Unconventional Oil & Gas Extraction 

Wastewater Treatment Technologies

June 2016

DCN SGE01186
Disclaimer

ii

DISCLAIMER 

This report was prepared by the EPA with assistance from Eastern Research Group, Inc., 

an EPA contractor, to support the EPA’s Technical Development Document for Effluent 

Guidelines and Standards for Oil and Gas Extraction (DCN SGE01188). This report compiles 

information and data from the literature and provided by industry representatives. Mention of 

trade names or commercial products does not constitute endorsement or recommendations for 

use.
Contents

iii

CONTENTS

Page

PART A. UNCONVENTIONAL OIL AND GAS: INTRODUCTION AND BACKGROUND .............. 1

1 UOG Extraction Wastewater Characteristics...................................................................... 2

1.1 Total Dissolved Solids in UOG Extraction Wastewater......................................... 3

1.2 Hardness of UOG Extraction Wastewater.............................................................. 4

1.3 Other Constituents in UOG Extraction Wastewater............................................... 4

2 UOG Extraction Wastewater Management Strategies and Treatment ............................... 4

2.1 Applicable Effluent Limitations Guidelines and Standards.................................... 6

2.2 Types of UOG Wastewater Treatment Technologies............................................. 7

2.3 Treatment of UOG Extraction Wastewater........................................................... 10

3 Summary of Information Reviewed.................................................................................. 11

3.1 How the Technology Works................................................................................. 11

3.2 Capabilities and Limitations................................................................................. 11

3.3 Costs...................................................................................................................... 12

3.4 Summary of Vendors............................................................................................ 13

PART B. WASTEWATER TREATMENT TECHNOLOGIES CURRENTLY USED BY THE 

UOG INDUSTRY.................................................................................................... 14

1 Non-TDS Removal Wastewater Treatment Technologies ............................................... 14

1.1 Filtration/Flotation/Sedimentation........................................................................ 14

1.2 Chemical Precipitation.......................................................................................... 22

1.3 Electrocoagulation ................................................................................................ 30

1.4 Advanced Oxidation and Precipitation ................................................................. 38

1.5 Disinfection........................................................................................................... 45

2 TDS Removal Treatment Technologies............................................................................ 49

2.1 Evaporation/Condensation.................................................................................... 51

2.2 Crystallization....................................................................................................... 70

2.3 Reverse Osmosis................................................................................................... 79

PART C. POTENTIAL TECHNOLOGIES ................................................................................ 90

1 Potential Technologies for Application in UOG Extraction Wastewater Treatment ....... 90

2 Description of How Each Potential Technology Works................................................... 93

2.1 Ion Exchange ........................................................................................................ 93

2.2 Electrodialysis Reversal........................................................................................ 94

2.3 Capacitive Deionization........................................................................................ 98

2.4 Membrane Distillation ........................................................................................ 101

2.5 Forward Osmosis................................................................................................ 103

PART D. REFERENCE LIST AND SOURCE FLAGS.............................................................. 105

PART E. ATTACHMENTS ................................................................................................... 114
List of Tables

iv

LIST OF TABLES

Page

Table A-1. Summary of Reported Information on Treatment Technologies Used from 

2005-2012 to Treat UOG Extraction Wastewater across the United States..................9

Table A-2. Reported Reuse/Recycle Criteria.................................................................................10

Table B-1. Filtration Removal Efficiency in UOG Extraction Wastewater Applications.............18

Table B-2. Filtration/Flotation/Sedimentation Capital and O&M Costs for UOG 

Extraction Wastewater Applications............................................................................21

Table B-3. Filtration Costs to UOG Operators at CWT Facilities.................................................21

Table B-4. Filtration/Flotation Technology Vendors for UOG Extraction Wastewater ...............21

Table B-5. Common Additive Chemicals and Targeted Constituents for UOG Extraction 

Wastewater...................................................................................................................23

Table B-6. Chemical Precipitation Removal Efficiency in UOG Extraction Wastewater 

Applications.................................................................................................................26

Table B-7. Sludge Generated by Chemical Precipitation of UOG Extraction Wastewater...........28

Table B-8. Chemical Precipitation Capital and O&M Costs for UOG Extraction 

Wastewater Applications.............................................................................................29

Table B-9. Chemical Precipitation Costs to UOG Operators at CWT Facilities...........................29

Table B-10. Chemical Precipitation Technology Vendors for UOG Extraction 

Wastewater...................................................................................................................30

Table B-11. Electrocoagulation Removal Efficiency in UOG Extraction Wastewater 

Applications.................................................................................................................34

Table B-12. Electrocoagulation Energy Use in UOG Extraction Wastewater Applications.........37

Table B-13. Electrocoagulation Capital and O&M Costs for UOG Extraction Wastewater 

Applications.................................................................................................................37

Table B-14. Electrocoagulation Technology Vendors for UOG Extraction Wastewater..............38

Table B-15. AOP Removal Efficiency in UOG Extraction Wastewater Applications..................41

Table B-16. AOP Rental Costs for UOG Extraction Applications................................................44

Table B-17. AOP Technology Vendors for UOG Extraction Wastewater....................................45

Table B-18. Disinfection Technology Vendors for UOG Extraction Wastewater ........................49
List of Tables

LIST OF TABLES (Continued)

Page

v

Table B-19. Performance Data of Evaporation/Condensation in UOG Extraction 

Wastewater Application...............................................................................................60

Table B-20. Concentrated Brine Composition Evaporation/Condensation...................................63

Table B-21. Evaporation/Condensation Energy Use in UOG Applications..................................66

Table B-22. Evaporation/Condensation Capital and O&M Costs for UOG Extraction 

Wastewater Applications.............................................................................................67

Table B-23. Evaporation/Condensation Costs to UOG Operators at CWT Facilities...................68

Table B-24. Evaporation/Condensation Technology Vendors for UOG Extraction 

Wastewater...................................................................................................................68

Table B-25. Energy Usage of Crystallization in UOG Extraction Wastewater 

Applications.................................................................................................................76

Table B-26. Crystallization Capital and O&M Costs for UOG Extraction Wastewater 

Applications.................................................................................................................77

Table B-27. Crystallization Costs to UOG Operators at CWT Facilities......................................78

Table B-28. Crystallization Technologies for Treating UOG Extraction Wastewater..................79

Table B-29. RO Removal Efficiency in UOG Extraction Wastewater Applications....................82

Table B-30. Influent TDS Concentration Versus Water Recovery ...............................................85

Table B-31. RO Energy Use in UOG Extraction Wastewater Applications .................................87

Table B-32. RO Capital and O&M Costs for UOG Extraction Wastewater Applications............87

Table B-33. RO Costs to UOG Operators at CWT Facilities........................................................88

Table B-34. RO Technology Vendors for UOG Extraction Wastewater ......................................88

Table C-1. Potential Technologies for Application in UOG Extraction Wastewater 

Treatment .....................................................................................................................91

Table C-2. Resin Type and Corresponding Regenerate Solutions ................................................94

Table D-1. Reference List............................................................................................................105
List of Figures

vi

LIST OF FIGURES

Page

Figure A-1. UOG Produced Water Wastewater Management Methods..........................................5

Figure A-2. Drilling Wastewater Management Methods ................................................................6

Figure B-1. Flow Diagram of Sedimentation Principle .................................................................16

Figure B-2. Flow Diagram of Gas Flotation Principle ..................................................................17

