatment levels associated with BOAT standards (normally in the low (<10) part per million or part per billionrange) can be achieved by simply changing treatment conditions. Accordingly, EPA is very cautious in its decisions to transfer treatment standards where the WCAP analysis shows that treatment modifications are needed from the previously tested waste.

f:\document\15254031.01.002 xvi(c) Use of New Data and Information. In developing the WCAPs for the various treatment technologies, EPA found little and, in some cases, no information ont.-the relative importance of the various WCAPs for a given technology (i.e., which waste characteristics have the most significant impact on treatment performance). Where information was available with regard to the specificWCAPs that are importantwhen assessing the performance ofaparticular technology, EPA was unable to find any supporting data that would quantify the relative impact of each of the WCAPs on treatment performance. As data become available either from industry or through EPA's BOAT data collection program, EPA may modify the WCAP analysis to further refine the parameters identified as affecting treatment technology performance. As previouslynoted, before itadopts anew WCAP, the Agencymustunderstand how the parameters affect treatment relative to the underlying principles ofoperation. 5. Design and Operating Parameters ' 

# . EPA uses design and oparating information in several ways. First, this information is used, in conjunction with the Agency's BOAT data collection program, in determining whether aparticular treatment system is well designed. That is, the Agency assesses design data prior to determining whether to test a particular piece of equipment or treatment train for potential use in the develQprnent of BOAT treatment standards. EPA obtains operating data during the course 

### ofan**Agency-~ponsored**treatment test to ensure that the treatment system is well operated. Secondly, EPA expects facilities to provide the appropriate design and operating data when submitting treatment data to be considered in the development of the BOAT treatment standards. Again, the Agency assesses these data to·determine whether the treatment system**~as** we11 designed and we11 operated.
Forexample, some ofthecritical design and operating parameters for steam strippinginclude the numberofequilibrium stages inthecolumn, the temperature

f:\docum.nt\15Z5403l.Ol.OOZ xvii Iat which the unit isdesigned to operate, andhow well the design temperature is controlled. In evaluatingperformancedatafromasteam strippingoperation, the Agencywould**ex~ine**the design specifications (e.g., the basis for selecting the number of stages and design temperature) for the treatment unit in order to determine the extent to which the hazardous constituents could be expected to volatilize. After the design specifications are established, the Agency would collect data (e.g., hourly readings of the column temperature) throughout the operation of the treatment process demonstrating that the unit was operating according to design specifications. Ifthe datacollectedvary considerably from the design requirements, that variation could form the basis for determination that the treatment unit was improperly operated. Ifthe temperature data show, for example, that for significant periods of time the temperature varied considerably from the design requirements, the Agency would not usa these data to determine the levels ofperformance achievable by BOAT.

.. Finally, EPA requires facilities petitioning for atreatment variance to submit the plant's design values and the operating data during the time of tbe treatment period to ensure that the treatment systemwas well designed and well operated.

f:\document\15254031.01.002l

I. 

### TREATMENT TECHHOLOIHES A. DESTRUCTION TECHNOLOGIES1. BIOLOGICAL TREATMENT
1.1 ApPiicability Biological treatment can typically be divided into two ciassifications: aerobic biological treatment and anaerobic biological treatment. Aerobic biological treatment takes place in the presence of oxygen, while anaerobic biological treatment is an oxygen-devoid process. Aerobic biological treatment is a treatment technology applicable to wastewaters containing biodegradable organic constituents**~nd** :ome nonmetallic inorganicconstituents including sulfides and cyanides. Fourofthe most common aerobic biological treatment processes are (a) activated sludge, (b) aerated lagoon, (c) trickling filter, and (d) rotating biological contactor (RBC). The activated sludge and aerated lagoon processes are suspended-growth processes**~n** whichmicroorganisms aremaintained in suspensionwiththe liquid. The trickling filterand the RBC are attached-growth processes in which microorganisms grow on any inertmedium such as rocks, slag, orspecificallydesigned ceramicorplastic materials. This section discusses these four processes as well as the powdered activatedcarbon (PAC) adsorption process, which is avariation ofthe activated sludge**treat~ent.** _Anaerobic digestion is best suited to wastes with amoderate to high pH, honhalogenated hydrocarbons, moderate to low organic loadings, and low to zero biological oxygen demand. The waste should also be in a semisolid or sludge form. Anaerobic biological treatment typically takes place in an anaerobic digester. 

### 1.2 UnderlYing Principles of

### Operation Thebasicprincipleofoperationfor aerobicbiological treatmentprocesses isthatliving, oxygen-requiringmicroorganismsdecompose organic andnonmetallic inorganics constituents into carbon dioxide, water, nitrates, sulfates, simpler**f:\~cument\15254031.01.003** 1low-molecular-weight organic byproducts, and cellular biomass. Wastes that can be degradad by a_given species or genus of organisms may be very limited. A mixture of**orga~sms** may be required to achieve effective treatment, especially for wastes containingmixtures oforganic compounds. Nutrients such as nitrogen and phosphorus are also required to aid in the biodegradation process. The aerobic biodegradation process can be represented by the following generic equation: microorganisms >H0 +COz + biomass nutrients 2 Microorganisms produce enzymes that catalyze the biodegradation reactions, degrading theorganicwaste to obtain energyfor cell metabolismandcell growth. Aerobicbiologicaltreatmentofwastewaterscontainingorganicconstituents results in thenet accumulation ofabiomass ofexpiredmicroorganisms**consist~~g** mainly of cell protein. However, the cellular biomass or sludges may**al~o** contain entrained constituents from the wastewater or partially degraded constituents. These sludges must beperiodicallyremoved (•wasted•) to maintain proper operation of the aerobic biological treatment system. The basicprincipleofoperation ofanaerobic biological treatment isthat microorganisms in the absence of oxygen transform organic constituents and nitrogen-containing compounds into carbon dioxide and methane gas. Often other nutrients such as nitrogen and phosphorus are necessary to aid digestion. The anaerobic biological treatment process can be described by the fallowing equation:

ex Hy + microorganisms >CO + CH4 + biomass nutrients 2

f:**\docunent\152~031.01.**003 2 

# 11.3 Description of Biological Treatment Processes

- 1.3.1**Ac~**vated Sludge The activated sludge process is currently the most widely used biological treatment process. This is partly the result ofthe fact that recirculation of the biomass, which is an integral part of the process, allows microorganisms to adapt to changes in wastewater composition with arelatively short acclimation time and also allows a·greater degree of control over the acclimated bacterial**pop~:lation.** An activated sludge system consists of an equalization basin, a settling tank, an aeration basin, aclarifier, and asludge recycle line. Wastewater is homogenized in an equalization basin to reduce variations in the feed, which may cause process upsets of the microorganisms and diminish treatment efficiency.

. . Settleable solids are then removed in a settling tank. Next, wastewater enters an aeration basin, where an aerobic bacterial population is maintained in suspension and oxygen, as well as nutrients, is provided. The contents ofthebasin are referred to as the mixed 1iquor. Oxygen is supplied to the aeration basin by mechanical ordiffused aeration, which also aids in keeping the microbial population in suspension. The mixed liquor is continuously discharged from the aeration basin into a clarifier, where the biomass is separated from the treated wastewater. Aportion of the biomass is recycledto the aerationbasin tomaintain an optimumconcentration ofacclimated microorganisms in the**a~ration** basin. The remainder ofthe separated biomass is discharged or Nwasted.• The biomass may be further dewatered on sludge drying beds or by sludge filtration (which isfurther discussed in Section 11.8.2} prior to disposal. The clarified effluent is discharged. Aschematic diagram of an activated sludge treatment system is shown in Figure 1.

f:\docllll!nt\15254031.01.003 3

# .

WASTEWATER EQUALIIATIOH**~** IHfLUEHT

.. 

### TANK 8ETTLINO 

### f-+ TANK OXYGEN AND NUTRIENTS 

# •

AERATION BASIN**~** BASIN EFFLUENT CLARIFIER


# -

SLUDGE RECYCLE t

\.. ... 

### . ' . Figure 1 Activated Sludge System 1-+-



### ... -**----~----**

"" •'

TREATED EFFLUENT TO DISPOSAL

WASTE SLUDGE TO SLUDGE fiLTRATION AND DISPOSAL

.

## ....-...The recycled biomass is referred to as activated siudge. The term nactivateG" is u_sed because the biomass contains living and acclimated mict·oorganisms**~at** metabolize and assimilate organic material at ahigher rate when returned to the aeration basin. This occurs because of the low food-to-microorganism ratio in the sludge from the clarifier.
An important variation on the activated sludge process is the Powdered Activated Carbon Treatment (PACT) process. This process offers a combined treatment and pretreatment system in which noncompatible and toxic constituents are adsorbed onto activatedcarbon, while microorganism-compatiblewaste remains in solution. Powdered activated carbon is added directly to the aeration basin ofthe activated sludge treatment system. Overall removal efficiency isimproved because compounds that are not readily biodegradable or that are toxic to the microorganisms are aasorbed onto the surface of the powdered activated carbon. The carbon is removed from the wastewater in the c larifier a 1 ong with the biological sludge. Usually, theactivated carbon is recovered, regenerated, and recycled.
1.3.2 Aerated Lagoon ' ,

Like an activated sludge system, an aerated lagoon is a suspended-growth process. The aerated lagoon system consists of a large pond or tank that is**equipp~d** with mechanical aerators to maintain an aerobic environment and to prevent settling of the suspended biomass. Initially, the population of microorganisms in an aerated lagoon is much lower than that in an activated sludge system because there is no sludge recycle. Therefore, a significantly longerresidencetime is requiredtoachieve the same effluentquality. However, this longerresidence timemaybean advantage when complex organicchemicals are to be degraded. Also, the microorganisms in aerated lagoons are more resistant to process upsets caused by feed variations than those in activated sludge systems because ofthe largertank volumes and longerresidence times used. The effluent from the aerated lagoon may flow to a settling tank for removal of suspended solids. Alternatively, the mechanical aerators in the system may be

f:\document\15254031.01.003 5shut off for a period of time to facilitate settling prior to discharge of the effluent.·The se!_tled sol;ds are generally dewatered prior to disposal. l. 1.3.3 Trickling Filters
Atrick.ling filteris an attached-growth biological treatment process. The system consists of an equalization basin, a settling tank, a filtermedium, an influentwastewaterdistribution system, an underdrain system, aclarifier, and arecirculation line. The filtermedium consists of abed of**~n** inert material to which the microorganisms attach themselves and through which the wastewater is percolated. Rocks or syntheticmaterial suchas plasticrings and saddles are typically used as filter media. Fallowing equa1ization and settling of settleablesolids in thewastewater, it is distributed over the top ofthe filter medium by a rotating distribution ann or a fixed distributor system. The wastewater forms a thin layer as it flows downward through the filter and over

.. the microorganism layer on the surface of the medium. As the distribution**~** rotates, the microorganism layer is alternatelyexposed to aflow ofwastewater and a flow of air. In the fixed distributor system, the wastewater flow is cycled on and off at a specified dosing rate to ensure that an adequate supply of oxygen is available to the microorganisms. Oxygen from air reaches the microorganisms through the void spaces in the medium. Figure 2is adiagram of a trickling filter system. Atricklingfilter system is typicallyused as aroughing filterto reduce the organic loading on adownstreamactivated sludge process. Trickling filters can be used for the**tr~atment** of wastewaters that could potentially produce**~bulkingN** sludge (i.e., a sludge with poor settling characteristics and poor compactabilityin an activated sludgeprocess) because the microbial solids that slough offthe trickling filtermedium are relatively dense and can be readily removed in a clarifier.

f:\dor.ument\15254031.01.003 6

### -**--~·----------------** ---**··--~·--·-**

WASTE DISTRIBUTOR WASTEWATER**INFLUENT--~~-,------~------r------r------,-----~**

Figure 2 Trickling Filter System TREATED**."'A--~**EFFLUENT TO CLARIFIER ,r"1.3.4 Rotating Biological Contactor
Arotatirg- biological contactor (RBC) consists of a series of closely spaced, parallel disks that are rotated at an average rate of2to 5revolutions per minute while submerged to 40 percent of their diameters in a contact tank containing wastewater. The disks are constructed of polystyrene, polyvinyl chloride, or similar materials. Each disk is covered with a biological s1ime that degrades dissolved organic constituents present in the wastewater. As the disk is rotated out of the tank, it carries a film of the wastewater into the air, where oxygen is available for aerobic biological decomposition. As excess biomass is produced, it sloughs off the disk and is separated from the treated effluent in a clarifier. The sloughing off process is similar to that which occurs in a trickling filter. There is no recycle of sludges or recirculation of treated effluent in an RBC process. Several RBCs are often operated in series, with the effluent from the last RBC being discharged. Biological solids are usually dewatered prior to disposal. 1.3.5 Anaerobic Biological Treatment
In anaerobic biological treatment, the influent sludge is settled and equalized, then pumped to the anaerobic digester (Figure 3) along with an alkaline adjustment additive. There may or may not be mechanical agitation of the digester. After an adequate residence time to allow for proper digestion,**~he** dtgester contents are allowed to settle. .The supernatant is pumped to an aerobic treatment area (typicallyto an activated sludge unit), while the sludge is taken to disposal areas or subjected to additional treatment, such as drying or incineration. 

### 1.4 Waste Characteristics Affecting Performance (WCAPsl
In determining whether biological treatmentwill achieve the same level of performance on an untested waste that it achieved on a previously tested waste and whether performance levels can be transferred, EPA examines the following

f:\document\15254031.01.003 8SLUDGE INFlUENT**~** EQUALIZAT10N.,_....,.....,

SLUOOE TANK

ALKALINITY

.... 

# 'Q- ADJUSTMENT I**~~** ADDITIVE PUMP

# d$fl~E t GASCOMPRESSION

# ~~~-, I FlOATING

# I I COVER 

# I 

# I

MIXERS
DIGESTER (CONCRETE)

RECYCLESLUDGE

Figure 3 Anaerobic Digestion SUPERNAlANTTO ACTIVATEDSLUDGE
SLUDGE SLUDGE EFFLUENT HOLDING BASIN PUMPwaste characteristics: (a) the r<ltio of the biological oxygen demand to the total organic carbon content, (b) the concentration of surfactants, and (c) the concentration or-toxic constituents and waste characteristics. l. 1.4.1 Ratio of Biological Oxygen Demand to Total Organic Carbon Content
Because organic constituents in the waste effectively serve as a food supply for the microorganisms, it is necessary that a significantpercentage be biodegradable. If they.are not, it will be difficult for the microorganisms to successfully acclimate to the waste and achieve effective treatment. The percentage of biodegradable organics can be estimated by the ratio of the biological oxygendemand (BOD) to thetotal organic carbon (TOC) content. Since the biological oxygen demand is a measure ofthe amount of oxygen required for complete microbial oxidation of biodegradable organics, the BOD analysis is mostly relevant to aerobic biological treatment. (In anaerobic biological treatment, BOO is one ofthe main restrictive characteristics in that BOD must be relatively low or zero.) Ifthe ratio ofBOO to TOC in an untested waste**1~** significantlylower thanthat inthetestedwaste, the systemmay not achieve the same performance and other, more applicable technologies may need to be considered for treatment of the untested waste. 1.4.2 Concentration of Surfactants Surfactants can affect biological treatment performance by forming afilm

, on organic constituents, thereby establishing a barrier to effective biodegradation. If the concentration of surfactants in an untested waste is significantly higher than that in the tested waste, the system may not achieve the same performance and other, more applicable technologies may need to be considered for treatment of the untested waste.

f:\document\15254031.01.003 101.4.3 Concentration ofToxic Constituents and Waste Characteristics Anumber

### at constituents and waste characteristics have been identified as potentiallytoxic tomicroorganisms. Specifictoxic concentrationshavenot been determined for most of these canstituents and waste characteristics. The constituents and waste characteristics found to be potentially toxic to microorganisms include metals and oil and grease, ammonia, and phenols. High concentrations of dissolved solids are treated more effectively by anaerobic treatment than by aerobic treatment. Ifthe concentration oftoxic constituents andwaste characteristics in an untestedwaste is significantly higher than that in the tested waste, the system may not achieve the same performance and other, more applicable technologies may need to be considered for treatment of the untested waste. 1.5 Design and Operating Parameters
In assessing theeffectiveness ofthe design and operation ofabiologica-l treatment system, EPA examines the following parameters: (a) the amount of nutrients, (b) the concentration of dissolved oxygen, (c) the food-tomicroorganism ratio, (d) the pH, (e) the biological treatment temperature, {f) the mean cell residence time, (g) the hydraulic loading rate, (h) the settling time, and {i) the degree ofmixing.
For many hazardous organic constituents, analytical methods are not availableorthe constituent cannot be analyzed in thewastematrix. Therefore, it would normally be impossible to measure the effectiveness of the biological treatment system. In these cases EPAtries to identifymeasurable parameters or constituents that would act as surrogates in order to verify treatment. For organic constituents, each compound contains a measurable amount of total organic carbon (TOC). Removal of TOC in the biological treatment system indicates removal oforganic constituents. Hence, TOC analysis is likely to be

f:\dccument\15254031.01.003 11

### an adequate surrogate analysis where the specific organic constituent cannot be measured.
{_ 

### However, TOC 

### analysis may not be able to adequately detect treatment of specific organics in matrices that are heavily organic-laden (i.e., the TOC 

### analysis may not be sensitive enough to detect changes at the milligrams per liter (mg/1) level in matrices where total organic concentrations are hundreds or thousands of mg/1). In these cases other surrogate parameters should be sought. For example, if a specific analyzable constituent is expected to be treated as well as the unanalyzable constituent, the analyzable constituent concentration should be monitored as a surrogate. 1.5.1 Amount ofNutrients Nutrient addition is important incontrolling the growth ofmicroorganisms because an insufficientamountofnutrients resultsinpoormicrobial growth**wi~h** 

### poorbiodegradation oforganic constituents. The principal inorganic**nutrien~s** 

### used are nitrogen and phosphorus. In addition, trace amounts of potassium, calcium, sulfur, magnesium, iron, and manganese are also used for optimum microbial growth. The percent distribution ofnitrogen and phosphorus added to microorganisms varies with the age of the organism and the particular environmental conditions. The total amount ofnutrients requireddepends on the net mass of organisms produced. EPA monitors the amount ofnutrients added and theirmethod ofaddition to the wastewater to ensure that a sufficient supply is provided to achieve an effective growth ofmicroorganisms. 1.5.2 Concentration ofDissolved Oxygen Asufficient concentration of dissolved oxygen (DO) 1s necessary to metabolize anddegrade dissolved organic constituents in aerobic treatment. The DO concentration iscontrolledbyadjusting the aerationrate. Theaeration rate

f:\document\1SZS4031.01.003 12must be adequate to provide a sufficient DO concentration to satisfy the BOD requiremeAts of**t~e** waste, as well as to provide adequate mixing to keep the microbial popu1t_tion in suspension (for activated sludge and aerated lagoon processes). The reverse is true for anaerobic treatment, in that DO must be absent for anaerobic treatment to occur. EPA monitors the DO concentrations continuously, if possible, to ensure that the system is operating at the appropriate design condition and to diagnose operational problems. 1.5.3 Food-to-Microorganism Ratio The food-to-microorganism (F/M) ratio, which applies only to activated sludge systems, is ameasure ofthe amount ofbiomass available to metabolize the influent organic loading to the aeration unit. This ratio can be determined by dividing the influent BOD concentration by the concentration of active biomass, also referred to as themixed liquor volatile suspended solids 

### (HLVSS). The 

### F/H

. . ... ratio is controlled by adjusting the wastewater feed rate or the sludge recycfe rate. Ifthe F/M ratio is too high, too few·microorganisms will be available

### to degrade the organics. EPA periodically analyzes the influent BOD and the aeration unit's 

### MLVSS concentrations to ensure that the system is operating at the appropriate design condition.
1.5.4 pH Generally, neutral or slightly alkaline pH favors microorganism growth. The optimum range for most microorganisms used in biological treatment systems is between 6and 8. Treatment effectivenessis generally insensitiveto changes within this range. However, pH values outside the range can lower treatment performance. EPAmonitors the pH continuously, ifpossible, to ensure that the system is operating at the appropriate design condition and to diagnose operational problems.**f:\doc~nt\15254031.01.003** 131.5.5 

### Biological Treatment Temperature Microbial'growth can occurunder awiderangeoftemperatures, althoughthe majority ofthe microbial species used in aerobic biological treatmentprocesses are active between 20 and 3S"C (68 to 95"F}. For anaerobic systems, the temperature is typically between 30 

### and 70"C (86 

### to ISS"F}. 

### The rate of biochemical reactions in cells increases with temperature up to amaximum above which the rate ofactivity declines and microorganisms either die offor become less active. 

### EPAmonitors the biological treatment temperature continuously, if possible, to ensure that the system is operating at the appropriate design condition and to diagnose operational problems.
1.5.6 

### Mean Cell Residence Time
In activated sludge, aerated lagoon, and anaerobic digestion systems,**t~e** 

### mean cell residence time (HCRT) or sludge age is the lengthoftime organisms ar.e retained in the unit before being drawn offas waste sludge. Bycontrolling**t~e** 

### MCRT, the growth phase ofthe microbial population can be controlled. The MCRT must be long enough to allow the organisms in the unit to reproduce. The MCRT is determined by dividing the total active microbial mass in the unit (HLVSS) by the total quantityofmicrobial mass withdrawn daily (wasted). 

### EPAmonitors the MCRT to ensure that a sufficient number of microorganisms are present in the unit. 1.5.7 Hydraulic Loading Rata The hydraulic loading rate determines the length of time the organic constituents are in contact with the microorganisms and, hence, the extent of biodegradation that occurs. In trickling filters, the hydraulic loading rate also determines the shear velocities on the microbial layer. Excessively high hydraulic loading ratesmaywash awaythemicrobial layerfaster than itcangrow back. However, the hydraulic loading rate must be high enough to keep the microbes moist and to 

### remove dead or dying microbes that have lost their ability

f:\document\15254031.01.003 14 

# 1 fto cling to the filter media. For all aerobic biological treatment processes, the hydraylic loading rate is controlled by adjusting the wastewater feed rate. In addition,**fo~RBCs,** the hydraulic loading rate can be controlled by changing the disk speed or adjusting the submersion depth. EPA monitors the wastewater feed rates to ensure that the hydraulic loading provides sufficient time to achieve an effective biodegradation of organic constituents in the wastewater. 1.5.8 SettlingTime Adequate settlingtime must be provided to separate the biological solids from the mixed liquor. Activated sludge systems cannot function properly ifthe solids cannot be effectively separated and a portion returned to the aeration basin. EPA monitors the settling time to ensure effective solids removal. 1.5.9 Degree ofMixing Mixing provides greater uniformity of the wastewater feed in the equalizatior. basin to reduce variations that may cause process upsets of the microorganisms and diminish treatment efficiency. For activated sludge and aerated lagoon systems, sufficient aeration in the aeration unit provides mixing to ensure adequate contact between the microorganisms and the organic constituents in the wastewater. The quantifiable degree ofmixing is acomplex**assess~ent**that**include~,** among otherfactors, the amount ofenergy supplied, the length of time thematerial ismixed, and the related turbulence effects ofthe specific size and shape ofthe mixing unit. The degree ofmixing is beyond the scope of simple measur.ement. EPA, however, evaluates the degree of mixing qualitatively by considering whether mixing is provided**~nd** whether the type of mixing device is one that could be expected to achieve uniform mixing of the wastewater.

f:\document\152S403l.Ol.OOJ 151.6 References



### . Barley, J., and Ollis, D. 1977. Biochemical engineering fundamentals. New York: Hctraw-Hill Book Co. Burchett, H., and Tshobanoglous, G. 1974. Facilities for controlling the activated sludge process by mean cell residence time. Journal Water Pollution Control Federation. Vol. 46, no. 5 (May 1974), p. 973. Clark, J.W., Viessman, W., and Ha1t111er, H. 1977. Water supply and pollution control. New York: Harper 

### &Row,**P~blishers.** Eckenfelder Jr., W.W., Patoczka, J., and Watkins, A. 1985. Wastewater treatment. Chemical engineering. September 2, 1985. Johnson, S.J. 1978. Biological treatment. Unit operation for treatment of hazardous industrial wastes. Park Ridge, N.J.: Noyes Data Corporation. Kobaya5hi, 

### H., and Rittmann, 

### B. 1982. Microbial removal ofhazardous organic compounds. Environmental Science and Technology. Vol. 16, no. 3, pp. 170-183.

. . Metcalf&Eddy, Inc. 1979. Wastewaterengineering: treatment, disposal, reuse. New York: McGraw-Hill Book Co. : Nemerow, N.L. 1978. Industrial water pollution origins, characteristics. and treatment. Reading, Mass.: Addison-Wesley Publishing Company. Perry, R., andGreen, 0. 1984.**Ch~mical** engineers' handbook. 6th ed. NewYork: McGraw-Hill Book Co. Rittmann, 8. 1987. Aerobic biological treatment. Environmental Science and Technology. February 1987. p. 128. USEPA.· 1985. U.S. Environmental Protection Agency. Final report. Assessment oftreatment technologies for hazardous waste and their restrictivewaste characteristics. Vol 1. Washington, D.C.: U.S. Environmental Protection Agency. USEPA. 1986. U.S. Environmental ProtectionAgency. Bestdemonstrated available technology background document for FOOl-FOOS spent solvents. Vol. 1, EPA/530-SW-86-056. pp. 4-43. Washington, D.C.: U.S. Environmental Protection Agency.

f:\document\1525403l.Ol.003 16 

# '

I2. CHEMICAL OXIDATION 2.1**Appi~cability** Chemical oxidation is a treatment technology used to treat wastes containing organics. It is also used to treat sulfide wastes by converting the sulfide to sulfate. The destruction of cyanides in wastes is usually accomplished by chemical oxidation. Chemical oxidation can also be used to change the oxidation state of metallic compounds to valences that are less soluble, such as converting arsenic in wastes to the relatively insoluble pentavalent state. Chemical oxidation is applicable to dissolved cyanides in aqueous solutions, such as wastewaters from metal plating and finishing operations, or to inorganic sludges from these operations that contain cyanide-compounds. For cyanides, chemical oxidation ismost applicableto solutions containingless than 500 mg/1 of cyanides when the cyanides are in a form that can be easily disassociated in water to yield free cyanide ions. If cyanides are present in wateras atightlyboundcomplex ion (e.g., ferrocyanide), only limitedtreatment may occur. Ifthe waste contains greater than 500 mg/1 ofcyanide, but no more than about 100,000 mg/1, electrolytic oxidation may be more appropriate. See Section I.A.4. Chemical oxidation may also be used for destruction of the organic componentoforganometalliccompounds inwastes, thus freeing themetal component for treatment bychemical precipitationor stabilization. Organiccompounds such as EDTA, NTA, citric acid, glutaric acid, lactic acid, and tartrates are often used as chelating agents to prevent metal ions from precipitating out in electroless plating solutions. When these spent plating solutions require treatment for metals removal by chemical precipitation, the organic chelating agents must first be destroyed. Chemical oxidants, potassium permanganate in particular, are effective in releasingmetals from complexes with these organic compounds.

f:\document\15254031.01.004 17

### 2.2 Underlying Principles of Operation



### - The basilprinciple ofoperation for chemical oxidation is that inorganic cyanides, some -dissolved organic compounds, and sulfides can be chemically oxidized toyieldcarbondioxide, water, salts, simpleorganic acids. and, in the case ofsulfides, sulfates. Metallic ions such as arsenites can be oxidized to higher, less solublevalences such as arsenates. Theprincipal chemical oxidants used are hypochlorite, chlorine gas, chlorine dioxide, hydrogen peroxide, ozone, and potassium permanganate. The reaction chemistry for each is discussed below. 2.2.1 Oxidation with Hypochlorite or Chlorine (Alkaline Chlorination) This type of oxidation is carried out using sodium hypochlorite (NaOC1}, calcium hypochlorite (Ca(OC1)2), 

### chlorine gas (Cl2}, 

### or sometimes chlorine dioxide gas (Cl02). 

### The reactions are normally conducted under slightly**~r** 

### moderately alkaline conditions. Alkaline chlorination ofcyanide is atwo-step process usually operatedat apH of 10to 11.5 for the first step and 8.5 for tfie second step. The toxic gas cyanogen chloride (CNCl) is formed as a reaction intermediate in the first stepof this process and may be liberated ifthe pH is less than 10 and incomplete reaction occurs. Example reactions forthe oxidation ofcyanide, phenol, and sulfide using sodiumhypochlorite are shown below: Cyanide: CN- +

### NaOCl

.. OCN- +

### NaCl {Step 1) 20CN- +

### 3Na0Cl

.. C03

### z- +

### C02+

### N 2+

### 3NaCl {Step 2) Phenol:**0H** + 

### 14Na0Cl • 6C02 + 

### 3H2 

### 0 + 

### 14NaCl Sulfide: 

## s· +

### 4NaOC1**~**

## so,· +

### 4NaC1

Chlorine dioxide also oxidizes the same pollutants under identical conditions. Chlorine dioxide first hydrolyzes 

### to form amixture of chlorous

f:\document\15254031.01.004 18(HC102) and chloric (HC103) acids. These acids act as the oxidants, as shown in the equattons belQw, for phenol: 2Cl02 +H 20**~**HC102 +HC103 C

6 H

50H + 7HC102• 6C02 + 3H2 0 +7HC1 3C6H 5 0H + 14HC103 ..8C02 +9H20 + 14HC1 2.2.2 Peroxide Oxidation Peroxide oxidizes the same constituents that alkaline chlorination oxidizes under similar**~onditions.** The relevant reactions are the following:

2.2.3 Oxidation with Ozone (Ozonation) ' '

Ozone is an effective oxidizing agent for the treatment of organic**compou~ds** and for the oxidation of cyanide to cyanate. Cyanogen gas (C2N 2) is 

## areaction intermediate in thisreaction. Furtheroxidation ofcyanateto carbon dioxide and nitrogen compounds (N2 or NH3) occurs slowly with ozone. The oxidation ofcyanide to-cyanate proceeds by the following reaction:

The rates of ozonation reactions can be accelerated by supplying ultraviolet (UV) radiation during treatment. Some literature sources indicate that even the cyanide complexes most difficult to treat, the iron-cyanide complexes, can be oxidized completely.

f:\document\1525403l.Ol.JO• 192.2.4 Oxidation with Potassium Permanganate Potassium<P.ermanganate can also be used to oxidize the same constituents as the other chemical oxidants. The reactions of potassium permanganate with phenol and sulfide at acidic pHs and with cyanide at pH 12 to 14 are as follows:

In cyanide oxidation using potassium permanganate, cyanide is oxidized only to cyanate. Furtheroxidation ofcyanate can be accomplished by acid hydrolysis or by the use of another oxidizing agent. 2.2.5 S02 /A1r Oxidation 

# . . Cyanide can be oxidized to cyanate in an aqueous solution by bubbling air containing from 1to 10 percent 502through the waste. The 502 is also oxidized to sulfate in this reaction. This treatment process occurs by the following reaction:

This oxidation reaction requires the use of a soluble copper salt catalyst. Copper sulfate {CuS04) ismost often used. 502 /airoxidation is used frequently inthe treatment ofwastewaters from gold production, which contain both cyanide and thiocyanate, because 502 /airoxidizes cyanidemore strongly than thiocyanate while alkalinechlorinationandotherco11111onoxidizing agents oxidizethiocyanate more strongly than cyanide. As with potassiumpermanganate, further oxidation of cyanate can be accomplished by acid hydrolysis or by the use of another oxidizing agent.

f:\docum!nt\15254031.01.004 202.3 Description ofChemical Oxidation Processes 2.3.1**Al~line** Chlorination Alkaline chlorination can be accomplished by either batch or continuous processes. For batch treatment, the wastewater is transferred to a reaction tank, where the pH is adjusted and the oxidizing agent is added. In some cases, the tank may be heated to increase the reaction rate. For oxidation of most compounds, a slightly to moderately alkaline pH is used. It is important that the tank be well mixed for effective treatment to occur. After treatment, the wastewater is either directly discharged or transferred to another process for further treatment. Inthe continuous process, automatic instrumentation isused to control pH, reagentaddition, andtemp.erature. Anoxidation-reductionpotential (ORP) sensar is usually used to measure the extent of reaction.
In both types of processes, agitation is typically provided to maintain thoroughmixing. Typical residencetimes forthese and otheroxidationprocesses range from 1to 2hours. 

### 2.3.2 Peroxide Oxidation· The peroxide ox1dat1on process is run under similar conditions, and with similarequipment, to those used in the alkaline chlorination process. Hydrogen peroxide is added as a]iquid solution. 

### 2.3.3 Ozonatton Ozonationcan be conducted in abatch orcontinuousprocess. The ozone for treatment is produced onsite because ofthe hazards oftransporting and storing ozone as we11 as its short she1 f 1 ife. The ozone gas is supplied to the reactIon vessels by injection into the wastewater. The batch process uses a single

f:\dbcument\15254031.01.004 

### 21reaction tank. As with alkaline chlorination, the amount ofozone added and the reaction**~ime** usee!_aredetermined bythe type and concentrationofthe oxidizable contaminants,**a~~** vigorous mixing should be provided for complete oxidation.
In continuous operation, two separate tanks may be used for reaction. The first tankreceives an excess dosage ofozone. Any excess ozone remaining at the outlet of the second tank is recycled to the first tank, thus ensuring that an excess of ozone is maintained and also that no ozone is released to the atmosphere. As with alkaline chlorination, an ORP control system is usually necessary to ensure that sufficient ozone is being added. 2.3.4 Permanganate Oxidation Pennanganate oxidation is conducted in tanks in amanner similar to that used for alkaline chlorination, as discussed previously. Potassiumpermanganate is normally dissolved in an auxiliary tank and added as asolution. As with**t~e** otheroxidizingagents, ORP (forcontinuous processes) and excess oxidizing ageat (for batch processes) are monitored to measure the extent of reaction. 2.3.5 S02 /A1r Oxidation S02 /air oxidation of cyanide depends on efficient mixing of air with the waste to ensure an adequate supply of oxygen. Because of this factor, the equipmentrequirements for this process are**si~ilar** to those for ozonation. 502 is sometimes supplied with the air by using flue gas containing 502 as the air source. Otherwise, sulfur fn the +4 oxidation state can be fed as gaseous sulfur dioxide (502), liquid sulfurous acid (H2 S03), sodium sulfite (Na2 S03) solution, orsodiumbisulfite {NaHS03) solution. Sodiumbisulfitesolution, made by dissolving sodium 10etabisulfite (Na2 S

20 5) in water, is the most frequently used source of502• This process is usually run continously, with the addition ofoxidizingagent andacid/alkalibeing controlledthroughcontinuous monitoring ofORP and pH, respectively.

f:\docunent\15254031.**01.0~** 22 

# 1

- J2.4 Waste Characteristics Affecting Performance (WCAPs)
In**determt~ing** whether chemical oxidation will achieve the same level of performance on an untested waste that it achieved on apreviously tested waste**a~d** whether performance levels can be transferred, EPA examines the following waste characteristics: (a} the concentration of other oxidizable contaminants and (b) the concentration ofmetal salts. 2.4.1 Concentration ofOther Oxidizable Compounds The presenceofotheroxidizablecompounds in addition to the constituents ofconcern will increasethe demand for oxidizing agents and, hence, potentially reduce the effectivenessofthe treatmentprocess. As asurrogate forthe amount of oxidizable organics present, 

### EPA analyzes for total organic carbon (TOC) in the waste
..Inorganic requcing compounds such as sulfidemay also createa**dema~d** for additional oxidizing agent; 

### EPA also attempts to identify and analyze far these canstituents. IfTOC and/or inorganicreducing compoundconcentratiens t'n the untested waste are significantly higher than those in the testedwaste, the systemmay not achieve the same performance. Additional oxidizing agent may be required to effectively oxidize the waste and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment ofthe untested waste. 2.4.2 Concentration ofMetal Salts Metal salts, especially lead and silver salts, will react with the oxidizing agent(s) to fona metal peroxides, chlorides, hypochlorites, and/or chlorates. These reactions can cause an excessive consumption of oxidizing agents and potentially interfere with the effectiveness of treatment. An additional problem with metals in cyanide solutions is that metal-cyanide complexes are sometimes formed. These complexes are negatively chargedmetal-cyanide ions that are extremely soluble. Cyanide in the complexed

f:\document\1SZ5403l.Ol.OC4 23form may not be oxidizable, depending on the strength of the metal-cyanide bond in the complex and the type of oxidizing agent used. Iron complexes (for example, the**fe~ocyanide** ion, Fe(CN)6-4) are the most stable of the complexed cyanides. Ifthe concentrations ofmetal salts and/ormetal-cyanide complexes in the untested waste are significantly higher than those in the tested waste, the systemmay not achieve the same performance. Additional oxidizing agent and/or adifferent oxidizing agent may be required to effectivelyoxidize the waste and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment of the untested waste. 2.5 Design and Operating Parameters
In assessing the effectiveness of the design and operation of a chemical oxidation system, EPAexamines the following parameters: {a) the residence**ti~,** (b) theamount and type ofoxidizingagent, (c) thedegree ofmixing, (d) thepff, (e) the oxidation temperature, and (f) the amount and type ofcatalyst.
For many hazardous organic constituents, analytical methods are not available or the constituent cannot be analyzed in the wastematrix. Therefore, it would normally be impossible to measure the effectiveness of the chemical oxidation treatment system. In these cases EPA tries to identify measurable parameters or constituents that would act as surrogates to verify treatment. For organic**cons~1tuents,** each compound contains a measurable amount of total organic carbon {TOC). Removal ofTOC fn the chemical oxidation treatment system will indicate removal of organic constituents. Hence, TOC analysis fs likely to be an adequate surrogate analysis where the specific organic constituent cannot be measured. However, TOC analysis may not be able to adequately detect treatment of specific organics in matrices that are heavily organic-laden (i.e., the TOC

f:**\doc~~~~ent\15254031.01.**004 24analysis may not be sensitive**eno~gh** to detect changes at the milligrams/liter (mg/1) 181/el in matrices where total organic concentrations are hundreds or thousands of**mg/~).** In these cases other surrogate parameters should be sought. For example, if a specific analyzable constituent is expected to be treated as well as the unanalyzable constituent, the analyzable constituent concentration should be monitored as a surrogate. 2.5.1 Residence Time The residence time impacts the extent of volatilization of waste contaminants. For abatch system, the residence time is controlled by adjusting the treatment time in the reaction tank. for acontinuous system, the waste feed iate is controlled to make sure that the system is operated at the appropriate design residence time. EPAmonitors theresidence time toensurethat sufficient time is provided to effectively oxidize the waste. 2.5.2 Amount and Type of Oxidizing Agent Several factors influence thechoice ofoxidizing agents and the amountto be added. The amount of oxidizing agent required to treat a given amount of oxidizable cunstituent(s) will vary with the agent chosen. Enough oxidant must be added to ensure complete oxidation; the specific amount depends on the type of ox.idizable compounds in the waste and the chemistry of the oxidation reactions. Theoretically, the amount of oxidizing agent to be added can be computedfrom oxidationreaction stoichiometry; in practice, an excess ofoxidant should be used. Testing for excess oxidizing agent will determine whether the reaction has reached completion. In continuous processes, oxidizing agent is added by automatedfeed methods. The amountofoxidizing agent needed is usually measured and controlled automatically by an oxidation-reduction potential 

### (ORP) sensor. EPA examines the amount of oxidant added to the chemical oxidation systemto ensure that it is sufficientto effectively oxidize the waste and, for continuous processes, examines how the facility ensures that the particular addition rate ismaintained. EPA also tests for excess oxidizing agent for batch**f:\document\1525~031.01.004** 25processes and continuously monitors the ORP for continuous processes to ensure that excess oxidLzing agent, ifpossible, is supplied. t 2.5.3 Degree ofMixing
Process tanks must be equipped with mixers to ensure maximum contact between the oxidizing agent and the waste solution. Proper mixing also limits the production of any solid precipitates from side reactions that may resist oxidation. Mixing also provides an even distribution of tank contents and a homogeneous pH throughout the waste, improving oxidation of wastewater constituents. The quantifiable degree of mixing is i complex assessment that inC"ludes, among other factors, the amount ofenergy supplied, the length oftime the material is mixed, and the related turbulence effects of tt.c specific size and shape of the tank. This is beyond the scope of simple measurement. EPA, however, evaluates the degree of mixing qualitatively by considering whether mixing is provided and whether the**typ~** ofmixing device is one that could be expected to achieve uniform mixing of the waste solution.
2.5.4 pH ' ,

Operation at the optimal pHmaximizes the chemical oxidation reactions and may, depending on the oxidizing agent being used, limit the formation of undesirable reaction byproducts or the escape ofcyanide from solution as HCN, CNCl, or C 2 N

2 gas. The pH is controlled by the addition ofcaustic, lime, or acid to the solution. In most cases, a slightly or moderately alkaline pH is used, depending on the tJpe ofoxidizing agentbeingused and the compound being treated (see Section 2.2, Underlying Principles of Operation). In alkaline chlorination treatment of organics, a slightly acidic pH may be selected as an optimum. In permanganate oxidation, a pH of 2 to 4 is often selected. EPA manitorsthe pHcant1 nuously, ifpassib 1 e, toensure that the system 1 soperating at the appropriate design condition and to diagnose operational problems.**f:\document\1525~031.01.00~** 26 

# , '2.5.5 Oxidation Temperature Temperature affects the rate of reaction and the solubility of the oxidizing agent in the waste. As the temperature is increased, the solubility of the oxidizing agent, in most instances, is increased and the required residence time, in most cases, is reduced. EPA monitors the oxidation temperature continuously, ifpossible, to ensure thatthe system is operating at the appropriate design condition and to diagnose operational problems.
2.5.6 Amount and Type ofCatalyst Adding acatalystthatpromotes oxygen transferand thus enhances oxidation has the effectoflowering thenecessary reactortemperature and/or improvingthe level of destruction of oxidizable compounds. For waste constituents that are more difficult to oxidize, catalyst addition may be necessary to effectively destroy theconstituent(s) ofconcern. Catalyststypicallyused for this purpose include copper bromide and copper nitrate.. If a catalyst is required, EPA examines the amount and type added, as we11 as the method of addition of the catalyst to the waste, to ensure that effective oxidation is achieved.

f:\docU!IInt\15254031.01.004 272.5 References

- Gurnham, C.F. 1985. Principles of industrial waste treatment. New York: John Wi1 ey ana·Sons. Gural, M.D., and Holden, T.E. 1988. The effect ofcopper and iron complexation on removal ofcyanide by ozone. Ind. Eng. Chem. Res. 27(7}:1157-1162. McGraw-Hill. 1982. Encyclopedia of science and technology. Vol. 3, p. 825. New York: McGraw-Hill Book Co. Metcalf & Eddy, Inc. 1986. Briefing: Technologies applicable to hazardous waste. Prepared for U.S. Environmental Protection Agency, Hazardous Waste Engineering Research Laboratory. Cincinnati, Ohio: U.S. Environmental Protection Agency. Nutt, S.G., and Zaidi, S.A. 1983. Treatment ofcyanide-containing wastewaters by the copper-catalyzed 502 /airoxidation process. In Proceedings ofthe 38th Industrial Waste Conference, Purdue University, West lafayette, Indiana, Hay 10-12, 1983. Stoneham, Mass.: Butterworth Publishers. Patterson, J.W. 1985. Industrial wastewater treatment technology. 2nd e<t.**Stoneh~1,** Mass.: Butterworth Publishers. Schroeter, J., and Painter, C. 1987. Potassium permanganate oxidation of electroless olating wastewater. Carus Chemical Company, 1001 Boyce Memorial Drive, P.O. Box 1500, Ottawa, Illinois 61350. Weast, R.C., ed. 1978. Handbook ofchemistry and phvsics. 58th ed. Cleveland, Ohio: CRC Press.