Figure B-3. Flow Diagram of Chemical Precipitation Principle ...................................................23

Figure B-4. pH Versus Concentration of Constituents..................................................................24

Figure B-5. Flow Diagram of Chemical Precipitation and Settling Principle ...............................25

Figure B-6. Principle of Electrocoagulation ..................................................................................32

Figure B-7. Flow Diagram of Electrocoagulation .........................................................................33

Figure B-8. Flow Diagram of AOP Treatment On-the-Fly with Hydraulic Fracturing in 

UOG Extraction Wastewater Applications..................................................................40

Figure B-9. Flow Diagram of AOP Treatment at Wastewater Impoundments in UOG 

Extraction Wastewater Applications............................................................................41

Figure B-10. AOP Performance in Reducing Scaling Potential in the Eagle Ford Shale 

Formation.....................................................................................................................43

Figure B-11. Cost of TDS Removal Treatment Technologies versus Influent TDS.....................51

Figure B-12. Diagram of Evaporation/Condensation Principle.....................................................53

Figure B-13. Evaporation/Condensation Mechanical Vapor Compression Process Flow 

Diagram........................................................................................................................55

Figure B-14. Flow Diagram of a Multiple Stage Flash (MSF) Evaporator...................................57

Figure B-15. Heartland LM-® Concentrator Flow Diagram.........................................................58

Figure B-16. Schematic of Heartland LM-® Evaporation Zone and Entrainment 

Separator ......................................................................................................................58

Figure B-17. Typical Distillate Recovery versus Influent TDS Concentration for MVC 

Technology ..................................................................................................................63

Figure B-18. Mechanical Vapor Compression Crystallization Process.........................................71

Figure B-19. INTEVRA’s EVRASTM Crystallization Process......................................................72

Figure B-20. Flow Diagram of Reverse Osmosis Principle ..........................................................80

Figure B-21. Spiral-Wound Membrane Flow Diagram.................................................................81
List of Figures

LIST OF FIGURES (Continued)

Page

vii

Figure B-22. TDS Concentration Versus Water Recovery Percent...............................................86

Figure C-1. Ion Exchange Process Using a Cation Exchange Resin.............................................93

Figure C-2. Regeneration Process of a Cation Resin.....................................................................94

Figure C-3. Flow Diagram of Electrodialysis Principle ................................................................96

Figure C-4. Flow Diagram of Electrodialysis Reversal Principle .................................................97

Figure C-5. Flow Diagram of Electrodialysis Reversal.................................................................97

Figure C-7. RDITM Purification Process Diagram .........................................................................99

Figure C-8. RDITM Regeneration Process Diagram.....................................................................100

Figure C-9. Membrane Distillation Pressure Gradient ................................................................101

Figure C-10. Process Flow Diagram from Refrakt Vacuum Membrane Distillation 

System........................................................................................................................103

Figure C-11. Flow Diagram of Forward Osmosis.......................................................................104
Acronyms

viii

ACRONYMS

API American Petroleum Institute 

AWWA American Water Works Association

bbl barrels

BOD biochemical oxygen demand

bpd barrels per day

CBM coalbed methane

CFR Code of Federal Regulations

COD Chemical Oxygen Demand

CSM Colorado School of Mines

CWT centralized waste treatment

EC electrical conductivity

ED electrodialysis

EDR electrodialysis reversal

EIA Energy Information Administration

ELGs Effluent Limitations Guidelines and Standards

EPA U.S. Environmental Protection Agency

ME multiple effect

mg/L milligrams per liter 

MSF multiple stage flash

MVC mechanical vapor compression

MWCO molecular weight cutoff

O&M operation and maintenance

PA DEP Pennsylvania Department of Environmental Protection

pCi picocurie

POTW publicly owned treatment works

psi pounds per square inch

RO reverse osmosis

RS rapid spray

TDS total dissolved solids

TOC total organic carbon

TPH total petroleum hydrocarbons

TSS total suspended solids

TVC thermal vapor compression

UOG unconventional oil and gas

UV ultraviolet

VC vapor compression

ZLD zero liquid discharge
Part A

1

Part A. UNCONVENTIONAL OIL AND GAS: INTRODUCTION AND BACKGROUND

Recent advances in oil and natural gas well development that combine hydraulic 

fracturing and horizontal drilling have dramatically improved the technical and economic 

feasibility of oil and gas extraction from unconventional oil and gas (UOG)1resources. As a 

result, in 2012, U.S. crude oil and natural gas production reached their highest levels in more 

than 15 and 30 years, respectively. Further, the U.S. Department of Energy (DOE) projects that, 

in the next 30 years, the majority of the country’s crude oil and natural gas will come from 

unconventional resources (DCN SGE01192). As a result of increased UOG extraction, industry 

experts such as IHS Inc. and Lux Research, Inc. expect volumes of wastewater that are coproduced with UOG to continue to increase (DCN SGE00709; DCN SGE00479; DCN 

SGE00722) and, consequently, that industry investment in wastewater treatment will also 

continue to grow (DCN SGE00708; DCN SGE00709; DCN SGE00479). 

This report provides background information and data related to wastewater treatment 

technologies considered in the development of revised effluent limitations guidelines and 

standards (ELGs) for the Oil and Gas Extraction point source category to address discharges 

from onshore UOG extraction facilities to municipal wastewater treatment facilities (referred to 

as publicly owned treatment works or POTWs). Specifically, this report focuses on wastewater 

treatment technologies used to treat UOG extraction wastewater that enable UOG operators to 

manage their extraction wastewater by means other than discharge to POTWs. The two 

management strategies that involve treatment are reuse/recycle in drilling or hydraulic fracturing2

and transfer to centralized waste treatment (CWT) facilities3. Because some CWT facilities treat 

UOG extraction wastewater, many examples of treatment technologies used by CWT facilities 

are relevant to this review of treatment technologies and are discussed further in this report (see 

Section A.2.1 for further background on the ELGs as they relate to CWT facilities). Some of 

these technologies may also be used to treat wastewaters from conventional oil and gas 

extraction operations and/or coalbed methane (CBM) extraction operations, as well as 

wastewater from other industrial categories, including CWT facilities.

This report comprises five parts:

 Part A – the remaining subsections of Part A describe the characteristics of UOG 

extraction wastewater, management strategies for UOG extraction wastewater, the 

 

1 UOG is defined in the rule as “crude oil and natural gas produced by a well drilled into a shale and/or tight formation

(including, but not limited to, shale gas, shale oil, tight gas, tight oil).” Crude oil includes “lease condensates,” 

components that are liquid at ambient temperature and pressure. Natural gas can include “natural gas liquids,” 

components that are liquid at ambient temperature and pressure. While coalbed methane (CBM) is sometimes referred 

to as an unconventional resource, it is not generally further discussed in this report because it is not within the scope 

of this rule.

2 Reuse in fracturing occurs through blending wastewater with other sources to create the hydraulic fracturing base 

fluid. Base fluid is the final fluid to which proppant (sand) and chemicals are added. Base fluids are typically waterbased; however, there are cases of non-aqueous fracturing fluids (e.g., compressed nitrogen, propane, carbon dioxide). 

Water-based fluid can consist of only fresh water or a mixture of fresh water, brackish water (e.g., treated municipal 

wastewater, groundwater) and reused/recycled wastewater.