f:\docunent\15254031.01.004 283. CHEMICAL REDUCTION 3.1**App~cability** Chemical reduction is a treatment technology used to reduce hexavalent chromium and selenate ions to the less soluble trivalent chromium ion and elemental selenium, respectively. It is also used to treat oxidizing wastes containing reducible organics and inorganic oxidizers such as calcium hypochlorite, hydrogen peroxide (and other peroxides), and nitricacid. Because this technology frequently requires that the pH be in the acidic range, itwould not normally be applicableto wastes thatcontain significant amounts ofcyanide or sulfide. In such wastes, lowering of the pH can result in the release of toxic gases such as hydrogen cyanide or hydrogen sulfide. Hexavalentchromium is usuallypresent inwastes fromthe plating industry, metal surface preparation processes, the chromium pigments industry, and leather tanning processes. Selenates are frequently found in some mining and or-e processing wastes. Organic and inorganic oxidizers are found in propellant explosives and in the chemical manufacturing industries. 3.2 UnderlYing Principles of Operation !he basic principle of chemical reduction isto reduce the valence ofthe oxidizer in solution. •Reducing agents• usedtoeffectthe reduction includethe sulfur compounds sodium sulfite (Na2S03), sodium bisulfite (NaHS03), sodium metabisulfite (Na2S2 0

5),_sulfur dioxide (502), and sodium hydrosulfide (NaHS). The ferrous form of iron (Fe.2) is a popular reducing agent in many cases. Elemental magnesium (Hg), zinc (Zn), and copper (Cu) are also effective reducing agents. Frequently, hydrazine (N2 H

2) is used as areducing agent also. Typical reduction reactions are as follows:

f:\document\15254031.01.005H 202 + 2H+ + 

### Hydrogen Peroxide
t. 4Zn + 

### Metallic Zinc Nitrate Ion Ferrous iron

+ 

### Zinc Ion 2Fe·3 

### Ferric Iron NH/ + 

### 3H2 

### 0 Anlnonium Ion
H

2

### {Cr.6)207 + 

### 3Na2S03 +

### 3H2S04 + 

### {Cr.3)2(S04)3 +**3Na SO~**  + 4H20 

### Chromic Acid Sodium Sulfuric Chromium Sodium**~ulfite** 

### Acid Sulfate Sulfate

H

2Se03 + 2503**250~** + 

### Se Selenic Acid Sulfite Ion Sulfate Ion Elemental Selenium These reactions are usually accomplished at pH values from 2to 3. 3.3 ·Description ofChemical Reduction Process

r 

# . The chemical reduction treatment process can be operated in a batch or continuous mode. Abatch system consists of a reaction tank, a mixer to homogenize the contents ofthe tank, asupply ofreducing agent, and asource of acid and base for pH control. A**co~tinuous** 

### chemical reduction treatment system, as shown in Figure 4, usually includes aholding tank upstream of the reaction tank for flow and concentration equalizat1on. It also typically includes**i~strumentation** 

### to automatically control the amount ofreducing agent added and the pH ofthe reaction tank. The amount ofreducing agent is controlled by the use of a sensor called an oxidation-reduction potential (ORP) 

### cell. The ORP 

### sensor electronically measures, in millivolts, the level to which the oxidation/reduction (redox) reaction has proceeded at Figure 4any given time. It must be noted, however, that the ORP 

### reading is very pH dependent. Consequently, ifthe pH is not maintained at a steady value, the ORP 

### will vary somewhat, regardless ofthe level ofchemical reduction.

f:\document\15254031.01.005 30REDUCING AGENT FEED 8Y8TEII

WASTEWATER

---- INFLUENT

I I I I I I 

# DO
CRt....ApH

IIHQD REDUCTION REACTION TANK 

# r-------------------------1 : ELECTRICAL CONTROLS : 

# ! 'i) IIIXER 

# ! • .1. •**~-------------------------·** ACID • FEED SYSTEM ALKALI FEED 8Y8TEII

I I I 

# 0



# ... 

# ..... PRECIPITATION TANK

Ftgure 4 Continuous Chemtcal Reduction System

### When chemical reduction is used for treating hexavalent chromium, the trivalent chromium that is formed is either reused or further treated by stabilization and land disposed. likewise, far selenium reduction, the precipitated efemental seleniummay be recovered or stabilized and disposed of. 3.4 Waste Characteristics Affecting Performance (WCAPs)
In determining whether chemical reduction will achieve the same level of performance on an untested waste that it achieved on apreviously tested waste, and whether performance levels can be transferred, EPA examines the following waste characteristics: {a) the concentration ofother reducible compounds and (b) the concentration ofoil and grease. 3.4.1 

### Concentration of Other Reducible Compounds The presence of other reducible compounds {also called oxidizers) fn addition to the BOAT list constituents of concern will increase the demand of reducing agents, therebypotentiallyreducing the effectiveness ofthe treatment process. As a surrogate for the amount of organic oxidizers present in the waste, EPAmight analyze fortotal organic carbon (TOC) in thewaste. Inorganic oxidizing compounds such as ionized metals (e.g., silver, selenium, copper, mercury) may also create a demand for additional reducing agent. EPA might attempt to identify and analyze for these metal constituents. If TOC or**~norganic** 

### oxidizer concentration in the untested waste is significantly higher than that in previously tested wastes, the system may not achieve the same performance as that achieved previously. Additional reducing agent may be requiredto effectivelyreduce the untested waste and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment 

### ofthe untested waste.

f:\document\15Z54031.01.005 323.4.2 Concentration ofOil and Grease EPAbelie(es that oil and grease compounds could cause monitoring problems because of fouling ofinstrumentation {e.g., electrodes for pH and ORP sensors}. If the concentration of oil and grease in an untested waste is significantly higher than that in atestedwaste, the untested system may not achieve the )arne performance. Therefore, other, more applicable treatment or pretreatment technologies may need to be considered for treatment of the untcstea waste. 3.5 Design and Operating Parameters
In assessing the effectiveness ofthe design and operation of achemical reductionsystem, EPAexamines the fallowing parameters: {a} theresidencetime, {b) the amount and type of reducing agent, {c) the degree ofmixing, {d) the pH, and (e)**th~** reduction temperature. For many hazardous organic constituents, analytical methods are no't availableorthe constituent cannot be analyzed in the waste matrix. Therefore, it would normally be impossible to measure the effectiveness of the chemical reduction treatment system. In these cases EPA tries to identify measurable parameters or constituents that would act as surrogates to verify treatment. for organic constituents, each compound contains ameasurable amount of total organic carbon {TOC). Removal ofTOC in the chemical reduction treatment system indicates removal oforganic constituents. Hence, TOC analysis is likely to be an adequate surr.ogate analysis where the specific organic constituent cannot be measured. However, TOC analysis may not be able to adequately detect treatment of specific organics in matrices that are heavily organic-laden {i.e., the TOC analysis may not be sensitive enough to detect changes at the milligrams per liter (mg/1) level in matrices where totai organic concentrations are hundreds or thousands of mg/1)". In these cases other surrogate para.11eters should be

f:**\d~t.ment\1525•031.01.005** 33sought. For example, if a specific analyzable constituent is expected to be treated**a~** well !S the unanalyzable constituent, the analyzable constituent concentration skould be monitored as a surrogate. 3.5.1 Residence Time The residence time affects the extent of reaction of waste contaminants with reducing agents. For a batch system, the residence time is controlled by adjustment ofthe treatment time in the reaction tank. For acontinuous system, thewaste feed rate is controlled to make sure that the system is operated at the appr?priate design residence time. 

### EPA monitors the residence time to ensure that sufficient time is provided to effectively reduce the waste. 3.5.2 Amount and Type ofReducing Agent Several factors influence the choice of reducing agents and the amount to be added. The amount of reducing agent required to treat a given amount 

### rif reducible constituent will vary with the agent chosen. Enough reducing agent must be added to ensure complete reduction; the specific amount will depend on the type ofreducible compounds in the waste and the chemistry ofthe reduction reactions. Theoretically, the amount of reducing agent to be added can be computed from reduction reaction stoichiometry. In practice, however, an excess of red.ucing agent should be used. Testing for excess reducing agent, if possible, will determine whether the reaction has reached completion.
In continuous processes, the addition of reducing agent fs usually accomplished by automated feed methods. The amount ofreducing agent needed fs usuallymetered andcontrolled automaticallyby anoxidation-reduction potential (ORP) sensor. 

### EPA**ex~ines** the amount ofreduction agent added to the chemical reduction systemto ensure that ft is sufficientto effectivelyreduce the waste and, for continuous processes, examines how the facility ensures that theparticular addition rate is maintained. 

### EPA may also test for excess reducing agent in the systemeffluent. For continuous processes, 

### EPA monitors the ORP to

f:\docum.nt\15254031.01.005 34ensure that enough reducing agent is supplied. EPA may also monitor pH to determine· whether_ it is controlled to the appropriate optimum range. For continuous**syst~s,** pH is monitored to ensure that it is kept steady to avoid changes in ORP caused by pH variations.
3.5.3 Degree ofMixing
Process tanks must be equipped with mixers to ensure maximum contact between the reducing agent and the waste oxidizing solution. Propermixing also homogenizes any solid precipitates that may be present, or that may form from side reactions, so that they can also be reduced ifnecessary. Mixing provides an even distribution oftankcontents and ahomogeneous pH throughout the waste, improving reduction of wastewater constituents. The quantifiable degree of mixing is a complex assessmentthat includes, among other factors, the amount of energy supplied, the length of time the material is mixed, and the related turbulence effects of the specific size and shape of the tank. This is beyond the scope of simple measurement. EPA, however, evaluates the degree of mixing qualitatively, using engineering judgment, by considering ··hether mixing is provided and whether the type ofmixing device is one that could be expected to achieve uniform mixing ofthe waste solution.
3.5.4 pH For batch and continuous systems, the pH affects the reduction reaction. The reaction speed is usually significantly reduced at higher pH values (typically above 4.0)

.. It is worth noting that some reduction reactions may proceed better under alkaline conditions, in which case pH must be properly controlled to the appropriate alkalinerange. For abatch system, the pH can be monitored intermittently during treatment. For acontinuous system, the pHmust be continuously monitored because it affects the ORP reading. EPA monitors the pHto ensure thatthe system**i~ op~rating**  at the appropriate design condition and to diagnose operational problems.

f:\document\15254031.01.005 35

### 3.5.5 Reduction Temperature Temperature- affects the rate of reaction and the solubility of the t. reactants in the waste. As the temperature is increased, the solubility ofthe reactants, in most instances, is increased and the required residence time, in most cases, is reduced. EPAmaymonitor the reduction temperature to ensure that the system is operating at the appropriate design condition and to diagnose operational problems.

f:\document\15ZS4031.01.005 36 

# '3.6 References McGraw-Hill. :t982. Encyclopedia of science and technology. Vol. 9, pp. 714-718. New York: McGraw-Hill Book Co. Nebergall et al. General chemistry. 5th ed. Lexington, Mass.: O.C. Heath and Company. Patterson, J.W. 1985. Industrial wastewater treatment technology. 2nd ed. Stoneham, Mass.: Butterworth Publishers.

f:\dccument\15254031.01.005 

### 374. ELECTROLYTIC OXIDATION OF CYANIDE



### - 4.1 Appticability Electrolytic oxidation is a treatment technology with demonstrated applicability to the treatment of wastes containing high concentrations of cyanide in solution. Because of excessive retention time requirements, the processis often applied as preliminarytreatment forhighly concentrated cyanide wastes, prior to more conventional chemical cyanide oxidation. This treatment technology is used in industry for the destruction of cyanide in (a) concentrated spent plating solutions and stripping solutions, (b) spent heat treating baths, (c) alkalinedescalers, and (d) metal passivating (rust-inhibiting) solutions. Electrolytic oxidation has been demonstrated successfully for treatment ofwastes containing concentrations of cyanide up to 100,000 mg/1. However, for concentrations of cyanide 1ower than 500 mg/1, chemical oxidation treatment may be more efficient (see Section 

### I.A.2}. , 4.2 Underlying Principles ofOperation The basic principle of operation for electrolytic oxidation ofcyanide is that concentrated cyanide waste subject to an electrolytic reaction with dissolved oxygen in an aqueous solution is broken down to the gaseous products**~arbon** dioxide (C02}, nitrogen (N2), and ammonia**(NH ~.**  The process is conducted at elevated temperatures for periods**ra~~ing** from several hours to over aweek, depending on the initi.al cyanide concentration and the desired final cyanide concentration. The theoretical destruction process that takes place at the anodes is described by the following reaction:

cyanide ion oxygen

f:\document\15254031.01.006 Electricity 

# ----:1>

38 2C02 carbon dioxide + nitrogen electronsThe effectiveness of electrolytic oxidation is dependent on the conductiyity ofthe waste, which is afunction of several waste characteristics including the Concentration of cyanide and other ions in solution. As the process continues, the waste becomes less capable ofconducting electricity as the cyanide concentration is reduced, causing the electrolytic reaction to be much less efficient at longer retention times. 4.3 Description of Electrolytic Oxidation Process Typically, electrolytic destruction of cyanide takes place in a closed cell. This cell consists of two electrodes suspended in an aqueous solution, with direct current 

### (DC) electricity supplied to drive the reaction to completion. The temperature of the bath containing the cyanide waste is maintained at or above 

## s2•c (125.F). Sodium chloride may be added to the solution as an electrolyte (conductor) to increase the conductivity ofthe waste being treated. Since the reaction maytake days orweeks, water is usually**add~d** tothetank periodically to make up for losses due to evaporation from the heated tank. This is necessary to ensure that the electrodes remain fully submerged so that a full flow of current is maintained in the solution during treatment. Following treatment, the treated waste is usually further treated' in a conventional chemical oxidation system to destroy residual cyanides. 

### 4.4 Waste Characteristics Affecting Performance (WCAPsl
In determining whether electrolytic oxidation will achieve the same level ofperformance on an**u~tested** waste that it achieved a previously tested waste and whether performance levels can be transferred, 

### EPA examines the following waste characteristics: (a) the concentration ofother oxidizablematerials and (b) the concentration of reducible metals.

f:\document\1SZS403l.Ol.006 39f 4.4.1 Concentration of Other Oxidizable Materials The**pre~nce** of oxidizable organics (such as oil and grease and surfactants) and the presence ofinorganic ionic species in areduced state (such as trivalent chromium or sulfide) may increase the treatment time required to achieve destruction of cyanide because these materials may be oxidized preferentiallyto thecyanide in solution. Ifconcentrations ofother oxidizable materials are significantly higher in the untested waste than in the tested waste, the systemmaynot achieve the same performance. Longerreaction timemay be required to oxidize cyanide and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment ofthe untested waste. 4.4.2 Concentration of Reducible Metals The electrolytic process may cause some ofthe more easily reduced metals in the waste, such as copper, to plate out onto the cathode as the pure**met~l.** ThP. plating ofmetals onto the cathode may result in changes 1n current density and, hence, may change the rate ofcyanide oxidation. Ifthe concentration of reducible metals in the untested waste is significantly higher than that in the tested waste, the system may not achieve the same performance and other, more applicable treatment technologies may need to be considered for treatment ofthe untested waste. 4.5 Design and Operating Parameters
In assessing the effectiveness of the design and operation of an electrolytic oxidation system, EPA examines the following parameters: (a) the oxidation temperature, (b) the residence time, (c) the pH, (d) the electrical conductivity, (e) the electrode spacing and surface area, and (f) the degree of mixing.

f:\document\15254031.01.006 404.5.1 Oxidation Temperature
For the**~Jectrolytic** process, elevated temperatures are used. Normal temperatures range from 52 to 93'C (125to 200'F). The temperaturecan beraised by increasing the flow of steam to the coils or jacket supplying heat to the reactor contents. EPA monitors the oxidation temperature to ensure that the system is operating at the appropriate design condition and to**diagnos~** operational- problems.
4.5.2 Residence Time Electrolytic oxidation is usually a batch process. The time allowed to complete the reaction isan important factor in electrolysis and is dependent on the initial concentration of the waste and the desired final cyanide concentration. The rate of cyanide destruction decreases as the cyani:de concentration decreases {i.e., the rate of cyanide destruction asymptotica1ly approaches zero). Typical residence times range from periods of several**ho~rs** to more than aweek. EPA observes the residence time to ensure that sufficient time is provided to effectivelydestroy the cyanides in the wastes. 4.5.3 pH

.Typical solutions for electrolytic oxidation have apH ranging from 11.5 #to 12.0. The pH must be maintained in the alkaline range to prevent liberation

of toxic hydrogen cyan;de. Typically, pH is controlled by the addition of caustic or lime. EPA-monitors the pH to ensure that the treatment system is operating at the appropriate design condition and to diagnose operational problems.
4.5.4 Electrical Conductivity The so1ution must have an electrical conductivity high enough to allow the reaction to proceed at an acceptable rate. If the conductivity is not high

f:\document\15254031.01.006 41 

# 'enough, it can be improved by adding an electrolytesuch as sodium chloride. The conductivity of-the waste during the reaction is normally determined by monitoring botit-.the current and voltage ofthe cell. EPAmonitors the electrical conductivity to ensure that the treatment systemisoperating at the appropriate design condition. 4.5.5 Electrode Spacing and Surface Area The spacing and surface area ofthe electrodes directly impact the current flowing through the waste. The reaction rate is increased by both closer electrode spacing and more electrode surface area because each increases the currentdensity in the cell. EPAobserves the electrode spacing and surface area to ensure that sufficient currentdensity is provided to effectivelydestroy the cyanides in the waste. 4.5.6 Degree ofMixing Electrolyticdestruction ofcyanides requires good mixing in the reaction vessel. Mixing helps ensure an adequate supply ofoxygen (fromthe air} for the electrochemical reaction (see Section 4.2, Underlying Principles ofOperation}, enhances mass transfer to promote the oxidation reaction, and keeps suspended solids in suspension. Mixing may be provided by the bubbling of air from the bottom of the reactor, or an external source of mixing may be provided. The 'quantifiabledegree ofmixing is acomplex assessment that includes, among other

factors, the amount ofenergysupplied, the length oftimethe material is mixed, and the related turbulence effects ofthe size and shape of the reaction vessel used. The degree of mixing is beyond the scope of simple measurement. EPA, however, evilluates the degree of mixing qualitatively by considering whether mixing is provided and whether the type of mixing device is one that could be expected to achieve uniform mixing of the waste.

f:\document\15254031.01.006 424.6 References Cushnie, G.C., t..Jr. 1985. Electroplating wastewater pollution control technology. p. 205. Park Ridge, N.J.: Noyes Publications. Easton, J.K. 1967. Electrolytic decomposition of concentrated cyanide plating wastes. Journal Water Pollution Control Federation 39(10):1621-1626. Patterson, J.W. 1985. Industrial wastewater treatment technology. 2nd ed., pp. 123-125. Stoneham, Mass. Butterworth Publishers. Pearson, G.J., and Karrs, S.R. 1984. Electrolytic cyanide destruction. In Proceedings for plating and surface finishing, pp. 2and 3. Roy, C.H. 1981. Electrolytic wastewater treatment. In a series of American Electroplaters Society, Inc., illustrated lectures, pp. 8-10.

f:\document\15254031.01.006 43 : 

## . 

# 1

### 5. INCINERATION 5.1**Appj~cability** Incineration is a treatment technology applicable to the treatment of wastes containing awide range oforganic concentrations and low concentrations of water, metals, and other inorganics. The four most common incineration. systems are liquid injection, rotary kiln, fluidized bed, and fixed hearth. Liquid injection incineration is applicable to wastes having sufficiently lowviscosityvalues (less than 750 sayboltuniversal seconds (Sus) such thatthe waste can be atomized in the combustion chamber. However, viscosity is temperature dependent so that while liquid injection may not be applicable to a waste at ambient conditions, itmay become applicable when the waste is heated. In addition, the number of waste particles and the concentration of suspended solids need to be sufficiently low to avoid clogging of the burner nozzle (or atomizer openings). Rotary kiln, fluidized bed, and fixed hearth incineration are applicable to wastes having awide range ofviscosity, particle size, and suspended solids concentration. Incineration of highly explosive constituents may require treatment in units that are specially designed and fitted with certain explosion-proof equipment. Incinerators for corrosive waste should be equipped, ifnecessary, with pollution control**~evices** to remove corrosive gases that may be generated from the burning of corrosive waste. The incineration of hazardous waste must be performed in accordance with the incinerator design and emissions regulations in 40 CFR 

### 264, Subpart 0.

f:\document\15254031.01.007 44-,--**~-**

5.2 Underlying Principles of Operation The basic- principle of operation for incineration is the thermal decomposition

## hf organic constituents via cracking and oxidation reactions at high temperatures (usually between 760 and ISSO"C (1400 and 3000"F) to convert them into carbon dioxide andwatervapor alongwith nitriteoxides, nitrates, and arrmonia (fornitrogen-containingwastes); sulfuroxides and sulfate {for sulfurcontaining wastes); or halogen acids (for halogenated wastes).
In liquid injection incineration the organic constituents in the waste are volatilizedandthe chemical bonds are destabilized. Once the chemical bonds are brqken, thesecanstituentsreactwith oxygen to form carbondioxide, watervapor, and other aforementioned compounds.
Inrotarykiln and fixed hearth incineration, two chambers are involved in the incineration process. In the primary chamber, the organic constituents-in the waste are volatilized. During this volatilization process, some of the organic constituents oxidize to form carbon dioxide and water vapor. In the secondarychamber, the chemical bonds are destabilized, resulting in theorganic constituentsreactingwith oxygen to form carbon dioxide, water vapor, and other aforementioned compounds.
In fluidized bed incineration, a single chamber contains the fluidizing sand and a freeboard section above the sand. The fluidized bed aids in the volatilizationand combustion ofthe organicwaste constituents. The sand inthe bed provides asufficient heat capacityto volatilize organic constituents. The forced airused to fluid.izethe bed provides sufficientoxygen and turbulence to enhance the reactions of organics with oxygen to form carbon dioxide, water vapor, andotheraforementionedcompounds. Additional time forconversionofthe organic constituents is provided by the freeboard above the fluidized bed.

f:\document\152SC031.Dl.DD7 45 

# '5.3 Description of Incineration Processes The physi**~1** form ofthe waste determines the appropriate feed method into the**incinerati~~** system. Liquids are pumped into the combustion chamberthrough nozzles orvia speciallydesigned atomizing burners. Wastes containing suspended particles may need to be screened to avoid clogging of small nozzle or atomizer openings. Sludges and slurries are fed using positive displacement pumps and water-cooled injection ports. Bulk solid wastes may require shredding for control ofparticle size. Wastes may be fed to the combustion chamber via rams, gravity feed, air lock feeders, vibratory or screw feeders, or belt feeders. Containerized waste is gravity-fed or ram-fed. Although sustained combustion is possible with waste heat content as low as 2230 kcal/kg (4010 Btu/lb), wastes are typicallyblended to anet heat content of 4450 kcal/kg (8000 Btu/lb) or higher or auxiliary fuel is used in the combustion chambers to raise the heat content to a level sufficient to sustain the combustion process. Following incinerationofwastes, fly ashparticulates, acidgases (halogen acids), and other gaseous pollutants (nitric oxides (NOx) and sulfur oxides (SOx)) are further treated in an air pollution control system. Particulate emissions from most waste combustion systems generally have particle diameters less**t~an** 1micron andrequire high-efficiencycollection systems to minimize air emissions. The most common airpollution control system used includes aquench (forgas cooling and conditioning), followed by ahigh-energy venturi scrubber* (forparticulateand acidgas removal), apacked bed orplate tower absorber (for acid gas removal), and ademister (for vapor mist plume elimination). Packed bed or plate tower scrubbers are commonly used without venturi scrubbers in the air pollution control systems at liquid injection incinerator

*A venturi is a short tube or duct with atapering constriction that causes an

increase in the velocityoffluid flowand acorresponding decrease in pressure.

f:\document\15254031.01.007 46

### facilities, where absorption of gasscus**ii~llutants** 

### is more important than particul,ate control. (Wastes burned in liquid injection incinerators typically have alow ashcontent and, hence, generate alow level offly ash particulates.) Some liquid injection incinerator facilities do not employ any air pollution control systembecause thewastes burned contain low levels ofboth ash and halogen content, therebygenerating low {i.e., untreatable) levels offly ash particulates and acid gases. Many air pollution control system designs in recent years have begun to incorporate waste heat boilers as a substitute for gas quenching as ameans of energy recovery. Wet electrostaticprecipitators (ESP), ionizing wet scrubbers (IWS), and fabric filters are also being incorporated into newersystems because these devices have high removal efficiencies for small particles and a lower pressure drop than that ofventuri scrubbers.
The inorganicconstituentsofwastes (noncombustible ash) arenotdestroyed by incineration. These materials, depending on their composition, exit the incinerator as either bottom ash from the combustion chamber 

### or fly ash particulates suspended in the combustion gas stream. Bottom ash is typically eitherair-cooled orquenched with water following discharqe from the combustion chamber. This waste is then stabilized (if levels of leachable metal constituents ofconcern are found) and/or land disposed. Fly ash particulates, as well as acid gases and other gaseous pollutants, are entrained 1n the**s~rubber** 

### waters of the air pollution control system and collected in the sumps ofrecirculation tanks. Here the acids are neutralized with caustic and much of the water is returned to the air pollution control system. Eventually, aportion

### orall ofthese scrubberwaters aredischarged for treatment anddisposal when thetotal dissolved solids level becomes excessively high. Scrubber waters are discharged eitherto asettling tank or lagoon or to a chemical precipitation system (if 

### treatable levels of soluble metal constituents of concern are found) to remove these solids prior to their land

f:\document\15254031.01.007 47 

### i

# 'disposal. Depending on the nature of the remaining dissolved constituents and their concentrations, treated scrubber waters may be returned to the air pollutioncontrlll_ system, furthertreatedin filtrationprocesses, ordischarged. Below are descriptions of the incineration processes for the four most common**incine~ator** systems. 5.3.1 Liquid Injection
In aliquid injection incineration system, aburnerornozzle atomizes the waste and injects it into the combustion chamber, where it is incinerated in the presence ofairoroxygen. Aforced-draft systemsuppliesthe combustion chamber with air to provide oxygen for combustion and turbulence for mixing. The combustion chamber is usually a cylinder lined with refractory (i.e., heatresistant) brick and can be fired horizontally, verticallyupward, or vertically downward. Figure 5 illustrates a liquid injection incineration system. 5.3.2 Rotary Kiln
Arotary kiln is a slowly rotating, refractory-lined cylinder that is mounted at aslight incline from the horizontal. Solidwastes enter at the high end ofthe kiln, and liquid or gaseous wastes generally enter through atomizing**nozzl~s** in the afterburner section of the kiln. Aforced-draft system supplies the kiln with air to provide oxygen for combustion and turbulence for mixing. Rotation of the kiln enhances the exposure of the solids to the heat, thereby aiding theirvolatilization as well as providing additional mixing ofthe solids with air combustion. In addition, the rotation causes the ash to move to the lower end of the kiln, from which it is removed. Rotary kiln systems usually have asecondarycombustion chamberor afterburner following the kiln forfurther combustion of the volatilized waste constituents. Figure 6 is adiagram of a rotary kiln incineration system.

f:\document\15254031.01.007 48AUXILIARY fUEL

LIQUID OR GASEOUS WASTE INJECTION :--:aunNER

AIR 

# - .

:::BURNER flY ASH PARTICULATF.9 AND COMBUSTION GASES TO AIR POLLUTION CONTROl. SYSTEM AND/OR THE ATMOSPHERE 

# t
I

PRIMARY AFTERBURNER COMBUSTION (SECONDARY COMBUSTION CHAMBER CHAMBEHt**~** BOTTOM ASH TO 8lABIUZATION AND/OR LAND DISPOSAL

Figure 5 L1qu1d Injection lnctneratton System 

# ·--SOL.ID t.

Fl..Y ASH PART1Ctii..A-rES AND COMBUsnON GASES TO

AJR POLLUTION CONTROL 

# i

UQUID OA GASEOUS WASTE IN..IECTlON

# -------...,...1 AFTERBURNER AUXIUARY

### FUE~----------..1 BURNER

### ._.-~--...J
WASTE

### INFL.UENT~

BO'TTOM ASH TO STAIIUZATION AND/OR LAND DISPOSAL



### Figure 6 Rotary Kiln Incineration System

505.3.3 Fluidized Bed
A**fluidiz~**bed incineratorconsists ofacolumn containing inertparticles such as sand, which is referred to as the bed. Air, driven by a blower, enters the bottom ofthe bed to fluidize the sand. Air passage through the bed provides oxygen for combustion and promotes rapid and uniformmixing ofthe injected waste material within the fluidized bed. The fluidized bed has an extremelyhigh heat capacity (approximately three times that offlue (combustion) gases at the same temperature), thereby providing a large heat reservoir. The injected waste reaches incineration temperature quickly and transfers the heat of combustion back to the bed. The freeboard above the fluidized bed provides additional time for combustion of organic constituents. Because of the excellent mixing properties associated with fluidized bed incinerators, they can operate at lower. temperatures more effectivelythan other incinerators. Figure 7is adiagramof a fluidized bed incineration system.
.. 5.3.4 Fixed Hearth Incineration Fixed hearth (also called controlled air or starved air} inciner3tion is a two-stage combustion process.**Wa~te** is ram-fed into the first stage, or primary chamber, and burned at less than stoichiometric conditions (not enough oxygen for complete combustion). The resultant smoke and pyrolysis products, consis.tingprimarilyofvolatilehydrocarbons and carbonmonoxide, a 1 ongwith the typical products ofcombustion, pass to the secondary chamber. Here additional air is injected to complete the combustion process. This two-stage process generallyyieldslow flyashparticulate and carbonmonoxide (CO} emissions. The primary chamber combustion reactions and resultant combustion gas velocities are maintained at low levels by the starved air conditions so that particulate entrainment and carryover in the combustion gases are minimized. Figure 8 is a diagram of a fixed hearth incineration system.

f:\document\15254031.01.007 51 

# ,BURNER FREEBOARD

BOTTCU ASH TO STABIUZATION 4HD/OA LAND DISPOSAL Ft.Y ASH PARTICULATES t-----1• ANC COMBUSTION GASES TO AIR POLLUTION CONTROL SYSTEM

... --MAKE·UP SANC



### Figure 7 Fluidized Bad Incineration System

52U1 w WASTE IN.JECTION 

## . AIR 

# ..

# ~ - PRIMARY COMBUSTION CHAMBER**~BURNER**

BOTTOM AStt TO STABILIZATION AND/OR LAND DISPOSAL AIR 

# •

SECONDARY COMBUSTION CHAMBER

Figure 8 Ftxed Hearth 

### Jnc1neratton System FLY ASH PARTICULATES AND COMBUSTION GASES TO AIR POLLUTION CONTROL SYSTEM**~~ DURNER1~**  AUXILIARY FUEL



# ·--5.4 Waste Characteristics Affecting Performance (WCAPs}
In deternti_ning whether incineration will achieve the same level of performance on an untested waste that it achieved on a previously tested waste and whether performance levels can be transferred, EPA examines the following waste characteristics: (a) the thermal conductivity of the waste, (b) the component boiling points, (c) the component bond dissociation energies, (d) the heating value ofthe waste, (e) the concentration ofexplosive constituents, and {f) the concentration of noncombustible constituents.
5.4.1 Thermal Conductivity of the Waste
Amajorfactordetermining whetheraparticularconstituentwill volatilize is the transfer ofheat through the waste. For rotary kiln, fluidized bed, and fixed hearth incineration, heat is transferred through the waste by radiation, convection, and conduction.
EPA examined all three methods ofheat transfer. For agiven incinerator, heat transferred through various wastes by radiation and convection is more a function of the design and type of incinerator than of the waste being treated; therefore, EPA believes that conduction would be the primary cause of heat transferdifferences between wastes. Heat flow by conduction is proportional to the temperature gradient across the material. The proportionality constant, referred to as the thermal conductivity, is a property of the material to be incinerated. Thermal conductivitymeasurements, as partofatreatabilitycomparison for two differentwastes to be treated by a single incinerator, are most meaningful when applied to wastes that are homogeneous (i.e., uniform throughout). As wastes exhibit greater degrees of nonhomogenaity, thermal conductivity becomes less accurate in predicting treatability because the measurement essentially reflects heat flow through regions having the greatest conductivity (i.e., the path of least resistance) and not heat flow through all parts of the waste.

f:\dacument\15254031.01.007 54Nevertheless, EPAbelievesthatthermal conductivitymayprovide the bestmeasure of performance tr.ansfer. If the thermal conductivity of an untested waste is significantly**l~er** than that ofthe testedwaste, the systemmay not achieve the same performance. Higher temperatures may be required to improve heat transfer through the waste and achieve the same treatment performance, or other, more applicable treatment technologiesmay need to beconsidered for treatment ofthe untested wastes. 5.4.2 Component Boiling Points**Foll~wing** transfer of heat to a constituent within a waste, the constituent's removal depends on its volatility. EPA recognizes, however, that volatilities are difficult to measure or calculate directly for the types of wastes generally treated by incineration because the wastes usually consist of a mixture of components. However, because the volatilities of components are usually inversely proportional to their boiling points (i.e., the higher the boiling point, the lower the volatility), EPA uses the boiling points ofwaste components as a surrogate waste characteristic for volatility. If the boiling points ofwaste components in the untested waste are significantly higher than those in the tested waste, the system may not achieve the same performance. Higher temperatures may be required to volatilize less volatile components and achieve the same treatment performance or other, more applicable treatment technqlogies may need to be considered for treatment ofthe untested wastes. 5.4.3 Component Bond Dissociation Energies
The activation energy is the amount of heat energy needed to destabilize molecular bonds so that the exothermic combustion reactions can proceed. Typically, the activation energy required for incineration ofsolids is greater than that required for liquids, and the activation energy required for liquids is higher than that required for gases. However, the activation energies for components are difficult to measure or calculate directly and usually must be determined empirically. The bond dissociation energy is the amount of energy**f:\~ument\15254031.01.007** 55needed to break each ofthe individual bonds in amolecule. Theoretically, the bond disS"Ociation_energy and the activation energy are equivalent. However, otherenergyeff1!_cts including interactionsbetween differentmolecularbondsmay have a significant influence on the activation energy. Nevertheless, EPA believes that bond dissociation energy is the best indicator for activation energy and therefore uses it as a surrogate waste characteristic. If the bond dissociation energies ofwaste components in an untestedwaste are significantly higher than those in the tested waste, the system may not achieve the same performance. Higher temperatures may be required to destabilizemolecularbonds for waste components with high bond dissociation energies and achieve the same treatment performance, orother, more applicable treatment technologies may need to be considered for treatment of the untested waste. 5.4.4 Heating Value ofthe Waste

.. The amount ofheat released from the exothermic combustion reactions of'a waste is referred to as itsheating value. To maintain combustion, the heatidg value ofawaste must be sufficient to heat incoming waste up to the appropriate design incineration temperature and provide the necessary activation energy for additional combustion reactions to occur. Higher waste heating values are requiredforhigherincinerationtemperatures and higheramounts ofexcess oxygen to sustain combustionwithoutauxiliaryfuel consumption. Lowheating values for an organic waste are usually caused by high concentrations of water or halogenated compounds. If the heating value of an untested waste is significant1 y 1 owerthan thatofthe testedwaste, the systemmaynot achieve the same performance. Auxiliaryfuel may be required to provide the necessary heat to maintaincombustion and achieve the same treatment performance, orother, more applicable treatment technologies may need to be considered for treatment ofthe untested waste.

f:\document\15Z54031.01.007 56

### 5.4.5 Concentration of Explosive Constituents Explosive -constituents may interfere with the smooth operation of 

### an incinerator, clusing process upsets resulting in ineffective treatment of the waste. If the concentration of explosive constituents in an untested waste is significantly higher than that in the tested waste, the system may not achieve the same performance and other, more applicable treatment technologies may need to be considered for treatment of the untested waste. 5.4.6 

### Concentration ofNoncombustible Constituents Noncombustible constituents include water, metals, and other inorganics. High concentrations ofnoncombustible constituents result in low waste heating values, requiring auxiliary fuel; large quantities of bottom ash, requiring stabilizationtreatment (if 

### treatable levels ofleachable metal constituents of 

### concern are present) and/or disposal; and large quantities of fly ash particulates and volatile metals in the combustion gases, requiring removal tn an airpollution control systemand treatment in asettlingtank or lagoon or by means of 

### achemical precipitation system (iftreatable levels of soluble metal constituents ofconcern are present) followed bydisposal. Volatilemetals such as arsenic may also fuse to the refractory walls in the combustion chamber, inhibiting effective operation of the incinerator. If the concentration of noncombustible constituents in an untested waste is significantly higher than that iA the tested waste, the system mJy not achieve the same performance and



### - other, more applicable treatment technologies may need to be considered for treatment of the ur.tested waste. 

### 5.5 Design and Operating 

### Parameters In assessing the effectiveness of the design and operation of an incineration system, EPA

### examinesthefollowing parameters: (a) the incineration temperature, (b) the concentration of excess oxygen in the combustion gas, (c) the concentration of carbon monoxide in the combustion gas, (d) the waste

f:\dOcument\15254031.01.007 57feed rate, and (e) the degree ofwaste/air mixing. In addition, incineration of**hazardou~waste**myst be performed in accordancewith the incineration design and emissions regulra:tions in 40 CFR 264, Subpart 0. For many hazardous organic constituents, analytical methods are not available or the constituent cannot be analyzed in the waste matrix. Therefore, it would normally be impossible to measure the effectiveness ofthe incineration treatment system. In these cases EPA tries to identify measurable parameters or constituents that would act as surrogates to verify treatment. Fororganic constituents, each constituentcontains ameasurable amount of total organic carbon (TOC). Removal ofTOC in the incineration treatment system indicates removal oforganic constituents. Hence, TOC analysis is likely to be an adequate surrogate analysis where the specific organic constituent cannot be measured. However, TOC analysis may not be able to adequately detect treatment of specific organics in matrices that are heavily organic-laden (i.e., the TOC analysis may not be sensitive enough to detect changes at the milligrams per liter (mg/1) level in matrices where total organic concentrations are hundreds or thousands of mg/1). In these cases other surrogate parameters should be sought. For example, if a specific analyzable constituent is expected tc be treated as well as the unanalyzable constituent, the analyzable constituent concentration should be monitored as a surrogate. 5.5.1 Incineration Temperature Temperature provides an indirect measure of the energy available (i.e., Btu/hr) to both volatilize organic waste constituents and overcome their activation energy. As the design temperature in the combustion chamber increases, more constituents with lower volatilities and higher activation energies**~ill** be destroyed. EPA monitors the incineration temperature continuously to ensure that the system is operating at the appropriate design condition and to diagnose operational problems.

f:\document\15254031.01.007 58

### 5.5.2 Concentration of Excess OxYgen in the Combustion Gas Asufficient supply of oxygen must be supplied to the combustion chamber t 

### to effectively incinerate the organicwaste constituents. The stoichiometric or minimum theoretical oxygen requirement to completely combust the waste is based on the amounts ofcombustible constituents in the waste. Ifperfectmixing could be achieved and the waste burned instantaneously, only the stoichiometric amount of oxygen would be needed for complete combustion. However, neither of these phenomena occur in commercial incinerators. The amount of excess oxygen in a given incinerator depends on the degree of waste/air mixing achieved in the combustion chamber and the desired degree ofcombustion gas cooling. Because excess air (oxygen) supplied to the combustion chamber acts as adiluent in the combustion process, itreduces the overall temperature inthe incinerator {i.e., maximumtheoretical incinerationtemperatures areachieved atzeropercentexcess air). This temperature reduction might be desirable to limit refractory degradation·when high-heating valuewastes arebeing burned. However, when low-

, 

### heating-valuewastes arebeingburned, exces.s airshould beminimized to keep tfie system temperature as high as possible. Even with high-heating-value waste, it is desirable

### for equipment design considerations to limit the amount of excess airto someextent so thatcombustionchambervolumeand downstreamairpollution control system sizes can be limited. An inadequate supplyofoxygen, ontheotherhand, will lead to ineffective i_ncineration with higher concentrations of carbon monoxide (CO) 

### and organic products ofincomplete combustion (PICs), resulting in aheavier load on the air pollutioncontrol system. Typically, 20

### to 60percent excess oxygen is required to provide adequate waste/oxygen contact and, subsequently, effective incineration ofthe waste. EPA monitors the concentration ofexcess oxygen in the combustion gas continuously to ensure that the system is operating at the appropriate design condition and to diagnose operational problems.

f:\doclftllnt\15254031.01.007 595.5.3 Concentration of Carbon Monoxide in the Combustion Gas The**concan~ration** of carbon monoxide in the combustion gas provides an indication of the extent to which organic waste constituents are converted to carbon dioxide and water vapor. Highercarbon monoxide levels are an indication ofineffective incineration with the presence ofgreater amounts ofunreacted or partiallyreacted organic waste constituents in the combustion gas, resulting in a heavier load on the air pollution control system. Higher carbon monoxide levels can result from an ir.sufficient incineration temperature; an inadequate supply of excess oxygen; a waste feed rate that is too high, resulting in an insufficient residence time for the waste; and impropermixing in the combustion chamber. EPAmonitors the concentrationofcarbonmonoxide in the combustion gas continuously to ensure that the system is operating at the appropriate design conditions and to diagnose operational problems. 5.5.4 Waste Feed Rate The waste feed rate determines the residence time of the waste in the combustion chamber. Sufficient residence time must be provided to allow for volatilization of the organic waste constituents, mixing with oxygP.n in the combustion chamber, and completion of the combustion reactions. The total residence time required for these processes to occurdepends on the incineration temperature, the amount ofexcess oxygen provided in the combustion chamber, the degree of waste/air mixing in the combustion chamber, the size and type of incinerator used, the physical form ofthe waste, and the waste particle size (which determines the amount ofwaste surface area available for heat transfer). Typical incineratorresidencetimes range from approximately 2seconds for liquid and gaseous wastes in liquid injection incinerators and the afterburner, freeboard, and secondary**cc~bustion** chamters ofrotary kiln, fluidized bed, and fixed hearth incinerators to 30 minutes to 1hour for solid wastes in a rotary kiln incinerator. EPAmonitors the waste feed rate continuously to ensure that sufficient residence time is provided to effectively incinerate organic waste constituents.

f:\document\15254031.01.007 605.5.5 Degree ofWaste/Air Mixing The incin\ration temperature, the amount of excess oxygen, and the residence time required to achieve effective incineration of awaste all depend to some extent on the degree ofwaste/airmixing in the combustion chamber. For liquid injection incinerators, the degree of waste/air mixing is primarily detennined by the specific burner design and the degree of atomization of the waste/air mixture achieved. The degree of atomization is dependent on the viscosityofthe liquid waste andthe amount ofsolid impurities present. Ifthe waste viscosity exceeds 750 Sus or the amount of solid impurities is too high, the degree of atomization may not be fine enough, resulting in ineffect·ive incineration.
Forrotary kiln incineration, the degree ofwaste/airmixing is detennined by the airflow rate into the kiln as well as the rate of rotation (revolutions perminute (RPM)) ofthe kiln. As the airflow rate is increased, the degree of waste/air mixing is improved although this also reduces the**incinerati~n** temperature and residence time ofthe combustion gases. Increasing the rate of rotation ofthe kilnalso improves waste/airmixing; however, the residence time of the waste solids is also reduced. Typical rotation rates for rotary kilns range from 0.3 to 1.5 meters per minute (1 to 5 feet per minute)• .Forfluidized bedincineration, thedegree ofwaste/airmixing is indicated by the pressuredrop through the bed caused by the airflow rateused to fluidize the bed. The higherthe pressure drop, the greater the degree ofmixing in the fluidized bed. However, this also reduces the incineration temperature and the residence time ofthe waste solids and combustion gases. Forfixed hearth incineration, thedegreeofwaste/airmixing isdetermined by the airflow rate into the combustion chamber. As the airflow rate is increased, the degree of waste/air mixing is improved. However, this also reduces the incineration temperature and the residence time of the combustion gases.

f:\document\15254031.01.007 61The quantifiable degree ofwaste/air mixing is a complex assessment that is difficult to express in absolute terms. However, for liquid injection incineration,**E~** evaluates the degree ofmixing qualitatively by examining the burner design and detennining whether it could be expected to achieve effective atomization of the waste/air mixture. For rotary kiln incineration, EPA estimates the degree of mixing by monitoring the airflow rate into the kiln as well as the kiln's rate ofrotation to ensure that effective mixing ofthe waste and air is achieved. For fluidized bed**incin~ration,** EPA estimates the degree of mixing by manitorfng the pressure drop through the bed to ensure that effective mixing ofwaste and air is achieved. For fixed hearth incineration, EPA estimates the degree of mixing by monitoring the airflow rate into the combustion chamber to ensure that effective mixing of the waste and air is achieved.**f:\doc~t\15254031.01.007** 625.6 References Ackerman, O.G.,**~cGaughey,** J.F., and Wagoner, 

### D.E. 1983. At sea incineration of PCB-containing wastes on board the H/T vulcanus. 600/7-83-024. U.S. Environmental Protection Agency, Washington, D.C. Bonner, T.A., et al. 1981. Engineering handbook for hazardous waste incineration. Prepared by Monsanto Research Corporation for U.S. Environmental Protection Agency. PB 81-248166. Holler, J.J., and Christiansen, 0.8. 1984. Dry scrubbing of hazardous waste incinerator flue gas by spray dryer absorption. In Proceedings of the 77th annual APCA meeting. Novak, R.G., Troxler, W.L., and Dehnke, T.H. 1984. Recovering energy from hazardous waste incineration, Chemical engineering progress 91:146. Oppelt, E.T. 1987. Incineration ofhazardous waste, JAPCA val. 37, no. 5, May 1987. Santoleri, J.J. 1983. Energy recovery--a by product of hazardous waste incineration systems. In Proceedings ofthe 15th Hid-Atlantic Industriar Waste Conference on Toxic and Hazardous Waste. Vogel, G., et al. incinerated. Agency. , ' 1983. Composition of hazardous waste streams current1 y Prepared by Mitre Corp. for 

### U.S. Environmental Protection Vogel, G., et al. 1986.**Incin~ration** and cement kiln capacity for hazardous waste treatment. In Proceedings of the 12th Annual Research Symposium on Incineration and Treatment of Hazardous Wastes, Cincinnati, Ohio.

f:\document\15254031.01.007 63 

# l

J

# '



# ' 6. WET AIR OXIDATION

- 6.1 Apilicability
Wet air oxidation is a treatment technology applicable to wastewaters containing organics and oxidizable inorganics such as cyanide. The process is typically used to oxidize sewage sludge, regenerate spent activated carbon, and treat process wastewaters. Wastewaters treated using this technology include pesticide wastes, petrochemical process wastes, cyanide-containing metal finishing wastes, spent caustic wastewaters containing phenolic compounds, and some organic chemical production wastewaters. This technology differs from other treatment technologies generally used to**tre~t** wastewaters containing organics in the following ways. First, wet afr oxidation can be used to treat wastewaters that**~ave** higher organic concentrations than are normally handled by biological treatment, caroon adsorption, and chemical oxidation but may be too dilute to be effectively treated by thermal processes such as incineration. Wet air oxidation is most applicable for waste streams containing dissolved or suspended organics in the 500 to 50,000 mg/1 range. Below 500 mg/1, therates ofwet airoxidation ofmost organic constituents are too slow for efficient application ofthis technology. Forthese more dilutewaste streams, biological treatment, carbon adsorption, or chemical oxidation may be more applicable. For more concentrated waste streams _(above 50,000 mg/1), thermal processes such as incineration may be more

applicable. Second, wet air oxidation can be applied to wastes that have significant concentrations of metals (roughly 2percent), whereas biological treatment, carbon adsorption, and chemical oxidation may have difficulty in treating such wastes. It is important to point out that wet air oxidation proceeds by a series ofreaction steps and the intermediateproducts formed are not always as readily oxidized as are the original constituents. Therefore, the process does not always achieve complete oxidation of the organic constituents. Accordingly, in

f:\document\15254031.01.008 64applying this technology it is important to assess potential products of incomplete oxida.tion to determine whether further treatment is necessary or whether this**tt~hnology** is appropriate at all. Studies of the wet air oxidation of different compounds have led to the following empirical observations concerning a compound's susceptibility to wet air oxidation based on its chemical structure: 1. Aliphatic compounds, even with multiple halogen atoms, can be destroyed within conventional wet air oxidation conditions. Oxygenated compounds (such as low-molecular-weight alcohols, aldehydes, ketones, and carboxylic acids) are formed, but these compounds are readily biotreatable. 2. Aromatic hydrocarbons, such as toluene, acenaphthene, or pyrene, are easily oxidized.

r 

## . 3. Halogenated aromatic compounds can be oxidized provided there is at least one nonhalogen functional group present on the ring (e.g., pentachlorophenol (-OH) or 2,4,6-trichloroaniline 

### (-NHz)). 4. Halogenated aromaticcompounds, such as 1,2-dichlorobenzene, and PCBs, such as Aroclor 1254, are resistant to wet air oxidation under conventional conditions. 5. Halogenated.ring compounds, such as the pesticides aldrin, dieldrin, and endrin, are expected to be resistant to conventional wet air oxidation. 

### 6. DDTcan be oxidized, but results in the formation of intractable oils in conventional wet air oxidation.

f:**\doc~~nent\152~031.**01.008 65 

# 1

# ) 7. Heterocyclic compounds containing oxygen, nitrogen, or sulfur are

·**expect~d** to be destroyed by wet air oxidation because the 0, N, or 

### s**atom~_provide** a point of attack for oxidation reactions to occur. 6.2 Underlying Principles of Operation
The basic principleofoperation for wet airoxidation is thatthe enhanced solubility of oxygen in water at high temperatures and pressures aids in the oxidation of organics. The typical operating temperature for the wet air oxidation treatment process ranges from 175 to 325"C (347 to 617'F). The pressure is maintained at a level high enough to prevent excessive evaporation of the liquid phase at the operating temperature, generally between 300 and 3000 psi. At these elevatedtemperatures and pressures, the so1 ubi1 ityofoxygen in water isdramatically increased, thus providing astrong driving force for the oxidation. The reaction must take place in the aqueous phase because the chemical reactions involve both oxygen (oxidation) and water (hydrolysis). The wet air oxidation process for a specific organic compound generally**involve~**a number ofoxidation and hydrolysis reactions in series, whichdegrade the initial compound by steps into a series ofcompounds of simpler structure. Complete wet airoxidation results in theconversion oforganiccompounds intocarbondioxide, water vapor, arrmonia (for nitrogen-containing wastes), sulfate (for sulfur-containing wastes), and halogen acids (for halogenated wastes). However, treatable quantities of partial degradation products may remain in the treatedwastewaters fromwet airoxidation. Therefore, effluentsfromwet air oxidation**processe~** may be given subsequent treatment including biological treatment, carbon adsorption, or chemical oxidation before being discharged. 

### 6.3 Description ofWet Air Oxidation Process
Aconventional wet airoxidation systemconsists ofahigh-pressure liquid feed pump, an oxygen source (air compressor or liquid oxygen vaporizer), a**f:\document\1525~031.01.008** 66reactor, heat exchangers, avapor-liquid separator, and process regulators. A basic flow**diagr~m** is shown in Figure 9. (_ Atypical batch wet air oxidation process proceeds as follows. First, a copper catalyst solution may be mixed with the aqueous waste stream if preliminary testing indicates that a catalyst is necessary. The waste is then pumped into the reaction chamber. The aqueous waste is pressurized and heated to the design pressure and temperature. After reaction conditions have been established, air is fed to the reactor for the duration of the design reaction time. At the completion ofthe wet air oxidation process, suspended solids or gases are removed and the remaining treated aqueous waste is either discharged directly to disposal or fed to a biological treatment, carbon adsorption, or chemical oxidation treatment system if further treatment is necessary prior to discharge ta disposal.
Wet air oxidation can also be operated in a continuous process. In ' continuous operation, the waste is pressurized, mixed with pressurized air or oxygen, preheated in a series ofheat exchangers by thehot reactor effluent and steam, and fed to the reactor. The waste feed f1ow rate centro1 s the reactor residence time. Steam is fed into the reactor column to adjust the column temperature. The treatedwaste is separated in agas-1iquid separator, with the gases treated in an air pollution control system and/or discharged to the**atmos~here,** and the liquids either further treated, as mentioned above, and/or ·discharged to disposal. 6.4 Waste Characteristics Affecting Performance CWCAPsl
In determining whether wet air oxidation will achieve the same level of performance on an untested waste that it achieved on apreviously tested waste and whether performance levels can be transferred, EPA examines the following waste characteristics: {a) the chemical oxygen demand and (b) the concentration of interfering substances.

f:\document\15254031.01.008 67 10\ Ol PRESSURIZED WASTEWATI:R IHflUEHT PRESSURIZED AIR OR OXYOEH 

### BEACTOR

STEAM

STEAM

Figure 9 Continuous Wet A1r Ox1dat1on System ,r"

VENT OASES TO AIR POLLUTION 

### ----41•CONTROL SYSTEM ANDIOR THE ATMOSPHERE

GAS-LIQUID 

### SEPARATOR

TREATED EFFLUENT '----__. TO FUR'JttER TREATMENT AND/OR DISPOSAL6.4.1 Chemical Oxygen Demand The**chem~al** oxygen demand (COD) of the waste is ameasure of the oxygen required for complete oxidation ofthe oxidizablewaste constituents. The limit to the amount of oxygen that can be supplied to the waste is dependent on the solubilityofoxygen in the aqueous waste and the rate of dissolution of oxygen from the gas phase to the liquid phase. This sets an upper limit on the amount ofoxidizable compounds thatcan be treated bywet airoxidation. Thus, high-COD wastes may require dilution for effectivetreatment to occur. Ifthe COD ofthe untested waste is significantlyhigher than that ofthe tested waste, the system may not achieve the same performance. Pretreatment of the waste or dilution as part oftreatment may be needed to reduce the COD to within levels treatable by the dissolved oxygen concentration andto achieve the same treatmentperformance, or other, more applicable treatment technologies may need to be considered for treatment gf the untested waste. 6.4.2 Concentration of Interfering Substances
In some cases, addition of awater-soluble copper salt catalyst to the waste before processing is necessary for efficient oxidation treatment (for example, for oxidation of some halogenated organics). Other metals have been tested and have been found to be less effective. Interfering substances for the wet air oxidation process are essentially those that cause the formation of ·insoluble copper salts when copper catalysts are used. To be effective in

catalyzingthe oxidationreaction, the copperionsmustbedissolved in solution. Sulfide, carbonate, and othernegative ions that form insoluble copper saltsmay interfere with treatment effectiveness if they are present in significant concentrations in wastes for which copper catalysts are necessary for effective treatment. If an untested waste for which acopper catalyst is necessary for effective treatment has a concentration of interfering substances (including sulfide, carbonate, or other anions that form insoluble copper salts) significantlyhigher than that in atestedwaste, the systemmay not achieve the**f:\document\1525~031.01.008** 69 

# 1same performance and other, more applicable treatment technologies may need to be**consid~red** for treatment of the untested waste.
t. 6.5 Design and Operating Parameters
In assessing the effectiveness of the design and operation of a wet air oxidation system, EPA examines the following parameters: (a) the oxidation temperature, (b) the residencetime, (c) theexcess oxygenconcentration, (d) the oxidation pressure, and (e) the amount and type ofcatalyst. Formany hazardous organic constituents, analytical methods are not available or the constituent cannot be analyzed in the waste matrix. Therefore, it would normally be impossible to measure the effectiveness of the wet air oxidation treatment system. In these cases EPA tries to identify measurable parameters or constituents that would act as surrogates to verify treatment. For organic constituents, each compound contains ameasurable amount of total organic carbon 

### (rOC). Removal of

### roc in the wet air oxidation treatment system indicates removal oforganic constituents. Hence, 

### TOC analysis is likely to be an adequate surrogate analysis where the specific organic constituent cannot be measured. However, 

### TOC analysis may not be able to adequately detect treatment of specific organics in matrices that are heavily organic-laden (i.e. 1 the 

### roc analysis may not be sensitive enough to dete.ct changes at the milligrams per liter (mg/1) level in matrices where total organic concentrations are hundreds or thousands of mg/1). In these cases other surrogate parameters should be sought. For example, if a specific analyzable constituent is expected to be treated as well as the unanalyzable constituent, the analyzable constituent concentration should be monitored as a surrogate.

f:\document\1SZS4031.01.008 706.5.1 Oxidation Temperature Temperatu_re is the most important parameter affecting the system. The design temperature must be high enough to allow the oxidation reactions to proceed at acceptable rates. Raising the temperature increases the wet air oxidation rate by enhancing oxygen solubility and oxygen diffusivity. The process is normally operated in the temperature range of 175 to 32S"C (347 to 

### 617.F), depending on the hazardous constituent(s) to be treated. 

### EPA monitors the oxidation temperature continuously, ifpossible, to ensure that the system is operating at the appropriate design condition and to diagnose operational problems. 6.5.2 Residence Time The residence time impacts the extent ofoxidation ofwaste contaminants. For a batch system, the residence time is controlled directly by adjusting the

r treatment time in the reaction tank. For a continuous system, the waste feed rate is controlled to make sure that the system is operated at the appropriate designresidence time. Generally, the reactionratesare relativelyfast for the first 30 minutes and become slow after 60 minutes. Typical residence times, therefore, are approximately 1hour. EPA monitors the residence time to ensure that sufficient time is provided to effectively oxidize the waste.**~.5.3** Excess**OxYg~n** Concgntration The systemmust**~e** designed to supply adequate amounts ofoxygen for the compounds to be oxidized. An estimate ofthe amountofoxygenneeded canbemade based onthe COOcontent oftheuntreatedwaste; excessoxygen shou1 dbe supp1ied to ensure complete oxidation. The source of oxygen is compressed air or a high-pressure pure oxygen stream. 

### EPA monitors the excess oxygen concentration (the concentration of oxygen in the gas leaving the reactor) continuously, if possible, by sampling the vent gas from the gas-liquid separatorto ensure that an effective amount of oxygen or air is being supplied to thewaste.
f:\document\15254031.01.008 716.5.4 Oxidation Pressure The**desi~** pressure must be high enough to prevent excessive evaporation of water and volatile organics at the design temperature. This allows the oxidation reaction to occur in the aqueous phase, thereby improving treatment effectiveness. Typical oxidation pressures range from 900 to 3000 psig. EPA monitors the oxidation pressure continuously, if possible, to ensure that the system is operating at the appropriate design condition and to diagnose operational problems. 6.5.5 Amount and Type ofCatalyst Adding acatalystthatpromotes oxygentransfer and thusenhances oxidation has the effectof 1 owering thenecessaryreactortemperature and/orimproving the level ofdestruction ofoxidizable compounds. For waste constituents that are more difficult to oxidize, the addition of a catalyst may be necessary to effectivelydestroy the constituent(s) ofconcern. Catalysts typically used for this purpose include copper bromide and copper nitrate. If a catalyst is required, EPA examines the amount and type added, as we11 as the method of addition of the catalyst to the waste, to ensure that effective oxidation is achieved.

f:\doclllll!nt\15254031.01.008 72 

# ,

.6.6 References Detrich, H.J., landall, T.L., and Canney, P.J. 1985. Wet air oxidation of hazardous organics in wastewater. Environmental Progress 4:171-197. Randa11, T.L. 1981. Wet oxidation of toxic and hazardous compounds, Zimpro technical bulletin I-610. Presented at the 13th Hid-Atlantic Industrial Waste**Conf~rence,** June 29-30, 1981, University ofDelaware, Newark, Del. USEPA. 1990. U.S. Environmental ProtectionAgency, Office of Solid Waste. Best demonstrated available technology {BOAT} backgrounddocument addendum for acrylonitrile wastes. Washington, D.C.: U.S. Environmental Protection Agency.

f:\dacument\15254031.01.008 73 

# ,L



### I. TREATMENTTECHNOLOGIES (CONTINUED) B. TECHNOLOGIES THAT REDUCE THE SOLUBILITY OR 

### LEACHABILITY OF METALS 

### t I1. AMALGAMATION 1.1 ApPlicability The termamalgamation refer.s to two types ofprocesses that can be used as treatmentformercurywastes. Neitheramalgamation process significantlyreduces the leachability ofmercury; both processes only.convert it into amore easily processed fcrm. In both processes, a solid alloy ofmercury and abase metal, such as zinc, is formed. This alloy can be subsequently processed by retorting to recover mercury. The two processes differ from each other in the types ofwastes managed. The first process is applicable only to solutions containing dissolved mercury salts. The principal current use for the process is in treatment ofwastewaters containing organomercury salts. The second process is usable only for wastes rich in elemental mercury. Since the use of this second process is merely a convenience to avoid handling mercury in liquid fonn, its use is negligible. Bothprocesses are applicable only to wastes containing mercury where selective recovery of the mercury is deemed viable.
1.2 Underlying Principles of Operation 

### Jhe amalgamation processes depend on the ability ofmercury to form low-**~elting-point** solid alloys with metals such ar copper and zinc, which have the thermodynamic capabilityofsimultaneouslyreducing mercuric andmercurous salts to elemental mercury•.Basically, an excess of the less noble metal (zinc or copper) is contacted with a waste containing mercury or mercury salts. The chemical reactton reducing the mercury in the mercury salts occurs and the elemental mercuryliberatedforms an alloywith the excess matal added. For zinc and mercuric nitrate, the reaction may be written:

f:\docunent\1SZS4031.01.009 74 

# ,Hg t Zn • mercury zinc amalgam 1.3 Description ofAmalgamation Treatment Processes The two types of amalgamation processes are operated as follows: 1. The aqueous replacement process {solution process) involves addition of excess base metal, such as zinc, to a wastewater solution containing dissolved mercury salts. The elemental zinc, or otherbase metal, reacts with the mercuric or mercurous salts to fonn elemental mercury, which subsequently alloys with the excess base metal to form a solid amalgam (or alloy) that can be recovered by filtration and then sent for mercury recovery if applicable. Generally, finely divided zinc {zinc dust) is used. The high surface area of this material allows for rapid reaction and alloy formation.
2. The nonaqueous process, which is seldom used, involves contacting waste 1iquid mercury with finely divided zinc powders. The mass rapidly solidifies into a solid amalgam, which may be more easily managed than 1 iquid mercury. This type of process i s typica11y limited in utility only to waste scrap elemental mercury.

1.4 Waste Characterization Affecting-Performance CVCAPs) I In determininq whether amalgamation will achieve the same level of performance on an untested waste that it achieved on apreviously tested waste and whether performance levels can be transferred, EPA examines the following waste characteristics: (a) the chemical form of the mercury, (b) the solution pH, (c) the presence of solids, and (d) the presence of other interfering materials.**f:\docum~nt\1525~031.01.009** 

### 75 

# , I 

### I1.4.1 Chemical Form of the Mercury The soluttQn process requires that the mercury be present in the form of a dissolved mercury salt. As aresult, the process is not applicable to wastes containing insoluble mercury compounds. The nonaqueous process is applicable only to waste scrap mercury in elemental form.
1.4.2 So1 ution PH. The solutionprocess involves reactionsoffinelydivided zincwithmercury salts in solution. Reactions such as those consuming zinc by reaction with the acidic content of wastewaters are undesirable. Therefore, the pH of the wastewater solution should be adjusted tonear neutral value before the process is used. This characteristic does not apply to the second process, where scrap liquid mercury is arequired feedstock.
1.4.3 Presence of Solids
The solution process is aimed atrecovery of a solid amalgam that can be shipped tomercury reprocessors. The presence ofothersolids in the amalgammay be undesirable. Therefore, ifmercury isto be recovered, wastewater solutions should be filtered to remove extraneous solids before the process is used. This characteristic does not apply to the second process. 1.4.4 Presence of Interfering Matari'als · The solution process requires a clear solution as a feedstock. Solutions containing oils, greases, and emulsified or suspended materials need to be pretreated before use of the process. The presence of many other dissolved salts, such as those ofcopper, which can reactwith zinc, is also undesirable, but does not exclude use of the process. The presence of such salts will increase the amounts ofzinc required for process operation.

f:\document\15254031.01.009 76

### The nonaqueous process requires elemental mercury as afeedstock. Scrap mercury contamina_ted with oils, greases, and emulsion is better managed by retorting**dire~ly** 

### since these interfering substances may inhibit amalgam formation. 1.5 Design and Operating Parameters 1.5.1 Solution Process Design and Operating Parameters In assessing the effectiveness of the design and operation of a solution process, EPA examines the following parameters: (a) temperature, (b) degree of mixing, (c) zinc usage, (d) solution pretreatment, and (e) residual mercury in the treated wastewater. 1.5.1.1 Temperature The solution process is normally operated at**~tent.**

### temperature but can be run attemperatures up to about

### so•c to enhance the reaction ratebetween zinc and dissolved mercury salts. EPA will examine the basis for the choice of operating temperature and temperatura monitoring equipment to ensure proper process operation.
1.5.1.2 

### Degree ofMixing Finelydividedzincpowder

### tsnormallyadded to the solution containing the mercury compound. To e.nsure adequate contact between the zinc par:ticles and mercuryions presentin solution, good agitationisneeded. EPAwill examine the equipment used to determine that the treatment vessel contains the proper stirring equipment.

f:\document\15254031.01.009 771.5.1.3 Zinc Usage**Sufficien~zinc** must be added to the solutions to ensure that all of the mercury present is converted to an amalgam. To achieve this end, the concentration of mercury in the solution to be processed must be known to estimate the minimum amount of zinc to be added. EPA will examine afacility's calculationsfor zinc addition for individual batches to ensure properoperation.
1.5.1.4 Solution Pretreatment
In a properly operated unit, the mercury-containing solutions processed should be clear and free ofoil, grease, and suspended solids when introduced to the processing equipment. EPA will inspect the solutions entering the process to ensure that proper pretreatment is being used.
1.5.1.5 Residual Mercury Levels in Treated Liquid Phase Onetinal design andoperating parameterofimportance isthe concentration ofmercury in the treated water after amalgam removal. For aproperly designed and operated unit, both the entering and final mercury**concent~ations** should be determined on abatch-by-batch basis. EPA will examine these records to ensure proper operation. EPA will a 1 so determin_e_proper operatJon- by_**exa~~~i**nation of capabi.lities for posttreatment to precipitate any residual mercury from the treated wastewaters prior to their discharge. Amalgamation processes are normally used as part of treatment trains devoted to recovering elemental mercury. The reaction ofzinc with mercury salts in solution occurs rapidly at highermercury saltconcentrations but may become very slow as the concentration falls to low levels. As aresult, treated solutions are likely to contain some residual mercury salts requiring separate treatment.

f:\document\1SZS4031.01.009 78 

# , !

### 1.5.2 Nonaqueous Precess Design and Operating**Par~ters** 

### The

### nonaqu~~us (solid) process is very rarely used on asignificant scale. Generally, waste mercury is either retorted or redistilled as such without formation of amalgams. There are, however, afew instances in which itmight be desirable to amalgamate elemental**mercur~,** 

### the most important·ofwhich is when the mercury is contaminated by radioisotopes. The solid process invohing amalgamation with zinc is basically simple, and there are two design and operatingparameters ofconcern: (a) the amountofzincused and (b) theadequacy of the mixing. 1.5.2.1 

### Amount ofZinc Used The properties of the final amalgam prepared will depend on the ratio of zinc powder to mercury used. Mercury and zinc form amalgams over a very wide composition range. However, it is necessary to add sufficient zinc so that an alloy that is solid at room temperature is obtained. This entails using sufficient zinc toensure that an amalgam with at least 25 percent zinc content is obtained. 1.5.2.2 Adequacy ofMixing
To fonn uniform zinc-mercury amalgams, the constituents need to be unifonnly mixed. Historically, such amalgams have been prepared in small quantities. If a facility desires to process mercury by this route in higher volumes, aspeciallydesignedmixing systemmaybeneeded. EPAwill examine the design and operation ofthe mixing system to determine whether adequate mixing is likely to be 

### achieved.

f:**\doc~nnt\15ZS<C031.01.009** 79 

# , '1.6 References Mellor, J.W., f9.48. Comprehensive treatise on theoretical and inorganic chemistry. Vol. 4, pp. 1022-1049. London, U.K.: Longmans Green. Signer, W., andNowakfot., 1978. Mercury compounds. In Kirk-Othmerencvclopedia of chemical technology. Vol. 15, pp. 157-171. New York: John Wiley Interscience. Rissmann, 

### E.F., and Schwartz, 

### S., 1989. Treatment ofwastes containing arsenic, selenium, thallium, and mercury compounds. In Proceedings of the 44th Industrial Waste Conference, Purdue University. pp. 643-648. Ann Arbor, Mich.: Lewis Publishers.

f:\ja:ument\15254031.01.009 80 l

### 2. CHEMICAL PRECIPITATION 2.1 App!.icability Chemical precipitation is atreatment technology applicable to wastewaters containing awide range ofdissolved andothermetals, as well as other inorganic substances such as fluorides. This technology removes these metals and inorganics from solution in the formof insoluble solid precipitates. The solids formed are then separated from the wastewater by settling, clarification, and/or polishing filtration.
For some wastewaters, such as chromium plating baths or plating baths containing cyanides, the metals exist in solution in avery soluble form. This solubilitycan be caused by the metal's oxidation state (for example, hexavalent chromium wastewaters) or by complexing of the metals (for example, high cyanide-containingwastewaters). Inbothcases, pretreatment, such as hexavalent chromium reduction or oxidation of the metal-cyanide complexes, may be required before the chemical precipitation process can be applied effectively. In the case of arsenic, the arsenic-containing solution is normally treated first with oxidizing agents such as alkali hypochlorite solution to convert the lowervalence arsenic compound to arsenate. The arsenic ion is then typically precipitated out as ferric arsenate. Some compounds must be reduced prior to precipitation. For**instance~** selinites and selenates are oxidants and are readily reduced to elemental selenium, which is insoluble in aqueous solutions. Sulfur dioxide, sulfides, sulfites, and ferrous ion are all effective for this reduction reaction. Chemical precipitationmay also be applicabletomixedwaste for separating radionuclides from other hazardous canstituents in wastewaters. Specifie conditions ofpH, temperature, and precipitating reagent addition are required to selectivelyremove partorall ofthe radioactive component as aprecipitate.

f:\document\1SZ5403l.Ol.Ol0 81

### 2.2 UnderlYing Principles of

### Operation The**basic~rinciple** 

### ofoperation ofchemical precipitation is that metals and inorganics inwastewaterareremoved bythe addition ofaprecipitatingagent thatconverts the solublemetals and inorganics to insolubleprecipitates. These precipitates are settled, clarified, and/or filtered out of solution, leaving a lower concentration ofmetals and inorganics in the wastewater. The principal precipitation agents used to convert soluble metal and inorganic compounds to less soluble forms include lime (Ca(OH)2), 

### caustic (NaOH), sodium sulfide (Na2 S), 

### and, to alesserextent, soda ash (Na2C03), 

### phosphate (P04·), 

### and ferrous sulfide (FeS).The solubilityofaparticularcompound depends on the extent to which the electrostaticforces holding the ions ofthe compound together can be overcome. The solubilitychanges significantlywithtemperature, with mostmetal compounds becomingmore soluble as the temperature increases. Additionally, the solubility isaffectedbyotherconstituentspresent inthe wastewater, including otherions and complexing agents. Regarding specific ionic forms, nitrates, chlorides, and sulfatesare, ingeneral, moresoluble thanhydroxides, sulfides, carbonates, and phosphates. Once the so1 ub1 e meta1 and inorganic compounds have been converted to precipitates, the effectiveness of chemical precipitation is determined by how successfullythe precipitatesarephysicallyremoved. Removal usuallyrelieson a settling process; that is,. a particle of a specific size, shape, and composition will settle.ataspecificvelocity, as described by Stokes' Law. For a batch system, Stokes' Law is agood predictor of settling time because the pertinentparticleparameters essentiallyremainconstant. Inpractice, however, settling time for abatch system is normally determined by empirical testing. For acontinuous system, the theory of settling is complicated by such factors as turbulence, short-circuiting ofthe wastewater, and velocitygradients, thus increasing the importance ofempirical tests toaccuratelydetermine appropriate settling times.
f:\document\15254031.01.010 822.3 Description ofChemical Precipitation Process The**equi~ent** and instrumentation required forchemical precipitationvary depending on whether the system is batch or continuous. Both systems are discussed below.
For abatch system, chemical precipitation requires afeed system for the treatment chemicals and a reaction tank where the waste can be treated and allowed to settle. When lime is used, it is usually added to the reaction tank in aslurry form. The supernatant liquidis generally analyzed before discharge to ensure that settling ofprecipitates is adequate.
For a continuous system, additional tanks are necessary, as well as the instrumentation to ensure thatthe system is operating properly. Aschematic of a continuous chemical precipitation system is shown in Figure 10. In this system, wastewateris fed into an equalizationtank, where itismixedto provide more uniformity, thus minimizing the variability in the typP. and concentration of constituents sent to the reaction tank. Following equalization, the wastewater is pumped to areaction tank where precipitating agents are added. This is done automatically by using instrumentation that senses the pH of the system for hydroxide precipitating**agen~s,** ortheoxidation-reductionpotential (ORP) fornonhydroxideprecipitating -agents, and then pneumatically adjusts the position of the treatment chemical

feed valve until the design pH or ORP value is achieved. (The pH and ORP values are affected by the concentration of hydroxide and nonhydroxide precipitating agents, respectively, and are thus used as indicators oftheirconcentrations in the reaction tank.)
In the reaction tank, the wastewater andprecipitating agents are mixed to ensure commingling ofthe metal and inorganic constituents to be removed and the precipitating agents. In addition, effective dispersion ofthe precipitating

f:\document\15254031.01.010 83WAIJIWAUII INflUIMI-----,

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### nrlagents throughout the tank is necessary to properly monitor and thereby control the**amoun~** added. t. Following reaction of the wastewater with the stabilizing agents, coagulating or flocculatingcompounds areadded to chemically assistthe settling process. Coagulants and flocculants increase the particle siie and density of the precipitated solids, both of which increase the rate of settling. The coagulant or flocculating agent that best improves settling characteristics varies depending on the particular precipitates to be settled. Settling can be conducted in alarge tank by relying solely on gravity or can be mechanically assisted through the use of a circular clarifier or an inclined plate settler. Schematics of the two settling systems are shown in Figures 11 and 12. Following the additionofcoagulating orflocculating agents, the wastewater is fed to alarge settling tank, circular clarifier, or inclined plate settler, where the precipHated solids are removed. These solids are generally further treated in asludge filtration systemtodewater them priorto disposal. Sludge filteration is discussed in Section 11.8.2 ofthis document. The supernatant liquid effluent can be further treated in a polishing filtration system to remove precipitated residuals both in cases where the settling system is underdesigned and in cases where the particles are difficult to settle. Polishingfiltration is discussed in Section II.B.2 ofthis document. 2.4 Waste Characteristics Affecting Performance (WCAPsl
In determining whether chemical precipitationwill achieve the same level ofperfonnance on an untested waste that itachieved on aprevious1 ytestedwaste and whether performance levels can be transferred, EPA examines the following waste characteristics: (a) the concentration and type of metals, {b) the concentration of total dissolved solids {TOS), {c) the concentration of complexing agents, and (d) the concentration of oil and grease.

f:\document\15254031.01.010 85

# '') Tit!ATID E"I.U!NT**~~~TO** IIOUSHJNQ II'ILT'ItATtON AHOIOR**OII~OS.U.**

CENTER FE!D C:URIFtER vtrni SCRAPER SLUDGE AEUOVAJ. SUST!M

### ~:::::::::::::::----..IOTTOMa

# TO ILUDGI·JI1LntAT10N UID**CU.~U.L** RIM 11!1D

- e!N'1'P T AJCIOPfr C:UiaJitiR Wl"nf HYDIIIAUUC SUCTION SLUDGI RIIIOVAI.. SYS'TIM**L~==;--~IOTT'CIMI** TO a,uacq I'I.,'TIU.TION AICO OIPOIAL
RIM**~-** RIM TAK!OFfr C:URIPIEJII 

### Figure 11 Circular Clarifier Syst81S
86WASTEWATER INFLUENT t.



### Figure 12 Inclined Plate Settler**Systa~**



### 87 TREATED EFFLUENT TO POL.JSHING FIL.TRATION ANO/OR OISPOSAt.

BOTTOMS TO SL.UDGE FIL.n.A TlON AND DISPOSAL 

# , I2.4.1 Concentration and Type ofMetals
For most**~etals,** there is aspecific pH at which the metal precipitate is least soluble. As aresult, when awaste contains amixture ofmany metals, it is not possible to operate a treatment system at a single pH or ORP vaiue that is optimal for the removal of all metals. The extent to which this affects treatment depends on the particular metals to be removed and their respective concentrations. One alternative is to operate multiple precipitations, with intermediate settling, when the optimum pH occurs at markedly different levels for the metals present. If the concentration and type ofmetals in an untested waste differ from and ar.e significantly higher than those in the tested waste, the system may not achieve the same performance. Additional precipitating agents, alternate pH/ORP values, and/or multiple precipitations may be required to achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment ofthe untested waste. 2.4.2 Concentration ofTotal Dissolved Solids High concentrations of total dissolved solids (TDS) can interfere with precipitationreactions, aswell as inhibit settling. Poorprecipitate formation and flocculation are results of high TDS concentrations, and higher concentrations of solids are found in the treated wastewater residuals. Ifthe TDS concentration in an untested waste is significantly higher than that in the -tested waste, the system may not achieve the same performance. Higher concentrations of precipitating agents may be required to achieve the same treatment performance, .or'other, more applicabletreatmenttechnologies may need to be considered for treatment ofthe untested**~aste.** 2.4.3 Concentration of Complex1ng Agents
Ametal complex consists of a metal ion surrounded by a group of other inorganic ororganic ions ormolecules (oftencalled ligands). In the complexed form, metals have a greater solubility. Also, complexed metals inhibit the
f:\document\152S4031.01.010 

### as 

# ,reaction of the metal with the precipitating agents and therefore may not be removed as effectively from solution by chemical precipitation. However, EPA does not have**'~alytical** methods to determine the concentration of complexed metals inwastewaters. TheAgency believes that the best indicatorfor complexed metals is to analyze for**compl~xing** agents, such as cyanide, chlorides, EDTA, anunonia, amines, and methanol, for which analytical methods are available. Therefore, EPAuses the concentration ofcomplexing agents as a surrogate waste characteristic for the concentration of metal complexes. Ifthe concentration of complexing agents in an untested waste is significantly higher than that in the tested waste, the system may not achieve the same performance. Higher concentrations of precipitating agents may be required to achieve the same treatment performance, orother, more applicabletreatment technologies may need to be considered for treatment of the untested waste. 2.4.4 Concentration of Oil and Grease The concentrationofoil and grease in awaste inhibits the settlingofthe precipitateby creating emulsions that require along settlingtime. Suspended oil droplets in water tend to suspend particles such as chemical precipitates that would otherwise settleout of solution. Even with the use of coagulants or flocculants, the settling of the precipitate is less effective. If the concentrationofoil andgrease in an untestedwaste h significantlyhigher than that .in the tested waste, the system may not achieve the same performance. ·Pretreatment of the waste may be required· to -reduce the oil and grease

concentration and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment ofthe untested waste. 

### 2.5 Design and Operating Parameters
In assessing the effectiveness of the design and operation ofa chemical precipitation system, EPA examines the following parameters: (a) the pH/ORP value; (b) the precipitationtemperature; (c) theresidence time; (d) the amount
f:\document\1SZS4031.01.010 89and type ofprecipitatingagents, coagulants, and flocculants; (e) the degree of mixing; ind {f)**t~e** settling time.
t_ 2.5.1 pH/ORP Value The pH/ORP value in continuous chemical precipitation systems is used as an indicator of the concentration of precipitating agents in the reaction tank and thus is used to regulate their addition to the tank. The pH/ORP value also affects the solubility of metal pr·ecipitates formed and therefore directly impacts the effectiveness of their removal. EPA monitors the pH/ORP value continuously, if possible, to ensure that the system is operating at the appropriate design condition and to diagnose operational problems. 2.5.2 Precipitation**T~perature** The precipitation temperature affects the solubility of the metal precipitates. Generally, the lower the temperature, the lower the solubilityof the metal precipitates and vice versa. EPA monitors the precipitation temperature continuously, ifpossible, to ensure that the system is operating at the appropriate design condition and to diagnose operational problems. 2.5.3 Residence Time the residence time impacts the extent of the chemical reactions to form metal precipitates and, as a result, the amount of precipitates that can be settled out of**solution~** For batch systems, the residence· time is controlled directly by adjusting the treatment time in the reaction tank. For continuous systems, the wastewaterfeed rate is controlled to make sure that the system is operating at the appropriate design residence time. EPA monitors the residence time to ensure that sufficient tfme is provided to effectively precipitate metals and inorganics from the wastewater.

f:\document\15254031.01.010 902.5.4 Amount and TypeofPrecipitatingAgents, Coagulants, and Flocculants The amountand type of precipitating agent used to effectively treat the wastewaterdepends on the amount and type ofmetal and inorganic constituents in thewastewaterto be treated. Other design and operating parameters, such as the pH/ORP value, the precipitation temperature, the residence time, the amount and type ofcoagulants and flocculants, and the settlingtime, aredetermined by the selection of precipitating agents. The addition of coagulants and flocculants improves the settling rate ofthe precipitated metals and inorganics and allows for smaller settling systems (i.e., lower settling time) to achieve the same degree of settling as amuch larger system. Typically, anionic polyelectrolyte flocculating agents aremost effectivewithmetal precipitates, although cationic or nonionic polyelectrolytes also are effective. Typical doses range from 0.1 to 10 mg/1 of the total influent wastewater stream. Conventional coagulants, such as alum (aluminum sulfate), are also effective, but must be dosed at much higher concentrations to achieve the same result. Therefore, these coagulants add more to the settled sludge volume requiring disposal than do the polyelectrolyte flocculants. EPA examines the amount and type ofprecipitating agents, coagulants, and flocculants added, and their method of addition to the wastewater, to ensure effective precipitation.
2.5.5 Degree of Mixing Mixing provides greater uniformity of the wastewater feed and disperses precipitating agents, coagulants, and flocculants throughout the wastewater to ensure the most rapid precipitationreactions and settling ofprecipitate solids possible. The. quantifiable degree of mixing is a complex assessment that includes, among other things, the amount ofenergy supplied, the length oftime the material is mixed, and the related turbulence effects of the specific size and shape of the tank. This is beyond the scope of simple measurement. EPA, however, evaluates the degree of mixing qualitatively by considering whether mixing is provided and whether the type of mixing device is one that could be expected to achieve uniform mixing ofthe wastewater.

f:\document\15254031.01.010 912.5.6 SettlingTime Adequate**~ttling** time must be provided to make sure that removal of the precipitated solids from the wastewater has been completed. EPA monitors the settling time to ensure effective solids removal.

f:\document\15254031.01.010 922.6 References Cherry, K.F.**19~?-** Plating waste treatment. pp. 45-62. Ann Arbor, Mich.: Ann Arbor Scien·ce Pub1ishers, Inc. Cushnie, G.C., Jr. 1985. Electroplating wastewater pollution control technology. pp. 48-62, 84-90. Park Ridge, N.J.: Noyes Publications. Cushnie, G.C., Jr. 1984. Removal ofmetals from wastewater: neutralization and precipitation. pp. 55-92. Park Ridge, N.J.: Noyes Publications. Gurnham, C.F. 1955. Principles of industrial waste treatment. pp. 224-234. New York: John Wiley and Sons. Kirk-Othmer. 1980. Flocculation. In Encyclopedia ofchemical technology, 3rd ed., vol. 10, pp. 489-516. New York: John Wiley and Sons. USEPA. 1983. U.S. Environmental Protection Agency. Treatabilitymanual: Vol. III, Technology for control/removal of pollutants, p. 111.3.1.3.2. EPA-600/2-82-00lC. Washington, D.C.: U.S. Environmeotal Protection Agency.

f:\document\15254031.01.010 93**~** I l3. ENCAPSULATION
3.1 Appticabi1ity Encapsulation processes refer to afamily ofprocesses whereinhigh-solids nonwastewaters are mixed with an organic polymeric substance-or with asphalt. The mixture is then allowed to cure into a solid mass pr1or to disposal. These processes are applicable to awide variety ofwastes. They are not applicable to wastes containing materials that decompose at high temperatures or to wastes containing oxiders thatcan reactwith the bindermaterials. Also, some aromatic solvents such as xylene and**to~uene** can diffuse through the encapsulating agent. Oils, greases, and some chelating agents may interfere with the hardening and solidification of the encapsulating material. EPA believes that encapsulation technologies are applicable primarily to wastes containing hazardous metal constituents. Encapsulationmay i11111obilizehazardous organics as well as metals; however, incineration is more applicable to organics since incinerationdestroys organics completely, whereas encapsulation can only i11111obilize them.
3.2 UnderlYing Principles ofOperation:·

- - :: There are a**numb~r**ofvery sfmilarencapsulationprocesses thatdifferfrom each other only in the encapsulating agent used. In all ofthe processes, the waste.is firstdried to remove moisture. The waste is then usua}ly reheated and 1nixed with hot asphalt or thermoplastic material such as polyethylene. The mixture is then cooled to solidify the mass.. The ratio ofmatrix {fixative or encapsulating agent) to waste is generally high {i.e., 1:1 or 1:2 fixative to waste on adry basis). The matrix, once solidified, coats the waste to minimize leaching.
3.3 Description ofEncapsulation Processes Encapsulation processes can take the form of macroencapsulation, microencapsulation, orboth. Microencapsulation isthecontainmentofindividual

f:\document\15Z54031.01.011 94 

### 1 •

### waste particles in the polymer or asphalt matrix. Macroencapsulation is the encasement of amass ofwaste in a thick polymer coating. The waste mass may have been**micro~capsulated** 

### prior to macroencapsulation. 3.3.1 Microencapsulation Microencapsulation processes typically involve the following unit operations in series:

• Predrying of the waste to remove entrained moisture.

• Mixing of the heated waste with molten encapsulating agent (asphalt, polyethylene, thermosetting resins).

• Cooling of the hot mixture to allow the mixed mass to harden into a solid mass. Generally, ratios of matrix to waste used are high compared to those of pozzolanic stabilizationprocesses (i.e., for encapsulation the ratio ts in the 1:1 to 1:2 range). Mixing is generally done at 120 to 130°C depending on the melting characteristics ofthe matrix and the typeofequipment used for mixing. Afew processes differ from the above description in that polymerization of monomers mixed with waste is conducted at ambient or near ambient temperatures i-n the presence of catalysts. The monomer (or monomeric mixture) then polymerizes at room temperature, coating the individual waste particles. 3.3.2 Macroent4psulat1on The macroencapsulation process ofhazardous waste solids usually involves two steps. In the first step, the hazardous wastes maybe chemically treatedby using low-cost dehydrating agents such as lime, kiln dust, or Portland cement. This operation does not increase the volume ofthe solids significantly because

f:\document\15254031.01.011 95 

# ,only a small amount of dehydrating agent is needed to dewater the solids. The resulting·mixtures are friable, and they can easily be ground. ( In the second step, the dehydrated sludges are ground and the particlesmay be microencapsulated, typically by a polybutadiene binder. Then the mass is macroencapsulated, or coated, typically by high-density polyethylene. The typical apparatus for macroencapsulation processes features heated or cooledmolds, amethodofwasteand hardenedproductmanipulation, and hydraulics for mold actuation. The molds typically contain electrical band heaters and water cooling channels. Afterthe polymer coating hardens, the mold is split to facilitate product demolding.
3.4 Waste Characteristics Affecting Performance (WCAPsl
In determining whether encapsulation will achieve the same level of performance on an untested waste that it achieved on apreviously tested waste and whether performance levels can be transferred, EPA examines the following waste characteristics: {a) the water content ofthe waste; {b) the presence of oxiding agents in the waste; (c) the presence of certain organic solvents; (d) the presenceofoils, greases, and chelating agents; and {e) the presence of thermally unstable materials in thewaste::·These characteristics are described below

.. 3.4.1 Water Content The processes normally require adry solid waste. Wet solids need to be dried at elevated temperature, or chemically treated, to remove entrained moisture before they can be mixed with molten polymers, asphalt, or monomeric mixtures. The presence of free water interferes with the elevated temperature encapsulation processes by forming steam during the mixing and preventing a smooth coating of the particles. In ambient temperature processes, water may

f:\document\15Z54031.01.011 96

### react with the polymerization catalyst, preventing it 

### from initiating the polymerization reactions.**3.4~2** 

### Presence ofOxidizing Agents Strong oxidization salts such as nitrites, chlorates, or perchlorates will reactwith the organicmatrixmaterials and slowlydeteriorate the matrix. These oxidants may also react spontaneously with the heated matrix material to cause a fire or explosion. Wastes containing such strong oxidants should not be managed by polymer encapsulation processes.**3.4~3** 

### Presence of Organic Solvents Organic solvents, particularly aromatic solvents, may be capable of dissolving the polymer matrix material. They will also cause significant air emissionsdue to volatilizationduring the mixing ofthe heated waste andmatrix materials. The process should not be used.on wastes containing such solvents unless the wastes have been pretreated to remove such materials. 