3 40 CFR Part 437 defines a CWT facility as one that treats (for disposal, recycling or recovery of material) any 

hazardous or non-hazardous industrial wastes, hazardous or non-hazardous industrial wastewater, and/or used material 

received from off-site (DCN SGE00601).
Part A

2

targeted constituents for each management strategy that utilize wastewater 

treatment, and the treatment technologies used to remove these targeted 

constituents.

 Part B – describes technologies that are currently used to treat UOG extraction 

wastewater at full-scale treatment operations.

 Part C – describes technologies that the U.S. Environmental Protection Agency 

(EPA) did not identify as currently used to treat UOG extraction wastewater at 

full-scale operations but the literature suggests may be used in the future. 

 Part D – provides a list of references the EPA identified during this review.

 Part E – provides the excel file where the EPA documented all costs and 

performance data as reported by literature that are summarized throughout the 

report. 

The data included in this report are based on data generated or obtained in accordance 

with EPA’s Quality Policy and Information Quality Guidelines. EPA’s quality assurance (QA) 

and quality control (QC) activities for this rulemaking include the development, approval, and 

implementation of Quality Assurance Project Plans (QAPPs) for the use of environmental data 

generated or collected from sampling and analyses, existing databases, and literature searches.4

Information presented in this document was taken from existing data sources, including 

state and federal agency databases, journal articles and technical papers, technical references, 

vendor websites, and industry/vendor telephone calls, meetings, and site visits. As shown in 

Table D-1, the EPA assigned a source flag (A, B, C or D) to all references used in these 

calculations. Part D provides definitions of each source flag. 

1 UOG EXTRACTION WASTEWATER CHARACTERISTICS

This section focuses on constituents found in UOG extraction wastewater that may be 

targeted for removal during treatment for reasons that are explained in Part A.2. The EPA is 

defining “UOG extraction wastewater” as “sources of wastewater pollutants associated with 

production, field exploration, drilling, well completion, or well treatment for unconventional oil 

and gas (UOG) extraction”.5 This includes the following wastewater streams, relevant to this 

report:

 Produced water—the fluid (brine) brought up from the hydrocarbon bearing strata 

during the extraction of oil and gas, and includes, where present, formation water, 

injection water, and any chemicals added downhole or during the oil/water separation 

 

4 The relevant QAPPs for this rulemaking are the Environmental Engineering Support for Clean Water Regulations 

Programmatic Quality Assurance Project Plan (PQAPP) (DCN SGE00957) and the Unconventional Oil and Gas 

(UOG) Supplemental Quality Assurance Project Plan (SQAPP) (DCN SGE00958).

5 Stormwater is not considered a source of UOG extraction wastewater. In general, no permit is required for discharges 

of stormwater from any field activities or operations associated with oil and gas production, except as specified in 40 

CFR 122.26(c)(1)(iii) for discharges of a reportable quantity or that contribute to a violation of a water quality 

standard.
Part A

3

process. Based on the type of oil and gas extraction method, produced water can be 

further broken down into the following components:

— Flowback—the wastewater generated by UOG wells during the flowback 

process of well completion. After the hydraulic fracturing procedure is 

completed and pressure is released, the direction of fluid flow reverses, and the 

fluid flows up through the wellbore to the surface. The water that returns to the 

surface is commonly referred to as “flowback.”

— Long-term produced water—the wastewater generated by UOG wells during 

the production phase after the initial flowback process which can include 

increasing amounts of formation water. Long-term produced water continues to 

be produced throughout the lifetime of the well. 

 Drilling wastewater6—the liquid waste stream separated from recovered drilling mud7

(fluid) and drill cuttings8during the drilling process. 

The following subsections briefly describe the primary constituents in UOG extraction 

wastewater that have been targeted for removal in treatment operations. Refer to Chapter C of 

the Technical Development Document for Effluent Limitations Guidelines and Standards for Oil 

and Gas Extraction (TDD), Document No. EPA 820-R-16-003 (DCN SGE01188), for more 

information on the constituents in UOG extraction wastewater.

1.1 Total Dissolved Solids in UOG Extraction Wastewater

Total dissolved solids (TDS) are one of the primary constituents found in UOG extraction 

wastewater. TDS provides a measure of dissolved matter including salts (e.g., sodium, chloride, 

nitrate), metals, minerals, and organic material (DCN SGE00046; DCN SGE01188). TDS is not 

a specific chemical, but is defined as the portion of solids that pass through a filter with a 

nominal pore size of 2.0 micrometers (μm) or less (Standard Method 2540C-1997, ASTM 

D5907-03, and USGS I-1750-85).

9

Based on data reported in literature across many different types of UOG operations (e.g., 

shale gas, tight oil), TDS concentrations in UOG extraction wastewater vary by UOG formation 

and are often greater than that of seawater (i.e., 35,000 milligrams per liter (mg/L)) (DCN 

SGE01188).10 Reported data also shows that TDS concentrations are typically higher in longterm produced water than in flowback and drilling wastewater (DCN SGE01188). TDS 

 

6 Additional information about drilling wastewater can be found in ERG’s Unconventional Oil and Gas (UOG) 

Drilling Wastewater memorandum (DCN SGE01181).

7 Drilling mud is the circulating fluid (mud) used in the rotary drilling of wells to clean and condition the hole and to 

counterbalance formation pressure.

8 Drill cuttings are the particles generated by drilling into subsurface geologic formations and carried out from the 

wellbore with the drilling fluid.

9 40 CFR Part 136 lists standard method 2540C-1997 as an approved test method for TDS.

10 All characterization data in this section about TDS, hardness, and other constituents is based on the EPA’s 

memorandum Unconventional Oil and Gas (UOG) Produced Water Volumes and Characterization Data Compilation 

(DCN SGE01184) which is based on data identified as of February 2015.
Part A

4

concentrations in UOG long-term produced water can be higher than 350,000 mg/L, which is 

over ten times the concentration of TDS typically found in seawater.

Salts (primarily sodium and chloride) constitute over 50 percent of the TDS in UOG 

extraction wastewater (DCN SGE00046; DCN SGE01188). Calcium and other group II alkaline 

earth metals (e.g., strontium, barium, magnesium) may also contribute to TDS. Similar to UOG 

produced water, sodium chloride is also the largest contributor to TDS in UOG drilling 

wastewater (DCN SGE01188).

1.2 Hardness of UOG Extraction Wastewater

Water hardness is a measure of the sum of multivalent cations dissolved in water, where 

the primary contributing cations are calcium (Ca+2) and magnesium (Mg+2). Total hardness is a 

measure of the sum of carbonate hardness and non-carbonate hardness. Carbonate hardness is 

due to the presence of bicarbonate and carbonate in the wastewater; non-carbonate hardness is 

due to salts (e.g., calcium chloride, magnesium sulfate) (DCN SGE00178). 

Based on data reported in literature across many different types of UOG operations (e.g., 

shale gas, tight oil), UOG extraction wastewater is classified by the EPA as a “very hard” water 

(>300 mg/L hardness) (DCN SGE00178; DCN SGE01188). Reported data shows hardness 

concentrations in UOG extraction wastewater is often greater than 1,000 mg/L with the primary 

contributors being calcium and magnesium (DCN SGE01188). In fact, hardness concentrations 

in UOG produced water can be higher than 100,000 mg/L.

1.3 Other Constituents in UOG Extraction Wastewater

UOG extraction wastewater contains many other constituents that, as Part A.2 explains, 

may be targeted for removal in UOG extraction wastewater. Depending on the fate of the treated 

wastewater, these constituents include but are not limited to: total suspended solids (TSS), oil 

and grease, metals (e.g., barium, strontium, iron, boron), radioactive elements (e.g., radium 226, 

radium 228), and certain anions and cations (e.g., sulfate, bromide). pH is another parameter that 

is often monitored as it can vary significantly with the type of UOG extraction wastewater. UOG 

extraction wastewater may also contain microbial contaminants that can lead to growth of sulfate 

reducing bacteria (SRB), which are further discussed in Part B.1.4: Advanced Oxidation and 

Precipitation. On average, the pH and TSS in UOG drilling wastewater are higher than in UOG 

produced water (DCN SGE01188). Depending on how thoroughly drill cuttings are removed 

from drilling wastewater by the operator, solids can be as high as 50 percent by mass (DCN 

SGE00245; DCN SGE01188) in UOG drilling wastewater. 

2 UOG EXTRACTION WASTEWATER MANAGEMENT STRATEGIES AND TREATMENT 

For management of UOG produced water, UOG operators primarily use the three 

methods listed below and shown in Figure A-1 (DCN SGE00613; DCN SGE00276; DCN 

SGE00528).

 Dispose of wastewater via underground injection for disposal wells (“disposal 

wells”)

 Reuse/recycle wastewater in subsequent fracturing jobs
Part A

5

 Transfer wastewater to a CWT facility

For management of UOG drilling wastewater, UOG operators primarily use the methods 

listed below and shown in Figure A-2 (DCN SGE01181). 

 Dispose of wastewater via disposal wells

 Reuse/recycle wastewater in subsequent drilling 

 Transfer wastewater to a CWT facility

 Other (e.g., Onsite burial11, disposal via landfill, land application)

Across the United States, operators most often manage their produced water via disposal 

wells (DCN SGE01188). However, reuse/recycle in hydraulic fracturing or drilling and transfer 

to CWT facilities are becoming more popular to handle increasing volumes of UOG extraction 

wastewater, both of which require some level of wastewater treatment (DCN SGE01178; DCN 

SGE01188).12 Part B describes the types of wastewater treatment currently used to treat UOG 

extraction wastewaters and the targeted constituents. 

Figure A-1. UOG Produced Water Wastewater Management Methods

 

11 Onsite burial involves temporary fluid storage in on-site open earthen or lined pits with burial of residual solids 

after fluids are solidified, removed from the top, or evaporated.

12 Wastewater pretreatment may be required prior to injection into class II disposal wells, but this treatment is not the 

subject of this report.
Part A

6

Figure A-2. Drilling Wastewater Management Methods

Although operators have discharged UOG extraction wastewater to publicly owned 

treatment works (POTWs), these discharges were discontinued in 2011 (DCN SGE01188). 

Therefore, the EPA does not consider discharge to POTWs a primary UOG extraction 

wastewater management process. In select areas, UOG operators also use evaporation ponds for 

disposal of UOG produced water and drilling wastewater. However, there are certain 

requirements for using evaporation ponds, including very dry climates, which mainly occur in 

the western United States (DCN SGE00710).

2.1 Applicable Effluent Limitations Guidelines and Standards

EPA promulgated the first Oil and Gas Extraction ELGs (40 CFR Part 435) in 1979, and 

substantially amended the regulation in 1993 (Offshore), 1996 (Coastal), and 2001 (Syntheticbased drilling fluids). The Oil and Gas Extraction industry is subcategorized in 40 CFR Part 435 

as follows: (1) subpart A: Offshore; (2) subpart C: Onshore; (3) subpart D: Coastal; (4) subpart 

E: Agricultural and Wildlife Water Use; and (5) subpart F: Stripper.

The existing subpart C regulation covers wastewater discharges from field exploration, 

drilling, production, well treatment, and well completion activities in the oil and gas industry. 

Although unconventional oil and gas resources occur in offshore and coastal regions, recent 

development of UOG resources in the U.S. has occurred primarily onshore in regions to which 

the regulations in subpart C (Onshore) and subpart E (Agricultural and Wildlife Water Use) 

apply. 40 CFR 435, Subpart C specifies no discharge of wastewater pollutants from onshore oil 

and gas extraction facilities to waters of the U.S. The existing regulations do not include national 

categorical pretreatment standards for discharges to POTWs. 40 CFR 435, Subpart E specifies 

that onshore oil and gas extraction facilities located west of the 98th meridian may discharge 

produced water into navigable waters for use in agriculture or wildlife propagation. The EPA has 
Part A

7

not found that these types of permits are typically written for unconventional oil and gas 

extraction wastewater.

13

Discharges from centralized waste treatment (CWT) facilities that accept oil and gas 

extraction wastes are not subject to 40 CFR Part 435, but rather are subject to the effluent 

limitations guidelines and pretreatment standards under 40 CFR Part 437, the Centralized Waste 

Treatment Category. EPA defines a CWT at 40 CFR 437.2(c) as “any facility that treats (for 

disposal, recycling or recovery of material) any hazardous or nonhazardous industrial wastes, 

hazardous or non-hazardous industrial wastewater, and/or used material received from offsite.

2.2 Types of UOG Wastewater Treatment Technologies

EPA classifies the treatment technologies discussed in this report by the types of 

constituents they remove, as described below. 

 Non-TDS removal technologies – Technologies that remove non-dissolved14

constituents from wastewater. Examples in UOG extraction wastewater 

applications include suspended solids, oil and grease, metals, bacteria, and/or

certain ions that potentially cause scale to form on equipment and interfere with

fracturing chemical additives. These technologies do not remove sodium and 

chloride ions, which make up more than 50 percent of the TDS in UOG extraction 

wastewater, as well as some other dissolved constituents that contribute to TDS.

 TDS removal technologies –Technologies capable of removing dissolved 

constituents that contribute to TDS (sodium, chloride, calcium, etc.), in addition 

to the constituents removed by non-TDS removal technologies.

Table A-1 summarizes the UOG extraction wastewater treatment technologies the EPA

reviewed that are currently in use (see Part B). For TDS removal technologies, the table indicates 

the maximum influent TDS concentration for cost effective operation. The table also indicates:

 Residual waste streams generated;

 Range of cost for UOG operators to treat as reported by vendors or found in the 

literature to purchase or rent, operate, and maintain the technology (Total Cost 

Range for Treatment by UOG Operator); and 

 Identified prices charged to UOG operators by CWT facilities that accept UOG 

extraction wastewater (Cost to UOG Operator at CWT Facilities) as reported in 

site visit notes and/or calls with CWT facilities. 

 

13 EPA notes that the requirements in the existing effluent guidelines for onshore oil and gas extraction facilities 

(Subpart C and Subpart E) do not apply to coalbed methane extraction, as this industry did not exist at the time that 

the effluent guidelines were developed and was not considered by the Agency in establishing the effluent guidelines 

(DCN SGE00761). 

14 EPA has categorized treatment technologies into two categories in this report: those that are designed to remove 

dissolved constituents and those that are not designed to remove dissolved constituents. However, it should be noted 

that some of the technologies in the non-TDS removal category do in fact remove some dissolved constituents. For 

example, chemical precipitation will remove certain metals. However, these technologies typically will not remove 

salts and hardness, which are the primary components of TDS in UOG extraction wastewater.
Part A

8

The total costs consist of values reported by vendors, UOG operators, CWT operators, 

and in the literature. The costs are sometimes reported as a ball park number; may include a 

company’s amoritization of capital costs with O&M added on (where the amortization rate or 

amortization period are not reported); and may be reported as a rental cost which may or may not 

include the full capital costs of the technology. These costs may not be comparable against each 

other since there are regional differences and the data represents differing timeframes from 2005 

through 2011. More details on the cost data collected by EPA is provided in the technologyspecific subsections of Part B and the original sources of the information provides more context. 