### 3.4.4 Presence of Oils, Greases, and Chelat1ng Agents Oils, greases, and organic chelating agents are likelyto dissolve in and migrate through the polymeric matrices used for encapsulation. They may also, to some extent, coat individual waste particles and prevent firm microencapsulation binding between waste particles and the polymer matrix surrounding them.**Beca~se** 

### ofthe ability ofthese organics to diffuse through polymericmatrices, wastescontainingoils, greases, andorganicchelatingagents should not be managed by polymer encapsulation. 

### 3.4.5 Presence of

### Ther.allyUnstable Materials Hydrated salts are likely to decompose during the initial hot mixing of matrix and waste materials, liberating water vapor. These salts will also
f:\docum.nt\15254031.01.011 97 

# ,

### rehydrate during cooling and thus interfere with the uniform coating of waste particles·bythematrix polymer. Wastes containing hydrated salts should not be managed by thislprocess. Salts that are known to cause such problems include hydrated sodium sulfate, magnesium sulfate, and hydrated metal chlorides. The soluble hydrates need to be removed from the waste by chemical or physical means before the wastes are managed by polymer microencapsulation. 3.5 Design and Operating Parameters There are five design and operating parameters for this set ofprocesses: (a) 

### the choice ofthe polymeric matrix material, (b) the mixing equipment used, (c) the ratio ofpolymer to waste used, (d) process temperature control, and (e) air emissions control. These are described in the following paragraphs. 

### 3.5.1 Choice ofPolymeric Matrix Several polymeric matrices are available for use in these encapsulation processes. These include asphalt, polyethylene, thenmosetting plastics (such as urea formaldehyde type resins), and resins that can be polymerized under ambient temperature in the presence ofa catalyst. The choice of the polymeric matrix detenmines the temperature and equipment to be used and strongly influences the needed cure time. It also determines to some degree the choice of**~~stes** 

### that can be accepted because ofdifferences in the properties ofthe polymers. 

### EPA will examine the basisfor the choiceofpolymermatrix, available testdata, and the wastes being accepted for processing. 

### 3.5.2 Mixing Equ1pient Used
For microencapsulation, polymers or monomers and catalysts must be well mixed with wastes to ensure that uniformly coated waste particles are produced. EPA will examine the design and operating characteristics of the mixing system to ensure that it is capable ofgenerating uniform mixes.

f:\document\15Z5403l.Ol.Oll 98

### 3.5.3 Ratio ofPolymer to Waste Used

- 

### Sufficien\ polymer must be used to ensure that the waste is uniformly coated. Generally, a 1:1 or 1:2 polymer-to-waste ratio on a weight basis is used. EPA will examine the basis for the choice ofpolymer-to-waste ratio used to ensure that sufficient polymer is being added. 3.5.4 Process Temperature Control To achieve uniform mixing, the encapsulation matrix must be in a 1iquid state. The melting points of the different thermoplastic polymers will differ from each other. Duringmixingofthemolten polymer and waste, the temperature needs to be maintained above the thermoplastic polymer melting point and below the point at which polymer vaporization or thermal decomposition begins. Thus, for agiven thermoplastic polymer, there is only acertaintemperature range in which the process can be satisfactorilyoperated. For thermosetting resins the temperature selected must be appropriate to cause polymerization (hardening) afterthorough mixing. EPAwill examinedata on the properties ofthe polymers, including decomposition, to ensure that a proper operating temperature was selected. EPAwill also**ex~ine** 

### the temperature control instrumentation in use to ensure that it is operating properly. 3.5.5 Air Emissions Control Heating ofmixtures ofwastewith polymers or asphaltcancausetherelease ofhydrocarbon air**emis~ions** 

### thatmay include volatilecomponents ofthe waste, plasticizers present in the polymers, polymer decomposition products, and lowmolecular-weightingredientsofthe asphalt. In aproperlyoperating system, air emissions testing may be neededduring at least initial operation to determine levels ofemissions and to assess the need for air emissions control. EPA will**ex~ine** 

### such air monitoring data to determine whether air emissions control systems are appropriate. The Agency will also examine the iiremissions control

f:\document\15254031.01.011 99systems in use to ensure that they are operating and in proper operating condition:

f:\documant\15254031.01.011 100 

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.3.6 References Pierce, J., and Wesilind, P.A. 1981. Hazardous waste management. pp. 82-4. Ann Arbor, Mich.: Ann Arbor Science Publishers. Rich, G., and Cherry, K. 1987. Hazardous waste treatment technologies. Chapter 6, pp. 9-3. Northbrook, Ill.: Purdue Publishing Company.

f:\docunent\15254031.01.011 

### 1014. STABILIZATION OF METALS

Stabilization is atreatment technology applicable to wastes containing leachable metals and having a high filterable solids content, low total organic carbon (TOC) content, and 1 ow oi1 and grease content. This technology is commonly**!!~~d** to treat residuals generated from treatment of wastes such as electroplatingwastewaters, incineration ashresidues, andcharacteristic0-metal wastes such as cadmium (0006), chromium (0007), lead (0008), andmercury (0009). For wastes with recoverable levels ofmetals, high temperature metals recovery and retorting technologies may be applicable. Stabilization refers to a broad class of treatment processes that inunobilize hazardous constituents in a waste. Related technologies are encapsulation and thermoplastic binding. However, EPA considers stabilization technologies tobe distinctfromtheothertechnologies in thattheiroperational principles are significantly different. Stabilization typically requires a chemica1 reaction between the waste and the stabilizing agent for- effective treatment, while thermoplasticbinding andencapsulationusually**e~ploy** physical containment of hazardous particulates by the encapsulating agent. 4.2 Underlying Principles of Operation Thebasicprincipleofoperationfor stabilizationisthatleachable metals in awaste are i11111obilized following the additionofstabilizing agents and other chemicals. The leachability is reduced by the formation of alattice structure and/or chemical bonds that chemically bind the metals to the solid matrix and thereby limitthe amount ofmetal constituents thatcan be leached when wateror amild acid solution comes into contact with the waste material. Stabilization is most effective when the waste metal is in its least soluble state, thereby decreasing the potential for leaching. For example, hexavalent chromium is much more soluble and more difficult to stabilize than trivalent chromium.

f:\document\1SZS4031.01.012 102The two principal stabilization processes used are cement-based and lime/pozzolan-based processes. Abrief discussion of each is provided below. In both**cement-~ased** and lime/pozzolan-based techniques, the stabilizingprocess can be modified through the use of additives, such as silicates, that control curing :-ates, reduce permeability, and enhance the properties of the solid materia1. 4.2.1 Portland Cement-Based Process Portland cement is a mixture of powdered oxides of calcium, silica, aluminum, and iron, produced by kiln burning of materials rich in calcium and silica at high temperatures (i.e., 1,400 to 1,5oo·c (2,552 to 2,732.F}). When the anhydrous cement powder is mixed with water, hydration occurs and the cement begins to set. The chemistry involved is complex because many different reactions occur depending on the composition of the cement mixture.
As the cement begins to set, acolloidal gel ofindefinitecomposition and structure is formed. Over time, the gel swells and forms amatrix composed of interlacing, thin, denselypackedsilicatefibrils. Constituents present in the waste slurry (e.g.,hydroxides and carbonates ofvarious metals} are incorporated into the interstices of the cement matrix. The high pH of the cement mixture tends to keep metals in the form of insoluble hydroxide and carbonate salts. It has been hypothesized that metal ions may also be incorporated into the crystal -structure of the cement matrix, but this hypothesis has not been verified.
4.2.2 L1me/Pozzo1an-lased Process _,. Pozzolan, which contains finely divided, noncrystalline silica (e.g., fly ash or components of cement kiln dust), is a material that is not cementitious in itself, but becomes so upon the addition of lime. Metals fn the waste are converted to insoluble silicates or hydroxides and are incorporated into the interstices ofthe binder matrix, thereby inhibiting leaching.

f:\document\152>4031.01.012 103

### 4.3 Description of Stabilization Process The stabilizationprocess consists ofa**weighi~g**device, amixing unit, and a curing vessel or pad. Commercial concrete mixing and handling equipment is typically used in stabilization processes. Weighing conveyors, metering cement hoppers, andmixers similartoconcrete batching**pl~n~s** have been adapted in some operations. When extremely dangerous materials are treated, remote-control and in-drum mixing equipment, such as that used with nuclear waste, is employed.
In most stabilization processes, the waste, stabilizing agent, and other additives, ifused, are mixed in amixing vessel and then transferred to acuring vessel orpad and allowed to cure. The actual operation (equipment requirements and process sequencing) depends on several factors including the nature of the waste, the quantity of the waste, the location of the waste in relation to the disposal sjte, the particular stabilization formulation used, and the curing rate. Following curing, the stabilized solid formed ts recovered from the processing equipment and disposed of. 

### 4.4 Waste Characteristics Affecting Performance CWCAPsl
In determining whether stabilization will achieve the same level of performance on an untested waste that it achieved on a previously tested waste and**w~ether** performance levels can be transferred, EPA examines the following -waste characteristics: (a) the concentration of fine particulates, (b) the concentration of oil and grease, (c) the concentration of organic compounds, (d) the concentration 

### ofsulfate and**chloride~nds,** and (e) the solubility of the metal**c~mpound.** 

### 4.4.1 Concentration 

### of Fine Particulates
For both cement-based and lime/pozzolan-based processes, very fine solid materials (1.e., those that pass through a Ko. 200 mesh sieve (less than 74**~m** particle size)) weaken the bonding between waste particles and the cement or

f:\document\15Z540Jl.Ol.Ol2 104lime/pozzolan binder by coating the particles. This coating inhibits chemical bond formation,**t~ereby** decreasing the resistance of the material to leaching. Ifthe concentration offine particulates in an untested waste is significantly higher than that in the tested waste, the system may not a chieve the same performance. Pretreatment of the waste may be required to reduce the fine particulate concentration and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment ofthe untested waste. 4.4.2 Concentration ofOil and Grease Oil and greasein both cement-based and 1 ime/pozzolan-based systems result in the coating of waste particles and the weakening of the bond between the particle and the stabilizing agent, thereby decreasing the resistance of the material to leaching. Ifthe concentration ofoil and grease in the untested waste is significantly higherthan that in the tested waste, the system may not achieve the same performance. Pretreatmentmay be required to reduce the oil and grease concentration and achieve the same treatmentperformance, or other, more applicable treatmenttechnologies may need to be considered fortreatment ofthe untested waste. 4.4.3 Concentration ofOrganic Compounds Organic compounds in the waste interfere with the stabilization chemical reactions andbond formation, thus inhibiting curingofthe stabi1izedmaterial. This interference results in a stabilizedwaste having decreased resistance to leaching. -Ifthe total organic carbon {TOC} content of the untested waste is significantlyhigherthan that of the tested waste, the system may not achieve the sameperformance. Pretreatmentmaybe required to reducethe TOC and achieve the same treatment performance, orother, more applicable treatment technologies may need to be considered for treatment of the untested waste.

f:\documant\15254031.01.012 1054.4.4 Concentration of Sulfate and Chloride Compounds Sulfate**~d** chloride compounds interfere with the stabilization chemical reactions, weakening bond strength and prolonging setting and curing time. Sulfate and chloride compounds may reduce the dimensional stabilityofthe cured matrix, thereby increasing leachability potential. If the concentration of sulfate and chloridecompounds in the untestedwaste is significantlyhigher than that in the tested waste, the system may not achieve the same performance. Pretreatment may be required to reduce the sulfate and chloride concentrations and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment of the untested waste. 4.4.5 Solubilityof the Metal Compound The metal to be stabilized should be in its least soluble state, or the stabilized waste may exhibit a potential for increased leachability. Pretreatmentmay be required to chemicallyreduceoroxidizethe metal to alower solubility state and achieve maximum stabilization performance. For example, hexavalent chromium is much more soluble and more difficult to stabilize than trivalent chromium. 4.5 Design and Operating Parameters
In assessing the effectiveness of the design and operation of a stabilization system, EPAexamines the following**par~ters:** (a} the amount and type of stabilizing ageo.t,...and**additives~. (.b.),.;tl\er.~ee.** ..of mixing, (c} the residence time, (d} the stabilization temperature andhumidity, and (e} the form of the metal compound. 4.5.1 Amount and Type of Stabilizing Agent and Additives The stabilizing agent and additives used will determine the chemistry and structureofthe stabilizedmaterial and thereforeitsleachability. Stabilizing**f:\doc~t\15254031.01.012** 106 

## 1agents and additives must be carefully selected based on the chemical and physical characteristics of the waste to be stabilized. To select the most effective type tfstabilizingagent and additives, the waste should be tested in the laboratory with a variety of these materials to determine the best combination.
The amount of stabilizing agent and additives is acritical parameter in that sufficient stabilizing materials are necessary to properly bind the waste constituents of concern, making them less susceptible to leaching. The appropriate weight ratios of stabiHzing agent and additives to waste are established empirically by setting up a series of laboratory tests that allow separate leachate testing of different mix ratios. The ratio of water to stabilizing agent (including water in waste) will also impact the strength and leaching characteristics ofthe stabilized material. Too much water will cause low strength; too littlewill make mixing difficult and, more important, may not allow the chemical reactions that bind the hazardous constituents to be fully completed. EPA evaluates the amount of stabilizing agent, water, and other additivesused in the stabilizationprocessto ensurethatsufficientstabilizing materials areaddedto thewaste to effectivelyi11111obilize the**~aste**constituents ofconcern. 4.5.2 Degree of Mixing Hhfng is necessary to ensure homogeneous distribution of the waste, stabilizing agent, and additives. Both undermixing and overmixing are undesirable. The fi,rst· condition results in a nonhomogeneous mixture; consequently, areaswill existwithinthewastewherewasteparticlesare neither chemicallybondedto the stabilizingagent norphysicallyheldwithinthelattice structure. Overmix1ng, on the other hand, may inhibit gel formation and ion adsorption in some stabilization systems. Optimal mixing conditions are usually determined through laboratory tests. The quantifiable degree of mixing is a camp1 ex assessment that inc1 udes, among other factors, the amount of energy supplied, the length of time the material is mixed, and the related turbulence

f:\document\15254031.01.012 107effects ofthe specific size and shape of the mix tank or vessel. The degree of mixing**i~ ~eyond_the**  scope of simple measurement. EPA, however, evaluates the degree of**mix~iig ~ual** itatively by considering whether mixing is provided and whether the type of mixing device is one that could be expected to achieve homogeneous distribution of the waste, stabilizing agent, and additives. 

### 4.5.3 Residence Time The residence time or duration ofcuring ensures that the waste particles have had sufficient time in which to incorporate into lattice structures and/or form stable chemical bonds. The time necessary for complete stabnization depends on the waste and the stabilization process used. The performance ofthe stabilized waste (i.e., the levels ofwaste constituents in the leachate) will be highly dependent on whether complete stabilization has occurred. Typical residence times range from 7 to 28 days. EPA monitors the residence time to ensure that sufficient time is provided to effectively stabilize the waste. 

### 4.5.4 StabilizationTemperature and Humidity Higher temperatures and lower humidity increase the rate of curing by increasing the rate of evaporation ofwater from the stabilizationmixtures. If temperatures are too high, however, the evaporation rate can be excessive, resul.ting in too littlewaterbeing availableforcompletion ofthe stabilization ·reaction. EPAmonitors the stabilizationtemperature andhumidity continuously,

ifpossible, to ensure that the system is operating at the appropriate design conditions and to diagnose operational problems. 

### 4.5.5 For. of the Metal 

### Compound Ideally, the waste metal to be stabilized should be in its least soluble state to reduce leaching ofthe stabilizedwaste. Pretreatment such as chemical oxidation or chemical reduction may be required to oxidize or reduce the metal to a state of lower solubility. Additionally, the solubility ofthe metal can

f:\docuaent\152S4031.01.012 108be decreased by precipitating it with an appropriate compound. For example, ferric arsenatejs less soluble and less leachable than calcium arsenate. EPA can monitor sctJubility of the metal by performing a standard leaching test (Extraction Procedure (EP) orToxicityCharacteristicLeaching Procedure (TCLP))

.

.**~** 

## -..

f:\document\15254031.01.012 1094.6 References Ajax Floor Prod&cts Corp. n.d. Product literature: technical data sheets, Hazardous Waste Disposal System. P.O. Box 161, Great Meadows, N.J. 07838. Austin, G.T. 1984. Shreve,s chemical process industries. 5th ed. New York: McGraw-Hill Book Co. Bishop, P.L., Ransom, S.B., and Grass, D.L. 1983. Fixation mechanisms in solidification/stabilization of inorganic hazardous wastes. In**.;,.:Pr:..::o::..:::c~e::.:ed~i~n~g s=--=o:.:..f~t:.:.h:..:e~3~8;.;::t~h~l:.:.n~d=u** =s**t:::.:-r~i**.-a 1"---'=W=a**s::;-:t;.::e~Co~n:.:..;f** e:.:.r..::.e.:.:.;n c=e, May 10-12, 1983, at Purdue University, West Lafayette, Indiana. Conner, J.R. 1986. Fixation and solidification of wastes. Chemical Engineering. Nov. 10, 1986. Cullinane, M.J., Jr., Jones, L.W., and Malone, P.G. 1986. Handbook for stabilization/solidification of hazardous waste. U.S. Army Engineer Waterways Experiment Station. EPA report no. 540/2-86/001. Cincinnati, Ohio: U.S. Environmental Protection Agency. Electric Power Research Institute. 1980. FGO sludgedisposal. annual. 2nd ed. Prepared by Michael Baker Jr., Inc. EPRI CS-1515 Project 1685-1. Palo Alto, Calif.: Electric Power Research Institute. Malone, P.G., Jones, L.W., and Burles, J.P. Application of solidification/ stabilization technology to electroplating wastes. Office of Water and Waste Management. SW-873. Washington, D.C.: U.S. Environmental Protection Agency. Mishuck, E., Taylor, D.R., Telles, R., and Lubowitz, H. 1984. Encapsulation/ fixation CE/Fl mechanisms. Report no. DRXTH-TE-CR-84298. Prepared by S-Cubed under Contract no. DAAK11-81-C-0164. Pojaselt RB. 1979. Solid-waste disposal: solidification. Chemical Engineering 86(17): 141-145. USEPA. 1980. U.S. Environmental Protection Agency. U.S. Army Engineer Waterways· Experiment Station. Guide to the disposal of chemically stabilized and solidified waste.**Pre~ared forMERL/0~**  under Interagency Agreement No. EPA-IAG-04-0569. PB 81 181 505. Cincinnati, Ohio: U.S. Environmental Protection Agency.

f:\document\15254031.01.012 110

### 5. VITRIFICATION 5.1 App'kicability Vitrifkation technologies include glass and shg vitrification and elevated-temperature calcination processes. Vitrification processes involve dissolving the waste at high temperatures into glass or a glasslike matrix. Calcination involves merely heating the material at high temperatures. High-temperature vitrification is applicable to nonwastewaters containing arsenic* or other characteristic toxic metal constituents that are relatively**~onvolatile** at the temperature: at which the process is operated. This technology isa 1 so applicable tomanywastes containingorganometa11i ccompounds, where the organic portion of the compound can be completely oxidized at process-operating conditions. Afterburners may be required to convert unburned organics to carbon dioxide. The process is not generally applicable to volatile metallic compounds or to wastes containing high levels of constituents that will interfere with the vitrificationprocess. High levels ofchlorides and other halogen salts should be avoided in the**~~stes** being processed becausethey interferewith glassmaking processes and cause corrosion problems. Calcination processes are applicable to inorganic wastes that do not contain volatile constituents.

*Volatile arseniccompounds areusuallyconverted tononvolatile arsenate salts

such as calcium arsenate prior to use ofthisprocess. In ordinary glass- making, arsenic volatilization problems are minimized by adding arsenic as arsenate salts.

f:\dccument\15254031.01.013 111 

# ,

### 5.2 Underlying Principles ofOperation The basic\>rinciples ofoperation for vitrification technologies dependon the technology used. In glass and slag vitrification processes, the waste constituents become chemically bonded inside aglasslike matrix in many cases. In all instances, the waste becomes surrounded by aglass matrix that immobilizes the waste constituents and retards or prevents their reintroduction into the environment. Arsenates are converted to silicoarsenates, and other metals are converted to silicates. High-temperature calcination processes remove water ofhydration from the toxicmetal-bearing solids, converthydroxides presentto oxides, and sinterthe material, reducing its surface area to aminimum. Conversion of hydroxides to oxides and minimization ofavailable surface area retard surface reactions that would reintroduce the material into the environment. Calcination may also be accompanied by chemical reaction ifamaterial such as lime is blended with the waste before it is heated. For example, lime will react with arsenic oxides at higher temperatures to form calcium arsenate, and this material will then be sintered at elevated temperatures. Brief descriptions of each of the high-temperature processes are given in the following subsections. 5.2.1 Glass Vitr1f1cat1on
In the glass vitrification process, the waste and normal glassmaking constituents are first blended together and then fed to aglassmaking furnace, where the mixed feed materials are introduced into apool ofmolten glass. The feed materials then react with each other to form additional molten glass, in which particlesofthewaste material become dissolved or suspended. The molten glass is subsequently cooled. As itcools, itsolidifies into asolid mass that contains the dissolved and/or suspended waste constituents. Entrapment and chemical bor.ding within the glass matrix render the waste constituents unavailable for reaction.**f:\document\152540~1.01.013** 112 

# , I



### c5.2.2 Slag Vitrification Slag**vit~ification** differs from glass vitrificatior. in that finelyground slag from metal-refining**processe~** and waste are premixed and fed to the same type offurnace as that used for glassmaking. The slag liquifies at the process temperature {1100 to 1200"C), and the waste constituents either dissol'le or become suspended ir. the molten slag. Subsequent cooling ofthe slag causes it to solidify, trapping the waste inside a glasslike matrix and rendering it unavailable for chemical reaction or migration into the environment. 5.2.3 High-Temperature Calcination
In the high-tr:mperature calcination process, the waste is heated in a furnace or kiln to between 400 and

## aoo·c. In some instances, the waste may be blended**wi~h** lime prior.to heating. In those cases, chemical reaction mayoccur during the calcining process. Water present as either free water or water of hydration is evaporated, and hydroxides present are thermally decomposed to the corresponding oxides and water vapor. At the higher temperatures, the surface area of the dehydrated material is decreased by thermal sintering. Conversion of hydroxides to oxides and substant1a1 1 asses of surface area render the material less reactive in the environment and lower the leachability of characteristic toxic metals present. In general, the higher the calcination**temp~ratures** used, the- more camp1 ete the 1**os~** of water and the greater the -accompanying loss of surface area, resulting in lower leachability potential.

5.3 Description ofVitrification Processes This chapter discusses three types of high-temperature stabilization processes, which differ considerably from each other. Individual process descriptions are given in the following subsections.

f:\aocument\15ZS4031.01.013 1135.3.1 Glass Vitrification Soda ash,tlime, silica, boron oxide, andotherglassmakingconstituents are first blended with the waste to be treated. The amount of waste added to the blend is dependent on the waste composition. Different metal oxides have differing solubility limits in glass matrices. The blended waste and glass raw material mixture is then fed to a conventional, heated glass electric furnace. The introducedmaterial typically is added through aport atthe top ofthe furnace and falls into apool ofmolten glass. The glass constituents dissolve in the molten glass and form additional glass. Molten glass is periodically withdrawn from the bottom of the furnace and cooled. This material then solidifies on cooling into solidblocks ofglasslikematerial. Organics present in the feed mixture undergo combustion at the normal operating temperatures of 1100 to 140o•c and are fully oxidized to carbon dioxide and water vapor. The top ofthe furnace isnormally cooled so that volatilematerials, such I as arsenic oxides, that are present in the feed mixtures can condense on the cooled surface and fall back into the melt, where they can undergo chemical reaction to form silicoarsenates involved in the glassmaking process. Host of the arsenic used in making glass by this method is present as salts such as calcium arsenate. This approach was introduced into the glass industry to minimize fugitive arsenic losses. Gases, such as carbon dioxide, that are liberated during the glassmaking process exitthe**furna~e** through the top and are generally wet-scrubbed priorto reentering the atmosphere. 

### 5.3.2 Slag Y1tr1f1cat1on The slag vitrificationprocess isbasically similarto glass vitrification except that granulated slag, instead ofthe normal glassmaking constituents, is blendedwith the waste for feed to the system. Apool ofliquid slag is present

f:\dacument\15254031.01.013 114 

# 1in the furnace, and the blended raw material mix typically is introduced at the top of tne**furna~e** and falls into this molten slag. The granulated slag-waste mixture liquiftes to form additional slag. Slag is periodically withdrawn from the slag pool and cooled into blocks. The type offurnace used for glass vitrificationcan also be used for slag vitrification. The operating parameters are similar. 5.3.3 High-Temperature Calcination
In the high-temperature calcination process, wastes containing inorganic compounds are fed to ovens or kilns, where they are heated to high temperatures (i.e., 500 to 9oo·c) to drive offwater ofhydration and to convert hydroxides present to the corresponding oxides. This process is primarily applicable to inorganic wastes that contain nonvolatile constituents. The waste is heated in the oven or kiln to the desired temperature, moisture and water of hydration are driven off; and, at the 500 to goo·c temperature range, hydroxides decompose to the corresponding oxides and water vapor. The high-temperature treatment also significantly reduces the surface areas ofthe oxides formed by sintering, thereby reducing the reactivity ofthe material. Afterthewaste material has beencalcined at an elevated temperature, it is. withdrawn from the oven or kiln, cooled, and either land disposed or *forwarded to another process, such as stabilization, for further treatment. 5.4 Waste Characteristics Affecting Performance (WCAPsl The waste characteristics affecting perfonnance are different for the two vitrification processes and the calcination process. Accordingly, they are discussed separately in the following subsections.

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# ,5.4.1 Waste Characteristics Affecting Performance (WCAPs}
In determning whether vitrification will achieve the same level of performance on an untested waste as on a previously tested waste, and whether performance levels can be transferred, EPA examines the following waste characteristics that affect performance of the vitrification processes: (a) organic content of the waste, (b) concentrations of specific metal ions in the waste, (c) concentrations ofcompounds in the waste that interfere with the glassmaking process, and (d) moisture content of the waste.
5.4.1.1 Organic Content
Atprocess operatingtemperatures (1100tv**l~ijO'C),** organics are combusted to carbon dioxide, water, and other gaseous products. The combustion process liberates heat, reducing the external energy requirements for the process. The amount of heat liberated by combustion is afunction ofthe Btu value ofthe waste. The Btu content merely changes the energy input needs for the process and does not affectwaste treatment performance. Theamount ofmaterial that may not oxidize completely is afunction ofthe organic halogen content of the waste. The presence of these halogenated organics does impact process performance because sodiumchloride has alow solubility in glass. The presence of high chlorides results in a porous glass that 1s undesirable. If the balogenated organiccontent ofan untested waste is the sameas or less than that present in an already tested waste, the system should achieve the same performance for organic.destruction.
5.4.1.2 Concentrations of Specific Metal Ions
Mostmetal oxides have solubilitylimits in glassmatrices. Hence, their concentrationdetermines the amountofglass-formingmaterialsorslagwithwhich they must be reacted in this process to generate a nonleaching slag or glass. The solubility limits ofmost common metal oxides and salts in glass are found

f:\document\15254031.01.013 116 

# ,in the Handbook of Glass Manufacture and other treatises on glass production. Oxides far which_extensive solubility information is available are alumina, antimony oxide,_arsenic oxides, barium oxide, cadmium oxide, chromium oxides, copper oxides, cobaltoxides, iron oxides, lead oxides, manganese oxides, nickel oxides, selenium oxides, tin oxides, and zinc oxides. Analysis for individual metal concentrations in the waste can be performed according to EPA-approved methods. Ifthe concentrations ofspecificmetals in an untested waste are less than those in atestedwaste, then the same ratio of slag or glass raw materials to waste may be used for vitrification purposes. If, however, the concentration ofmetal is greater than that in the tested waste, adifferent formulation must be used.
5.4.1.3 Concentrations of Deleterious Materials Some waste constituents, such as chlorides, fluorides, and sulfates, interfere with the vitrification process if they are present at high levels. These saltshave 1imited solubilities in glass; therefore, when they are present, additional glass-fanning raw materials must be added to compensate for their presence. The solubilitylimits of various salts in glasses are discussed in references on glass production such as the Handbook of Glass Manufacture. Generally, iftheconcentrations ofsuch materials in an untestedwaste are lower than those in atestedwaste, then the same ratio ofglass-forming constituents to**wa~te** may be used. Reducing agents such as carbon or ferrous salts reduce arsenates and selenatesto lowervalence compounds thataremore volatile. These compounds should not be present in significant quantities in arsenic- or selenium-containing wa$tes to be vitrified.
5.4.1.4 

### Moisture Content Materials fed to the vitrificationprocess shouldbe reasonablydry (i.e., contain less than5 percentfree moisture). Ifawaste has excess moisture above this level, it should be thermally dried before it is blended with glass-forming

f:\document\15254031.01.013 117 1



## .

### materials; otherwise, itmay react violentlywhen introduced to the molten glass or slag pool. t. 

### 5.4.2 Waste Characteristics Affecting Performance ofHigh-Temperature Calcination
In determining whether high-temperature calcination will achieve the same level of performance on an untested waste as on a previously tested waste and whether performance levels can be transferred, EPA examines the following waste characteristicsthat impact the performance ofthe high-temperature calcination process: (a) the organic content ofthe waste, (b) the moisture content ofthe waste, and (c) the inorganic composition ofthewaste. Thesecharacteristiesare discussed below. 5.4.2.1 Organic Content Calcination temperatures normally used are too low to initiatecombustion of some types of organic compounds. However, they are high enough to cause volatilizationoforganics, which have to beremoved fromprocess off-gases. For these reasons, the presence ofsignificant levels of**organi~s** 

### is undesirable but can be handledwith appropriate airpollution controls. Organics, perse, do not interfere with the conversion of oxides to hydroxides or with sintering processes. Afterburners may be required on vitrification units managing high9rgantc-content wastes to ensure complete combustion ofthe organics present. 5.4.2.2 Moisture Content Excesswaterthathas to beremoved fromthe wastebyheating increases the amount of time needed to bring the waste to the calcination temperature. For this reason, wastes with highmoisture content should be dewatered priorto the use ofthis process.**f:\doc~t\l5ZS403l.Ol.OlJ** 1185.4.2.3**Inorg~nic** Composition Calcinatid'n temperatures are normally selected based on the temperatures at which hydroxides are thermally decomposed-to the corresponding oxides and water vapor. To select an optimum operating temperature, one should know the approximate composition of the waste. Afew toxic metal oxides have fairly low volatilizationtemperatures. Arsenicoxide,_-seleniumdioxide, andmercuric oxide all volatilizebelow

## soo·c. High-temperature calcination should not be used for wastes that contain these volatile constituents unless the wastes are blended with materials such as lime, which will react with the constituents before they can_vaporize. Nonvolatile arseniccompounds such as ferric and calciumarsenates can be calcined without concern for vaporization ofmaterial.**-~** 5.5 Design and Operating Parametarj ·' The design and operating parameters for the vitrification processes are similar t: each other, but differ considerably from those for high-temperature calcination. The**foilo~ing** subsections discuss these two technologies separately. 5.5.1 Design and Operating**Par~ters** for Vitrification Processes
.In assessing**th~- effectivenuo-~e**  design and operation of a vitrificationsystem, EPAexamines**t~~·ingparameters:** (a) thecomposition**~** ofthe vitrifying agent, (b) the oper&l-fosli&emperature, (c) the residence time, and (d) the vitrificat}on.furnace design.

--- 5.5.1.1 Composition ofthe VitrifYing Agent Slag and various glassmaking for"'IIIUlaiions are used as vitrifying agents. The choice ofthe vitrifying agent isdetarmined by the solubilityofthe waste constituents to be vitrified. Different inorganic oxides have differing solubilities in various glass matrices.

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# 1

;

### For slags, the presence ofcarbon or other reducing agents isundesirable when arsenic-bearing orselenium-bearingwastes are vitrified. Carbon or ferrous salts in the sl•g reduce arsenates in the waste to arsenic trioxide, which has a low volatilization temperature. In a similar manner, these same reducing agents reduce selenates to elemental selenium, which also has a low volatilization temperature. When slags are used for vitrifying arsenic-bearing andselenium-bearingwastes, EPAmonitorsthe compositionofthegranulatedslags to ensure that they do not contain significant concentrations of carbon or ferrous salts.
In glass vitrification, various glassmaking formulations can be used. EPA examines the proposed formulations to ensure that the toxic metal ion concentrations ofthe final productdo not exceed solubility limits. Hence, EPA examines the material balances based on waste composition and glassmaking additives**a~d**

### thepublished solubilitylimits formetal oxides in variQUS glasses to ensurethat thevitrifiedproduct is indeed aglass containing thesolubinzed toxic waste constituents. 5.5.1.2 Operating Temperatura Vitrification furnaces are normally operated in the 1100 

### to 1400'C 

### range. The exact operating temperature is usually selected based on the desired composition of the final product. Furnaces are normally equipped with automatic temperature control systems._EEA examines the basis of choice for operating temperatures and the nature andphysical condition ofthe tenperaturemonitoring and control equipment 

### to ensure that the system is being properly operated. 5.5.1.3 

### Residence Till8 Sufficienttime must be allowed for the materials added to glass furnaces to reach operating temperatures and then undergo the chemical reactions needed to produce glasses. Residence times are normally on the order of 1to 2hours for processes operated at 1100 

### to 1200'C. 

### For glasses or slags requiring

f:\docur.ent\15254031.01.013 120 

# ,

### slightly higher temperatures, slightly longer residence times are usually selected.· EPA 

### examines the basis for the facility's choice of residence times to ensure that the system is well operated.
5.5.1.4 

### Vitrification Furnace Design Vitrificationfurnaces normally incorporatethe following design features:

• Withdrawal ofthe product in liquid form from the base of the furnace.

• Maintenance of a liquid pool ofproduct in the furnace.

• Addition ofproduct constituent mix at the top of the furnace.

• Design of the top area of the furnace in amanner that allows for cooling ofthisarea. (This is important because volatileconstituents ofthe input feed may vaporize from the melt. The cool top area allows these constituents to condense and fall back into the melt.)

• Presence and proper operation ofan a1r emissions control afterburner and scrubbing systemto manage vent gas emissions from the system such as volatilized noncombusted organics and hydrogen chloridevapors from combustion of any chlorinated organics present.

EPAexamines the**furnace~ t~** **b~** 

### 11sedforwaste·vitriffcat"ian·taensurethat the design features mentioned above are present since they are important for proper operation ofthe systems.

f:**\doc~~~~e~~t\15254031.01.**013 1215.5.2 Design and Operating Parameters for High-Temperature Calcination Systems
t In assessing the effectiveness of the design and operation of a high-temperature calcination process, EPA examines the following parameters: (a) the operating temperature, (b) the residence time, and (c} the air emission control units in place on the ovens or kilns used. 5.5.2.1 Operating Temperature Calcination temperatures offrom 500 to 900"C have been used in industry. Thecalcinationtemperature selected isgenerally atemperature abovewhichmetal hydroxides present will decompose to the corresponding oxides. Data on decomposition temperatures of some metal hydroxides are given in Table 2. The temperature chosen isnormally high enough to causeextensive sintering (surface area loss) of the oxides formed, while at the same time not volatilizing these materials. EPA examines the technical basis for selection of the calcining temperature to determine whether the system is properly operated. EPA also examines the temperature monitoring and control systems in place to determine whether they are properly operated and reliable. Table 2 Metal Hydroxide Decomposition Temperatures

Metal hydroxide
Cadmium hydroxide Chromic acid Lead hydroxide Nickel hydroxide Zinc hydroxide

Source: Weast 1977.

f:\document\15ZS4031.01.013 Decomposition temperature ("C)

122 300 400 145 230 125 

# 1

I 1 

### l5.5.2.2 Residence Time**Calcinatie~** is generally a batch process, and sufficient time must be allowed far samples to be brought to the operating temperature. Residence times ofseveral hours are normally used to minimize the effects ofheat-up time. EPA examines the technical basis for the choice of residence time to ensure that sufficient heating at the required temperature is allowed to complete the dehydration and sintering processes. Residence time is a function of the time needed to bring the calcination furnace or kiln to the desired temperature and the time needed to camplete the dehydration and sintering processes at tt:e selected temperature. 5.5.2.3 Air Emission Control Systems During the calcination process, watervapor is driven offas it is formed by the decomposition of hydroxides present in the waste. These hot gases exit the calcination furnace or kiln as they are·formed. Some particulates from the waste material, as well as organics present in the waste, may become entrained in these vent gases. Therefore, for air pollution control purposes, the calcinationunits must beequippedwithwet ordryparticulatecoliection systems that are properly designed and operated. If wastes containing organics are processed by high-temperature calcination, the calcination furnaces need to be equipP.ed with afterburners to combust organic vapors emitted. EPA examines the aesign basis, physical condition, and maintenance ofthese air emission control units to determine whether they are properlydesigned, maintained, and operated. EPA also examines the system of management in use for·bandling and subsequent treatmentofthecollectedparticulatesto ensure thatthese finely divided waste particles are properly managed.

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# 15.6 References Penberthy, L. t 1984. Electric melting of glass. In Handbook of glass manufacture. Vol. I, pp. 387-399. New York: Ashlee Publishing Co. Penberthy, 

### L. 1981. Method and apparatus for converting hazardous material to a relatively harmless condition. U.S. Patent 4299.611. November 10, 1981. Steitz, W.R., Hibscher, C.W., and Mattocks, G.R. 1984. Electric melting of glass. In Handbook of glass manufacture. Vol. I, pp. 400-428. New York: Ashlee Publishing Co. Tooley, F.V. 1984. Rawmaterials. In Handbook ofglass manufacture. Vol. I, pp. 19-56. New York: Ashlee Publishing Co. Twidwell, L.G., and Mehta, A.K. 1985. Disposal of arsenic bearing copper smelter flue dust. In Nuclear and chemical wastemanagement. Vol. 5, pp. 297-303. Butte, Mont.: Montana College of Mineral Science and Technology. Weast, R.C., ed. 1978. Handbook ofchemistry and ohys1cs. 58th ed. Cleveland, Ohio: CRC Press.

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# 1(



### II. REMOVAL TECHNOLOGIES A. RECOVERY, REUSE*, AND/OR SEPARATION TECHNOLOGIES FOR ORGANICS

*The Agency encourages pollution prevention efforts such as those In recovery and reuse practices (see 40 CFR Part 261.1 for the definition of reus•. reclal1111tlon, and recycltng). He-ever, the Agency recognizes that currently there Is some confusion over the definition of what constitutes 1 solid waste that has led to the proltferatlon of so-called "shul**recycltng~** by sane facilities. 5114111 recycltng are tllegitiiMte waste 1111nagement practices wharelly hazardous wast• 1111terlah having no saleabl• value (no 1114rket for reuse) are claimed to be recycled/reused tn order to escape the stringent RCR.A hazardous waste definitions.

### 1. CARBON ADSORPTION
1.1 

### AppMcability Carbon adsorption is a treatment technology used to treat wastewaters containing dissolved organics at concentrations less than about 5percent and, to alesser extent, dissolved metal and other inorganic contaminants. The most effective metals removal is achieved with metal complexes. Thetwo most colll!lon carbon adsorption processes are the granular activated carbon (GAC), which is used in packed beds, and the powdered activated carbon (PAC), which is added loosely to wastewater. This section discusses the GAC process; the 

### PAC process is discussed in Section 

### I.A.1 of this document, i.e., Biological Treatment. 1.2 

### Underlying Principles ofOperation Thebasicprincipleofoperation forcarbon adsorption is the mass transfer and adsorption of a molecule from a liquid or gas onto a solid surface. Activated carbon is manufactured in such away as to produce extremely porous carbon particleswhose internal surface area is very large (500 

### to 1,400 

### square meters per gramofcarbon). This porous structure attracts and holds (adsorbs)**organi~** 

### molecules as well as certain metal and inorganic molecules. Adsorption occurs because (a) the contaminant has alow solubility in the waste, (b) the contaminant has a greater affin1

## trror the carbon than for the waste, or (c) acombination ofthe two. The amount ofcontaminants that can be adsorbed by activated carbon ranges from 0.10 

### to 0.15 

### gram per gram of carbon.
1.3 

### Description ofCarbon Adsorption Process
In GAC systems, the carbon is packed 1

### n a co1 

### umn and the wastewater f

### s passed through the carbon bed(s). The flow can be eitherdown or up through the

f:\document\15ZS4031.01.014 125 

# 1vertical column(s). Figure 13 shows two carbon adsorption systems. In the carbon adsorption_process, the wastewater is passed through a**stat~onary** bed of carbon. The**~ntaminants** in the wastewater are adsorbed most rapidly and effectivelyby the upper layers ofcarbonduring the initial stages ofoperation. These upper layers are in contact with the wastewater at its highest concentrations ofcontaminants. The small amounts ofthe contaminants that are oot adsorbed in the first few layersofthe activated carbon bed are removed from solution in the lower or downstreamportion ofthe bed. Initially, none of the contaminants escapes from the carbon bed.
As the wastewater flows down the column (or the location in the column where the majority of adsorption is occurring) and the adsorption capacity is reached in the top layers, the adsorption zone moves down the column. As the adsorption zone approaches the end ofthe carbon bed, the concentration in the effluent rapidly approaches the influent concentration. This point in the process is referred to as breakthrough. Abreakthrough curve (Figure 14) shows the plot of the ratio of effluent to influent concentrations versus time of process operation. At breakthrough, the adsorptive capacityofthe carbon bed !s exhausted, and little additional removal of contaminants occurs. Treated wastewater is then either treated further in another carbon adsorption column, if necessary, or disposed of. Once the carbon bed is spent andcanno 1 angerremove contaminants from the waste, it istaken off-line. The activated carbon is then eitherregenerated by thermal or chemical methods for further use or treated by incineration and disposed of. If carbon adsorption is used to·treat very taxic or hazardous materials, the spent carbon usually is incinerated and disposed ofdirectly. Regeneration is accomplished thermally by heating the carbon to a temperature (between 1,500 and 1,700•f) at which most of the adsorbed contaminants are volatilized and destroyed but which is not high enough to burn the surface ofthe carbon. About 4 to 9 percent ofthe carbon is lost in this process. Steam can also be used to regenerate carbon by volatilizing adsorbed

f:\document\15254031.01.014 126WASTEWATER INFLUENt

DOWHFLOW SERIES ARRAHOEUEHT TREATED EFFLUENT .ASTEWATER lO INFLUENT DISPOSAL TflEATED**EFFLUE~T** TO DISPOSAL

UPFLOW SERIES ARRANGEMENT

Figure 13 Carbon Adsorption Systems



# -·-

# - N DC) WASTEWATER INFLUENT

ADSORPTION

# I ZONE Co 

# l

II 

### c EFFLUENT Co 

# l

[XXX1'**~** c 

### co co 

# .l l

,l1\.**~** JX)j 'X IXlC :lC**~ t.Dr------------------------y---------,~~.r**  RATIO OF EFFLUENT TO INfLUENT COHCENTRATIOH8 0.1 WITH RESPECT TO TIME

TIME

Figure 14 Plot of Breakthrough Curve "' ,, '·'**.·~** !: H



# .....

### organics for subsequent condensation, recovery, and reuse or for treatment and disposal. ·Chemica] regeneration involves the use ofan acid, alkali, ororganic solvent to reditsolve contaminants for subsequent recovery and reuse or for further treatment and disposal. There is a loss of performance with each regeneration of spent carbon because metals (such as calcium, magnesium, and fran) plug small pores in the carbon and prevent some organic contaminants from being desorbed at the thermal regeneration temperature. In each thermal regeneration process, some carbon becomes spent, requiring treatment and disposal. As aresult, makeup carbon has to be added to the regenerated carbon being placed back in service. The n!.!mber oftimes thatthe carbon r.anbe regenerated is detennined by the extentofitsphysical erosion andthe loss ofitsadsorptive capacity. Isotherm tests can be performed on the rege!'lerated carbon to determine adsorptive capacity; such tests can thus aid in predicting the number oftimes the carbon can be regenerated. 1.4 Waste Characteristics Affecting Performance (WCAPsl
In determining whether carbon adsorption will achieve the same level of performance on an untested waste as itachieved on apreviouslytestedwaste and whetherperformance levels can be transferred, EPA examines the following waste**charac~eristics:** 

### (a) thewa:;tetype andconcentrationofadsorbablecontaminants and (b) the concentrations of suspended solids·and oil and grease. 1.4.1 Wasta Type and Concentration 

### ofAdsorbable Contaminants The concentration ofadsorbable**cont~inants** 

### is ameasure ofthe fraction of the wastewater constituents that can be expected to be adsorbed by acarbon adsorption column. Concentrations of organics in the wastewater greater than about 5 percent result in excessive activated carbon consumption requiring frequent regeneration. At the higher organic concentrations other treatment

f:\document\15254031.01.014 129 

# ,

### technologies, such aswet airoxidation, solventextraction, orincineration, may be more**~propriate.** t 

### Although all organics can be adsorbed to some dearee, activatedcarbon has agreater affinity for aromatic than for aliphatic compounds and for nonpolar than for polar compounds. If the type and concentration of adsorbable contaminants in an untested waste are significantly less adsorbable and higher, respectively, than in the tested waste, the system may not achieve the same performance. 1.4.2 Concentrations of Suspended Solids and Oil and Grease Suspended solids and oil andgrease can reduce theeffectiveness ofcarbon adsorption by clogging and coating the pores, as well as by competing for adsorption sites, thereby interfering with the treatment of contaminants of concern. EPA 

### has information showing that this treatment interference occurs with suspended solids at levels greater than about 50 mg/1 and with oil and grease at above 10 

### mg/1. 1.5 Design and Operating Parameters
In assessing the effectiveness of the design and operation of a carbon adsorption system, EPAexamines the following parameters: (a) the type and pore size of the carbon particles, (b) the adsorption temperature, (c) the pH, and (d) the hydraulic loading rate. For many hazardous organic constituents, analytical methods are not available orthe constituent cannot be analyzed in the wastematrix. Therefore, it would nonaally be impossible to measure the effectiveness of the carbon adsorption treatment system. In these cases EPA tries to identify measurable parameters or canstituents that wauld act as surrogates in order to verify treatment.

f:\document\15254031.01.01• 130 

# ,

### For organic constituents, each compound contains ameasurable amount of total organic carbon (TOC). Removal ofTOC in the carbon adsorption treatment

- 

### system will inc¥_cate removal of organic constituents. Hence, 

## roc analysis is likely to be an adequate surrogate analysis where the specific organic constituent cannot be measured. However, TOC analysis may not be able to adequately detect treatment of specific organics in matrices that are heavily organic-laden (i.e., the 

## roc analysis may not be sensitive enough to detect changes at the milligrams/liter (mg/1) level in matrices where total organic concentrations are hundreds or thousands ofmg/1). In these cases, other surrogateparameters should be sought. For example, if a specific analyzable constituent is expected to be treated as well as the unanalyzable constituent, the analyzable constituent concentration should be monitored as a surrogate. 1.5.1 Type and Pore Size ofCarbon Particles Activated carbon is made from avarietyof substances (e.g., coal, wood), ground tomany different sizes, and manufacturedwith anumberofd1fferent pore sizes. The pore size detenu1nes the surface area available for adsorption and, hence, the carbon's adsorptive capacity. The type and-pore size of carbon particles exhibit different adsorptive capacities for different contaminants. Another property that·;s.

### important in assessing the effectiveness of carbon particles is the iodine.number; this value is an indicator of the adsorptive capacityfor**low-molecular-weight-organics~** 

### taboratory benchtesting isused to determine themost effective type and pore sizeof·carbon particles for treating particular wastewaters. EPA examines the type and pore size of the carbon particles used to ensure that effective adsorption is achieved. 1.5.2 Adsorption Ta.parature As the temperature increases, the solubilityofthe contaminants generally increases as well, which results in less effective adsorption. EPAmonitors the

f:\document\15254031.01.014 131temperature continuously, ifpossible, to ensure that the system isoperating at the appropriate**d~sign** condition and to diagnose operational problems. 1.5.3 pH The pH impacts both the solubility of the various contaminants and the potential for chemical bonding to occur. EPA monitors the pH continuously, if possible, to ensure that the system is operating at the appropriate design**condition~** and to diagnose operational problems. 1.5.4 Hydraulic Loading Rate The amount of time that the waste contaminants are in contact with the carbon particles (i.e., residence time) impacts the extent to which adsorption occurs. Higher residence times generally improve adsorption performance but require 1 anger carbon beds to maintain the same overall throughput. Typical residence times for GAC adsorption systems range from 30 to 100 minutes. For a given size carbon bed, the residence time can be determined by the hydraulic loading rate. Typical hydraulic loading rates for downflow adsorption systems range from 0.5 to 8.0 gal/min-ft2
, while upflow systems typicallyoperate around 15 gal/m1n-ft2• EPA monitors the hydraulic loading rate to ensure that sufficient time is provided to effectively adsorb contaminants.

f:\document\15254031.01.014 132 

# ,1.6 References
Authur D.**Litt'~,** Inc. 1977. Physical, chemical and biological treatment techniques for industrial wastes. Vol. I., pp. 1-1 to 1-18 and 1-37 to 1-41. NTIS, PB275-054. DeJohn, P. B. 1975. Carbon from lignite or coal: Which is better? Chemical Engineering, April 28. Eckenfelder, W.W. Jr., Patoczka, J., and Watkins A. 1985. Wastewater treatment. Chemical Engineering, September 2, 1985. GCA Corp. 1984. Technical assessment of treatment alternatives for wastes containing halogenated organics. Prepared for U.S. Environmental Protection Agency, Contract No. 68-01-6871, pp. 150-160. Metcalf & Eddy, Inc. 1985. Briefing: Technologies applicable to hazardous waste. Prepared for U.S. Environmental Protection Agency, Office of Research and Development, Hazardous Waste Engineering Research Laboratory. Section 2.13. Patterson, J. W. 1985. Industrial wastewater treatment technology, 2nd ed. Stoneham, Mass.: Butterworth Publishers. pp. 329-340. Touhill, Shuckrow & Assoc. 1981. Concentration technologies for hazardous aqueous waste treatment. NTIS, PB81-150583. pp. 53-55. USEPA. 1973. U.S. Environmental Protection Agency. Process design manual for carbon adsorption. NTIS, PB227-157. pp. 3-21 and 53. USEPA. 1982. U.S. Environmental Protection Agency. Development Document for the Porcelain Enameling Point Source Category. pp. 172-241. Washington, 

## 9.c.: U.S. Environmental Protection Agency.



## - USEPA. 1986. U.S. Environmental Protection Agency. Best demonstrated available technoloav CBDATl backaround document for F001-F005 Spent Solvents, Vol. 1, EPA/530-SW-86-056, p. 4-4. Washington, D.C.: U.S. Environmental Protection Agency.·---

-- Versar. 1985 • Versar, Inc. An Overview of Carbon Adsorption. Draft final report prepared for U.S. Environmental Protection Agency, Exposure Evaluation Division, Office ofToxic Substances. Contract No. 68-02-3968, Task No. 58.

f:\document\15254031.01.014 133 

# 1

### 2. DISTILLATION TECHNOLOGIES 2.1 Apqlicability Distillation is athermal treatment technology applicable to thetreatment of wastes containing organics that are volatile enough to be removed by the application of heat. Constituents that are not volatilized may be reused or incinerated as appropriate. The four most co11111on distillation processes are**~atcn** distillation, fractionation, steam stripping, and thin film evaporation. Thermal drying is also included in this section because of its similarity to distillation processes. Thermal drying uses heat to volatilize water from wastes. Batch distillation can be used to treat wastes having a relatively high percentage ofvolatile organics. In general, batch distillation is applied to spent solventwastes where the wastes are highly concentrated in the solvent and yield significant amounts of recoverable· materials upon separation. Batch distillation is particularly applicable forwastes that have both very volatile and very nonvolatile components since the separation of that combination of components is amenable to the relatively unsophisticated batch distillation equipment. Fractionation istypically applied towastes containing greater than about 1 percent organics. It is designed to achieve the highest degree ofdistillate purity of the separated components. Fractionation can be operated to produce multiple product streams for recovery ofmore than one organic constituent from awaste while generatingrelativelysmall amounts ofresidue tobeland disposed. In general, this technology is used where recovery ofmultiple constituents is desired and where the waste contains minimal amounts ofsuspended solids.
Steam stripping is a form ofdistillation applicable to the treatment of wastewaters containing organics that are volatile enough to be removed by the

f:\dacument\15254031.01.015 134application ofheat using steam as the heat source. Typically, steam stripping is applied where_the waste contains less than 1percent volatile organics.
t Thin film evaporation is typically applied to wastes containing greater than 40 percent organics. However, the feed stream to the thin film evaporator must contain low concentrations of suspended solids. Thermal drying is a treatment technology applicable to solid wastes typically having a filterable solids content of approximately 40 percent or greater. Thermal drying removes water and volatile organics from asolid waste through evaporation. Thermal dryers operate in the range of 300 to 700'F and usually have mechanical agitation to improve heat transfer. Use of this technology results in a smaller volume of waste with reduced concentrations of water and volatile organics.
Athermal dryer or •sludge dryer• is an encloseddevice that is typically used to dehydrate sludge. The dryer's input (from wastes and auxiliary fuel} usually does not exceed 1500 Btu per pound ofwastes treated, compared to 3,300 to 19,000 Btu per pound for incineration. 2.2 Underlying Principles ofOperation
The basic principle of operation for distillation processes, i.e., batch distiTlation, fractionation, thin film evaporation, and steam stripping, is the volatilizttion of hazardous components through the application of heat. The components that are**vol~tilized** are then condensed and typically either reused orfurthertreated, usuallyby liquid injection incineration. In thermal drying, the basic principle of operation for drying is the removal of a liquid from a solid wasta by evaporation. This is similar to distillation in that volatilizationoforganicconstituentsalso occurs. However, theprimary purpose ofthermal drying isto volatilizewater. Liquid constituents will vaporize as a result of applied heat. In thermal drying, the rate at which liquid evaporation occurs depends on the thermal conductivity of the solidwaste to be

f:**\doc~~~~ent\15254031.**01.015 135dried and the boiling points of the volatile liquid constituents to be evaporatad. t. An integra1partofthe theory ofthe d isti11ation process is the princip 1 e ofvapor-liquid equilibrium. When aliquidmixture oftwo or more components is heated, the vapor phase present above the liquid phase becomes more concentrated in the more volatile constituents {those having higher vapor pressures). The vapor phase above the liquid phase is then removed and cooled to yield a condensate that is also more concentrated in the more volatile components. The degree of separation of components depends on the relative differences in the vapor pressures of the constituents; the larger the difference in the vapor pressures, the more easily the separation can be accomplished. Ifthe differencebetween the vapor pressures is extremely large, asingle separationcycle orasingle •equilibriumstage• ofvaporization and condensation may achieve a significant separation ofthe constituents. In such cases, batch distillation or thin film evaporation would be used. Typically, batch distillation units and thin film evaporation units contain only one equilibrium stage and are thus limited in the degree of separation by the relative volatilities ofthe constituents. If the difference between the vapor pressures of volatile components is small, then multiple equilibrium stages are needed to achieve effective -separation. In pr.act..ice·, the' raultiple equilibrium stages are obtained by stacking •trays• or placing •packing• into a column. Essentially, each tray represents one equilibrium stage. In a packed steam stripping column or fractionation column, the individual equilibrium stages arenot**discer~~ble,** but thenumberofequivalenttrays canbecalculated frommathematical relationships. The vapor phase from a tray rises to the tray above it, where it condenses; the liquidphase falls tothe traybelow it, where it 1s again heated and separated. The vapor-liquid equilibrium ofthe waste components can be expressed as relative volatility, which is the ratioofthe vapor-to-liquid concentrations of**f:\document\152~031.01.015** 136 

# , Ia constituent divided by the ratio of the vapor-to-liquid concentrations of anJther 'onstitu!nt. The relative volatility is adirect indicator ofthe ease of separation.t_ If the numerical value is 1, then separation is impossible because the constituents have the same concentrations in the vapor and liquid phases. When the relative volatility is 1, the liquid mixture is called an azeotrope. Separation becomes increasingly easier as the value ofthe relative volatility becomes increasingly different from unity. 2.3 Description of Distillation Processes 2.3.1 Batch Distillation
Abatch distillation unit usually consists of a steam-jacketed vessel, a condenser, and aproduct receiver. As the name implies, it is abatch process, not acont!nuous process. Figure 15 is aschematic showing the majorcomponents of a batch distillation unit. The steam jacket provides the heat required to vaporize the volatile constituents in the liquid fraction of the waste. The rising vapor is collected in the condenser, cooled, and condensed. The liquid product stream is then routed to the product receiver.
It is important to note that this technology treats wastes by vaporizing constituents, not destroying them. Accordingly, an integral part of this**tech~ology** is a condensation system to collect the organics, as well as an air -emission control system to collect 

### or destroy those organics that are not

condensed. The cooling load of the condenser is calculated in the design to ensure that the product recovery rate ismaximized and emissions from condenser venting areminimized. The •bottoms,• which are the least volatileconstituents of the waste, are withdrawn from the bottom of the batch still. Because batch distillation isused to remove the volatileorganics

### from wastes, the bottoms are reduced in volatile organic content. However, prior to disposal, the bottoms generallyrequire additional treatment, such as incineration, for residual, less volatile organics.**f:\doc~nt\15254031.01.015** 137 

# ' I {(_

WASTE INFLUENT

___ _

ST1U. BOTTOMS

TD FIEUSI OR INCINIRATION VENT OF NON·CONCENSEC VAPORS TO AIR POUUT10N CONTROL SYSTEM AND/OR THE ATMOSPHERE

"HEATeD JACKET



### Figure 15 Batch Dtst111at1on Systea
138 CONCENSER

PRODUCT RECEIVER

RECOVERED ORGANICS TO REUSE OR FURTHER lliEATMENT2.3.2 Fractionation**Fraction\~ion** is acontinuous process conducted in aunit thatconsists of a reboiler, a column containing stripping and rectification sections, a condenser, and a nreflux" system. Figure 16 is a schematic showing the major components of afractionation unit. The reboiler is adevice that provides the heat required to vaporize the liquid fraction of the waste. It supplies enough heat to maintain the liquid in the column at its boiling point. The stripping and rectifying sections are composed ofaset oftrays in avertical column. The discrete trays may be replaced by loose packing consisting ofplastic, metal, or ceramic geometric shapes that provide surface area for the continuous boiling/condensing that takes place in the column. In the stripping section, vapor rising from the boiler is contacted with the downflowing liquid feed. Through this contact, the constituents with lower boiling points (i.e., those that are more volatile) are concentrated in the vapor. In the rectification section, the vapor rising above the feed tray is contacted with downflowing condensed liquid product (reflux). Through this contact, the vapor is further enriched in the constituents with lower boiling points (i.e., the more volatile constituents}. The rising vapor is collected at the top of the column and condensed in a condenser. The liquid product stream, except for the portion returned to the column as reflux, is then routed to aproduct receiver. The nbottoms," which are the leastvolatile components (i.e., those with thehighest boiling points), are continuously withdrawn from the reboiler. Because the .liquidcomposition varies slightly from one equilibrium stageto the next, it is also possible to withdraw streams of differing quality (sometimes called nfractions•) from**diff~rent** locations throughout the**c~1umn.** This is typically done inrefiningpetroleum, resulting in different grades or •cuts• ofpetroleum products. 

### 2.3.3 Steam Stripping Steam stripping is acontinuous process conducted in a unit that con$ists ofaboiler, astrippingcolumn, acondenser, and acollectiontank, as shown in

f:**\doc~~~~e~~t\1SZ~031.**01.015 139 

# ' IWASTE INFLUENT .



# .. VENT OF NON•CONOENSED VAPORS TO AIR POU.UTlON CONTROL SYSTEM ANO/OR THE ATMOSPHERE

I


# ..\ 

# r-**~_REFLUX ~----** 

### ·~ RECTIFIER SECTION
1f 

# t
STRIPPER SECTION



# -----
... 

# j"

1f**~**) CONDENS



# ,,

_.. ER

PRODUCT RECEIVER

RECOVERED ORGANICS SE TO REU

REBOIL 

# I

..I
RESOILER



### Figure 16 

### Fractionation System

140 

# ' J - BOTTOMS TC REUSE OR INCINERAT10NFigure 17. The boilerprovides the heat required to vaporize the 1iquid fraction of the waste. The stripping column is composed of a set of trays or packing placed in avertical column. The steam stripping process uses multiple equilibrium stages, with the initial waste mixture entering at the top, the uppermost equilibrium stage. The boiler is located beneath the lowermost equilibrium stage, allowing the vapor to move upward in the column, coming into contact with the falling liquid. As the vapor comes into contact with the liquid at each stage, the more volatile**compor.~nts** are removed or "stripped" from the liquid by the vapor phase. The concentration of the emerging vapor is enriched in the more volatile constituents, and the liquidexiting the bottom ofthe boiler ("bottoms"}, which is predominantlywater, contains high concentrations ofthe lower vaporpressure constituents. This effluent from the bottom of the stripper is reduced in organic content but may still require additional treatment such as carbon adsorption orbiological treatment. The steamand organic vapors exiting the top of the column are condensed. As condensed liquids, the organic components are usually immiscible with water. The two immiscible phases are then separated in a product receiver. Organics in the organic phase are typically recovered or disposed of in a liquid injection incinerator, while the aqueous condensate is recycled to the stripper. 2.3.4 Thin Film Evaporation
Thin film evaporation is a continuous process conducted in a unit that typically consists of. a steam-jacketed cylindrical vessel and a condenser. Figure 18 is a schematic showing the major components ofathin film evaporator. The steam-heated surface ofthe cylindrical vessel provides the heat required to vaporize thevolatileconstituents in the waste. The evaporatorwalls are heated from the outside as the feed trickles down the inside walls in a thin film. Unique to this form ofdistillation is the distribution device that spreads the thin film over the heated surface. The feed rate ofwaste iscontrolledto allow the more volatile**~aterial** adequate time to vaporize. The heat transferfrom the

f:\document\15254031.01.015 141 

## . 'lWASiEWATER

_ __, INFl.UENT t. VENT OF NOH•CQNOEHS&D VAPORS TO AIR POU.UT10H C:ONmOL SYSTEM AND/OR THI! A TMCSPHEAI!

STEAM

I OILER -
- CONDENSER

RECOVERED

.___. ORGANICS TO REUSE QR TREAT'MENT

TAUT!t2 EFFt.UENT**1----~-** TO**~ATHER** TAEATl.CEHT AND/OR DISPOSAl.



### Figure 17**Stem~** 

### Stripping**Systa~**

142LIQUID FILM VENT OF NON·CONOENSED VAPORS TO AlA POL.L.UT10N CONTROL. SYSTSM ANCIOA 1ltE ATUOSPHERE 

# t
CONDENSER



# r-..--- HEATED JACKET

BOTTOMS TO '-------..,REUSE OR INCINERATION



### F1gure 18 Thin Film Evaporation Syst81
143 PRODUCT RECeiVER

RECOVERED ORGANICS TO REUSE 

# ,
theatingmedium (steam) to the waste is determinedby their relativetemperatures, the heat transfer:.rate ofthe vessel materials, and the thermal properties ofthe waste stream farming the film. The rising vapor is collected at the top ofthe column, cooled, and condensed in a condenser. The condensed liquid product stream is then routed to aproduct receiver. The "bottoms," which are the least volatile components ofthe waste, are continuously withdrawn from the bottom of the thin film evaporator. Because thin film evaporation is used to remove the volatile organics from wastes, the bottoms are reduced in volatile organic content. However, prior to disposal, the bottoms usually require additional treatment, such as incineration, for residual, less volatile organics. 2.3.5 Thermal Drying
Awide range of batch and continuous dryers is available. One commonly used continuous type isthescrew-flightdryer, themajorcomponents ofwhich are shown in Figure 19. The screw-flight dryer consists of a screw surrounding a hollow shaft enclosed in atrough. Heat transferfluid is heated to temperatures as high as 7so•F and circulated, usually countercurrent to the flow ofwaste, through the hollow shaft. Heat transfers from the shaft to the screw blades, and then into the feed material, causing water and organics to be driven off in a vapor form. The dried cake is discharged from the dryer

.

.The dryer is designed to create good contact between the screw and feed material. The screw h usually equipped with breaker bars to ensure proper shearing**~f** the input materials and to prevent 

### the screw surfaces from fouling

.

.._. -.,: ,· I L**~** 

### .- ....-0...**.~**.....; Vapors emerging frJm this system are managed in one oftwo ways, depending on their composition. If the vapors. contain only water, they are usually directly vented to the atmosphere. However, if the vapors contain volatile organics, theyaregenerallypassed through awater-cooled condensersystem. The recovered organic liquids from the condenser unit are then forwarded to another process for treatment or recovery.

f:**\dac~~~~ent\15Z~031.**01.015 144 

# ,FEED fl IIIIEAIIER BARS**~** ....

# ~ 

# - - Sl£.ALf IN 

# =t

...... SCREWS HOllOW DRIED

..... U1 SHAFT UAlERIAL

Figure 19 Screw Flight Dryer



# ......2.4 Waste**Charact~ristics** Affecting Performance (WCAPs}
In determt_ning whether distillation technologies will achieve the same level of performance on an untested waste as on a previously tested waste and whether performance levels can be transferred, EPA examines the following waste characteristics: (a) thecomponentboiling points, (b) the thermal conductivity, (c) the concentration of volatiles, (d) the concentration of suspended solids, {e) the surface tension, and (f) the oil and grease content. The above-mentioned waste characteristics affecting performance vary for each distillation technology. The WCAPs for each specific distillation process are as follows:

• Batchdistillation: thermal conductivity, componentboilingpoints, and**conc~ntration** of volatiles.

• Fractionation, steam stripping, and thin film evaporation: concentrationofsuspended solids, componentboilingpoints, concentration of volatiles, surface tension, and oil and grease content.

• Thermal drying: thermal conductivity and component boiling points.

2.4.1 Component Bo111ng Points
As noted earlier., the greater the ratio of volatility of the waste constituents, the more easily the separation ofthese constituents can proceed. This ratioiscalledrelativevolatility. EPArecognizes, however, that relative volatilities cannot be measured orcalculated directly for the types ofwastes generally treated by distillation processes because such**••~tes** usually consist ofamyriad ofcomponents, all with different vapor pressure-versus-temperature relationships. However, because the volatility of components is usually inversely proportional to their boiling points (i.e., the higher the boiling

f:\document\1525403l.Ol.Ql5 146 

# , 1 

### ipoint, the lower the volat1l1ty), EPA uses the boiling point ofwaste components as asurrogate**was~e** characteristicfor relative volatility. Ifthe differences in boiling**poin~s** between the more volatile and less volatile constituents are significantly smaller in the untested waste than in the testedwaste, the system may not achieve the same performance and more rigorous operating conditions or other, more applicable treatment technologies may need to b·e considered for treatment of the untested waste. 2.4.2 Thermal Conductivity of the Waste A

majorfactordeterminingwhetheraparticularconstituentwill volatilize is the potential for transferofheat through the waste. Forbatch distillation, heat transfer is accomplished principallyby conduction from the external source of heat (with some convection within the waste). For thermal drying, heat transferis_accomplishedprimarilybyconductionratherthan convection sineethe wastes are usually not liquids. Thermal conductivity is not as critical a consideration with other forms ofdistillationbecause tile wastes are broken up into thin films, which conduct heat relatively rapidly.
Heat flow by conduction isproportional to thetemperature gradient across the material. The proportionality constant, referred to as the thermal conductivity, is apropertyofthe material to be distilled (ordried in the case of**th~rmal** drying). With regard to convection, EPAbelieves that the amount of**~eat** transferred by convection is not**de~endent** on the waste's thermal conductivity. Convection will usually be more a function ofthe system design than of the waste itself (f.e., how well the waste can be mixed during the process). Thermal conductivitymeasurements, aspartofatreatabilitycomparisonfor two differentwastes to be treated by a single batchdistillation unit, are most meaningful when applied to wastes that are homogeneous (i.e., uniform throughout). As wastes exhibit greater degrees of nonhomogeneity, thermal conductivity becomes less accurate in predicting treatability because the

f:\document\1SZ54031.01.015 147 

# lconductivity becomes less accurate in predicting treatability because the measurement**esse~tially** reflects heat flow through regions having the greatest conductivity**('~e.,** the path ofleast resistance) and not heat flow through all parts of the waste. Nevertheless, EPA believes that thermal conductivity may provide the best measure of performance of heat transfer. If the therma1 conductivity ofan untested waste is significantly lowerthan thatofthe tested waste, the system may not achieve the same performance, and other, more applicable treatment technologies may need to be considered for treatment ofthe untested waste. 2.4.3 Concentration of Volatile Components The concentration of volatile components is a measure of the maximum fraction of the waste that can be expected to volatilize during adistillation process. Arelativelylowconcentration ofvolatilecomponents implies thatmost of the waste may become bottoms (i.e., relatively nonvolatile). If the concentration of relatively volatile components in the untested waste is significantly lower than that in the tested waste, the untested system may not perfonn adequately. Hare rigorous operating conditions, such as higher temperatures, higher residence times, etc., may be required to volatilize less volatile components and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatmentofthe ur.tested waste. 2.4.4 Concentration of Suspended Solids
Wastes containing 1 arge amounts of suspended solids--organic or inorganic--may have an adverse effect on distillation treatment systems. For example, in thin film evaporation, large amounts of suspended solids may coat heat transfer surfaces, thereby disturbing the uniform film and inhibiting volatilization of constituents. In fractionation and steam stripping, large amounts of suspended solids may clog column internals and coat heat tranfer surfaces, thereby inhibiting heat transfer and mass transfer of constituents

f:\document\15254031.01.015 148 

# ,between the vapor and 1iqufd phases. Ifthe concentration of suspended solids in the untested**~aste** is significantlyhigher than that in the tested waste, the system may nott_achieve the same performance. Filtration may be required prior to distillation processes to reduce the**concentr~tion** of suspended solids and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment of the untested waste. 2.4.5 Surface Tension The surface tension ofthe waste is ameasure ofthe tendency ofthe waste to foam and to "wet" the heat and mass transfer surfaces. The higher the surface tension of the liquid, the higher its tendency to foam. Also, higher surface tcr.sions wi11 not a 11ow a film of the waste to coat heat and mass transfer surfaces as well as 1 ow surface tensf ons wi11

. The 1 ike11hood of foaming requires special column design or the incorporation of defoaming compounds. Packed columns are usually less susceptible to foaming than are tray columns. Waste with high surface tensions that cannot effectively wet column packing or evaporator walls will not form the thin films that enhance heat and mass transfer. Ifthe surface tension ofthe untested waste is significantlyhigher than that ofthe tested waste, the systemmay not achieve the same performance. Defoaming compounds and/or the use of apacked column may be required to reduce foaming and achieve the same treatment perfonmance, or other, more applicable treatment technologies may need to be considered for treatment of the untested

. -waste.

2.4.6 Concentration of011 and Grease High concentrations of oil and grease may clog steam stripping and fractionation equipment, thereby reducing their effectiveness. In thin film evaporation, high concentrations of oil and grease may result in the waste coating the evaporator walls, preventing a uniform film from forming and inhibiting volatilization ofwaste components. Ifthe concentration ofoil and grease in the untested waste is significantly higher than that in the tested

f:\document\15254031.01-015 149applicable treatment technologies may need to beconsidered for treatment ofthe untested waste. {_ 2.5 Design and Operating Parameters
In assessing the effectivenessofthe design andoperation ofdistillation technologies, EPAmay examine the following parameters: (a) the temperature and pressure, (b) the differential pressure, (c) the liquid and vapor flow rates, (d) the internal column design, (e) the number of separation stages, (f) the residence time, (g) the surface area, and (h) the mechanical system design. The above-mentioned design and operating parameters vary for each distillationtechnology. The design and operating conditions for each specific distillation process are as follows:

• Batch distillation: temperature and pressure, and residence time.

• Fractionation: number of separation stages, liquid and vapor flow rates, temperature and pressure, differential pressure, and internal column design.

e Steam stripping: number of separation stages, liquid and vapor flow rates, temperature and pressure, and**intern~l** column design.

• Thin film evaporation: evaporator surface area, temperature and pressure, resi.dence time, and the speed anddesign ofthe wastedisposal mechanism.

• Thennal**~ryer:** temperature andpressure, residence time, and the design and speed of the screw mechanism.

f:\document\1525403l.Ol.Ol5 150To evaluate the effectiveness of design and operating variables, it is necessary to measurethe concentrations ofthe components to be separated in both the feed syste"\and the process residuals (e.g., overheads and bottoms). For many hazardous organic constituents, analytical methods arenot availableorthe constituent cannot be analyzed in the wastematrix. Therefore, itwould normally be impossible to measure the effectiveness oftreatment ofdistillation systems. In these cases EPA tries to identify measurable parameters orconstituents that would act as surrogates to verify treatment. For organic constituents, each compound contains a measurable amount of total organic carbon (TOC). Removal ofTOC in the distillation treatment system will indicate removal oforganic constituents. Hence, TOC analysis is likely to be an adequate surrogate analysis where the specific organic constituent cannot be measured. However, TOC analysis may not be able to adequately detect treatment of specific organics in matrices that are heavily organic-laden; that is, the TOC analysis may not be sensitive enough to detect changes at the milligrams per liter (mg/1) level in matrices where total organic concentrations are hundreds or thousands of mg/1. In these cases other surrogate parameters should be sought. For example, if a specific analyzable constituent is expected to be treated as well as the unanalyzable constituent, the analyzable constituent concentration might be monitored as a surrogate. 2.5.1 Temperature and Pressure These parameters are integrally related to the vapor-liquid equilibrium conditions. In steam stripping and fractionation, tr.e temperature at any point in the column is an indicator of the constituent concentrations at that point, thus revealing whether the separation ofcomponents is taking place as expected. Overall column pressure influences the boiling point of the liquid at any location in the column. For example, through application ofapartial vacuum to the column, the temperatures required to achieve the desired separation can be

f:\document\15254031.01.015 151reduced because liquids volatilize at lower temperatures when pressures are reduced. ·EPA monitors the temperature and pressure of a steam stripping column and a fractionation column continuously, ifpossible, to ensure that the system is operating at the appropriate design conditions and tc diagnose operational problems.
In thin film evaporation, to achieve the desired volatilization, the evaporatormay be**oper~ted** atpressures below atmospheric (slight vacuum). At vacuum conditions, lower temperatures can be used, requiring less heat input, because boiling points decrease as pressure decreases. EPA monitors the thir. film evaporator temperature as well as the pressure (if pressures other than atmospheric are used) continuously, if possible, to ensure that the system is operating at the appropriate design condition and to diagnose operational problems.
In batch distillation and in thermal drying, temperature provides an indirect measure of the energy available {i.e., Btu/hr) to vaporize the waste constituents. As the design temperatm·e 1 ncreases, more constituentswith 1 ower volatilities will be removed from the waste. Pressure is integrallyrelated to the boiling point of the waste and the subsequent vaporization of the organic constituents. As the pressure is lowered below atmospheric (i.e., as vacuum is increased), the boiling point of the waste will also be lowered, thereby requiring less heat input to**~olatilize** waste constituents. EPA monitors the -distillation temperature as well as the pressure (if pressures other than atmospheric are used) to ensure that the system is operating at the appropriate design conditions and to diagnose operational**problems~** 

### 2.5.2 Differential Pressure
In fractionation, measuring the differential pressure between the top and bottom ofthe column indicateswhether the flow rate ofeitherthe liquid orthe vapor phase is excessive. For instance, ahigh pressure drop across the column may indicate a condition of •flooding,• in which the liquid phase cannot flow

f:\document\15254031.01.015 152down through ths column as fast as feed is entering, causing backing up or "flooding" to OCfur. EPA monitors the pressure drop across the fractionation column continuausly, ifpossible, to ensure that the system is operating at the appropriate design condition and to diagnose operational problems. 2.5.3 Liquid and Vapor Flow Rates
For steam stripping and fractionation, the vapor-liquid equilibrium data are also used to determine the liquid and vapor flow rates that provide sufficientcontact and residence time between the liquid and vapor streams. The appropriate flow rates are affected by the column diameter. EPA monitors the liquid and vapor flow rates to ensure that sufficient contact time between the liquid and vapor streams is provided to effectively separate the organics from the wastewater, and to ensure that the column does not "flood" {i.e., the vapor or liquid flow is so high that the vapor cannot exit the top of the column as rapidly as it isgenerated and/orthe liquid cannot run out the bottom as rapidly as it is fed into the column). Also see Differential Pressure, above. 2.5.4 Internal Column Design
In steam stripping and fractionation, column internals are designed to accormnodatethe physical andchemical propertiesofthewaste to be fractionated. Two types of internals may be used in steam stripping and fractionation: trays .andpicking. Traytypes include bubble cap, sieve, valve, and turbo-grid. Trays have several advantages over packing. They are less susceptible to blockage by solids, they have a**l~wer** capital cost for large-d4ameter columns {more than approximately 3 feet), and they accommodate a wider range of liquid and vapor flow rates. Compared to trays, packing has the advantages of having a lower pressuredrop pertheoretical stage, beingmore resistantto corrosivematerials, having a lowercapital cost for small-diameter columns (less than approximately 3 feet), and being less susceptible to foaming because of amore uniform flaw distribution (i.e., lower local variations in flow rates). EPA examines the internal column design of a steam stripping or fractionation column to ensure

f:\document\1SZS4031.01.015 153that the system is designed to handle potential operational problems (e.g., corrosion, foaming, channeling).
{_ 2.5.5 Number of Separation Stages The number of separation stages in a steam stripping or fractionation column required to achieve the desired separation of the more volatile constituents fromthe less volatileconstituents is calculated from vapor-liquid equilibriumdata, which are determinedempirically. Using the theoretical number of stages, one can determine the actua1 number of stages through the use of empirical tray efficiency data, typically supplied by equipment manufacturers. EPA examines the actual number ofstages in the steam stripping orfractionation column to ensure that the system is designed to achieve an effective degree of separation oforganics from the wastewater stream. 2.5.6 Residence Time The residence time determines the necessary energy input into the system as well as the degree ofvolatilization achieved for organic constituer.ts. The residence time requirement is dependent on the distillation or evaporation temperature (ordryer temperature in the case ofthermal drying} and the thermal conductivity of the waste. EPA observes the residence time to ensure that sufficient time is provided to effectivelyvolatilize organic constituents from -the waste. In the case ofthermal drying, the residence time must be sufficient to effectivelyevaporate the volatile liquid constituents and, hence, to dry the waste. 2.5.7 

### Evaporator Sur1ace Area
In th1n film evaporation, the evaporator surface area required to achieve the desired volatilization of organic components from the waste is calculated from the vapor-liquid equilibrium data, which are determined empirically, and from waste liquid flow rates. EPA examines the surface area ofthe evaporator

f:**\doc~~~~ent\1525~031.**01.015 154to ensure that sufficient surface area is provided to achieve effective**volatili~ation** of the more volatile organic components.
t 2.5.8 Mechanical System Design Boththinfilm evaporation and thermal drying have rotating parts. For the evaporator, the speed and design ofthe feed distributorwill help determine how well the feed will coat the evaporatorsurfaces. For the dryer, the size, screw flight, spacing, and speed ofthe screwmechanismwill affectresidence time and heat transfer. Typically, higher rotational speed will distribute feed more effectively in an evaporator and will provide more mixing turbulence in adryer (for improved heat transfer). However, increased speed will reduce residence time in the dryer and will cause earliermechanical failure in both evaporators and dryers (i.e., the bearings and shafts will wear more rapidly).

f:\document\15254031.01.015 1552.6 References DeRenzo, D.J., td. 1978. Unit operation for treatment ofhazardous industrial wastes. Park Ridge, N.J.: Noyes Data Corporation, Kirk-Othmer. 1965. Encyclopedia oFchemical technology. 2nd ed., vol. 7, pp. 204-248. New York: John Wiley and Sons. McCabe, W.L., Smith, J.C., and Harriet, P. 1985. Unit operations ofchemical engineering. pp. 533-606. New York: McGraw-Hill Book Co. Perry, R.H. and Chilton, C.H. 1973. Chemical engineers' handbook. 5thed., pp. 13-1 to 13-60. New York: McGraw-Hill Book Co. Rose, L.M. 1985. Distillation design in practice. pp. 1-307. New York: Elsevier. Van Winkle, M. 1967. Distillation. pp. 1-684. New York: McGraw-Hi"ll BookCo. Water Chemical Corporation. 1984. Process design manual for stripping of organics. PB84-232628. pp. 1-1 to F4. Prepared for the Industrial Environmental Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency.

156

### 3. EXTRACTION TECHNOLOGIES
3.1 ApPiicability
Extraction technologies (i.e., solvent extraction and critical fluid extraction) are used to treatwastes containing avarietyoforganic constituents and abroad range of total organic content. Extraction technologies have been demonstratedfortreatmentofAPI separatorsludges andotherhydrocarbon-bearing wastes generated by the petroleum and petrochemicals industries. In theory, thesetechnologies are also applicable to wastes ot similarcompositiongenerated by other industries such as the organic chemicals industry.
In solvent extraction, the selection of an extraction fluid (solvent) is dependent on the solubility of the organic waste constituents in the extraction fluid.
Critical fluid extraction is applicable to wastes containing organics that are soluble in pressurized fluids such as carbon dioxide, propane, butane, or pentane (extraction fluids). Compounds that have been successfully extracted from wastes by this process include aliphatic hydrocarbons, alkenes, simple aromatics such as benzene and toluene, polynuclear aromatics, and phenols.
3.2 Underlying Principles of Operation
The basic principle of operation in extraction technologies is that constituents are removed fr011 a waste by llixing the waste with an extraction fluid (solvent) that will preferentially dissolve the waste constituents of concern from the waste. In the simplest extraction systems, two components are mixed: (a) the waste stream to be extracted and (b) extraction fluid. The extraction fluid and waste stream are mixed to allow mass transfer of the constituent (the solute) from the waste stream to the extraction fluid.

f:\document\15254031.01.016 157Except for the waste constituents that are to be extracted, the waste must be**immis~ible** in the extracted fluid, so that aftermixing, the two immiscible phases can**phy~~cally** separate by gravity. Separation of the extraction fluid phase and the waste stream phase occurs under quiescent conditions, relying on tne density differences between the two phases. The extraction fluid, which now contains the extracted contaminants, is called the extract; the extracted waste stream from which the contaminants have been removed is calleathe raffinate. The extract can be eitherthe heavy (more dense) phase or the light (less dense) phase. In theory, the maximum degree of separation that can be achieved is provided by the selectivity value, which is the ratioofthe equilibriumconcentration ofthe contaminants in the extraction fluid to the equilibrium concentration of the contaminants in the waste. The solvent extraction process can be either batch or continuous.
In critical fluid extraction, the extraction fluids used are compounds that are usually gases at ambient conditions. Since the extraction fluid being used is a gas, it is first pressurized, which converts it to a liquid. As a liquid, it leaches (dissolves) the organic constituents out of the complex**wast~** with which it is mixed. The enhanced solubilities of variousorganiccompounds inhydrocarbons and otherextractionfluids athigh pressure aid in theirremoval from a waste. The process is usually carried out at or near the extraction fluid's "critical pressure," which is the pressure above which the liquid form .of the extraction fluid cannot be gasified, no matter how much the fluid is heated. (In fact, above the critical pressure liquid and gas phases become physically**indistingui~hable,** in that two phases do not really exist.) 