These numbers are presented for the reader in a single table to show what information EPA has 

collected and EPA is not providing a comprehensive analysis of costs in this report. Section A.3

provides more information about the type of information EPA reviewed for this report and is 

summarized in Table A-1.
Part A

9

Table A-1. Summary of Reported Information on Treatment Technologies Used from 

2005-2012 to Treat UOG Extraction Wastewater across the United States

Level of 

Treatment Technology

Maximum 

Influent TDS 

(mg/L) for 

TDS Removal 

Technologies

Types of Residual 

Wastes Generated

Cost Range 

for Treatment 

by UOG 

Operator ($ 

per bbl)a

Cost Range to 

UOG 

Operator for 

Treatment by

CWT Facility

($ per bbl)

b

Non-TDS 

Removal 

Technologies

Disinfection - None --

d N/Ae

Filtration/Flotation/

Sedimentation - Sludge/solid waste 0.15 – 0.50 1.00

Chemical 

precipitation - Sludge/solid waste 0.50 – 4.00 2.20 – 4.00

Advanced oxidation 

and precipitation - Nonec 0.50 – 1.30 N/Ae

Electrocoagulation - Sludge/solid waste 1.00 – 3.10 --

d

TDS 

Removal 

Technologies

Evaporation/ 

Condensation 150,000 Concentrated brine 2.00 – 6.50 3.00 – 10.00

Crystallization No limit Solid waste; potential 

liquid purge stream 5.00 – 22.00 5.00 – 11.00

Reverse osmosis 

(RO) ~50,000 Concentrated brine 3.50 – 4.40 2.00 – 3.00

Sources for treatment by operator: filtration/flotation/ sedimentation (Table B-2); chemical precipitation (Table 

B-8); advanced oxidation and precipitation (Table B-16); electrocoagulation (Table B-13); evaporation/condensation 

(Table B-22); crystallization (Table B-26); and RO (Table B-32).

Sources for treatment by CWT facility: filtration/flotation/ sedimentation (Table B-3); chemical precipitation (Table 

B-9); evaporation/condensation (Table B-23); crystallization (Table B-27); and RO (Table B-33).

N/A—Not applicable; mg/L—milligrams per liter; bbl—barrel; TDS—total dissolved solids.

a—The cost ranges for treatment by UOG operators reported in Table A-1 are as given by vendors, UOG operators, 

and CWT facility operators. See Part B technology-specific sections for details on their basis. These cost ranges do 

not include transportation costs and may vary based on wastewater characteristics and other factors. These data are 

exclusive of information provided for the last column to the right.

b—The cost ranges for treatment by CWT facilities reported in Table A-1 are as given by UOG operators and CWT 

facility operators. See Part B technology-specific sections for details on their basis. This range includes costs for 

different types of CWT services such as returning the treated wastewater back to the UOG operator for reuse/recycle

in fracturing or treating the wastewater for discharge to surface water or POTWs. Cost ranges do not include 

transportation costs and may vary based on wastewater characteristics and the type of service.

c—AOP vendors report that the solids generated by the technology remain suspended within the treated wastewater. 

See Part B.1.4 for more detail.

d—Cost information is unknown.

e—These costs may not be applicable because the EPA did not identify any CWT facilities that accept extraction 

wastewater from UOG operators and use the technology.
Part A

10

2.3 Treatment of UOG Extraction Wastewater

UOG extraction wastewater may require some form of treatment dependent upon the fate 

of the treated wastewater (DCN SGE00691). Reuse/recycle is one management strategy that may 

involve treatment of UOG extraction wastewater.15 When using this strategy, operators either 

transport UOG extraction wastewater directly to the next well they are fracturing or transport it 

to a temporary storage area until needed. Treatment typically consists of non-TDS removal 

technologies for removal of multivalent cations, microbial constituents, metals, TSS, and/or 

other specific constituents (DCN SGE01188). The wastewater is typically blended with other 

source water to reuse/recycle in fracturing, which may occur either before or after treatment 

(DCN SGE00616; DCN SGE00691). When this treatment occurs concurrently with fracturing at 

the next well, it is referred to as “on-the-fly” treatment, and is described in more detail in Part 

B.1.4.

If operators reuse/recycle UOG extraction wastewater with elevated concentrations of 

certain constituents one or more of the following problems may occur:

 Fluid instability (change in fluid properties)

 Well plugging (restriction of flow)

 Well bacteria growth (buildup of bacteria on casing)

 Well scaling (accumulation of precipitated solids)

 Formation damage (restriction of flow in the reservoir)

Therefore, it may be necessary to remove constituents that can interfere with fracturing 

fluid chemicals, damage the formation, and/or cause scaling down the wellbore and in equipment

prior to reuse/recycle. Table A-2 shows the associated impacts on the fluid or well that may 

occur with elevated concentrations of certain constituents or concentrations outside of a specified 

range as reported by industry. The importance of and the exact constituent concentration depends

on operator preference, geology, and the fracturing fluid chemistry (e.g., slickwater or gel) (DCN 

SGE01188; DCN SGE01179). 

Table A-2. Reported Reuse/Recycle Criteria

Constituent Reason for Limiting Concentrations for Reuse/Recycle

Bacteria Bacterial growth

Total dissolved solids (TDS) Fluid stability

Chloride Fluid stability

Sodium Fluid stability

Oil Fluid stability

Boron Fluid stability

pHb Fluid stability

Total suspended solids (TSS) Plugging

 

15 Treatment may not be required for reuse/recycle. In these cases, blending (with additional source waters) alone may 

be used to control TDS concentrations in the final base fluid. No constituents are actually removed by blending (DCN 

SGE00616; DCN SGE00691).
Part A

11

Table A-2. Reported Reuse/Recycle Criteria

Constituent Reason for Limiting Concentrations for Reuse/Recycle

Iron Scaling

Strontium Scaling

Barium Scaling

Silica Scaling

Calcium Scaling

Magnesium Scaling

Sulfate Scaling

Potassium Scaling

Other scale formersa Scaling

Source: DCN SGE01179

a—Includes barium, calcium, manganese, and strontium.

b—Operators require a specific range of pH rather than a limit as pH has a direct impact on the fracturing fluid 

chemistry.

CWT facilities may also treat UOG wastewater for reuse/recycle or for discharge 

indirectly to POTWs or directly to waters of the U.S. If being reused, the level of treatment 

depends upon operator needs. Discharges from CWT facilities directly to waters of the U.S. or 

indirectly to POTWs may be subject to effluent limitations guidelines and pretreatment standards 

under 40 CFR Part 437. 

3 SUMMARY OF INFORMATION REVIEWED

This report describes technologies that are currently used, or may potentially be used in 

the future, to treat UOG extraction wastewater. The report describes how each technology works, 

capabilities and limitations (e.g., effectiveness, design considerations, residual generation, 

energy use), costs, and identifies vendors that supply technologies. The following subsections 

describe the scope of the EPA’s technology reviews and provide relevant background 

information and definitions.

3.1 How the Technology Works 

EPA reviewed the basic wastewater treatment principles for each technology to 

determine how the technology removes or controls the targeted constituents in UOG extraction 

wastewater and how treatment operators use the technology. 