### 3.3 Description ofExtraction Process 3.3.1 Solvent Extraction The simplest, least effective solvent extraction unit is a single-stage sy3tem (mixer-settlersystem). The solvent andthe 1 iquid waste stream aremixed

f:\documant\1SZ54031.01.016 158together; the raffinate and extract are separated by settling**w:~~~Jt** further extractiop.
t. The more effective multistage contact extraction is basically aseries of batch mixer-settler units. The waste stream is contacted with solvent in a series ofsuccessive steps or stages. Raffinate from the first extraction stage is contacted with fresh solvent in a second stage, and so on. In countercurrent, multistage extraction columns, fresh solvent and the waste stream continuously enter at opposite ends of a column consisting of a series ofextraction stages. Extract and raffinatelayers pass continuously and countercurrently from stage to stage through the system. Several types of extraction systems are used for contact and separation. Threeofthemost common systems--mixer-settler systems, extraction columns, and centrifugal contactors--are discussed below. 3.3.2 Mixer-Settler Systems Single-stage mixer-settler systems are extraction systems composed of a mixing chamber for phase dispersion, followed by a settling chamber for phase separation. Mixer-settler systems are typicallyused to treat solids or highly viscous wastes and can handle difficult-to-mix components. The vessels may be either vertical orhorizontal. Dispersion in the mixing chamber occurs by pump circulation, nonmechanical in-line mixing, air agitation, or mechanical stirring. In a**two-s~age** mixer-settler system (a simple multistage contact extractor), as shown in Figure 20, the extract from the first stage is sent to arecoveryunitto separatethe solventfromthe remaining extractcontainingthe organic constituents of concern. The recovered solvent is used, and the remaining extract is either reused or further treated in an ir.cineration unit. The raffinate from the first stage is sent to the second-stage unit for additional extraction. Recycled solventfrom recoveryofthefirst-stageextract and/or fresh solvent makeup is added to the first-stage raffinate before it is

f:\document\15254031.01.016 159

# - 0\ C) EXTRACT RECYCLED SOLVENT FROM RECOVERY/FRESH SOLVENT .MAKEUP

MIXER

RECYCLED SOLVENT

EXTRACT TO RECOVERY RECYCLED TO PROCESS

EXTRACT SOLIDS BEPARA1;oiON I

EXTRACT TO

._ __RECYCLE OR DISPOSAL Figure 20 Two-Stage Mixer-Settler Solve.nt Extraction System TO DISPOSALmixed and sent to the second stage. The extract from the second stage, containing mainly solvent, is recycled to the first-stage unit as the solvent stream. The reeulting raffinate from the second stage may require filtering to remove solids before it is sent to further treatment (if required). If solids collected during filtration contain treatable levels ofhazardous constituents, they will require further treatment, such as stabilization (for metals) and/or incineration (for organics) prior to disposal.
Parameters such**~s** the density or specific constituent concentrations in the extract may be monitored to determine when the second-stage extract must be sent to solvent recovery andwhen fresh or recycled solvent must be added to the first-stage**u~it.** 3.3.3 Extraction Columns Extractioncolumns arecontinuous flow, countercurrent, multistage contact systems. Two types ofextraction columns are packed extractors and sieve-tray extractors. Figure 21 presents schematics of these two types of extraction columns. Apacked extractor contains plastic or ceramic materials in various geomP.tric shapes or structuredpackings ofwire gauze ormesh. Mass transfer of the contaminants from the wasteto the extract is promoted because ofbreakup and distortion ofboth phases as they contact th& packing, resulting in the intimate mixing of the waste and the solvent. The sieve-tray extractor is similar to the sieve-tray column used in fractionation distillation. Tray perforations cause the formation of liquid droplets thataid the mass transfer process byallowing for more intimate contact between the solute and the solvent. 3.3.4 Certr1fuga1 Cantactors Centrifugal contactors are based on the application of centrifugal force to increase rates ofcountercurrent flow and enhance separation of the phases.**f:\doc~nt\15254031.01.016** 161

# - "' N RAFFINATE TO**r----t~** TREATMENT AN RAFFINATE TO DISPOSAL**SOLVENT----~·~~----r-~--,--,**

WA8TE**----t~**1------....__...___. INFLUENT PACKING SUPORT

EXTRACT AND SOLVENT TO SEPARATOR AND RECOVERY UNIT A. PACKED EXTRACTOR 0/0R -:- TREATMENT DISPOSAL**SOLVENT~**

'- 

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EXTRACT AND SOLVENT TO SEPARATOR**~** AND RECOVER'/ UNIT B. SIEVE TRAY EXTRACTOR 

### F1gura 21 Packed and Steve Tray Solvent Extraction Columns AND/ORCentrifugal units are used when short contact times are required, such as when unstable.materi**~**s are being processed. One type of centrifugal contactor consists ofa**~um** that rotates around a shaft equipped with annularpassages at each end for feed and raffinate. The light phase is injected under pressure through a shaft and is then routed to the periphery of the drum through perforations. The heavy phase is also charged through the shaft, but it is channe1 ed to the center of the drum through perforations. Centrifuga1 force acting on the phase-density difference**pr~~otes** dispersion as the phases are forced through the perforations. Centrifugal extractors provide short contact time, haveminimal spacerequirements, and easilyhandle emulsifiedmaterials and fluids with small density differences. 3.3.5 Critical Fluid Extraction
Acritical fluid extraction system consists ofablending tank, one ormore extraction vessels, one or more decanters, one or more filters, and an evaporation unit. Organic wastes such as oil refinery sludges are firstcombined in ablending**t~nk** and mixedwell toyield ahomogeneous, pumpable mixture. This mixture is then pumped under pressure to an extraction vesse1 fi11ed with a liquified gas such as carbon dioxide, propane, butane, or pentane and is mixed under pressure to extract (dissolve) hydrocarbon components from the waste into the liquified gas extraction fluid. After the hydrocarbon components of the waste dissolve in the pressurized liqui"d, the resulting solution is ·gravity-separated in a decanter into awastewater (or waste solids) stream and

an extraction fluid-rich stream. The wastewater stream, containing inorganic solids, is**sometime~**filtered under pressure to remove the insoluble components. The extraction fluid-rich stream is fed to apressurized evaporation unit. The extraction fluid (carbon dioxide, propane, butane, or pentane) is evaporated by dropping the pressure and is subsequently recovered, repressurized, and recondensed forreuse. The residue from theevaporation, consisting ofaliquid hydrocarbon mixture, is then reprocessed or reused, blendedwith fuels for heat recovery, or incinerated. Ifthe extractedwaste stream still exceeds treatment

f:\document\15254031.01.016 163requirements, itmay be extracted again**~ith** fresh extraction fluid at the high pressure.conditions.
t If inorganic residuals {or waste solids) filtered from the waste/solvent mixturecontaintreatablelevels ofhazardous constituents such as certainmetals (e.g., chromium, lead) or organics, they will require further treatment such as stabilization or incineration prior to disposal. 3.4 Waste Characteristics Affecting Performance (WCAPs)
In determining whetherextractionprocesses will achieve the same level of performance on an untested waste as on a previously tested \iJste and whether performance levels can be transferred, EPA examines the following waste characteristics: {a) the concentration of extractable hydrocarbons, (b) the solubilityofthe waste constituents ofconcern in the extraction fluid, {c) the surface tension, and {d) the alkalinityof the waste. 3.4.1 Concentration ofExtractable Hydrocarbons The concentration of extractable hydrocarbons in the waste feed is a measure ofthemaximum fraction ofthe waste that can be expected to be extracted in the process. Arelatively low concentration of extractable hydrocarbons implies that most ofthe wasta may become wastewater or waste solids (i.e., is

-nonextractable). Total extractable hydrocarbon content can be estimated by

measurement ofthe total organic carbon {TOC) content. Ifthe TOC ofan untested waste is significantlY.lower than that of the tested waste, the untested system may not remove as much hydrocarbon as the tested system. More rigorous extraction conditions such as higher temperatures and pressures, additional mixing, and longer settling times may be required to extract less extractable components and achieve the same treatmentperformance, 

### orother, more applicable treatment technologies may need to be considered for treatment ofthe untested waste.

f:\document\15254031.01.016 164Critical fluid extraction processes are designed to extract hydrocarbon component. from m2xed oi1y and organic waste liquids and sludges. For critical fluid**extracti~** to be economically applied, the waste should contain at least a few percent by weight of extractable hydrocarbons. This process has been demonstrated on wastes containing from 5to 34 percent hydrocarbons. For lower concentrations, batch distillationorconventional solventextractionmay bemore economical. Also, critical fluid extraction is not economical for wastes containing high concentrations of extractable hydrocarbons (higher than 95 percent). These wastes are more amenable to fractionation treatment. 3.4.2 Solubility ofthe Waste Constituents ofConcern in the Extraction Fluid The constituents in the waste feed that are to be extracted determine the type ofextraction fluid that is best suitedfor the process. Forexample, polar organic molecules (e.g., phenol} in an organic feed can be extracted with an aqueous solvent. Organic constituents in aqueous feeds can be extracted with various organic solvents.**Hetal-contain~ng** wastes can be extracted with acids {e.g., trialkylphosphoric and carboxylic acids) or amine solvents. If the solubility of the waste constituents ofconcern in the extraction fluid in the untestedwaste is significantlylowerthan that in the testedwaste, the untested systemmaynot achieve adequatP- performance. Useofanotherextraction fluid may be required to increase the solubility ofthe waste constituents ofconcern and achieve the same treatment performance, or other, more applicable treatlilent technologies may need to be considered for treatment of the untested waste.
3.4.3 Surface Te"sion The surface tension ofthe waste is ameasure of the tendency ofthe waste to foam. The higher the surface tension of the liquid, the higher its tendency to foam. If foaming is likely, the system design must be modified or defoaming compounds may be required. For column extractors, packed columns are less susceptible to foaming than are tray columns. If the surface tension of the untested waste is significantly higher than that of the tested waste, the

f:\document\15254031.0! .016 165untested systemmaynot achieve adequate performance. Defoamingcompounds and/or the use ofapacked columnmay be required toreduce foaming and achieve the same treatment**perfo~ance,** orother, more applicable treatment technologies may need to be considered for treatment ofthe untestedwaste. Foaming has not been found to affect the performance of critical fluid extraction processes. 3.4.4 Alkalinity ofthe Waste
In critical fluidextraction, whencarbondioxide isused as the extraction fluid, high alkalinity will interfere with the process because carbon dioxide will react to form carbonates and bicarbonates. This will result in excessive carbon dioxide consumption. For wastes having high alkalinity levels, ar. extraction fluid other than carbon dioxide should be used in the critical fluid extraction process. The same problem does not arise if a hydrocarbon fluid (propane, butane, or pentane} is used. If carbon dioxide was the extraction fluid used on a tested waste and the alkalinity of the untested waste is significantly higher than that ofthe tested waste, the system may not achieve the sameperformance. Use ofanotherextractionfluid may be required to achieve the sarne treatment performance, orother, more app1 icab1 etreatmenttechno1 og;es mayneed tobe considered for treatment oftheuntestedwaste. Alkalinity ofthe waste has not been found to affect the performance of conventional solvent extraction processes. 

### 3.5 Design and Operating Parameters
In assessing the**~ffectiveness** of the design and operation of extraction systems, EPA examines the following parameters: (a) the number of separation stages, (b) the extraction temperature and pH, (c) the degree ofmixing, (d) the residence time, (e) the settling time, and (f) the extraction pressure. For many hazardous organic constituents, analytical methods are not available or the constituent cannot be analyzed in the wastematrix. Therefore, it would normally be impossible to measure the effectiveness of the extraction

f:\document\15254031.01.016 166treatment system. In these cases, EPA tries to identify measurable parameters or**consti~ents t~at**  would act as surrogates to verify treatment. t.. For organic constituents, each compound contains ameasurable amount of total organic carbon (TOC). Removal ofTOC in the extraction treatment system implies removal oforganic constituents. Hence, TOC analysis is likely to be an adequate surrogate analysis where the specific organic constituent cannot be measured. However, TOC analysis may not be able to adequately detect treatment of specific organics in matrices that are heavily organic-laden; that is, the TOC anaiysis may not be sensitive enough to detect changes at the milligrams per liter (mg/1) level in matrices where total organic concentrations are**hundred~** or thousands of mg/1. In these cases, other surrogate parameters should be sought. For example, if a specific analyzable constituent is expected to be treated as well as the unanalyzable constituent, the analyzable constituent concentration should be monitored as a surrogate. 3.5.1 Number of Separation Stages
For solvent extraction columns, the numberoftheoretical stages required to achieve thedesired separation ofhazardous constituents from aliquid waste into the selected extraction fluid is calculated from solvent equilibrium data, which are detennined empirically. Using the theoretical number of stages, one can then determine the actual numberof stages through the use ofempirical tray efficiencydata typicallY supplied by equipmentmanufacturers. EPA examines the actual numberofstages in asolvent extraction column system to ensure thatthe system is designed to achieve an effective degree ofextraction.
3.5.2 Extraction Ta.perature and pH Temperature and pH changes can affect equilibrium conditions (pH will affect equilibrium when the waste or the extraction fluid 1s aqueous) and,

f:\document\15254031.01.016 167consequently, the performance ofthe solvent extraction system. Critical fluid extraction is**nor~ally** performed at ambient temperature although it is possible to use higher**t~~peratures** when necessary. In all cases, temperatures used must be below the critical temperature* of the extraction fluid used to ensure that the fluid is present in the extraction vessel in the 1iquid phase (so that maximum contact with the waste can be achieved). EPA monitors the temperature and pH (as applicable) continuously, ifpossible, to ensure that the system is operating at the appropriate design conditions and to diagnose operational problems.
3.5.3 Degree ofMixing
For mixer-settler solvent extractors, mixing determines the amount of contact between the two immiscible phases and, accordingly, affects the degree of mass transfer of the constituents to be extracted. Intense agitation to

. provide high rates of mass transfer, however, can produce solvent waste dispersions that are difficultto separate into distinctphases. The waste must be premixed before introduction into the critical fluid extraction system to ensure a uniform, pumpable blend of material. The waste is normally mixed in tanks or other vessels. Any well-designed and well-operated system should have such waste blending equipment. The quantifiable degree of mixing is a complex assessment that includes, among other things, the amount of mhing energy supplied, the length oftime the material is mixed, and the related turbulence effects of the specific size and shape of the tank vessel. This is beyond the scope of simple measurement. During the fluid extraction, the extraction fluid and waste need to be**mi~ed** to ensure maximum contact and, hence, efficiency of extraction. Any well-designed system should include a pressurized extraction vessel that is equipped with an operable mixing system. EPA, however, evaluates the degree ofmixing qualitatively by considering whether the type of mixing

*The critical temperature of asubstance is that temperature above which the

the substance cannot be liquified, no matterhowhigh the operating pressures.

f:\document\15254031.01.016 168device**pr~vided** is one that could be expected to achieve adequate uniform mixing of the waste.**~** 3.5.4 Residence Time
The residence time in the extraction vessel impacts the extent of extractionoforganic contaminants from the waste. Residence time will vary with the so1 ubility of the organic contaminants in the solvent and the degree of mixing. For abatch solvent extraction system, the residence time is controlled directly by adjusting the treatment time in the extraction vessel. For a continuous solvent extraction system, thewaste feed rate iscontrolledto ensure that the system is operating at the appropriate design residence time. In critical fluidextraction, as withconventional solventextraction, the residence time in the extraction vessel impacts the extent of extraction of organic contaminants from the waste. EPA monitors the residence time to ensure that sufficienttime is provided to effectivelyextract the organic contaminants from the waste. 3.5.5 Settling Time
For mixer-settler solvent extractors and critical fluid extractors, adequate settling time must be provided to make sure that separation of the phases has been effectivelycompleted. EPA monitors the settling time to ensure -effective phase separation.
3.5.6 Extract1on.Pressure
Critical fluid extraction systems operate at pressures at which the extraction fluidswill be liquids at ambient temperatures. Pressure is normally monitored by means of gauges and recorders attached to the extraction vessel. EPA monitors the extraction pressure continuously, if possible, to ensure that the system is operating at the appropriate design condition and to diagnose operational problems.

f:\dcclllll!nt\15254031.01.016 1693.6 References
CF Systems Corporation. 1988. CF Systems units to render refinery wastes non-hazart:fous. DeRenzo, O.J., ed. 1978. Unit operations for treatmentofhazardous industrial wastes. Park Ridge, N.J.: Noyes Data Corporation. Gallacher, L.V. 1981. Liquid ion exchange in metal recovery and recycling. Third Conference on Advanced Pollution Control for the Metal Finishing Industry. USEPA 600/2-81-028. pp. 39-41. Hackman, E. 1978. pp. 109-111. Toxic organic chemicals, destruction and waste treatment. Park Ridge, N.J.: Noyes Data Corporation. Hanson, C. 1968. Solvent extraction theory, equipment, commercial operations, and economics. Chemical Engineering, August 26, 1968, p. 81. Humphrey, J.L., Rocha, J.A., and Fair, J.R. 1984. The essentials ofextraction. Chemical Engineering, September 17, 1984, pp. 76-95. Johnston, K. 1978. Supercritical fluids. In Kirk·Othmer encyclopedia of chemical technology. Supplement Vol. I, pp. 872-983. New York: Wiley-Interscience. Lo, Teh C., Baird, H.H.I., and Hanson, C., eds. 1983. Handbook of solvent extraction. pp. 53-89. New York: John Wiley and Sons. Perry, R.H., and Chilton, C.H. 1973. Chemical engineer's handboolc, 5th ed., pp. 15-1 to 15-24. New York: McGraw-Hill Book Company. Weast, R.C., ed. 1978. Handbook ofchemistry and ohysics. 58th ed. Cleveland, Ohio: CRC Press.

f:\document\1SZ54031.01.016 1704. FUEL SUBSTITUTION Fuel subsJ:i1ution involves using hazardous waste as a fuel in industrial furnaces or in boi 1 ers. The hazardous waste may be b 1 ended with other nonhazardous wastes (e.g., municipal sewer sludge) and/or fossil fuels. OnDecember31, 1990, EPApromulgated regulations to control emissions from industria1 furnaces and boilers from treatment of hazardous waste. Permit requirements are similar to those for incineration, in that controls limit the emissions oftotal organic carbons, toxicmetals, HCl, andwastewaters. Like the**in~inerator** regulations (40 CFR 264, Subpart 0), the boiler and furnace regulations (40CFR266, SubpartH) require 99.99 percent destruction and removal efficiency of principal organic hazardous constituents (POHCs). These regulations will also minimize products of incomplete combustion (PICs), includingcarbonmonoxide (CO). Theseregulations will alsominimize particulate

. . emissions by regulating the metal emissions. 4.1 Applicability Fuel substitution has been used with industrial waste solvents, refinery wastes, synthetic fibers/petrochemicai wastes, and waste oils. It can also be used when combusting other waste types produced during the manufacture of pharmaceuticals, pulp and paper, and pesticides. Thesewastes can be handled in a solid, liquid, or gaseous form. Industrial**furnac~s** include avariety of industrial processes that produce heat and/or products byburning fuels. They includeblast furnaces, electricarc smelting furnaces, cement kilns, lime kilns, smelters, coke ovens, and halogen acid furnaces (HAFs). Industrial boilers are units wherein fuel is used to produce steam for process and plant use. Industrial boilers typically use coal, oil, or gas as the primary fuel source.

f:\document\15254031.01.017 171

### The parameters that affect the applicabilityoffuel substitution are the fo11owing:.
t. 

### • Halogen content of the waste;
• Inorganic solids content (ash content} ofthewaste, particularlyheavy metals;
• Heating value of the waste;
• Viscosity of the waste (for liquids};
• Filterable solids concentration (for liquids}; and
• Sulfur content. 4.1.1 Halogen Content ofthe Waste Ifhalogenated organics are burned, halogenated acids and free halogen are among the products of combustion. These released corrosive gases may require subsequent treatment prior to venting to the atmosphere. Also, halogens and halogenated acids formed during combustion are likely to severelycorrode boiler tubes andotherprocess equipment. Tominimize suchproblems, halogenatedwastes are blended into fuels only at very low concentrations. High chlorine content can also lead to the incidental production (at verylowconcentrations} ofother hazardous compounds such as polychlorinated biphenyls (PCBs}, chlorinated dibenZQ-p-dioxins {COOs), chlorinated dibenzofurans (COFs), and chlorinated phenols. 4.1.2 Inorganic Solids Content of the Waste High inorganic solids content (i.er, ash content) ofwastes may cause two problems: (1) scaling in the boiler and (2) particulate airemissions. Scaling results from deposition of inorganic solids on the walls of the boiler. Particulateemissions are producedby noncombustible inorganic constituents that flow out of the boiler with the gaseous combustion products. Because of these

f:\document\15254031.01.017 172problems, wastes with significant concentrations of inorganic materials are not usually handled in boilers unless the boilers have an air pollution control system. ( Industrial furnaces vary in their tolerance to inorganic constituents. Heavy metal concentrations, found in both halogenated and nonhalogenated wastes used as fuel, can cause environmental concern because theymay be emitted in the gaseous emissions from the combustion process, in the dSh residues, or in**a~y** produced solids. The partitioningofthe heavymetals to these residual streams primarily depends on the valati1ity of the metal, waste matrix, and furnace design. 4.1.3 Heating Value ofthe Waste The heating value of the waste must be high enough (either alone or in combinat·lon withotherfuels) tomaintain combustiontemperatures consistentwith efficient waste destruction and operation of the boiler or furnace. For many applications, only supplemental fuels having minimum heating values of4,400 to 5,600 kcal/kg (8,000 to 10,000 Btu/lb) areconsidered to be feasible. Below this value, theunblended fuel would notbe likelytomaintain astable flame, and its combustionwould release insufficientenergy to provide oeeded steam generation potential in the boiler or the necessary heat for an industrial furnace. Some wastes with heating values ofless than 4,400 kcal/kg (8,000 Btu/lb) can be used }fsufficientauxiliaryfuel is used to support combustion or ifspecial designs are incorporated into the combustion device. Occasionally, for wastes with heating values higher than virgin fuels; blending with auxiliary fuel may be required to prevent overheating or overcharging of the combustion device.
4.1.4 Viscosity ofthe Waste
In combustion devices designed to burn liquid fuels, the viscosity of the liquid waste must be low enough that it can be atol!lized in the combustion chamber. Ifthe viscosityistoo high, heat;ng the storage tanks may berequired

f:\document\15254031.01.017 173priorto combustion. For atomization ofliquids. aviscosity of 165 centistokes (750 SaybQlt Universal Seconds (Sus)) or**lP~s** is typically required.
(_ 4.1.5 Filterable Solids Concentration Filterable materials suspended in the liquid fuel may prevent or hinder pumping or atomization and if so other technologies may need to be considered. 4.1.6 Sulfur Content
Awaste's sulfurcontentmay affectwhether itcan be burned ornot because the waste may emit sulfur oxide into the atmosphere. For instance, the EPA has promulgated sulfur oxide emission regulations for certain new source industrial boilers (40 CFR 266, Subpart H). Air pollution control devices are available to remove sulfur oxides from the stack gases. 4.2 Underlying Principles of Operation
Foraboilerandmost industrial furnaces thereare twodistinctprinciples ofoperation. Initially, anergy in the form ofheat is transferredto thewaste to achieve volatilization of the various waste constituents. For liquids, volatilizationenergymayalso be supplied by using pressurized atomization. The energy used to pressurize the liquid waste allows the atomized waste to break into smaller particles, thus enhancing its rate of volatilization. The volatilized constituents then require additional energy to destabilize the chemical bonds,**allowin~** the constituents to react with oxygen to form carbon dioxide and watervapor. The energy needed to destabilize the chemical bonds is referred to as the energy of activation. 4.3 Description of Fuel Substitution Process Since anumberofindustrial applications can use fuel substitution, there is no one process description that will fit all of these applications. The

f:\document\1525403l.O:.Ol7 174following section, however, provides ageneral description of industrial kilns (one form·of**indu~trial** furnace) ana industrial boilers. t 4.3.1 Kilns Combustible wastes have the potential to be used as fuel in kilns and, for waste liquids, are often used with oil to co-fire kilns. Coal-fired kilns are capable of handling some solid wastes. In the case of cement kilns, there are usually no residuals requiring land disposal since any ash formed becomes part ofthe product or is removed by particulatecollection systems and recycled back to the kiln. The only residuals may be low levels ofunburned gases that escape with combustion products. Ifthis is the case, airpollution control devices may be required. Threetypes ofk1lns areparticularlyapplicable: cement kilns, lime kilns, and lightweight aggregate kilns.
4.3.1.1 Cement Kilns The cement k1ln is a rotary furnace, which is a refractory-lined steel shell used to calcine a mixture of calcium, silicon, aluminum, iron, and magnesium-containing minerals. The kiln is normally fired by coal or oil. liquid and solid combustible wastes may then serve as auxiliary fuel. Temperatures within the kiln are typically between 1,380 and 1,540•c (2,500 to 2,Soo•F). To date, only 1iquid hazardous wastes have been burned in cement kilns.
Most cement kilns have adry particulate collection device (i.e., either an electrostatic precipitator or a baghouse), with the fly ash collected and recycled back to the kiln. Buildup of metals or other noncombustibles is prevented through their incorporation into the product cement. Many types of cement require a source ofchloride so that most halogenated liquid hazardous

f:\document\15254031.01.017 175wastes currentlycan be burned in cementkilns. Available information shows that scrubbers.are not used.
t. 4.3.1.2 Lime Kilns Quick lime (CaO} ismanufactured in acalcination process using limestone (CaC03) or dolomite (CaC03 and MgC03). These raw materials are also heated in a refractory-lined rotary kiln, typically to temperatures of 980 to 1,260'C (1,800 to 2,300'F). Limekilns are less likelyto burn hazardous wastes than are cement kilns because product lime is often added to potable water systems. Only one 1 ime kiln in the United States currently burns hazardous waste. That particular facility sells its product lime for use as flux or as refractory in b 1 ast furnaces.
As with cement kilns, any fly ash collected is recycled back to the lime kiln; thus, no residual streams are produced by the kiln. Available information shows that scrubbers are not used.
4.3.1.3 Lightweight Aggregate Kilns Lightweight aggregate kilns heat clay to produce an expanded lightweight inorganic material used in Portland cement formulations and other applications. The kiln has anormal temperature range of 1,100 to 1,1SO•c (2,000 to 2,1oo·F). Lightweight aggregate kilns are less amenable to combustion ofhazardous wastes as fuels than are the other kilns described above because these ki1ns lack material to adsorb halogens. As a result, burning of halogenated organics in these kilns would likely require afterburners to ensure complete destruction of the halogenated organics and scrubbers to control acid gas production. Such controls would produce a wastewater residual stream subject to treatment standards.

f:\document\15254031.01.017 176

### 4.3.2 Industrial Boilers A

boiler isaclosed vessel in whichwater is transformed into steamby the application ofheat. Normally, heat is supplied by the combustion ofpulverized coal, fuel oil, or gas. These fuels are fired into acombustion chamber with nozzles and burners that provide mixing with air. liquid wastes, andgranulated solid wastes in the case ofgrate-fired boilers, can be burned as auxiliary fuel in a boiler. However, few grate-fired boilers burn hazardous wastes. For liquid-fired boilers, residuals requiring land disposal are generated only when the bo"l1ci" is shut down and cleaned. This is generally done once or twice per year. Other residuals from liquid-fired boilers would be the gas emission

. 

### stream, which would consist ofany products ofincomplete**combust;~n,** 

### along with the normal combustion products. For example, chlorinated wastes would produce acid gases. Ifthis is the case, airpollution control devices may be required. For solid-fired boilers, an ash normally is generated. This ash may contain residual amounts of organics from the blended waste/fuels, as well as noncombustible materials. land disposal of this ash would require compliance with applicable 

### BOAT treatment standards. 

### 4.4 Waste Characteristics**Affe~ting** 

### Performance 

### CWCAPsl
In determining whether fuel substitution will achieve the same level of**perfo~ance** 

### on an untested waste as on a previously tested waste and whether performance levels can be transferred, EPA examines the following waste characteristics: (a) thecomponentboilingpoints, (b) the thermal conductivity of the waste, and (c) the component bond dissociation energies. 

### 4.4.1 

### ComponentBoiling Points The term relative volatil-Ity refers to the ease with which a substance present in asolidor liquidwastewill vaporize fromthat waste upon application of heat from an external source. Hence, it bears a relationship to the equilibrium vapor pressure of the substance.

f:\document\15254031.01.017 177

### EPA recognizes that the relative volatilities**canna~** be measured or calculated directlY for the types ofwastes generally treated in an industrial boiler or furn"=e. The Agency believes that the best measure of relative volatility is the boiling point ofthe various hazardous constituents and wi11, therefore, use this parameter in assessing volatility of the organic constituents. 4.4.2 Thermal Conductivity of the Waste Consistentwith**t~e** underlying principles ofcombustion in aggregate kilns or boilers, amajor factor with regard to whether aparticularconstituent will volatilizeis the transfer ofheat through the waste. In the case of industrial boilers burning solid fuels, heat is transferred through the waste by three mechanisms: radiation, convection, and conduction. For agiven boiler, it can be assumed.that the type of waste will have a minimal impact on the heat transferred from radiation. With regard to convection, 

### EPA believes that the range of wastes treated would exhibit similar properties with regard to the amount of heat transferred by convection. Therefore, 

### EPA will not evaluate the radiation orconvectionheattransferproperties ofwastes indetermining similar treatability. For solids, the third heat transfer mechanism, conductivity, is the one principally operative and most likely to change between wastes. Using thermal conductivity measurements as part of a treatability comparison for two different wastes through agiven boiler or furnace is most meaningful when applied to wastes that are homogeneous. As wastes exhibit greaterdegrees ofnonhomogeneity, thermal conductivitybecomes less accurate in predicting treatability because the measurement essentially reflects heat flow through regions having the greatest conductivity (i.e., the path of least resistance) and not heat flow through all parts ofthe waste. Nevertheless, 

### EPA has not identifiedabetter alternativeto thermal conductivity, even for**~astes** that are nonhomogeneous.

f:\doCIIIII!nt\15254031.01.017 1784.4.3 Component Bond Dissociation Energies Given an txcess of oxygen, an organic waste in an industrial furnace or boiler would be expected to convert to carbon dioxide and water vapor provided that the activation energy is achieved. Activation energy is the quantity of heat (energy} needed to destabilize molecular bonds so that the oxidation (combustion) reaction will proceed to completion. As a measure of activation energy, EPA is using bond dissociation energies. In theory, the bond dissociation energy would be equal to the activation energy; in practice, however, this is not**al~~ys** the case because ofmolecular interaction bonds. In some instances, bond dissociation energies will not be available and will have to be estimated, or other energy effects will have a significant 1nf1uence on activation energy. 4.5 Design and Operating Parameters
In assessing the effectiveness of the design and operation of a fuel substitution system, EPA examines the following parameters: (a} the combustion temperature, (b) the residence time, (c) the degree ofmixing, (d) the air feed rate, (e) the fuel feed rate, and (f) the steam pressure/rate ofproduction.
For many hazardous organic canstituents, ana1 ytica1 methods are not availableorthe constituentcannot be analyzed in the wastematrix. Therefore, it**;;;~uld** normally be impossible to measure ·the effectiveness of the fuel substitution treatment system. In these cases, EPA tries to identifymeasurable parameters or constituents that would act as surrogates to verify treatment. For**organ1~** constituents, each compound contains ameasurable amount of total organic cart,on (TOC}. Removal ofTOC in the fuel substitution treatment system will indic,,te removal of organic constituents. Hence, TOC analysis is likely to be an adequate surrogate analysis where the specific organic constituent cannot be measured.

f:\document\15254031.01.017 179However, TOC analysis may not be able to adequately detect treatment of specific organics in matrices that are heavily organic-laden (i.e., the TOC analysis may no\be sensitive enough to detect changes at the milligrams/liter (mg/1) level in matrices where total organic concentrations are hundreds or thousands ofmg/1). In these cases, other surrogate parameters should be sought. For example, if a specific analyzable constituent is expected to be treated as well as the unanalyzable constituent, the analyzable constituent concentration should be monitored as a surrogate. 4.5.1 Combustion Temperature Industrial boilers are generally designed based on their steamgeneration potential {Btu output). This factor is related to the design combustion temperature, which, in turn, depends on the amount of fuel burned and its Btu value. The fuel feed rates andcombustiontemperaturesofindustrial boilers are generally fixed based on the Btu values of fuels normally handled (e.g., No. 2 versus No. 6 fuel oils). When wastes are to be blended with fossil fuels for combustion, the blending, based on Btu values, must be such that the resulting Btu value of the mixture is close to that of the fuel value used in the design of the boiler. Industrial furnaces also are designed to operate at specific ranges of temperature to produce the desired product (e.g., lightweight aggregate). The blended waste/fuel mixture should be capableofmaintaining the design**temper~ture r~nge.**  4.5.2 Residence Time
Asufficient residence time of combustion products is normally necessary to ensure that the hazardous substances being combusted (or formed during combustion) are completely oxidized. Residence times on the order of a few seconds are generally needed at normal operating conditions. For industrial furnaces as well as boilers, the residence time is afunction ofthe size ofthe furnace and the fuel feed rates. For most boilers and furnaces, the residence time usually exceeds a few seconds.

f:\docunent\15254031.01.017 180

### 4.5.3 Degree ofMixing

- 

### Boilers**ar~**

### designed sothat fuel and airare intimatelymixed. This helps to ensure thatcomplete combustion takes place. The shape ofthe boiler and the method of fuel and air feed influence the turbulence required for good mixing.**Ind~strial** 

### furnaces also are designed for turbulentmixing where fuel andair are mixed. 4.5.4 

### Air Feed Rate An important operating parameter in boilers and many industrial furnaces is the oxygen content in the flue gas, which is afunction ofthe air feed rate. Stable combustion of a fuel generally occurs within a specific range of air-to-fuel ratios. An oxygen analyzer in the combustion gases can be used to control the_feed ratio of airto fuel to ensure complete thermal destruction of the waste and efficient operation ofthe boiler. When necessary, the air feed rate can be increased or decreased to maintain proper fuel-to-oxygen ratios. Some industrial furnaces do not completely combust fuels (e.g., coke ovens and blast furnaces); hence, oxygen concentration in the flue gas is ameaningless variable.
4.5.5 

### Fuel Feed Rata The rate at which fuel is injected into the boiler or industrial furnace will determine the thermal output ofthe system per unit oftime (Btu/hr). If steam is produced,**ste~** 

### pressure monitoring will indirectly determine whether the fuel feed rate is adequate. However, various velocity and mass measurement devices can be used to monitor fuel flow directly.
4.5.6 

### Stall Pressure orRata of Production Steam pressure in boilers**pr~~ides** 

### adirectmeasure ofthe thermal output of the system and is directly monitored by use of in-system pressure gauges.

f:\document\15254031.01.017 181Increases or decreases in steam pressure can be effected by increasing or decreasin9 the fuel and air feed rates within certain operating design limits. Most**industrial~FUrnaces** do not produce steam; instead they produce a product (e.g., cement, aggregate} and monitor the rate of production.

f:\document\15254031.01.017 1824.6 References Bonner, T.A., rt al. 1981. Engineering handbook for hazardous waste incinerat1on. Prepared by Monsanto Research Corporation for U.S. Environmental Protection Agency PB 81-248163. Castaldini C., et al. 1986. Disposal ofhazardous wastes in industrial boilers or furnaces, Park Ridge, N.J.: Noyes Publications. USEPA. 1990. Office of Solid W1ste. Standards for owners and operators of hazardous wastes in boilers and industrial furnaces; proposed and supplemental proposed rule, technical corrections, and request for convnents. 55 FR 17862, April 27, 1990. Versar. 1984. Estimating PMN incineration results. EPA Contract No. 68-01-6271, Task No. 66. Draft report for Exposure Evaluation Division, Office of Toxic Substances. Washington, D.C.: U.S. Environmenta1 Protection Agency.

f:\docl.llllnt\15254031.01.017 183l



### II. REMOVAL TECHNOLOGIES (CONTINUED) B. RECOVERY AND/OR SEPARATION TECHNOLOGIES FORMETALS1. ACID LEACHING 1.1 ApPlicability ( Acid leaching is atreatment technology used to treat wastes in solid or slurry form containing metal constituents that are soluble in a strong acid solution or can be**conv~rted** by reaction with a strong acid to a soluble fonn. This process has been used to recover metals such as mercury, copper, nickel, silver, and cadmium from inorganic wastes generated in the primary metals and inorganic chemicals industries. The acid leaching process is most effectivewith wastes having high (over 1,000 ppm) levels ofmetal constituents. Wastes containing lower levels ofsuch contaminants are more difficult to process because the low metal concentrations require longer contact times.
Acid leaching can also be used to extract heavy metals or radionuclides from mixed wastes, principally soils, separating the material into itshazardous and radioactive components. This process has greater utilitywhen combined with unitoperations such as ionexchange, solventextraction, chemical precipitation, and filtration. Another type of leaching process, alkaline 1eaching, is used to treat**~astes·** containing metal constituents that are soluble in a strong caustic or alkaline solution. This process is mainly useful in recovering aluminum from bauxite ore. Generally, the. following information on acid leaching would be applicable to alkaline leaching. 

### 1.2 UnderlYing Principles of

### Operation
The basic principleofoperation for acid leaching isthat**~nlubilities** of various metals in acid solutions aid in their removal from awaste. The process concentrates the constituent(s) leached by the acid solutions. These constituents can then be filtered to remove residual solids and neutralized to
f:\document\15254031.01.018 184precipitate solids containing high concentrations of the constituents of interest, which _can be further treated in metals recovery processes. Alternatively, the acid solutions can be electrolyzed to recover pure metals. An acid leaching system usually consists of a solid/liquid contacting unit followed by a solid/liquid separator. The most frequently used acids include sulfuric (H2S04), hydrochloric (HCl), and nitric (HN03). Although any acidic pH can theoreticallybe used, acid leaching processes are normally run at apH from 1to 4. 1.3 Description ofAcid Leaching Process Acid leaching processes can be categorized into two major types: (a) treatment by percolation ofthe acid through the solids or (b) treatment by dispersion ofthe solids within the acid solution. Both treatments are followed by subseque_nt separation of the solids from the liquid. In both types of systems, sufficient acid must be supplied to keep the pH at the level needed to effectively leach the metals from the waste. 1.3.1 Percolation Processes Percolation is typicallyconducted in batch tanks. Batch percolators are large tanks ranging in size up to 50,000 gallons. First, the solids are placed in the tank, and then acid is added. The acid percolates through the solids and drains out through screens or a porous medium in the tank bottom. Following treatment, the solids are removedand furthertreatedusing stabilization, and/or they are land**disposed~.** 1.3.2 Dispersed-Solids Processes Acid leaching by dispersion of fine solids into the acid is performed in batch tanks. The untreated waste and the acid are mixed in the reaction tank to ensure effective contact between the solids and the acid. Following mixing, the suspension may be**p~mped** to stirred holding tanks, where the leaching is allowed

f:\document\15254031.01.018 185to proceed to completion. The treated solids are then usually separated fromthe acid by filtration and further treated using stabilization, and/or they are land disposed. t 1.4 Waste Characteristics Affecting Performance (WCAPs)
In determining whether acid leaching will achieve the same level of performance on an untested waste that it achieved on a previously tested waste and whether performance levels can be transferred, EPA examines the following waste characteristics: (a) the solidwaste particlesize, (b) the alkalinity of the waste, (c) the solubility of metal**constituent~** in the acid, and (d) the concentration of leachable metals. 1.4.1 Solid Waste Particle Size Both the solubility reaction rate of the acid with the hazardous metal**c~nstituents** in the waste and the rate oftransport of acid to and from the site of the hazardous constituents are affected by the size of the solid waste particles. The smaller the particles, the more rapidly they will leach because ofthe increased surface area ofthe waste that is exposed to the acid. Ifthe particle size ofthe untested waste isgreaterthan thatofthetestedwaste, the systemmay not achieve the same performance. Grinding the untested waste may be required to reduce theparticlesize and achieve the same treatment performance, or it may be necessary to considerother, more applicable treatment technologies for treatment ofthe untested waste. 1.4.2 Alkalinity

### of the Waste The neutralizing capacity (or alkalinity) of the waste solids affects the amount of acid that must be added to the waste ta achieve and/or maintain the desired reactor pH. In addition to dissolving the waste contaminants, the acid will also dissolve some of the alkaline bulk solids; therefore, highly alkaline wastes require more acid or astronger acid tomaintain pH during treatment. If

f:\document\15254031.01.018 !86the alkalinity in an untested waste is greater than that in atested waste, the system may not a_chieve the same performance. Use of additional acid or a stronger acid**~Y** be required to compensate for the increased alkalinity and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment ofthe untested waste. 1.4.3 Solubility ofthe Metal Constituents in the Acid The metal constituentsmust dissolve in the acid to form soluble salts for the process to be effective. Thus, the acid selected should be one that forms soluble salts for all of the constituents to be removed. If the solubility of a metal constituent(s) of concern in an untested waste is less than that of another constituent(s) ofconcern in apreviously tested waste in the same acid,_ or less than the solubility of the same metal(s) tested with adifferent acid, the system may n.:)t achieve the same performance. Use of another acid may be required to increase the solubilitiesofthe metal constituent(s) ofconcern and achieve the same treatment performance, or other, more appl;cable treatment technologies may need to be considered for treatment of the untested waste. 1.4.4 Concentration of Leachable Metals The amount ofleachablemetals is ameasure ofthe maximum fraction ofthe waste that can be expected to leach in the acid leaching system. Arelatively low concentrationofleachablemetals implies thatmost ofthe waste will remain in the solid or slurry waste residues (i.e., it is nonleachable). If the concentration of**leach~ble** metals in the untested waste is significantly less than that in the tested waste, the system may not achieve the same performance. Use ofahigherconcentration ofacid or astrongeracid may be required to leach less leachable components and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment of the untested waste.

f:\document\15254031.01.018 1871.5 Design and Operating Parameters

- In**asses~ng** the effectiveness of the design and operation of an acid leaching system, EPA examines the following parameters: (a) the residence time, (b) the type and concentration of acid used, (c) the pH, and (d) the degree of mixing.
1.5.1 Residence Time The extent of reaction and dissa1ution ofthe contaminants in the acid is directly**r~lated** to the contact time. EPAmonitors the residence time to ensure that sufficienttime isprovided to effectively leach themetal contaminants from thewaste. 1.5.2 _Type and Concentration ofAcid Used Ifthe hazardous constituents to be removed in the acid leaching systemare alreadypresent in the waste in soluble form, or are solubilized bypHreduction, then any acid thatwill reduce the pH to the desired valuemay be used. However, if chemical reaction is necessary to form soluble species, then the appropriate acid, as well as the appropriate concentration of the acid, must be used to ensure effectiveleaching ofthe metal constituents. EPA examines the type and concentration ofacid used to ensure that the acid solution**select~d** is capable of effectively leaching the metal constituents from the waste.
1.5.3 pH
For dispersed solids systems, the feed of acid to the leaching reactor is based on pH 1110nitoring and control because the reaction rate is highly pH dependent. Therefore, apH should be determined, based on the residence time and amount of hazardous metal constituents in the waste, that provides for complete dissolutionofmetal constituents. Forpercolation systems, pHmonitoring ofthe acid percolating through the tank (i.e., leaving the system) should ensure that

f:\document\15Z54031.01.018 188enough acid is being added. EPA monitors the pH to ensure that the system is operating· at the_appropriate design conditions and to diagnose operational problems. t. 1.5.4 Degree of Mixing Mixing provides greater contact between the acid and the solid waste particles, ensuring more rapid leaching of metal contaminants from the waste. The quantifiable degree ofmixing is**~** complex assessment that includes, among other factors, the amount ofenergy supplied, the length oftime the material is mixed, and the related turbulence effects ofthe specific size and shape ofthe tank. Although the exact degree of mixing is beyond simple measurement, EPA evaluates it by considering whether mixing is provided and whether the type of mixing device is one that could be expected to achieve uniform mixing of the waste solution.

f:\document\15254031.01.018 1891.6 References

Kirk-Othmer.**1~78.** Encyclopedia ofchemical technology. Vol. 2, pp. 140-144. New York: John Wiley and Sons. McCabe, L., and Smith, J. 1976. Unit operations ofchemical engineering. 3rd ed., pp. 607-610. New York: McGraw-Hill Book Co. Perry, R.H., and Chilton, C.H. 1973. Chemical engineers' handbook. 5th ed., pp. 19-41 to 19-43. New York: McGraw-Hill Book Co.

f:\document\15254031.01.018 1902. FILTRATION TECHNOLOGIES 2.1 APPlicability Filtrationtechnologies (i.e., polishing filtrationand sludge filtration} are used to remove particles from waste streams that are predominantly water or to remove water from wet solids and sludges. Polishing filtration is atreatment technology applicable to wastewaters containing relatively low concentrations of solids (usually less than 1,000 mg/1). This type of filtration is typically used as apolishing step for the supernatant 1 iquid following chemical precipitation and settling/ clarificationofwastewaters containing metal and other inorganic precipitates. Polishing filtration removes particles that are difficult to settle because of their size and/or density, as well as precipitated particles from an underdesigned settling system. Sludge filtration, also known as sludge dewatering or cake-formation filtration, is a technology used on wastes that contain high concentrations of suspended solids, usuallyhigherthan 1percent (10,000 mg/1). Sludge filtration is commonly appliedto waste sludges, such as clarifier solids, for dewatering. Typically, these sludges can be dewatered to 19 to 50 percent solids concentration using this technology. 

### 2.2 UnderlYing Principles ofOperation Thebasicprincipleofoperation for sludge andpolishing filtration is the removal/separationofparticles from amixtureoffluid andparticles by amedium that permits the flow ofthe fluid but retains the particles. Usually, the larger the particles, the easierthey are to remove from the fluid. Extremely small particles, in the colloidal size range, maynot be removed orfiltered effectively in asludge or polishing filtration system and thus may

f:\document\1SZS4031.01.0!9 191appear in the wastewater passing through the filter. To mitigate this problem, the wastewater can be treated prior to filtration to modify the particle size distribution**~d/or** particle electrostatic charge by using appropriate precipitants, coagulants, flocculants, and filter aids. The selection of the appropriate precipitant and coagulant is important because they affect the type ofwaste particles formed. For example, lime (calcium hydroxide) precipitation usually produces larger, less gelatinous particles (which are easier to remove from aqueous wastes by using filtration) than does caustic soda (sodium hydroxide) precipitation. For particles that become too small or too highly charged to remove effectively, the use of coagulants and flocculants both decreases particle charge and increases the size of the particles. Also, if pumps are used, shear can be minimized by lowering the pump speed or using a low-sheartype ofpump. Excessiveshea:" breaks up agglomeratedparticles, making them smaller and more difficult to filter. Filter aids such as diatomaceous earth are used to precoat cloth-type filter media and to provide an initial filter cake onto which additional solids can be deposited during the filtration process. The presence ofthe precoat aids in theremoval ofsmall particles from the solution being filtered. These particles adhere to, and are actually filtered by, the precoat solids during the filtration process. 2.3 Description ofFiltration Processes 2.3.1 Polishing Filtration Processes During polishing filtration, wastewater may flow by gravity or under pressure to the filter

..The two most common**polishin~**filtration processes are cartridge and granular bed filtration. Both processes remove particles that are much smaller than the pore size of the filter medium by straining, adsorption, and coagulation/flocculation mechanisms; these processes are also capable of producing an effluentwith alow level of solids (typically less than 10 mg/1).

f:\document\15254031.01.019 1922.3.1.1 

### Cartridge Filtration Cartridgetfilterscan be used for relatively lowwaste feed flows. In this process, ahollow, cylindricallyshapedcartridgewith amattedcloth-type filter medium is placed within a sealed vessel. Wastewater is pumped through the cartridge wall until the flow drops excessively or until the pumping pressure becomes too high because ofplugging ofthe filtermedium. The sealed vessel is then opened, and the plugged cartridge is removed and replaced with a new cartridge. The plugged cartridge is then cleaned and/ordisposed of. Cartridge filterscan be assembled in aparallel arrangementto increase the overall system flow.
2.3.1.2 

### Granular Bed Filtration
For relatively large volume flows, granulated media such as sand, garnet, or anthracite coal are used singly or in combination to trap suspended solids within the pore spaces of the media. Dual· and multimedia filter arrangements allow higher flow rates andefficiencies. Typical hydraulic loading rates range from2to5gal/sq ft-min for single-mediumfilters and from4to 8gal/sqft-min for multimedia filters.
In this process, wastewater is either gravity-fed or pumped through the granular bed media and filtered until either the flow drops excessively or the pumping pressure becomes too high because of plugging of the granular filter media. Granularmediafilters are usuallycleanedbybackwashingwith previously filtered water in an upflowmanner to expand the bed, loosen the media granules, and resuspend the entrapped filtered solids. The backwash water, which may be as much as 10 percent ofthe volume ofthe filteredwastewater, is then returned to the head ofthewastewater treatment system so thatthe filtered solids in the backwash-watercan be settled out ofsolution and the water refiltered prior to discharge.**f:\docunent\1SZ~031.01.019** 1932.3.2 Sludge Filtration Process
For**sludg~_**filtration, waste is pumped through a cloth-type filter medium (also known as pressure filtration, such as that performedwith aplate-and-frame filter); drawn bt vacuum through the cloth ormetal mesh medium (also known as vacuum filtration, such as that performed with a vacuum drum filter); or gravity-drained and mechanically pressed through two continuous fabric belts (also known as beltfiltration, such as that performedwith abelt filter press). In all cases, the solids "cake" builds up on the filter medium and acts as a filter for subsequent solids removal.
For a plate-and-frame filter, removal of the solids is accomplished by taking the unit off-line,**~pening** the filter, and using mechanical or manual methods to scrape offthe solids (a batch process). Forthe vacuum filter, cake is removed continuously by using an adjustable knife mechanism to scrape the sludge from the vacuumdrum as the drum rotates. For the belt filter, the cake is continuouslyremoved by adischarge rollerand blade, which dislodge the cake from the belt. For a specific sludge, the plate-and-frame filter will usually produce the driestcake (highestpercentageofsolids). The beltfilterproduces adriercake than does a vacuum filter, but usually not as dry as that produced by aplate-and-frame filter. Dewatered solids are further treated in processes such as**slu~g~** diying, incineration, solvent extraction (iftreatable levels of organicsare present), stc:bfltzation (iftreatable levelsofleachablemetals are present), and/ordisposal. The liquidfiltratethatpenPtrates the filtermedium is further treated in processes such as polishing filtration, carbon adsorption, and biological treatment, and/or it is disposed of. 2.4 Waste Characteristics Affecting Performance (WCAPs)
In determining whether polishing and sludge filtration will achieve the same level ofperformance on an untested waste as on a previously tested waste and whether performance levels can be transferred, EPA examines the following**f:\doc~nt\15254031.01.019** 194waste characteristics: (a) the solid waste particle size and (b) the type of solid waste particles. (_ 2.4.1 Solid Waste Particle Size Extremely small particles, in the colloidal range, may not be filtered effectively in apolishing filter and thus may appear in the filtrate.
In sludgefiltration, the smallertheparticle size, the more theparticles tend to go through the filter media. This is especially true for a vavJum filter. For apressure filter (such as aplate and frame), smaller particles may requirehigher**pr~ssures** forequivalentfluid throughputbecause the smaller pore spaces between particles collected on the filter medium create resistance to flow. If the solid waste particle size distribution of an untested waste is significantlylower than thatofthetestedwaste, the systemmay not achieve the same performance. Ir. practice, it is usuallyaifficult to measure particle size accurately and representatively.**Ho~ever,** it can be said that individual particles formed by chemical precipitati<!n are typically much smaller than particles formed mechanically (e.g., by erosion, grinding, or abrasion). Pretreatment ofthe waste with coagulants and flocculants may be required to increase the particle sizes and achievethe same treatmentperformance, or other, more applicable treatment technologies may need to be considered for treatment of the untested waste. 

### 2.4.2 Type of 

### SolidWaste Particles
Some solids formed during metal precipitation are gelatinous in nature because of high levels ofelectrostatic charge. Such solids are difficult to filter by polisning filtration and may be impossible to dewater effectively by sludge filtration. In most cases, solids can be made less gelatinous by use of the appropriatecoagulantsand coagulantdosage priorto settling/clarification, or after settling/clarification but prior to filtration. In addition, the use or 11me instead of caustic in chemical precipitation of metals reduces the

f:**\doc~ment\15254031.01.**Ol9 195formation ofgelatinous solids. Aiso, in the case of sludge filtration, adding filterai"s,**such~s** 1ime ordiatomaceous earth, to agelatinous sludge increases its filterabilt_ty significantly. Finally, precoating filter media with diatomaceous earth prior to sludge filtration assists in dewatering gelatinous sludges. If solids in an untested waste are significantly more gelatinous than those in the tested waste, the system may not achieve adequate performance. Pretreatment of the waste with t:oagulants may be required to decrease the· gelatinous nature of the waste and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment of the untested waste. 2.5 Design and Operating Parameters
In assessing the effectiveness ofthe design and operation ofapolishing filtration system, EPA examines the following parameters: (a) the type and size of the filter; (b) the filtration pressure; (c) the amount and type of coagulants, flocculants, and filter aids used; (d) the hydraulic loading rate; and (e) the pore size ofthe filter media.
2.5.1 Type and Size of Filter The type and size of the filtration system used is dependent on the rate offeed, the nature ofthe particlesto be removed/separated, the desired solids concentration in the filtrate (usuallyjust forpolishing filtration) and in the filtercake (in sludge filtration), the amount and concentration ofsolids inthe feed, and the required downtime for solids removal and maintenance. As noted earlier, with polishing filtration, cartridge filtration is limited to lower volume wastewaters and those with lower solids concentrations as compared to granularbed filtration. Forgranular bed filtration, when more than one medium is used (dual and multimedia filter arrangements such as sand, garnet, and anthracitecoa1), ahigher capacitycan beexpected for the same size filterbed.

f:\document\15254031.01.019 196In sludge filtration, typically a pressure filter (such as a plate and frame) will yield adriercake than abelt or vacuum filterand will also be more tolerant of vatiations in influent sludge characteristics. Pressure filters, however, are characterized by batch processes requiring downtime for so1ids removal. When cake is built up to the maximum depth physically possible (constrained by**f~lter** geometry) or to the maximum design pressure, the filtration system is taken off-line while the cake is removed. (An alternate unit can be put on-line while the other is being cleaned.) Belt and vacuum filters are continuous systems (i.e., cake discharges continuously), but each of these filters is usually much 12rger than a pressure filter with the same capacity.
For all filtration processes, the 1 arger the filter, the greater its hydraulic capacity (overall throughput) and the longer the filter runs between solids remoyal. EPA examines the type and size of the filter chosen to ensure that it is capable of achieving effective filtration of the wastewater. 2.5.2 Filtration Pressure
Pressure impacts both the design pore size of the filter media and the design feed flow rate (hydraulic loading rate). The higher the feed pressure, the longerthe run will be priorto solids removal in polishing filtration. In**sludg~** filtration, at higher pressures the cake will be drier and the runs will usually belonger priorto cake discharge. However, for gelatinous solids, such as some metal hydroxides, excessive pressure may cause the solids to clog the filter pores and prevent additional polishing or sludge fiitration. Also, high pressures may force particles through the filter medium, especially early in a filter run, resulting 1n ineffective filtration. In vacuum sludge filtration, the maximum amount of vacuum typically applied ranges from 20 to 25 inches of mercury. (The absolute maximum amount of vacuum that can theoretically be applied is29.9 inches ofmercury, or atmospheric pressure.) Forbelt filters, neither hydraulic pressure nor vacuum is applied to the waste feed (although mechanical pressure is applied). For plate-and-frame and vacuum filtration

f:\doclllll!nt\15254031.01.019 197systems, EPA monitors the filtration pressure (or vacuum) applied to the waste feed continuouslYT if possible, to ensure that the system is operating at the appropriate**des~gn** condition and to diagnose operational problems. 2.5.3 Amount and Type ofCoagulants, Flocculants, and Filter Aids Coagulants, flocculants, and filter aids may be mixed with the waste feed prior to filtration. Coagulants and flocculants affect the type and size of the particles in the waste and, hence, theirease ofremoval. In vacuum filtration their effect is particularly significant since they may make the difference between no cake formation and the forming of a relatively dry cake. In a pressure filter, coagulants, flocculants, and filter-**~ids** can significantly improve overall throughput and cake dryness. Filteraids, such as diatomaceous earth, can be precoated on all sludge filters for particularly difficult-tofiltersludges (those containing ahigh concentrationofgelatinous solids). The precoat layer acts somewhat like a filter in that sludge solids are trapped in the precoat pore**spac~s.** In polishing filtration, filter aids both improve the effectiveness of filtering gelatinous particles and increase the time that the filter can stay on-line. Coagulants, flocculants, and filter aids are particularly useful when the sludge (in the case of sludge filters) and wastewater {in the case ofpolishing**filtr~tion)** have a high percentage of very small particles or when the ·concentration of solids in the waste feed or wastewater is low. Inorganic coagulants include alum, ferric sulfate, and lime. Organic flocculants, which are called polyelectralytes, are anionic, cationic, or nonionic in nature. Diatomaceous earth isthemost commonly used filter aid. The use ofcoagulants, flocculants, and filter aids increases the amount ofsolids requiring disposal. Polyelectrolyte flocculant usage, however, usually does not increase the solids volume significantly because the required dosage is relatively low. If the addition ofcoagulants, flocculants, and filter aids is required, EPA examines the amount and type added to the waste, along with theirmethod ofaddition, to ensure effective dewatering and filtration.

f:\document\15254031.01.019 1982.5.4 Hydraulic Loading Rate Lower hyd(aulic loading rates generally improve filtration**pe~formance.** For sludge filtration, higher hydraulic loading rates for a given size filter yield greater overall throughput but result in the formation of wetter cakes (lower percent solids) and, for plate-and-frame filters, shorter cycle times. Forpolishing filtration, higherhydraulicloading ratesyieldgreaterthroughput but result tn shorter cycle times. 

### EPA monitors the hydraulic loading rate to ensure effective dewatering and filtration of waste sludge and effective filtration of wastewater. 2.5.5 Pore Size ofthe Filter Media
For polishing filtration systems, the pore size of the filter media determines the particle size that will be effectively removed from the wastewater. 

### EPA examines the pore size ofthe filtermedia to ensure effective filtration ofwastewater. For sludge filters, the pore size and type relate to resistance to abrasion and corrosion.

f:\document\15254031.01.019 1992.6 References
Anonymous. 19d5. Feature report. Wastewater treatment. Chemical Engineering 92(18):71-72. Crain, R.W. 1981. Solids removal and concentration. In Third Conference on Advanced Pollution Control for the Metal Finishing Industry, pp. 56-62. Cincinnati, Ohio: U.S. Environmental Protection Agency. Eckenfelder, W.W., Jr., Patoczka, J., and Watkins, A. 1985. Wastewater treatment. Chemical Engineering, September 2, 1985. Kirk-Othmer. 1980. Encyclopedia ofchemical technology. 3rd ed. Vol. 10. New York: John Wiley and Sons. Perry, R.H., and Chilton, C.H. 1973. Chemical engineers' handbook. 5th ed., Section 19. New York: McGraw Hill Book Co.

f:\dacument\15254031.01.019 200

### 3. HIGH TEMPERATURE METALS RECOVERY 3.1**Ap~lfcability** 

### High temperature metals recovery (HTMR} is a technology applicable to wastes containing metal oxides and metal salts (including cadmium, chromium, lead, nickel, and zinc compounds} at concentrations ranging from 10 percent to over 70 percent with low levels (i.e., below 5percent} oforganics and water in the wastes. There are a number of different types of nigh temperature metals recovery systems, which generallydifferfromone another in the source ofenergy used and the method of recovery. These HTMR systems include the rotary kiln process, the plasma arc reactor, the rotary hearth electric furnace system, the molten slag reactor, and the flame reactor. HTMR is generally not used for mercury-containing wastes even though mercury will volatilize readily at the process temperatures present in the high temperature units. The retorting process is normally used for mercury recovery because mercury is very volatile and lower operating temperatures can be used. Thus, the retorting process is more economical than HTMR for mercury-bearing wastes. Retorting is discussed in Section II.S.S. TheHTHRprocesshas beendemonstratedonwastes such as baghousedusts and dewatered scrubber sludge from the production of steels and ferroalloys. Zinc, cadmium, and lead are themetals most frequently recovered. The process has not been extensively evaluated for use with metal sulfides. The sulfides are chemically identical t9 natural minerals ordinarily present in ores used as feedstocks by primary smelters. Some sulfide-bearing wastes from the chrome pigments industry have been sent to such primary smelters. However, with sulfides, a possibility exists for formation of either carbon disulfide from reaction with carbon or sulfur dioxide from reaction with oxygen in the HTMR processes.

f:\document\15254031.01.020 

### 201 

# ,

### Metal halide salts are also not directly used in HTMR processes. They, however,.may be converted to oxides or hydroxides, which are acceptable feedstocks for HTMR processes. (_ 

### 3.2 Underlying Principles of Operation The basic principle of operation for HTMR is thatmetal oxides and salts are separated from awaste through ahigh temperature thermal reduction process thatuses carbon, limestone, and silica (sand) as rawmaterials. The carbon acts as areducing agent and reacts with metal oxides to generate carbon dioxide and free metal. The silica and limestone serve as fluxing agents. This process yields ametal product for reuse and reduces the concentration ofmetals in the residuals and, hence, the amount of waste that needs to be land disposed. An example HTMR 

### reaction is the recovery of zinc, which proceeds as follows:
2

### ZnO +C• 2

### Zn +

### C02 

### 3.3 Description ofHigh Temperature Metals**~eco•ery** 

### Process The HTHR process consists of amixing unit, ahigh temperature processing unit (kiln, furnace, etc.), aproductcollection system, and aresidual treatment system. 

### Aschematic diagram for a high temperature metals recovery system is shown in Figure 22. 

### The mixing unit homogenizes metal-bearing wastes, thus minimizing feed variations to the high temperature processing unit. Before the wastes are fed into the hightemperatureprocessing unit, fluxing agents andcarbon canbe added to the mixing unit and mixed with the wastes. The fluxes used (sand and 1



### in1estone) are often added to react with certain meta1 

### components, preventing theirvolatilization and resulting in an enhanceapurity ofthe desired volatile metals removed.

f:\document\15254031.01.020 202WASTE INFLUENT 

# - ... CARBON 

# - MIXING CREDUCIHO AGENT)

... UNIT 

# . FLUXES 

# - ... CLIMESTONE, BAND)-

I 

# - 

# ..

.

,.

.

### .
l

.. !

.,

,.

j '., It
HIGH TEMPERATURE

PROCESSINO UNIT



### •



## •
RESIDUAL COLLECTION CQUENCH TANk) 

# - 

# --EXHAUST AIR OR GAS TO THE ATMOSPHERE

PRODUCT COLLECTION UNIT (CONDEHSOH on COHDENSOR AND BAGttOUSEt

NON-VOLATILE IIETAL PRODUCTS TO REUSE. FURJIIER RECOVERY IN A FURNACE,**STABILIZ~TION** FOLLOWED BY LAND OIPO:IAL1

OR DIRECTLY TO LAND DISPOSAL

Figure 22 High Temperature Metals Recovery Syste• 

# - - VQt.ATILE**IIET~L** PRODUCTS TO REUSE OR FUHTttER REFINEMENT PRIOR TO REUSE

....

# -----

### The blended waste materials are fed to afurnace, where they are heated to temperatures rangjng from 1100 to 1400"C (2012 to 2552"F), 

### resulting in the reduction and Glolatilization of the desirad metals. The combination of temperature, residence time, and turbulence provided by rotation ofthe unit or addition of an air or oxygen stream helps ensure the maximum reduction and volatilization ofmetal constituents. The product collection system can consist of either a condenser or a combination condenser and baghouse. The choice of aparticular system depends on whether the metal is to be collected in the metallic form or as an oxide. Recovery and collection are accomplished for the metallic form by condensation alone, and for the oxide by reoxidation, condensation, and subsequent collection of the metal oxide particulates in a baghouse. There is no difference in these two types ofmetal recovery and collectionsystems relative to the kinds ofwaste that can be treated; the use of one system or the other simply reflects the facility'spreferencerelativeto productpurity. In the former case, thedirect condensation of metals allows for the separation and collection of individual metals in arelatively uncontaminated form; in the latter case, the metals are collected as acombination of several metal oxides. The treated waste residual slag, containing higher concentrations of the less-volatile metals than the untreated waste, is sometimes cooled in aquench tank and (a) reused directly as a product (e.g., a waste residual**cont~ining** 

### -mostly iron can be reused**~-n** 

### steelmaking); (b) reused**a~:ter** 

### further orocessing

(e.g., awaste residual containing oxides of iron, chromium, and nicke1 

### :Jn be reduced to metallic fprm 

### and then recovered for use in the manufacture of stainless steel); (c) stabilized (material has no recoverable value) to immobilize any remaining metal constituents and then land disposed; or (d) directly land disposed as a slag.

f:\document\15254031.01.020 204 f

### 3.4 Waste Characteristics Affecting Performance (WCAPs)
In determtning whether high temperature metals recovery will achieve the same level ofperformance on an untested waste that it achieved on apreviously tested waste and whetherperformance levels can be transferred, EPA examines the following waste characteristics: (a) the concentrationsofundesirable volatile metals, (b) the metal constituent boiling points, and (c) the thermal conductivity of the waste. 3.4.1 Concentration ofUndesirable Volatile Metals
Because HTMR is a recovery process, the product must meet certain purity requirements prior to reuse. Ifthe waste contains other volatilemetals, such as arsenic or antimony, which are difficult to**separat~** 

### from the desired metal products andwhosepresencemay affecttheabilityto reuse the productorrefine it for subsequent reusf:, HTMR may not be an appropriate techno1 ogy. If the concentration of undesirable volatile metals in the untested waste is significantly higher than that in the tested waste, the system may not achieve the same performance, andother, more applicable treatment technologies may need to be considered for treatment of the untested waste. 3.4.2 Metal ConstituentBailing Points The greater the ratio of volatjlity of thewaste·constjtuents, the more easily the separation.of these constituents can proceed. This ratio is called relative volatility•.**~PA** 

### retognizes, hC*ever,**that~the** 

### relative volatilities cannot be measured or calculated directly for the types of wastes generally treated by high temperature metals recovery. This isbecause the wastes usually consist of a myriad 

### of components, all with different vapor pressure-versustemperature relationships. However, because the volatility of components is usually inversely proportional to their boiling points (i.e., the higher the boiling point, the lower the volatility), EPA uses the boiling point of waste components as asurrogate waste characteristic for relative volatility. Ifthe

f:**\doc~~n~nt**\15254031.01.020 205differences in boiling points between the more volatile and less volatile constituents are significantly smaller in the untested waste than in the tested waste, the**syst~**may not achieve the same performance and other, more applicable treatment technologies may need to be considered for tr2atment of the untested waste. 3.4.3 Thermal Conductivity ofthe Waste The ability to heat constituents within an HTMR process feed matrix is a function ofthe heat transfercharacteristics ofthe individual feed components (coke, limestone, untreated waste, etc.). The constituents being recovered from the waste must be heated to near or above theirboiling points in order for them tobe volatilized and recovered. The rate at which heat will be transferred to the feed mixture isdependent on themixture's thermal conductivity, which is the ratio of**t~e** conductive heat flow to the temperature gradient across the material. Thermal conductivity measurements, as part of a treatability comparison of two different wastes to be treated by a single HTHR system, are most meaningful when applied to wastes that are homogeneous (i.e., uniform throughout). As wastes exhibit greater degrees of nonhomogeneity, therma1 conductivity becomes less accurate in predicting treatability because the measurement reflects heat flow through regions having the greatest conductivity (i.e., the path of least resistance) and not heat flow through all parts of the waste. Nevertheless, EPAbelieves that thermal conductivitymay provide thebest

. measure of performance of heat transfer. If the thermal conductivity of the untested waste is significantly lower than thatofthe tested waste, the system may not achieve the same performance and other, more applicable treatment technologies may need to be considered for treatment ofthe untested waste. 

### 3.5 Design and Operating Parameters
In assessing the effectiveness of the design and operation of an HTMR system, EPAexamines the following parameters: (a) theHTMRtemperature, (b) the**f:\dcc~nt\15254031.01.020** 206 

# ,residence time, (c} the degreeofmixing, (d) the carbon content ofthe feed, and (e) the calcium-to-silica ratio of the feed. {_ 3.5.1 HTMR Temperature Temperature provides an indirect measure of the energy available (i.e., Btu/hr} to volatilize the metal waste constituents. The higher the temperature in the high temperature processor, the more likely it is that the constituents will react with carbon to form free metals and volatilize. The temperature must beequal to orgreaterthan theboilingpointofthe metals being volatilized for recovery. However, excessive temperatures could volatilize less-volatile, undesirablemetals into**th~**product, possibly inhibitingthe potential for reuse ofthe product. 

### EPA monitors the HTMR processor temperature continuously, if possible, to ensure that the system is operating at the appropriate design condition (at or above the boiling point(s} of the metal or metals being recovered, but not so high that it volatilizes other unwanted constituents} and to diagnose operational problems. 3.5.2 Residence Time The residence time affects the amount ofvolatile metals volatilized and recovered. It is dependent on the HTHR processor temperature and the thermal**condu~tivity** ofthe feed**~tend.** EPAmonitors the residence time to ensure that**~ufficient** time is provfded**t~effectfvely** volat111ze the volatile constituents for recovery. 3.5.3 Degree 

### ofMixing Effectivemixing ofthewaste withcoke, silica, andlimestone 1snecessary to produce auniformfeed blendto the system. The quantifiable degree ofmixing is acomplex assessment that includes, among other things, the amount ofenergy supplied, the length of time the material is mixed, and the related turbulence effects ofthe specific sizeand shape ofthe tank orvessel. This isbeyond the

f:**\doc~m~nt\152S.C031.01.020** 207

### scope of simple measurement. EPA, however, evaluates the degree of m1X1ng qualitatiyelyby considering whether mixing is provided and whether the type of mixing device is-one that could be expected to achieve uniform mixing of the (_ 

### waste. 3.5.4 Carbon Content of the Feed The amount of carbon added to the waste must be sufficient to ensure complete reduction of the volatile metals being recovered. EPA examines the basis for calculation ofthe amount ofcarbon added to the waste to ensure that sufficient carbon is being used in the feed blend to effectively reduce metal compounds. 3.5.5 Calcium-to-Silica Ratio oftha Feed The calcium-to-silica ratio in the feed blend must be controlled to limit precipitationofmetallic iron in thehigh temperature processor. The iron forms as solid calcium iron silicate, which is very difficult to subsequently process into any useful material. Aluminum oxide will also undergo reactions with lime and silica to form calcium aluminosilicates, which will lower the density and increase the volume of slag generated. Precipitates andmodified slags affect the reduction, volatilization, and recovery ofvolatile metals by changing heat flow characteristics in the system and by undergoing secondary, high temperature chemical reactions with metal oxides in thefeed, conv_ertingthemto the previously notec1inertmetal sil

### icates or silicoaluminates. The ratio of calcium to silicato be used is dependent on thewaste composition. Generally, aone-to-one silica-to-calciumoxideratio is highlydesired, so amounts oflimestone and sand need to be adjusted based on the calcium and silica content ofthe waste to achieve this ratio.
Excess limemay also be added to fix sulfurin the feed as calciumsulfate. This will**preve~t** 

### the volatile metals from rP.acting with sulfur to form metal

f:\document\1SZS40Jl.Ol.OZO 208sulfides, thereby lowering the recovery of metals or oxides. EPA monitors the amounts .of limestone and sand added to the waste to ensure that the calcium-to-siltca ratio selected to maximize metal or oxide recovery is maintained during treatment.

f:\dccument\15254031.01.020 2093.6 References

- Center for**Het~]s** Production. 1985. Electric arc- furnace dust--disoosal, recvcle and recovery. Pittsburgh, Pa. Duby, P. 1980. Extractive metallurgy. In**Kirk~Othmer** encyclopedia ofchemical technology. 3rd ed. Vol. 9, p. 741. New York: John Wiley and Sons. Lloyd, T. 1980. Zinc compounds. In**Kirk~Othmer** encyclopedia of chemical technology.**3r~** ed. Vol. 24, p. 824. New York: John Wiley and Sons. Haczek, H., and Kola, R. 1980. Recovery ofzinc and lead from electric furnace steelmaking dust at Berzelius. Journal ofMetals 32:53-58. Price, L. 1986. Tensions mount in EAF dust bowl. Metal Producing. February 1986.**f:\docuaent\152~031.01.020** 210 

# ,
!4• ION EXCHANGE
4.1 Appl'fcability
Ion exchange is a treatment technology applicable to (a) metals in wastewaters where the metals are present as soluble ionic species (e.g.,

## cr·3and Cr04-2); (b) nonmetallic anions such as halides, sulfates, nitrates, and cyanides; and (c) water-soluble, ionicorganiccompounds including (1) acids such as carboxylics, sulfonics, and some phenols, at a pH sufficiently alkaline to yield ionic species, (2) amines, when the solution**acicil~i** is**suffici~ntly** acid to form the corresponding acid salt, and (3) quaternary amines and alkysulfates. 4.2 Underlying**Principle~ ~f**  Operation
Ion**e~change,** when used in hazardous waste treatment, is a reversible process in which hazardous cations and/or anions are removed from an aqueous solution and are replaced by nonhazardous cations and/or anions such as sodium, hydrogen, chloride, or hydroxyl ions. Ion exchange resins are cationic ifthey exchange positive ions (cations) and anionic if they exchange negative ions (anions). When the waste streamtobe treated isbrought into contact with abed of resin beads (usually in apacked column), an exchange ofhazardous ions for nonhazardous ions occurs on the surface of the resin beads. Inithlly, a**nonhaz~rdous** ton is**loos~ly**bound to the surface ofthe resin. When ahazardous 1on is nearthe resin, it is preferentially adsorbed to the surface of the resin (based on the differences in ionic potential), releasing the nonhazardous ion. Cation exchange resins contain mobile positive ions, such as hydrogen (H.) or sodium (Na•), which are attached to immobile functional acid groups, such as sulfonic (501-) and carboxylic (COO-) groups. Anion exchange resins have immobile basic ions, such as amine (NH2-), to which the mobile anions, such as hydroxyl {OH-) or chloride {Cl-), are attached.

f:\document\15254031.01.021 211Ion exchange material is contactedwith the solution containing the ion to be removed until jhe active sites in the exchange material are partially or completely used**~p** ("exhausted") by that ion. For example, a cation exchange resin (designated R-) to which amobile positive ion (N+) is attached reacts with a solution ofelectrolyte 

### (H•x-) as shown below:

After exhaustion, the resin is then contacted with arelatively low volume of a very concentrated solution ofthe exchange ion to convert ("regeneraten) itback to its original form. The regeneration reaction may be written as follows:

For instance, in the case of a sodium-based resin, a strong solution of sodium chloride is typically the regenerant solution. The regenerant solution forces the previously removed ions back into solution. This relatively low volume solution, nowhighlyconcentratedwith thecontaminant ions, mustthen be treated prior to disposal for recovery or removal of the hazardous cation or anion contaminants. There will continue to be ahigh concentration ofthe regenerant ion (sodium in the above example) in the usedregenerant solution because excess regenerant ion is necessary to force the contaminant ions back into solution. The direction and extent ofthe completion of**th~ ~~ch;~;a**  reaction deptdd upon
• It

. the equilibrium that is established between the ions in the solution 

### (H•x-) and those in the exchange naterial 

### (R_N.). 4.3 Description of Ion Exchange 

### Process
Host ion exchange operations are conducted in packea columns. The aqueous solution tobe treatediscontinuously fed to either the top orthe bottomofthe column. Atypical fixed-bed ion exchange column consists of a vertical cylindrical pressure vessel with corrosion-resistant linings. If appropriate, a filter is installed at the inlet of the column to**reu~ve** suspended particles

f:\document\15254031.01.021 212 

# 1 I l I ' 1because they may plug the exchange resin. Spargers are provided at the top and bottom of. the cQ_lumn to distribute waste flow. Frequently, a separate distributor is 1sed for the regenerant solution to ensure an even flow. The resin bed, usually**cons~sting** of several feet of ion exchange resin beads, is supported by a screen near the bottom distributor or by a support bed of inert granular material. Externally, the unit has avalve manifold to permit downflow operation, upflow backwashing (to remove any suspended material), injection of the regenerant solution, and rinsing of any excess regenerant. Atypical process schematic for abasic two-step cation/anion ion exchange system is presented in Figure 23. The ion exchange system shown in this schematic includes a series treatment with separate cation and anion exchange systems. Some systems contain both anion and cation exchange resins in the same vessel. The pressure vessels used for ion exchange generallyrange in size from 2to 6feet in diameter for prepackaged modular systems, which typically handle 25- to 300-gpm flow rates, to amaximumcustom size of 12 feet in diameter, which can handle flow rates up to 1,150 gpm. The height of these vessels varies between 6 and 10 feet to provide adequate resin storage, distribution nozzle layout, and freeboard capacityfor bedexpansionduringbackwashing. The nominal surface loading area of the ion exchange vessels ranges from 8 to 10 gpm per square foot.
4.4 Waste Characteristics Affecting Performance (WCAPs)
In determining whether ion exchange will achieve the same level of performance on an untested waste as on apreviously tested waste and whether performance levels can be transferred, EPA examines the following waste characteristics: (a) the concentration and valence ofthe contaminant, (b) the concentration of competing ionic species, (c) the concentration of interfering inorganicsandorganics, (d) theconcentrations ofdissolvedand suspended solids and oil and grease, and (e) the corrosiveness relative to the resin material.

f:\doc1111ent\15254031.01.021 213 

# ,N 

# - ... USED BACKFLUSH WATER TO THEATIIENT

BACKFLUSH WATER

CATION EXCHANGE

SYSTEM

USED REOENERANT SOLUTION AND HINSJ:S TO RECOVERY

. ANDIOR TREATMENT RINSE WATER ACID REOENERANT**~-------------**

USED BACKFLUSH WATER TO 1REATMEN1

RINSE WATER CAUSTIC HEOENERANT

TREATED EFFI.UENT "----.TO L=URTffER ANION EXCttANGE

SYSTEM

USED REGENERANT SOLUTION AND RINSES TO RECOVERY ANOIOR TREATMENT TREATMENT

. AND/OR DISPOSAL

Ftgure 23 Two-Step Catton/Anton Jon Exchangct SJ•:c;tem4.4.1 Concentration and Valence of the Contaminant
As the cancentration and valence of adsorbable ions in the wastewater increase, the size of the resin bed required will increase as well, or, alternatively, the bed will become exhausted more rapidly. This is because a**~iven** amount of ion exchange resin has a 1imited number of sites to adsorb charged ions. If, for example, the valence is doubled or the concentration of the adsorbed ions is doubled, the sites will be exhausted twice as quickly. Hence, very high concentrations of the waste may be inappropriate for ion exchange because of rapid site exhaustion, which could conceivably require regenerant volumes to be essentialiy equal to waste flow volumes. If the concentration and/or the valence of the contaminant in an untested waste is significantly higher than that of the tested waste, the system may not achieve the same performance. Alarger exchange bed ormore frequent regeneration may be required to exchange higher concentrations and/or higher valences of the contaminar.tand achievethe sametreatmentperformance,. orother, more applicable treatment technologies may need to be considered for treatment ofthe untested waste. 4.4.2 Concentration ofCompeting Ionic Species
The presenceofothercontaminants or ions in thewastewater can affect the perforynance of the. ion exchange unit in removing the hazardous contaminant of -concern. Other ion.t-inr.thewastewater**wit~** the s-ame charge·as the contaminant of concern will compete for exchange sites on the resin.**.~1so,** ions with a higher valencewill be preferentiallyadsorbed., While alow-concentrationofthe contaminant of concern may be readily removed from a solution with a low concentration of other similarly charged ionic species, the contaminant may not be removed as efficiently from**s~1utions** where high concentrations of similarly charged ions exist, especially if 

### those ions have a higher valence than that of the contaminants. Ifthe ions of concern are removed from a solution with high concentrations ofother**~imilarly** charged ions, the resin will become exhausted more rapidly because 

### most resins cannot selectively adsorb one contaminant in a

f:\document\l525403l.Ol.021 215solution containingother similarly charged ionic species. Ifthe concentration ofcompeting ionic_species inan untestedwaste is significantlyhigher than that in the tested watte, the system may not achieve the same performance. Alarger exchange bed or more frequent regeneration may be required to exchange higher concentrations of competing ionic species and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment of the untested waste.
4.4.3 Concentration ofInterfering Inorganics and Organics Interfering inorganics, such as iron precipitates, can accumulate in the pores ofaninn exchangers; these ir.organics will physically breakdown or block the rasin particles. Some organic compounds, particularly aromatics, can be irreversibly adsorbed by the exchange resins. Also, some ions tend to oxidize afterthey are removed from solution. For instance, Mn•Z (manganese) mayoxidize to the insoluble**Mn~** state, thereby permanently fouling the exchange sites and requiring the premature replacement of the resin. If the concentration of interfering inorganics and organics in an untestedwaste is significantlyhigher than that in the tested waste, the system may not achieve the same performance and other, more applicable treatment technologies may need to be considered for treatment of the untested waste.
4.4.4 Concentrations ofDissolved and Suspended Solids and Oil and Grease High concentrations ofdissolved and suspended solids and oil and grease can affect the performance of ion exchange sites. Conventiona 1 1 on exchange systems are usually downflow; i.e., the wastewater flows down through the resin bed. Regeneration is accomplished in either the downflow or upflow mode. If excessiveconcentrations ofdissolved and suspended solids and/or oil and grease arepresent in the wastewater, thebedmay clog and require backwashing prior to exhausting its exchange capacity. Backwashing may prove ineffective in the removal ofsome solids or oils. Ifthe concentration ofdissolved and suspended solids and/or oil and grease in an untested waste is significantly higher than
f:\document\15254031.01.021 216 

# 1

### that in the tested waste, the system may not achieve the same performance and other, mare app1 icable treatment techno1 ogies may need to be considered for treatment ofthf_untested waste. 4.4.5 Corrosiveness Some wastewaters are extremely corrosive to ion exchange resin materials, reducing efficiency or increasing downtime for maintenance and repair. For instance, strong solutions of chromates may oxidize many resins, requiring premature replacement. If the corrosiveness of the untested waste is significantly higher than that of the tested waste, the system may not achieve thesame performance and other, more applicable treatment technologies may need to be considered for**treatm~nt** 

### of the untested waste. 4.5 

### Design and Operating Parameters In assessing the effectiveness of the design and operation of an ion exchange system, EPAexamines the following parameters: (a) the amount and type of resin, (b) the amount and type of regenerant solution, (c) the hydraulic loading, and (d) the exchange temperature. For many hazardous organic constituents, analytica1 methods are not available orthe constituent cannot be analyzed in the waste matrix. Therefore, ;twould nonmally be impossibleto measure the effectiveness ofthe ion exchange system. In these cases EPA 

### tries to identify measurable parameters or canstituents that would.act as. surrogates to verify treatment. For organic constituents, each compound contiins ameasurable amount of total organic carbon (TOC). Removal of TOC in the ion exchange system will indicate·removal oforganic constituents. Hence, TOC analysis is likely to be an adequate surrogate anilysiswhere the specific organic constituentcannot be measured. However, TOC analysis may not be ableto adequatelydetecttreatment of specific organics in matrices that are heavily organic-laden (i.e., the TOC

f:\docUQtnt\15254031.01.021 217 

# ,analysis may not be sensitive enough to detect changes at the milligrams/liter (mg/1} le¥el in J!atrices where total organic concentrations are hundreds or thousands ofmg/d}. Inthese cases other surrogate parameters should be sought. For example, if aspecific analyzable constituent is expected to be treated as well as the unanalyzable constituent, the analyzable constituent concentration should be monitored as a surrogate. 4.5.1 Amount and Type of Resin The main design parameter that affects the performance of ion exchange systems is the amount and type of resin used. Numerous cationic and anionic resins are conmercially available. The selection of a resin is based on a variety of factors. Different resins have different exchange capacities, and some have greater affinity than others for specific ions. Certain resins are designed to tolerate corrosive, oxidizing, or high temperature solutions, so theirexchange capacitydoes not degrade as rapidly with use. Most <esins will effectively remove contaminant ions from solution until they become exhausted. However, if resin bed exhaustion occurs too frequently, or if regeneration requires excessive volumes of the regenerant, the type and/or amount of resin might need to be changed. In some instances, pretreatment technologies may be required prior to ion exchange. For most metals removal, cation resins are usually required. However, some metal complexes, such as copper cyanide**(Cu(C~) ),**  chromates (Cr04-2), and arsenates (As04-3}, are anionic and require "the use of**~nion** exchange resins. EPA examines the amount and type of ion exchange resin inthe treatment system to ensure thatasufficient amount of ion exchange resin is provided to effectively exchange the metal ions of concern. 

### 4.5.2 Amount and Type ofRegenerant Solution
For hydrogen-based cation exchangers, acid regenerant solutions are used (e.g., sulfuric, nitric,orhydrochloric ;;cids). For sodium-basedcation resins, sodium chloride isgenerally used. For anion exchange resins,**al~:~i** (commonly sodiumhydroxide) is used to regenerate hydroxide-based resins. Sodiumchloride

f:\document\15254031.01.021 218 

# •

### is used for chloride-based anion resins. EPA 

### examines the amount and type of regeneraAt solutionused to ensure that it is compatible withthe resin andwaste treated and thtt effective removal of the contaminant ions from the exchange resin is achieved. 4.5.3 Hydraulic loading Rate The amount oftime that the wastewater contaminants are in contact in the ion exchange resin (i.e., residence time} impacts the extent to which ion exchange occurs. Higherresidence times generally improve exchange performance, but require larger ion exchange beds to maintain the same overall throughput. For agiven size ion exchange bed, the residence time can be determined by the hydraulicloading rate. Typical hydraulic loading rates for ionexchange systems range from 600 to 15,000 gal/day-ftz. 

### EPA monitors the hydraulic loading rate to ensurethat sufficienttime isprovided to effectively exchange contaminants. 4.5.4 Exchange Temperature High temperatures reduceresin life, requiring premature replacement. EPA 

### monitors the temperature in an ion exchange column continuously, ifpossible, to ensure that the system is operating at the appropriate design condition and to diagnose operational problems. EPA 

### has information showing that the high temperature limit for anionic resins may be approximately 60°C.

f:\document\15254031.01.021 2194.6 References DeRenzo,**D.J.,~d.** 1978. Unit operations for treatmentofhazardous industrial wastes. Park Ridge, N.J.: Noyes Data Corporation. Dorfner, K. 1972. Ion exchangers: properties and applications. Ann Arbor, Mich.: Ann Arbor Science Publishers, Inc. Metcalf

### & Eddy, Inc. 1979. Wastewater engineering: treatment disposal reuse. 2nd ed. New York: McGraw-Hill Book Co. Patterson, J.W. 1985. Industrial waste treatment technology. 2nded. Stoneham, Mass.: Butterworth Publishers. Perry, R.H., and Chilton, C.H. 1973. Chemical engineers' handbook. 5th ed. New York: McGraw-Hill Book Co. Sundstrom, D.W., and Klei, H.E. 1979. Wastewater treatment. Englewood Cliffs, N.J.: Prentice-Hall, Inc. USEPA. 1982. U.S. Environmental Protection Agency. Development document for the porcelain enameling point source category. pp. 172-241. Washington, D.C.: U.S. Environmental Protection Agency. USEPA. 1983. U.S. Environmental Protection Agency. Treatability manual:**~ol.** III. Technology for control/removal of pollutants. EPA-600/ 2·82-001c. Washington, D.C.: U.S. Environmental Protection Agency. Wheaton, 

### R.H. 1978. Kirk-Othmer encyclopedia of chemical technology. 3rd ed. Vol. 13. New York: John Wiley and Sons.

f:\documant\15254031.01.021 220 

# ,5. RETORTING
5.1 Apliicab11ity Retorting is a treatment technology applicable to wastes containing elemental mercury, as well as mercury present in the oxide, hydroxide, and sulfideforms, at 1 evels above 100 partspermillion, provided that thewastehas a low total organic content (i.e., below 1 percent).**Fo~** metals other than mercury, the typica·, retort operating temperatures (700 to 1000.F) are not high enough to decompose themeta1compounds. High temperaturemeta1s recovery (HTMR} processes must be used to recover most othermetals when they are not present in the pure metal form.
For most retorting processes, there is an additional requirement that the waste have**~** low water content, preferably below 20 percent. Dewatering reduces energy consumption by minimizing the amount of water evaporated and precludes problems involving the separation of recovered metals from large quantities of water. 5.2**Unde~lyinq** Principles 

### ofOperation
The basicprincipleofoperation for retortingis aprocess similarto that for high temperature metals recovery in that it provides for recovery ofmetals from wastes primarily by volatilization and subsequent collection and condensation ofthe volatilizedcomponents. Retortingyields ametal product for reuse and significantly reduces the concentration of- metals in the waste residual, and, hence, the amount oftreatedwaste thatneeds tobe land disposed. This technology 1s differentfrom HTHR in thatHTMR includes areductionreaction invo1 ving the use of carbon, while retorting does not use a reducing agent. Additionally, this process differs with regard to the form and, possibly, the leachability of the residue generated; HTHR generates a slag, while retorting generates a granular solid residue that may have lower leachability than a slag ifmercury is the only constituent of concern present in the untreated waste.

f:\docuroent\15254031.01.022 221

### The basic principleof

### operation ofretorting is that sufficientheat must be**transf~rred** 

### to the waste to cause elemental metals to vaporize. In the case ofmercury prestnt as an oxide, hydroxide, or sulfide compound, sufficient heat must be transferred to the waste to first decompose the compounds to the elemental form and then volatilize the mercury. In mercury wastes that are wastewater treatment sludges, mercury is most often present in the forrn of the sulfide (HgS) as a result of the use of sodium hydrosulfide treatment of mercury-bearing wastewaters. In a few instances, hydrazine is used to treat these same wastewaters; in such instances, a mercurous hydroxide s1iiC:;•.! 