3.2 Capabilities and Limitations 

EPA reviewed information for each technology to determine the following for UOG 

applications:

 Targeted constituents and effectiveness – Describes the targeted constituents 

that each technology is able to remove or control, as well as available 

performance data in UOG applications. If possible, the EPA calculated removal 

efficiencies using paired influent and effluent concentrations (i.e., performance 
Part A

12

data) reported in literature. Attachment 1 (DCN SGE01186.A01) presents these 

removal efficiency calculations. The number of data points that these removal 

efficiencies are based on are also presented in Attachment 1.

 Design considerations – Describes considerations specific to UOG applications, 

such as pretreatment requirements and maximum influent TDS concentrations for 

optimal performance.

 Residual generation – Describes wastes a treatment technology may generate 

that operators must dispose of or otherwise manage. Some residuals may be 

disposed of in landfills. As levels of radioactivity in treatment residuals exceed 

landfill acceptability limits, the treatment technology operator may be required to 

screen the waste stream for radioactivity prior to transport to landfills (DCN 

SGE00299; DCN SGE00300; DCN SGE00245). If radioactivity levels exceed the 

thresholds, residuals must be disposed of in landfills specifically licensed to 

accept such waste and typically impose a surcharge (DCN SGE00300).

 Energy use – Describes the types of energy sources (e.g., electricity from on-site 

diesel generator, natural gas boiler) a technology requires. When available, the 

EPA also quantified energy requirements in kilowatt hours (kWh) per barrel (bbl) 

of wastewater treated.

3.3 Costs

EPA reviewed available information on the costs associated with each technology. The 

EPA reviewed three types of costs:

 Total Cost Range for Treatment by the UOG Operator – This is the cost as 

reported in the literature, conference presentations, call notes, or site visits for 

UOG operators to purchase or rent, operate, and maintain the technology. These 

costs can further be broken down into:16

— Capital and O&M costs – Capital and O&M costs as reported by treatment 

vendors, UOG operators, and CWT facility operators to purchase, operate, and 

maintain the technology.

— Rental or Effective Cost – Rental cost UOG operators must pay vendors 

when they contract with a vendor to provide treatment with O&M costs 

included. This category may also represent the effective costs to the UOG 

operator if reported by literature when the technology is purchased.

 

16 The total costs consist of values reported by vendors, UOG operators, and in the literature. The costs are 

sometimes reported as a ball park number; may include a company’s amortization of capital costs with O&M added 

on (where the amortization rate or amortization period are not reported); and may be reported as a rental cost which 

may or may not include the full capital costs of the technology. Cost ranges do not include transportation costs and 

may vary based on wastewater characteristics. These costs may not be comparable against each other since there are 

regional differences, and the data represents differing timeframes from 2005 through 2011.
Part A

13

 Cost to UOG Operators by CWT Facilities – Cost charged to UOG operators 

by CWT facilities that accept UOG extraction wastewater.17

Because literature reports costs associated with different elements of treatment systems, 

the EPA assigned one of the following terms to each cost reported in the tables of this report: 

 Plant – Includes the facility, land, necessary infrastructure; treatment system 

infrastructure (e.g., connecting pipes, monitoring systems); storage of wastewater, 

treated wastewater, and chemicals; and all treatment units, including any required 

pretreatment units. 

 System – Includes treatment system infrastructure (e.g., connecting 

pipes, monitoring systems) and all treatment units, including any required 

pretreatment units.

 Mobile System – Same as system, but also includes a trailer as part of the 

infrastructure.

 Unit – Includes the treatment unit being discussed (i.e., does not include 

infrastructure or any required pretreatment units).

3.4 Summary of Vendors

EPA identified vendors that currently offer treatment systems either for purchase or on a 

contract basis to UOG operators18. This includes the types of facilities at which the UOG 

industry uses the technology and, when available, which UOG formations the technology is used 

in.

 

17 The cost ranges for treatment by CWT facilities as given by UOG operators and CWT facility operators. See Part 

B technology-specific sections for details on their basis. This range includes costs for different types of CWT services 

such as returning the treated wastewater back to the UOG operator for reuse/recycle in fracturing or treating the 

wastewater for discharge to surface water or POTWs. Cost ranges do not include transportation costs and may vary 

based on wastewater characteristics and the type of service. These costs may not be comparable against each other 

since there are regional differences, and the data represents differing timeframes from 2005 through 2011.

18 The EPA’s lists of vendors for each treatment technology described in Part B are not exhaustive, but rather include 

all vendor information that was available to EPA at the time of publication of this report.
Part B

14

Part B. WASTEWATER TREATMENT TECHNOLOGIES CURRENTLY USED BY 

THE UOG INDUSTRY

The following two sections discuss technologies currently used in full scale projects by 

the UOG industry. Part B.1 discusses non-TDS removal treatment technologies and Part B.1.4

discusses TDS removal treatment technologies.

1 NON-TDS REMOVAL WASTEWATER TREATMENT TECHNOLOGIES

One management strategy for UOG extraction wastewater is to treat it using non-TDS 

removal technologies so it is “just clean enough” to be reused in fracturing (DCN SGE00710; 

DCN SGE00638.A11). Non-TDS removal technologies reduce or destabilize materials such as 

suspended solids, microbial constituents, metals, and multivalent cations, but are not designed to 

remove sodium chloride and other salts. Non-TDS removal technologies target constituents that 

contribute to corrosivity, cause scale, interfere with fracturing chemical additives (e.g., boron is 

removed to prevent its interference with gel fracturing fluids), and/or interfere with well 

production and integrity. Because they often reduce hardness, they are sometimes referred to as 

wastewater softening technologies. Non-TDS technologies used to treat UOG extraction 

wastewater include (DCN SGE00667):

 Filtration/gas flotation/sedimentation

 Chemical precipitation

 Electrocoagulation

 Advanced oxidation and precipitation (AOP)

 Disinfection

These technologies may also be used as pretreatment prior to TDS removal treatment that 

may be required for other management strategies of UOG extraction wastewater. Some TDS 

removal treatment technologies are vulnerable to scaling and/or fouling caused by certain nonTDS constituents found in UOG extraction wastewater. Reducing concentrations of these 

undesired constituents prior to TDS treatment allows TDS removal technologies to operate more 

efficiently.

1.1 Filtration/Flotation/Sedimentation

Physical separation treatment technologies that remove free oil and TSS include 

filtration, flotation, and sedimentation. These technologies do not remove multivalent cations, 

hardness, or TDS (sodium chloride or other salts). Filtration/sedimentation/flotation is typically 

used to treat UOG extraction wastewater prior to reuse in fracturing, or to pretreat wastewater 

prior to TDS-removal treatment. In addition, these technologies may be used following chemical 

precipitation to remove precipitates.

This section describes the filtration/sedimentation/flotation processes, treatment 

capabilities and limitations, treatment costs, and vendors that market the technology for UOG 

extraction wastewater treatment.
Part B

15

1.1.1 How Filtration/Sedimentation/Flotation Works

This subsection describes filtration/sedimentation/flotation operating principles and how 

these processes have been used to treat UOG extraction wastewater.