### is generated. This lattercompound can be more easily treated to yield elemental mercury because this reaction occurs more readilythan the sulfidedecomposition at·the temperatures at**~hich** 

### the process is normally operated. Preheated airis provided to the retort to supply the oxygen necessary for the sulfide decomposition and to enhance the heat transfer to the waste. The equations for decomposition of both forms of mercury are presented below:(a} HgS +

### 0 2 • 

### Hg +

### 502



### 5.3 Description ofRetorting Process The retorting process generally consists ofaretort (typically an oven, i.e., mu1tiple hearth furnace or rotary kiln} fn which the waste is heated to volatilizethe metal constituents, acondenser, ametals collection system, and an airpollution control system. Figures 24 and 25 show aretort system without and with a scrubber-type air pollution control system. Trays of wastes are placed in the retort, where they are heated, and decomposition ofmercurycompounds and volatilizationofthemetallicmercury and

f:\document\15254031.01.022 

### 222PREHEATED AIR RETORT COOLING WATER

-------------... -•..__wAs·re INFLUENT**TRE~TED** RESIDUAL WASTE TO 8JABJLIZATION AHPIOH LAND DISPOSAL 

# ... AIR POLlUTION...__-.&...

__ CONTROL

SYSTEM

METAL COLLECTION

VOLATILE UI::TALS TO REUSE EXHAUST AIR TO THE ATMOSPHERE 

# r

-4--STACK

Ftgure 24 Retorttnv Process (Vtthout a Scrubber and Subsequent Wastewater Dtscharge)



# ..,**--~-------~**--------------- ---------------

EXttAUST AIR TO THE ATMOSPHERE 

# t

WATER

._STACK

PREHEATED AIR DECANTER**1---t~** WASTEWATER TO TREATMENT 

# u RETORT 

# r-------7.i::l-- WASTE INFLUENT

TREATED RESIDUAL WASTE TO STABILIZATION AND/OR LAND DISPOSAL VOLATILE**L----.t~** METALS TO REUSE

F1gure25 Retort1ng Process (M1th a Scrubbur and Subsequent Wastewater Dtscharge)

### other volatile elemental metals occur. Although most commonly carried out in an oven, retOrting can also be performed in amultiple hearth furnace. t_ 

### The vapor stream from the retort is cooled in acondenser. If a scrubber is not used as an airpollution control device, an electrostaticprecipitator is provided after the condenser to remove any residual metal in the exhaust vapor stream, as well as to control other potential emissions such as sulfur dioxide (S02), 

### fly ash, and hydrogen chloride (HCl) vapors. Condensedmetal is collected for reuse before the electrostatic precipitator. Residual solids remaining in the retort, stripped of volatile metal contaminants, are collected and may be either directly land disposed or stabilized, to i11111obilize any remaining metal constituents, and then land disposed. 5.4 Waste Characteristics**Affect~nq** 

### Performance CWCAPsl
Indeterminingwhetherretortingwill achieve thesamelevel ofperformance on an untested waste that it achieved on a previously tested waste and whether performance levels can be transferred, EPA examines the following waste characteristics: (a) the concentration ofundesirable volatile constituents in the waste and (b) the thennal conductivity ofthe waste. 5.4.1 Concentration of**Undesirabl~Yolatile** 

### Constituents
Because retorting is a recovery process, its product must meet certain purity requirements prfor· to,reuse. · If the waste contains other volatile constituents with boiling points equal to or below that of the metal(s) to be recovered, theywill be volatilizedandcondensed a 1ongwiththe desiredmeta1 (

### s) present in the waste. These constituents may be difficultto separate from the recovered productandmay affectthe abilitytoreusethe productmetal orrefine itfor subsequentreuse. Undesirable volatileconstituents sometimes present in mercury-bearing wastes include (a) mercury chlorides, whichdistill unchanged in

f:\document\15254031.01.022 225

# I I I I 

### !
I I i 

# I 

# I

I I I I I 

### the retorting process, and other volatile metal halides; (b) arsenic oxide and arsenic trichloride; and (c) organomercury compounds, such as phenylmercuric acetate, which**\~e**

### not decomposed to elemental mercury by the retorting process. For wastes containing significant levels (i.e., above 1percent) ofthese contaminants, retorting may not be an appropriate technology. If the concentration of undesirable volatile constituents in the untested waste is significantly higher than that in the tested waste, the system may not achieve the same performance. ·chemical pretreatmentmay be required to convertmercury chiorides and organomercury compounds to mercuric sulfide and/or elemental mercury and achieve the same treatment performance, or other, more applicable treatment technologies may need to be considered for treatment of the untested waste. 5.4.2 Thermal Conductivity of the Waste The abilityto heat canstituentswithin awaste matrix is afunction ofthe heat transfer characteristics of the waste material. Mercury and other recoverable metals in the waste must be heated to near or above their boiling points in order to be volatilized and recovered. The rate at which heat will be transferred to the waste materia1 is dependent on the materia1 's therma1 conductivity, which is the ratio of the conductive heat flow to the temperature gradient across the material. Thermal conductivity measurements, as part of a treatabilitycomparison oftwo differentwastes to be treated by asingle retort system, are most meaningfui when applied to wastes that are homogeneous (i.e., uniform throughout). As wastes exhibit greater degrees of nonhomogeneity, thermal conductivitybecoiiM!s lessaccurate in predictingtreatabilitybecause the measurement reflects heat flow through regions having the greatest conductivity (i.e., the path of least resistance) and not through all parts of the waste. Nevertheless, EPAbelieves that thermal conduct1v.1tymayprovidethebestmeasure of performance ofheat transfer. If the thermal conductivity of the untested waste is significantly lower than that of the tested waste, the system may not

f:\docunent\1525-4031.01.022 226 

# ,achieve the same performance and other, more applicable treatment technologies may need to be considered for treatment of the untested waste. t 5.5 Design and Operating**Parame~~~!** In assessing the effectiveness of the design and operation of a retort system, EPAexamines the following parameters: (a) the retorting temperature and (b) the residence time. 5.5.1 Retorting Temperature Temperature provides an indirect measure of the energy available (i.e., Btu/hr} to vaporize the metal of concern. The higher the temperature in the retort, the more likely it is that the metal will volatilize. The temperature must be equal to or greater than the boning point of the metal. However, excessive**tem~eratures** could volatilize undesirable constituents into the product, possibly inhibiting itspotential reuse, and also could cause sintering ofthe feed material. Formercuryretorting, EPAmonitors the retorttemperature to ensure that the system is operating at the appropriate design condition (a temperature at least equal to the boiling point of mercury (674.F) but below lOOO.F) and to diagnose operationa1 problems. 5.5.2 Residence 

### i1me The residence time impacts the amount of volatile metal volatilized and recovered. It is dependent on the retort temperature and the thermal conductivityofthewaste. Typical residence times in retortsystems formercury range from 4hours to 20 hours. EPA monitors the residence time to ensure that sufficient time is provided to effectively volatilize all ofthe mercury and/or other metals to be removed from the waste.

f:\document\1SZS403l.Ol.OZ2 2275.6 References Occidental**Chem~al** Corp. 1987. Oelisting petition, chloralkali plant, Muscle Shoals, Alabama. Submitted to U.S. Environmenta1 Protection Agency, July 20, 1987. Perry, R.A. 1984. Mercury recovery fr:= contaminated wastewaters and sludges. PB 238 600. Sittig, M. 1975. Resource recovery and recycling handbook of industrial wastes. Park Ridge, N.J.: Noyes Publications. Versar. 1987. Waste minimization audit report

- case studies of minimization of mercury bearing wastes from chloralkali plants. Prepared for U.S. Environmental Protection Ag::ncy, Office of Research and Developmer.t, Hazardous Waste Engineering Research Laboratory by Versar Inc., Contract No. 68-01-7053.

f:\document\15254031.01.022 228 

# , it



### III. TECHNOLOGIES APPLICABLE TO MIXED WASTE**(RADIOACTIVE~RDOUS)** 

# ,Introduction This sectiundescribes thetreatmenttechnologies applicabletomixedwaste (i.e.,wastethat is bothradioactive and hazardous). This introduction explains what mixed wastes are and how they are classified, where they are likely to be generated, and how they are regulated. Following this introduction are sections discussing (a) technologies for treating mixed wastes containing organics and in(jrganics other than metals, (b) technologies for treating mixed wastes containingmetals, and (c) technologies for treatingmixedwastes thatcannotbe treated by technologies d2termined to be BOAT for the corresponding nonradioactive wastes (i.e., special mixed wastes treatability group). Each of these three sections includes subsections describing applicable treatment technologies. Mixed-wastes are those wastes that satisfy the definition of radioactive**wa~te** subject to the Atomic Energy Act (AEA) and that also contain waste that either is 1 isted as a hazardous waste in Subpart 0 of 40 Code of Federal Regulations (CFR) Part 261 orexhibits anyofthe hazardous wastecharacteristics identified in Subpart Cof 40 CFR Part 261. Because they are hazardous, mixed wastes are subject to the Resource Conservation and Recovery Act (RCRA) Land Disposal Restrictions. All promulgated treatment standards for RCRA listed and characteristicwastes apply to the RCRAmixedwastes unless EPA has specifically estabLished aseparate treatabilitygroup for aspecificcategory ofmixed waste (see following Section C). Although mixed wastes are regulated by EPA under RCRA, the specific standards forradioactive material managementdeveloped under the AEA are administered by the Department ofEnergy (DOE) for government-owned facilities and by theNuclearRegulatory Commission (NRC) for commerciallyowned facilities. Themajorityofmixed wastes can be divided into the following three categories based on the radioactive component of the waste: (a) 1 ow-level wastes, (b) transuranic (TRU} wastes, and (c) high-level wastes. Low-level wastes include radioactive waste that is not classified as spent fuel from commercial nuclear powerplants or as defense high-level radioactive waste from the production ofweapons. TRU wastes are those wastes containing elements with

f:\document\15254031.01.023 229an atomic number greater than 92 (the atomic number for uranium). TRU wastes generally.pose greater radioactivity hazards than low-level wastes because they contain long-lited alpha radiation emitters. However, commercial transuranic waste is included as low-level radioactive waste. High-level mixed wastes havP. high levels ofradioactivity and are extremely dangerous to handle. High-level mixed wastes are generated from the reprocessing of irradiated fuel rods from commercial and military nuclear reactors. Mixed low-level wastes aregenerated principallyfromnuclearpowerplants, the Department of Energy (DOE), and academic and medical institutions. Some examples of low-level mixed wastes include spent solvents containing suspended



### - ordissolved radionuclides, scintillationcocktails fromdiagnostic procedures, spent Freon used for cleaning protective garments, acetone or solvents used for**cl~aning** pipes or other equipment, and still bottoms from the distillation of chlorofluorocarbon solvents (CFCs). Otherwastes in thiscategory include awide range of solid materials such as spent ion-exchange resins (contaminated with various metals), filters used in reclaiming CFCs, adsorbents, residues from the cleanup of spills, lead shields, lead-lined containers, welding rods, and batteries. Also, the production ofmilitary weapons produces large amounts of wastes that fall into the low-level and TRU categories of mixed waste.

f:\document\15254031.01.023 230 

# ,

.

### A. TECHNOLOGIES FOR MIXED WASTES CONTAINING ORGANICS AND INORGANICS OTHER THAN METALS

The following technologies have been determined to be applicable for treating mixed waste. These technologies were described in detail in previous sections in this document for hazardous wastes that are not mixed. Technologies for mixed waste operate under the same principles ofoperation used for treating nonmixed waste. However, with mixed waste these technologies**~ypically** separate the hazardous waste components from the radioactivecomponents, thereby reducing the volume ofthe radioactive component requiring treatment, or immobilize the waste {in the case of stabilization technologies}. If the hazardous component is also radioactive (e.g., a hazardous solvent whose structure contains radioactive carbon}, that component may sometimes be removed from the waste; leaving a less hazardous, less radioactive residual.
1. Carbon Adsorption
For organic low-level mixedwastes, carbon adsorption maybe usedto remove organics in wastewaters. Ifthe organic component is notradioactive, then this treatment reduces the quantity of the hazardous waste component in the mixed waste. 2. Distillation Technologies
Adistillation technology such as batch distillation, steam stripping, fractionation, thin film evaporation, orthermal dryingmay be applied to amixed waste in that it can be used to separate the mixed waste into the hazardous and radioactive waste components, as long as the hazardous component is not also radioactive. The separation can be made where the volatility of the hazardous components is significantly different from the volatility of the radioactive components. The distillation process will remove the more volatile organic components, leaving the less volatile constituents in the still bottoms.

f:\doc1111ent\15254031.01.023 231 

# ,

# ..

3. Extraction Technologies Aswithd{.stillation, extractiontechnologies {i.e., solventextractionand critical fluid extraction} may be used to separate a mixed waste into its radioactive and hazardous components ifeither the hazardous or the radioactive components can be selectively extracted by the extracting solvent.

f:\document\15254031.01.023 232B. TECHNOLOGIES FOR MIXED WASTES CONTAINING METALS
1.**Ac~d** Leaching Acid leaching may be used to extract hazardous metals (regardless of whether the metals are radioactive) from mixed wastes, principally soils, separatingthematerial into itshazardous andradioactivecomponents orremoving the hazardous and radioactive component from the rest ofthe waste. This process mayhave greaterutilitywhen combinedwith unitoperations such as ion exchange, solvent extraction, chemical precipitation, and filtration.
2. Chemical Precipitation Chemical precipitation may be applicable to mixed wastes for separating hazardousmetals and/orhazardous metal radionuclides from otherconstituents in wastewaters. Specific conditions of pH, temperature, and precipitating reagent addition are required to selectively remove part or all of the radioactive components**~c** aprecipitate.
3. Filtration Filtration technologies may be used following precipitation and settling proce.sses to separatelow-level mixed waste fromhigh-level mixed waste. Hence, -filtrationmay concentrate the high-level waste components in the filter cake,

leaving a relatively low-level filtrate.
4. Hfgh Teuperature Metals Recovery The hfgh temperature metals recovery (HtMR) process may be applicable to mixed wastes if the volatility of the radioactive metal component is significantlydifferent fromthatofthe nonradioactive portion. This technology is similar to distillation of organics, but instead •distills• more volatile inorganic components from less volatile ones.

f:\document\15254031.01.023 233 

# ,

I5. Ion Exchange
Ion exclfilnge treatment may be used to separate a mixed waste into its radioactive and hazardous constituents ifthe radioactive components are ionic. It will also concentrate the radioactive ionic species into a small volume, leaving a nonradioactive aqueous phase. The principal mixed waste application ofthis process is to recover metallic radionuclides from wastewaters or acid leach liquors. If more than one radionuclide exists in solution, it may be necessary to use either amixed bed ion exchange unit ordifferent types of ion exchange resins to recover all the radionuclides.
6. Stabilization of Metals Stabilization refers to a broad class of treatment processes that immobi1izs hazardous constituents in a waste. For treatment of metals in low-level mixed wastes and for some TRU wastes containing low-level radioactive components, stabilization technologies will reduce the leachability of the hazardous metal constituents (regardless ofwhether the metals are radioactive) in nonwastewater matrices. However, EPA does not believe that stabilization usingcementitiousbinders isan appropriatetreatmentforhigh-level radioactive mixed wastes generated during the reprocessing of fuel rods. It does not adequately immobilize the high-level radioactive portion of the mixed wastes.**f:\doc~nt\1SZ5403l.Ol.OZ3** 234

### C. TECHNOLOGIES FOR MIXED WASTES IN SPECIAL TREATABILITY GROUPS
1. AmaJsamation Amalgamation is applicable to radioactive wastes containing mercury and particularly to wastes containing radioactive mercury isotopes. Mercury compounds are converted into a solid mercury-zinc alloy, which is more easily managed and less mobile than solutions containing radioactive mercury. The process can be used directly with radioactive wastes provided that additional precautions are**t~ken** toprevent release of radioactivematerials and to protect operations from radioactive emissions. TheAgency has established amalgamation as amethod oftreatment for mixed wastes containing elemental mercury. These types ofwastes are typically found in vacuum pumps and related manometers. In the nuclear industry, this form of mercury has been contaminated with radioactive tritium (a radioisotope of hydrogen).
EPA has determined that amalgamation not only provides a significant reduction in airemissions ofmercury but also provides achange inmobilityfrom liquid mercury to a paste-like solid, potentially reducing leachability. The required method oftreatment, i.e., amalgamation, may be performed using any of the following elements: zinc, copper, nickel, gold, and sulfur. Further**~formation** on the amalgamation process may be found in Section I.B.l.
2. Encapsulation Encapsulation processes such as plastic and asphalt encapsulation may be used for themanagement ofmixed wastes. However, the equipment used for mi!ing of the wastes with molten encapsulating agents must be of special design to**prct~ct** workers from radioactive hazards. Additional precautions may be neaded to prevent generation ofairborne particulates orvapors ofradioactivematerial**f:\document\152~031.01.023** 235 

# ,during the processing. More information on encapsulation may be found in the encapsulation**se~tion** (see Section 1.8.3). {. The Agency has established a treatment standard of macroencapsulation (encapsulating an entire mass, rather than microencapsulation, which coats individual particles of a waste) as a method of treatment for**radi~active** lead solids. This treatment standard applies to all forms ofradioactivemixed waste containing_elemental lead (including discarded equipment containing elemental lead that served as personnel or equipment shielding prior to becoming a RCRA hazardous waste). These lead solids do not include treatment residuals such as

, hydroxide sludges, other wastewater treatment residuals, or incinerator ash, which are usually amenable to cu.wentional pozzolanic stabilization, nor do they include organolead materials that can be incinerated and then stabili:ed as ash.
3. Vitrification
Vitrification is a treatment technology tnat will provide effective inunobilization of the inorganic constituents (i.e., both radioactive and hazardous components) of amixed waste. Vitrificationhas been demonstrated to be an effective treatment technology for high-level mixed waste generatedduring the reprocessing of fuel rods. Since vitrification is a high-temperature process, small quantities of organics that may be present will be volatilized dur;ng the vitrification process. If there are gaiJitla-emitting radionuclides .present, the ga11111a dose rate will be reduced as a result of the increase in density of the vitrif;ed matrix (go;ng from the density of soil orother solids to the density of**glas~).** If rad;um is present, the radon flux rate wnl also be reduced because of the change in the dens;ty. Both alpha and beta emitters will be sealed in the glass matrix. More information on the vitrification process may be found in the vitrif;cation section (see Section I.B.S).

f:\document\15Z5403l.Ol.OZ3 236

# ~ I f4. Incineration
Incinerationis atechnologyapplicabletononradioactiveelemental mercury (i.e., retorting) waste containing high 1 evels of organics. The Agency has determined that incineration is also an applicable technology for mercury-containing hydraulic oil contaminated with radioactive material (low-level mixed waste) and has set incineration as the standard (method of treatment) for that waste. Incineration of radioactive mercury and other volatilemixed waste components is likelytocause themercury or other volatile components to volatilize. Therefore,**incinerator~** ::u:t be equipped with air pollution control devices to ensure that any volatilized hazardous and/or radioactivecomponents are notre1 eased tothe atmo5phP-re abovepermitted 1 eve1s. Incineration of organic wastes containing concentrations of the radionuclides tritium and carbon 14 will cause the esr.ape ofradioactive compounds since the combustion products oftritium(radioactivehydrogen) and carbon 14 are steamand carbon dioxide, respectively, both ofwhich will usually escape conventional air pollution control devices.

f:\document\15254031.01.023 237References U.S. Congress,**~ffi**ce of Technology Assessment. 1989. Partnerships under pressure: managing conunercial low-level radioactive waste. Washington, D.C.: U.S. Government Printing Office. OTA-0-426. USEPA. 1990. U.S. Environmental Protection Agency. Federal Register Notice, 55 FR 22626, June 1, 1990. U.S. General AccountingOffice. 1989. Fact sheet for theChairman, Environment, Energy, and Natural Resources Subcommittee, Committee on Government Operations, House of Representatives; Nuclear Waste, DOE's program to prepare high-level radioactive waste for final disposal. Washington, D.C.: U.S. General Accounting Office. U.S. General Accounting Office. 1989. Report to the Chairman, Committee on Governmental Affairs, U.S. Senate; Nuclear Regulation, the military would benefit from a comprehensive waste disposal program. Westinghouse Electric Corp. 1983. Waste technology reprints: Nuclear waste management in the United States.

f:\document\15254031.01.023 238t**APPEND!~** 

### A LIST OF BEST DEMONSTRATED AVAILABLE TECHNOLOGY (BDAT) BACKGROUND DOCUMENTS AND ASSOCIATED BDAT(S)

f:\document\15254031.01.024This appendix contains a list of BOAT background documents prepared for EPA's Office of Solid Waste, Waste Treatment Branch, in support of the Land Disposal Restrtctions. (The specific Third under which each document was prepared is a 1 so noted.) This appendix is meant to be a quick reference, however, for details on a specific waste code see the relevant background document for thatwaste code. In summary, this appendix presents the following:

• The waste codes, industries, or sources of the waste associated with each background document.

• The treatment technologies on which the treatment standards were based i.e., BOAT. The BOAT associated with each background document is also identified. (Note that BOAT(s) may vary for individual waste codes. contained in a background document. Fllr specific information on the BOAT applicable to acertainwaste code, see the applicable background document.)

• The source ofthe treatment data used to set the treatment standard and whethsr the data were collected or submitted to EPA (actual data) or transferred from existing data.

• The category ofwaste treated ( 1 .e., organics, inorg.anics, meta1s).

A-1 f:\document\15254031.01.024,J:>o I N Yaate Code/ Third CBackgrotnJ**Doc~.~~~ent)**

1/l f001·f005 (revlud for

..**thyl~** chloride) 1/] f006
1/l K001

1/l K01S

1/l 1(016, K018, K019, IC020, IC030 1/] IC022
1/3 IC024
1/3 1(0]7
1/l IC044, K04S, IC047

1/3 IC046 (nonreactlves) 

### ------------..----------- ·-- ---- -----------

LIST bF BOAT BACKGROUND DOCUMENTS AND ASSOCIATED BDAT(S)

Industry or Source of Yaate

f'tla,...ceutIcal Industry Electroplating operatlona Wood preaervlng Industry

Distillation of benzyl chloride
Chlorinated organics produc:tIon Phenol/acetone produc:tIon Phthalic anhydride produc:tIon Olaulfotonproduction "anufacturlng end proceBSinQ of explosives Lead-based lnltlatlns**c~** proc1Jction BOAT(a)

Ste

..stripping (waatewatera)
Stabilization (nonM8atewatera) Rotary kiln Incineration, Stabilization (nonwaatewatera, wastewaters): chealcal**precl~ltatlon** (

.. tala In waatewatora)**Ll~ld** InJection lnclfMiratlon (nonwaatewatera); che.lcal precipitation (wastewaters) Rotary kiln Incineration (nonwaatewatera,**waat~tera)** fuel substitution, atablllzatlon (nonwaatewatera) Rotary kllfl Incineration**<~•stCNatera,** waatewatera) Rotary kiln Incineration (nonwaatewaters, wastewaters) Open burning/Open detonation, Incineration (nonwaatewatera) Stabilization (nonwastewatera) Actual Data or Transferred and ortaln of Data**Data/lndustry·a~ltted Oata/lndustry·a~ltted**  Data/EPA test, tranafer/F006

Tranafer/K019

Data/EPA test**Data/lndustry·a~ltted,** tranafer/F006 Data/EPA test
Oata/fPA test
Data/DOD

Data/EPA test ' Types of Yastes Regulated

Methylene**ch~orlde** Metals, cyanides Organics, metals

organics, metals
Organics Orsanlcs, metals
Phthalic a!;ld Disutfoton, toluene
Reactive waste from IC044, IC04S, K047 Leac;l Cnaetals)



# ---LIST Of aDAT BACKGROUND DOCUHfNTS AND ASSOCIATED BDAl(S)

Actual Data or Transferred Waate Code/**l~try** or and Types of Third (BackgrCUld Doc..-ent) Source of Waste IOAT(II) origin of Data Uastea Regulated

..... 1/l l048·l052 Petrol refining Solvent extractloni fluidized bed Data/Industry-submitted Organlc.s,**~tala,** lnc1Jatry lnclneretlon, ateb llzetlon Inorganic& (nonMasteMatera); lnclneretlon, chr011IU1 racbctlon, ch•lcal precipitation, lind filtering (WaSteMatera) 1/] IC061 Prl•ry at
.. l High te.perature -tala recovery for D"ta/£PA teat "ctols production**l~try** hlih zinc aubcategory, atablllzatlon for low zinc atJJcateaorv 1/] l062 Steel finishing fru. Chru.IUI re<b:tlon, ch•t.:al Data/EPA test "etals Iron and ateel precipitation, aettllng, filtering procb:tlon (nonwaatewatera, wastewaters) );:a. Secondary 1 ead Recycling (noncalclu. aulfate**Data/lnduatry·s~ltted** "etaIs 

### • 1/l K069 w

... ltlna oporatlona category); (nonwaatewatera) 1/3 K071 Chlorineprocb:tlon Acid leaching, ch•lcal oxldation Oata/lndustry·submftted "ercury fr011 the•rcurv aludue dewatering/acid washing cell process (nonwesteMatera), ch•lcal preclphatIon end fIIterlng (wastewater•) 1/l IC081 Dlatlllatlonbotta.s Liquid Injection lnclneretlon Date/Industry-submitted Organics fr011 aniline prcOictlon (nonwasteMaters, wastewaters) 1/l 11:086 Solvent washea end Liquid Injection Incineration Data/EPA test, Organics, metals sludges**fro:~** the cnonwastewatera, wastewaters); tranafer/IC062 procb:tion of Inita, chr011ha recb:tlon, cheilllcol pluments, soaps, end precipitation, settling, stablllzera filtering (wastewaters)

### ·-----------

LIST Of BOAT BACKGROUND OOOUMfNTS AND ASSOCIATED BDAl(S)

Actual Pate or Transferred Waste Codef II'OJitry or and Types cU Third (8ac:kgr0t.nd**Doc~t)** Source of Waste BOAT(a) Origin of Date Wastes Regulated

II'\ I 113 KOll7 Tar aludge fr0111 ,Rotary kiln Incineration Data/EPA test, Organics, metals coking operatlooa (nonwaatewatera); transfer/K06Z chrcxahare<1ittion, thtllltal prccipitatton, aettllna, filtering (w.atewatera) \/3 1(099 2,4·Didhlorophenoxy· Chetalce\ oxidation (nonwastewatera, Data/EPA collected Z,4·Dichlorophenoxy· .cetlc .cld (2,4·D) Waatwetera) aoeticacid, dllorireted procb:tlon dibenzo·p·dioxins, dllcrlrateddii:Jcnrof\.nm 1/1 K1D1, IC1D2 Pradctlonof Rotary kiln Incineration Data/EPA test, Organics, metals v.terlnery (nonwaatwetera); ch.,.lcal tranafertK06Z pha.-..ceutIula trcxa precipitation, aettllne, ereenlc fllterlna (wastewaters)
):a liS l10:S, l104 Aniline/nitrobenzene solvent extr.ctlon, ate
..atrlpplng, DatatEPA teat Organics, inorganlcs I .$» procb:tlon end activated carbon ed$orptlon (cyanides)**followed~** Incineration of the aolvent atre
..fr0111 extraction cnonwaatewatera, waatewatera) \/:S 1(106 Sludges**fr~** the Therwal recovery (retorting) Date/Industry-submitted Mercury -rcurycell process (nonwastewatera) In chlorine procb:tlon 1/3 1(0(\ft·ICDOa, IC021 Plg.enta, fluoro· Chra.lusr.m.:tlon, carbon Datatlndustry·sua.ltted Metals, organics 1(025, K036, K060, -th-, nitrobenzene, edsorptlon; chetalcel oxidation l100 (no**doc~aent** dlaulfoton, coking end •t•l precipitation prepared) end lead**pr~tlon** (nonwastewetera, wastewaters)
2/'S f006·f012, f019 Electroplating, heat Alkaline chlorination, Deta/lndustry·submltted Cyanides, metals treating operations stabilization (nonuaatewaters), alkaline chlorination, chemical precipitation, settling, filtering (wastewaters)

l.\docoun-.1111i21i40l1.01.021i::J:a I Ul waate Code/ ThIrd C Background Doc..-nt)

2/l K011, K013, k014
2/3 Cyenlde P wastes (P013, P021, P029 POlO, P063, P074, P09B, P099, P104, P106, P1l1) 2/l f024

2/l Inorganic**pl~tl** (k002-k008) 2/3 k009, k010

2/l K02], K093, K094 U028, U069, U088, U102, U107, U190 2/3 k027, K111, K112 K11l, k114, K115, K116, K221, UZ23

2/l k028, kOZ9, K09S IC096

I**,...,~•~n•nr\lb1b40l1** 01 02b LIST Of BOAT BACKGROUND I)()(UtfNTS AND ASSOCI

..TED BDAf(S)

lnct.Jstry or Source of Waate

Acrylonitrile procb:tlon Cyanide P wutea 

# .

Chlorinated allphatlca procb:tlon

PIg11e0t1 procb:tI()t'. Acetaldehyde**product!~**
Phthalic anhydride procb:tlon
Toluene dllaocyanate production

1,1,1,-trichloroethane F>foduc:tIon BOAT(a)

Rotary kiln lnctneratlon (MonNUt-tara) Electrolytic oxidation, alkaline chlorination, atablllzatlon (nonwaatewatera), alkaltne chlorination, chealcal precipitation, settling and filtration (waatewetera) Rotary kiln Incineration (nonwaatewatera); rotary kiln IC1Cineratlon, U• and aultlde precipitation, vac:LUI filtering (weat-tera) Not eatablllhed U'lder Z/l rule; ae!l l/3 Rotary kiln Incineration**c~·t-tera); at~** ..atrlpplnu, biological treet.ent (waatewatera) Rotary kiln Incineration (nonwaatewatera and wastewater&)
Incineration or fuel**a~tltutlon** cnonwaatewatera); dlrec:t lnciner.ation, or carbon edsorptlon followed by Incineration or fuel substitution, stabilization (wastewaters) Incineration, ateblllzatlon (nonwastewatera); ll• and sulfide precipitation (waatewatera) Actual Data or Tr1101ferred and Origin of Data

Data/EPA t::.at**Data/lndustry·s~ltted,** tranafer/F006-f012, f019**Data/lndustry·a~itted,** tranafer/K062

See 3/l Tranafer/K.019, Transfer/data**tr~**

OttIce of Water**Tran~~fer/IC024** Transter/11:015, IC086, f006

Tranafer/IC019, Transfer/IC062 Typea of \laatea Regulated

Acryta11trIIes,qllllidcs Cyanides, .etala

Organics,**~tala**

See 3/3 Organics Organics
Organics, -.rats

Organics,**~tala** '> I I i



# ___j;J:a I 0'1 Waste Code/ Third (Beclt"rcxm**Doc~t)**

2/l KOl6, K038, K039, K040, P0l9, P040, P041, P043, P044, P062, P07, PD85, P089, P094, P097, P109, P111, uose, uoa7, U2ls l./l K04l
2/l K069 (Calclu. aulfate)
l/] DOOI

ltl DOOZ

l/l DOOl**1.~1116264031.01.026** ----------------------------**LIS~**Of RDAJ BACKGROUND DOCUMENTS AND ASSOCIATED BDAT(S)

lnduatry or Source of Waate

Organophoaphorous peatlcldo product,on, a.11., dlaulfoton, phoratea, .and othr• P endUwastes J 2,4-Dic:hlorophenol procb:tlon secondary a ..

ct -ltlng**·~try**
Waatea having the charecterlatlc of lenlteblllty Waatea having the characterlatlc of corroalvlty Uutea having the dlaracterlatlc of reactivity BOAT(a)

Rotary ltlln Incineration Cnonwastewatera); biological lneration Cwaatewetera)**~**•...,,. '"'"'"

.... ,p,loo

Incinerator (nonweatewetera, -tewetera) I Stabilization (nonweateNatera); c:hra.tu. reclJctlon, c:h•lcal preclpltatlon, t•ttllng, and/or filtering (Maatewatera) Deactivation" to re.we 181\ltablllty,**~Incineration/fuel** albstltutlon, ovary for hlahroc 0001 DfKtlvatlon" to r..ave corroalvlty

Deactivation" of cyanides; albtlne except for cyanides; alkaline chlorination (clanldea)
I Actual Data or Transferred and oriSIIn of Data

Transfer/IC037,**Data/lndustry·s~ltted**

Data/lndustry·aubaltted
Jransfer/f006 and K062**lnfo~tlon** referencea

lnfor.-tlon references

lnfor.etlon references, Industry**a~itted** data, transfer/Office of Water 

## . Types of Wastes Regulated

Organf cs, org3llQJilos- ,tau;cx:npa.rd;, dil»>illi and furans

Phenols, dioxins, and furans Metals**~astu** having the characteristic of fgnltablllty**~aste** having the character1stlc of corror.lvlty**~estes** having the charactc-rfstfcs of reactivity

. _ 

## __......,LIST qF BOAT BACICGRll.IHD DOCUMENTS AND ASSOCIATED l'OAT(S)

Actual Data or Tr-ferred Waste Code/ lrnatry or and Types of" Third (lackgrcxnd**DocU~mt)** Source of Waste BDAT(s) llrlgln of Data Wastes Regulated



### .... I 3/3 Arsenic, selenlua, (DOD4, characteristic and VItrification (nonwaatewaters); beta/Industry-submitted Arsenic,**~tats,** OD1D, K031, K084, K101, P&u wastes I k wastes cheatcal precipitation (wastewaters) trtnsfer/Offlce of Water lnorganlcs IC102, P010,**~011,** P012, for arsenic and P036, P038, P103, P114, aelenlu. and waatea P204, P205, U136) fra. veterinary pf'lar.Keutfcala proclJCtfon 3/3 Bartua (0005, P01J) Characteristic and Stabilization Cnonwastewaters); Data/Office of Uater, Barha P wasta for berlua ch•lcal precipitation**Data/lrO.Atry·a~ltted** settling, filtration (wastewaters)
J/J c..-lua (0006) Characteristic wasta 5tablltzatton, then.al recovery Data/lrO.Atry-submltted, CIKhlllll for c..-lua**(c~tua** bettert

..) (nonwastewaters); transfer FOD6, ICD62 ch

.. lcal precipitation, filtration (wast

....tara) :P I 3/3 Chro.h.- (0007, U032) Char.cterlallc .nd Chr0111l._**r~\**Ion, ChCIIIUl Transfer/l062 Chrllnlh.a -.... Uwastes for chra.lu. precipitation, settling, filtration, dewatering of ao\tda (nonwaatewatera and wastewatara) J/3 lead (0008, IC069, Characteristic and Stabilization/vitrification (non· Data/lnduatry·submltted Lead, organometallic K100, P110, U144·U146) u&P wast
.. for le8d, wastewater•>; ch•lcal precipitation,**c~** Mld Kwaate fro. flocculation, clarification, filtration, leMi

.. ttlne Md sludge thlckenlne (wastewaters) operations 3/J Mercury (0009, IC071, Characteristic and Therael proceastng, Incineration Data/lndustry·subml\ted, Ptetals, Of"9ii'UII!Ialllc K106, P065, P092, u&P waatea for acid leaching, roasting, retorting transfer/IC071**c:~** U151)
.. rcury and Kwaste -lg-tlon, stablllzatIon fro.chlorine (nonwastewaters); ch

.. lcal procb:tlon precipitation, filtration, Incineration, ion exchange, carbon adsorption (wastewaters) 3/l Silver (0011, P099, Characteristic wastes Recovery, stabilization Data/Industry-submitted, Hetala P104) for silver, and P (nonwastewater

..>; and transfer/F006/ allver wastes chemical preclflltation, fittration Offlce of Water (wastewaters)

l.\doc..,_,l\lb2b40JI 01.026

....-..A:J::o I Ol U.ate Code/ Third C&.ckground Docu.ent)

]/] Thalllu. (P11l, P114, P115, U214, U215, U216, U217)

]/] Venadlua (P119, P120)

]/] f002, fOOS

]/] f006

]/] f019

]/] F024

]/] f0Z5

:s,;s f039 and associated u&P wastes (Vol. A-E)**~---------** 

### ------

liST OF BDAT BACKGROUND DOCUMENTS AND ASSOCIATED BDAT(S)

lncbltry or Source of W.ate

UI.P thallua

.... t
..

u&P venwtlua

....t
.. '

Spent halogeneted W1d ..-ilal**ogan~~tad** solvents

Sludiea frCfl electroplatlna operation I Sludges frflfl tha c:h•fcal**c~ralon** coating of ah•l,....

I Productton of c:hlnrlnatad allphstlc**hyd·oca~** Wsatn frflfl**~cdJctfon** of chlorinated aliphatic hydrocsrbonll having can-tchain linkage Kultfsource leachate andu&P wastes IOAT(a)

Recovery, stabilization (nonwastewatera); cha.lcal oxidation chealcal precipitation

.. ttllne, filtration (

.... twatera) Sttblllzatlon (nonwaatewatera); recovery. ch•lcal precipitation (NIIat

....tera) Incineration (ncwwutwatera); biological treat.-nt, ate-. atrlpplne• carbon adsorption • -t air o111ldatlonlc:h•lcal olllldatlon liquide111trac:tlon (waatwaters) Stabilization**(nonwaat~tera); a~lne**  chlorination, ct\rOMI.,. r tlon. ch

.. tcal**~ec:lpltatlon** ,.,...t
.... ter-) Alkaline chlorination. stabilization (nonwastewatars); alkaline chlorination. c"ro.h• rocNt:tlon, chealcal precipitation (

.... tewaters) stabilization, Incineration (nonwastewatera) Incineration (,__Uewatera) blotrest.ent, are-. stripping, carbon adtorptlon, liquid extraction (wastewaters)
See Footnote b. ActUIIl Data or rr-ferred IIHld Origin .Jf Data

Data/lndustry-suaaltted**Data/lnduatry-aubmitt~**
Transfer/EPA dots**tron~** various aourLes

Transfer/JCD62

Transfer/F006-F012

Data/EPA test

Jranater/K019. K001, F039 (Vol. A)

Data/transfer/EPA data fr0111 verious sources and EPA test Types ·of Wastes Regulated

Metals

Metals
Organics

Hetels, cyanides

Metals. cyanides

Metals, organics
Organics

Metals, lnorganlcs, organics**~** jf ,, 'I ,,



# ---Waate Code/ Thlrd CBac:kgrOU'ld Doc"*fft)

3/3 K001, U051 (addendull)
3/3 KOOZ·KODa

l/3 ICOU, IC013, IC014
3/3 IC015

3/3 K017 :P I o.D 3/3 K021

3/3 IC073

3/3 KOZ2

3/3 K025

3/3 ICOZ6**l.~l\ll>2b40.ll.01.021>** LIST Of BOAY BACKGROUND DOtUMENTS AND ASSOCIATED BDAT(S)

lnct.atry or**~GurU** of Weate

Wood pre.ervlng II'Qatry PIs-ent IrQ.try 

# ...... Acrylonitrile, prcdlctlon Still botta.a froa dlattllatlon of benzyl chloride Procbctlon of eplchloroflrdrln Aqueoua ant**I~** catalyst froafluoroaethprocbctlon Chlorine productIon
BottOIIB, tara froa production of phenol/acetone Dlatlll•tlon bottar.a**fr~** the product!::., of nitro·benzfalla froa the produc:· tlon of**~thyt** ethyl pyridine• BOAT(a)

Incineration (norwastctwatera, wastewaters)**Che~~lcal** prcclpltetlon, atabltlzetlon Cnonwastewatera); alkaline chlorination followed by chr011ha rec1Jctlon (waatewatera) Wet air oxidation (weatcwatera) Incineration, atablllzatlon (nonwaatewatera)
Incineration cnonwaatewatera); blotraat..nt (waatewatera) Incineration (nonwaatewatera); blotreat.ent, ate
..atrlpplng, ll•conditioning, aedl.entatlon, Filtration (waatewatera) Incineration Cnonwastewatera);**blotreat~t.** ate
..atrlpplng, filtration (waatewatera)**Cha~lcal** preclplt11tlon, vaclUI filtration (wastewater•) Incineration (nonwaatewatera); llquld·llquld extraction, ate
..atrlpplng, carbon adsorption, Incineration of apent carbon (wastewatera) Incineration Cnonwaatewatera, wastewaters) Actual Data or Transferred 

# .,.. Originc,f Date

Data/EPA test Data/transfer/Industry, Ka62, trensfer/F006
Deta/lndustry·submltted Transfer/K048·5Z, K087, trenafer/F039 (VolURe A) Tranafer/F039, (Vol. Aand C) Tranafer/K019, K048·52, F039 (Vol. A)
Tranafer/K019, tranafer/F039 (Vol. A) Tranafer/F039 (Vol. A), Ktl6l Transfer/previous EPA Incineration tests, tranafer/K103·K104
Transfer/prevlcua Incineration tests 

# . Types of U&stea Regulated

Organics, metals Metals, lnorgonlcs

Metals, organics Organics,**~tala** Organics Metals, organics

Organics
Metala, organics
Organics

OrganicsJP> I

...... 0 Waste Code/ Third (Backl!rot.nd**Doc~t)**

3/3 IC028, IC029, 1(()95• 1(096
K03Z·K034, K041·K042, K005I K091I K09DI K105, DD12·DD17

3/3 IC035

3/3 IC036

l/3 IC037

3/3 IC044, IC045, K047

3/3 K046 (re.ctlves)**I.~I\H•21>4<l31** .01.025 ------------ -·-

### --------------

LIStOF BOAT BACKGROUND DOCUMENTS AND ASSOCIATED BDAT(S)

l,.._try or 5ourca of W.sta

Wastes fra. procb:tlon of 1,1,1-trlchloroethene Halogenated pesticides Md chlorabenlene·

....c.**wast~ter** treat.ent sludges fra. the prod;JCt Ion of creoaota Stitt botta.s fra. toluene recl

... tlon distillation In the procb:tlon of dlsulfoton**W.at~ter** treat.-nt Sludges fra. the Procb:tlon of Dlaulfoton Manuf.cturlng axptoalvea .,-d teed· based**lnltl~tlng** cOIIpO'nia Lead·baaed Initiating cOIIIpOUOda BDAT(s)

Stabilization (nonwastewaters); blotreatmeot, -tea. stripping carbon adsorption, filtration**c~•tewatera)** Incineration (nonMaatewatera) btotreat..nt, atea. stripping, • carbon adsorption, llq.ald

extr.ctlon Incineration/wet air**oxldatlon/ch~lcal** CIOJIIdatlon c ...**stW~~ters)** Incineration (nonwaatewaters); blotreat-.nt (wastewaters)

Incineration (nonwastewaters for dlsulfoton)

Biological treet.ent (wastewaters)

De.ctlvatlon, settling and**flltratlo~.** alkaline precipitation (wastewaters)

Deactivation by cha.lcat**tre~t~t** or specialhed Incineration followed by stabilization (nonwastewaters);**ch~lcal** deactivation followed by alkaline precipitation, settling, and filtrating (Nastewaters) Actual Data or Transferred Mld Origin of Data

Transfer/FD39 (Vol. A), transfer/FD24

Transfer/EPA data

Transfer/IC087

Transfer/K037

Data/Industry-submitted, EPA Data/Industry-submitted Transfer/K062 Types of Wastes Regulated

Organics, metals

Various halogenated pestlcl'*=s,**dllorin~~tocl** norbornane derIva· tlves, otherorganics
Organics

Organics

Organics.· >rgano· phosphorL's pesticides Reactive wastes

Lead



# -:bo I ,_.

..... ----------------,,

LIST**0~** BOAT BACKGROUND DOOUM[NTS AND ASSOCIATED BDAT(S)

Actual Data or Transferred Waste Code/ lrQ,atry or and Types of Third CS.ckgrOlntDocllri'nt) lource of W.ate BDATCI) Origin of Data Uastes Re;ulated ""' I l/l**IC~IHC052 Petrol~**  raflnlng Incineration, solvent extraction Oata/lndustry·aua.ltted Organics,**~netala,** (ecidenc!ull) lrQ,atry (nunwaatewatera) inorganlcs 3/3 K060**~Ia** atll\ ll• Incineration (nonwastuwaters) Transfer/Office of Water, Organics, lnorganlcs aludge fro. c:oltlng biological treatllent ,·wastewa(era) transfer/K087 operatlona 3/l IC061 E•laalon control Cha.lcal rect.ctIon, che.lcal Transfer/IC062, Metals duat/aludge fra. the prl•ry procb:tlon of precipitation (Meatewatera) Industry ciata steel In electric furn.ucn 3/3 I(Oil) Dlatlllatlonbotta.a Incineration, atablllzatlon Transfer/previous EPA Organics, .etals fro. the pro4,c;tlon (nonwaatewatera); llquld·llquld Incineration test, Transfer/ of llf'llllne extraction, ate
..stripping, f039 (Vol. A) carbon adSorption, biological treat.ent (waatewatera) 3/3 KOM Waates fra. cleaning Incineration, chra.lu. rect..ctlon, Data/EPA test, Organics, cyanides**~lpRflt** used In cha.lcal precipitation, filtration, transfer/f006·f01Z, (Inorganic) fonaulatlon of**I~** ataliiIhatIon (nonwautewatera), tranafer/f039 (Vol. A) fra. pls-enta, drlcra, Incineration, Net air oxidation or**ao.p~,** and atablllzera cha.lcal oxidation, cerbon containing**c:hra.l~** adsorption, biological treatment, and lead or ate
..atrlpplng**~h:** Agency haa pra.ulaated a treatllent atand.rd of Deactivation for weatea exhibiting the**cha~acterlatlc** of lgnltablllty (D001), Corroslvlty (D002), or Reactivity (D003). AI pert of the lllnd dlaposal reatrlctlona, treatera of thne ebove·.antlonedwastes are**r~lred** to use a deactivation technology that will re.ov, thecharac:terlatlc for which thewaste Iahazardous. Technologlea that areapplicable anddetloonstrated for treating thesecharacteristic wastes are llated In 40 CfR Part 268, Appendix 6. "The f039 backgrounddoc:..-nt (V·•lu.eaAthrough E) contains trear.ant**perfo~e** data fra.various oourcea auch as theBOAT progr-, rhe Office of Warer•a Industrial Technology Division, the National Pollutant Discharge Ell•lnatlon Syst._, the Hazardous Waste Engineering Resource laboratories, and orher aources. The f039 bec:ltgrOlnt doc..-nt presents ,._roua technologies as BOAT. for further lnfor11111tIon, refer to the FO:S9 background**doc:~t,** VoluneK A through E.

l.lclooun-.l\112fi40JII.01.02tl