Principle and Process Description: Filtration

Filtration works by routing wastewater through a porous media such as a rock, glass, 

walnut shell, or sand to filter out oil and suspended solids. Gravity, centrifugal force, pressure, or 

a vacuum forces the wastewater through the media, which may be a single fixed bed, multiple 

fixed layers, or a moving bed (DCN SGE00195). Suspended solids are trapped in the pores 

between the grains of the media (typically greater than 3 μm) and remain as the water passes 

through. As the media filter captures increasing amounts of solids, the pressure drop across the 

filter bed increases until it reaches a threshold at which point a backwash cycle is used to remove 

the accumulated solids. Other filter types use disposable bags or cartridges as filter materials. 

Filter backwash is typically recycled to the first unit of the treatment system, such as a 

sedimentation basin.

Wastewater may also be routed through ceramic or polymeric membranes by using a 

pressure differential. Membrane filtration systems include media with pore sizes 0.1-3 μm 

(microfiltration), 0.001-0.1 μm (ultrafiltration), 0.0001-0.001 μm (nanofiltration), and 0.0001 

(reverse osmosis). Microfiltration removes conventional clays, humic acids, bacteria, algae, 

cysts, and other suspended solids. Ultrafiltration removes viruses, color, odor, and some colloidal 

natural organic matter. Microfiltration and ultrafiltration require trans-membrane pressure of 1-

30 pounds per square inch (psi) to operate (DCN SGE00264, DCN SGE01140). Nanofiltration 

removes organics, BOD, COD, and detergents. Nanofiltration requires pressures of 50-300 psi to 

operate (DCN SGE01140). Reverse osmosis operates at applied pressures ranging from 250 to 

1,180 psi to push water through the membrane while blocking ions and other dissolved material 

(TDS) from passing (DCN SGE00175). Accordingly, reverse osmosis is well suited for 

desalination and is described as a TDS removal technology in Part B.2.3.

Many applications for UOG extraction wastewater use multiple stage filtration where 

each subsequent stage uses a smaller pore size than the previous stage to optimize performance. 

For example, one CWT facility that treats UOG extraction wastewater that the EPA visited uses 

100, 50, 25, and 10 micron filters sequentially to remove suspended solids (DCN SGE00299). In 

addition, another UOG operator reported they use 100 followed by 20 micron filters prior to 

reuse (DCN SGE00635).

Principle and Process Description: Sedimentation

Sedimentation removes suspended solids by gravity settling. Sedimentation works by 

allowing water to stagnate or flow very slowly through an impoundment or tank, thereby 

allowing suspended solids to settle to the bottom and dispersed oil and grease to float to the 

surface. Figure B-1 illustrates the principle of sedimentation. Constituents A (TSS) and O (oil 

and grease) are targeted for removal. UOG extraction wastewater also contains dissolved 

constituents (represented by constituent D) which sedimentation does not remove as illustrated in 

Figure B-1. Treated wastewater is gradually removed through the middle portion of the 
Part B

16

tank/impoundment so that it no longer contains the solids that have settled or the oil and grease 

that has risen to the surface. Sedimentation is most effective in removing suspended solids with 

specific gravity significantly greater than 1.0.

Figure B-1. Flow Diagram of Sedimentation Principle

In reuse/recycle applications, some UOG operators may rely on storage prior to reuse in 

fracturing as a means to simultaneously reduce suspended solids through sedimentation. UOG 

operators typically store the wastewater in fracturing tanks until they are ready to fracture the 

next well. Depending on logistics, the length of time the wastewater is stored may be relatively 

long (one month). One UOG operator, who typically stores wastewater for one month, reported 

they see a reduction in suspended solids before and after storage. This operator must periodically 

clean out these tanks to remove solids from the bottom (DCN SGE00275).

Principle and Process Description: Flotation

Gas flotation is the process of using fine bubbles to induce oil and suspended particles to 

rise to the surface of a tank where they can be collected and removed. Gas bubbles are 

introduced into the wastewater and attach to the particles. With the bubbles and oil and particles 

attached, the effective specific gravity of the two combined is less than that of water allowing the 

suspended particles to rise to the surface with the bubbles (DCN SGE00195). The gas bubbles 

are typically air, nitrogen, or other inert gases (DCN SGE00264). Flotation is most effective in 

removing suspended solids with specific gravity slightly greater than 1.0.

Figure B-2 illustrates the principle of flotation. Constituent A, which is suspended solids 

and oil, is targeted for removal. The influent UOG extraction wastewater also contains dissolved 

constituents, represented by constituent D in Figure B-2, which are typically not removed by 

flotation. Bubbles are generated at the bottom of the tank and float upwards towards the surface, 

sweeping up constituent A as they rise through the water column. A mechanical skimmer rotates 

and physically removes the constituent A out of the wastewater and transfers it into a collection 

tank. The treated wastewater leaves the unit from the middle or bottom portion of the tank. Note 

that dissolved constituent D is not removed during the process. 
Part B

17

Figure B-2. Flow Diagram of Gas Flotation Principle

The UOG industry uses two categories of gas flotation technologies: dissolved gas 

flotation and induced gas flotation. These two categories differ by the method used to create the 

bubbles. Consequently, the bubble sizes are also different for each method, which affects 

treatment efficiency (DCN SGE00264).

 Dissolved gas flotation – Gas is injected into wastewater in a pressurized retention 

tank or pipe, allowing the gas to dissolve in the wastewater. When the wastewater 

enters the flotation tank, the pressure is reduced, causing fine air bubbles to be 

released. 

 Induced gas flotation – Bubbles are generated or injected near the bottom of the 

flotation unit by mechanical means such as a propeller or diffuser.

1.1.2 Capabilities and Limitations

This subsection describes the targeted constituents and effectiveness, design and 

operation considerations, residuals, and energy use of filtration, sedimentation, and flotation. 

Targeted Constituents and Treatment Effectiveness

Filtration/sedimentation/flotation technologies primarily remove suspended solids and 

free oil and grease (DCN SGE00264; DCN SGE00625). The EPA identified publically available 

performance data for filtration in UOG applications, which is shown in Table B-1. The table 

includes untreated influent constituent concentrations, effluent constituent concentrations, and 

the resulting constituent removal efficiencies. Data in Table B-1 indicate that the removal of 

constituents other than TSS and free oil in UOG extraction wastewater is generally low for this 

technology.
Part B

18

Table B-1. Filtration Removal Efficiency in UOG Extraction Wastewater Applications

Constituent

Reported Influent 

Range

(mg/L)

Reported Effluent 

Range

(mg/L)

Calculated 

Removal Efficiency

(%)a,b Reference ID

Total dissolved 

solids (TDS)

11,000 – 190,000 8,100 – 190,000 –6.1 to +27 120

Chloride 15,000 – 150,000 12,000 – 110,000 –19 to +29 120

Sodium 5,600 – 45,000 5,800 – 43,000 –3.7 to +41 120

Metals

Magnesium 190 – 2,200 180 – 2,300 –5.1 to +35 120

Strontium 280 – 5,100 250 – 5,300 –8.1 to +19 120

Iron 6 – 64 8 – 66 –33 to +53 120

Calcium 1,600 – 21,000 1,500 – 22,000 –5.6 to +26 120

Potassium 120 – 1,800 130 – 1,900 –120 to +14 120

Barium 35 – 2,300 37 – 2,400 –5.7 to +54 120

Other

Oil and grease 13 ND >99c 120

Total suspended 

solids (TSS)

99 – 880 81 – 680 18 to 67 120

Sulfate 0 – 410 0 – 100 60 to 76 120

Hardness 4,900 – 66,000 4,700 – 74,000 –17 to +42 120

ND—Not detected; mg/L—milligrams per liter.

a—The EPA calculated all removal efficiencies using paired influent and effluent concentrations reported in 

literature. Attachment 1 (DCN SGE01186.A01) presents these removal efficiency calculations. The number of data 

points that these removal efficiencies are based on are also presented in Attachment 1.

b—Occasionally, literature reported higher constituent concentrations after treatment than before treatment. These 

instances are indicated by negative removal efficiencies. The following are potential reasons for these negative 

values: inaccuracy of reported paired influent and effluent samples, addition of chemicals, or the technology does 

not remove the constituent.

c—If effluent concentration was reported as not detected, the EPA reported greater than 99 percent removal 

efficiency for the purpose of this table.

Flotation has the following removal efficiency when treating UOG extraction wastewater 

(DCN SGE00264):

 Oil and grease: 93 percent removal efficiency

 Chemical Oxygen Demand (COD): 75 percent removal efficiency

 TSS: Removal of suspended solids down to 25 microns in size 

The EPA did not identify removal efficiency data for sedimentation in the context of 

UOG extraction operations.
Part B

19

Design and Operation Considerations for UOG Extraction Wastewater

This section provides information on design and operation considerations when 

filtration/sedimentation/flotation technologies are used in UOG applications. Data indicates that 

the performance of all three of these technologies is not affected by influent TDS concentration. 

Filtration

One of the most significant issues with filtration of UOG extraction wastewater is the 

presence of guar gum. Guar gum is a natural polymer UOG operators commonly use in gel 

fracturing fluid to assist in carrying heavy loads of proppant. It can be found in UOG extraction 

wastewater at concentrations between 100 and 20,000 mg/L, especially during early flowback 

(DCN SGE00616). This constituent can cause serious complications during filtration. When 

UOG operators expect the presence of guar gum they add a cation to chemically break down the 

polymer prior to filtration (DCN SGE00616). Conventional activated sludge has also been 

shown to degrade guar gum based on bench top studies, though it is not yet widely used by UOG 

operators (DCN SGE01193).

Most filtrations systems designed to treat UOG extraction wastewater include a pressure 

differential monitoring system. When a target pressure differential is detected across the filter, it 

indicates a backwash cycle is required or the filter bag or cartridge needs replacement (DCN 

SGE00616).

Sedimentation

During the sedimentation process, large particles settle quickly, but smaller suspended 

particles take longer to settle. For this reason, the removal rates of TSS increase with residence 

time (i.e., the amount of time that it takes a discrete quantity of water to flow through the system) 

and particle size and density (DCN SGE00264). This treatment method requires a relatively large 

infrastructure footprint and may result in water volume loss due to evaporation (DCN 

SGE00264). Footprint and evaporation can be reduced through plate or tube settler designs

(DCN SGE01343).

Circulation within the settling tank or basin reduces the effectiveness of treatment.

Circulation may be caused by the inertia of incoming fluid, density currents due to temperature 

differences between the incoming wastewater and the rest of the volume, or wind effects. Tank 

or basin design and operation should minimize these effects (DCN SGE00167). Gravity settling 

in ponds can be enhanced by several mechanisms including gas flotation and chemical coagulant 

addition. 

Flotation

Optimal removal efficiencies for the flotation technology occur with uniform distribution 

of high density of bubbles with small interstitial spacing. These are achieved by appropriate 

design of eductors to generate bubbles, nozzles or headers to distribute the bubbles, and 

interchamber divisions to prevent short circuits and other undesirable flow patterns (DCN

SGE01044). Flotation is most effective when operating in low temperature conditions, as higher 

temperatures require higher pressures to dissolve the gas in the water. Addition of chemical 
Part B

20

coagulants increases the range of particle sizes which may be removed by flotation (DCN 

SGE00264).

Residuals

Filtration

During filtration, solids are collected in the filtration media that periodically need to be 

removed to restore optimum removal. This can be achieved by backwashing the filter, with the 

backwash water typically recycled to the treatment system inlet, or by replacing and disposing 

the filter bag or cartridge. Nearly 100 percent of the influent wastewater is recovered as treated 

wastewater. However, a small fraction may be lost from backwash cycles (DCN SGE00264).

Sedimentation

Depending on the amount of suspended solids in the UOG extraction wastewater, 

sedimentation may require limited or no removal of the solids that settle at the bottom. In cases 

where sedimentation is performed in an impoundment, solids are typically dredged from the 

bottom of the impoundment on a periodic basis and disposed of offsite, typically at a landfill.

One UOG operator who reported settling suspended solids during long-term storage of UOG 

extraction wastewater in fracturing tanks stated that they periodically must clean the tank 

bottoms and dispose of the solids at a landfill (DCN SGE00275). Typically, all of the influent is 

recovered as treated wastewater. However, depending on the climate, some volume may be lost 

to evaporation (DCN SGE00264).

Flotation

During flotation, air bubbles, particulates, and free oil droplets form foam on the surface. 

This foam is skimmed off for disposal. Note that flotation does not remove soluble oil 

constituents, which remain in the effluent (DCN SGE00264).

Energy Use

Filtration requires energy to maintain the pressure differential. Energy use associated 

with sedimentation is very low, limited to that required to pump water to or from the settling area 

(DCN SGE00264). Flotation requires energy to compress gas and skim the foam off the surface.

Costs

Capital costs of filtration, sedimentation, and flotation typically include costs for settling 

tanks, basin liners, pressurized gas tanks, piping, low-pressure pumps, and monitoring 

equipment. Operating costs associated with filtration, sedimentation, and flotation typically 

include energy to pump water and pressurize the system, replacement filters, additive chemicals, 

disposal of generated sludge solids, and labor costs. 

Table B-2 shows approximate capital and operating costs for purchased or rented 

floatation, sedimentation, and filtration treatment systems, as reported in the literature. Table B-3
Part B

21

shows approximate costs UOG operators pay CWT facilities to treat UOG extraction wastewater 

using filtration.

Table B-2. Filtration/Flotation/Sedimentation Capital and O&M Costs for UOG 

Extraction Wastewater Applications

Technology Vendor

Cost 

Basis

Capacity 

(MGD)

Capital 

Cost 

($ per gpd)

O&M Cost 

($ per bbl)

Rental or 

Effective 

Cost ($ per 

bbl)a

Reference 

ID

Filtration NR Purchase 0.025 12.00 low NR 4

Sedimentation NR Not 

reported 0.63 NR NR 0.15 – 0.40 134

Gas Flotation Purestream

Purchase 

0.11

2.40 – 3.80 NR NR

100; 183

Rental N/A N/A 0.50

NR—Not reported; MGD—million gallons per day; gpd—gallons per day; bbl—barrels.

a— Represents rental cost if the cost basis was rental and is inclusive of O&M. Represents total effective cost when 

cost basis is purchase, which includes amortized capital costs and O&M costs combined if reported by the source 

unless otherwise noted.

Table B-3. Filtration Costs to UOG Operators at CWT Facilities

CWT Facility Name

Type of 

UOG 

Reported 

Typical Influent 

TDS (mg/L)

Type of 

Service

Cost to UOG 

Operator at CWT

Facilities ($ per 

bbl)a

Reference 

ID

Clean Streams, LLC Shale gas 100,000 Reuse Only 1.00 48

mg/L—milligrams per liter; bbl—barrels.

a—Cost ranges are as-reported in literature. Cost ranges do not include transportation and may vary based on 

wastewater characteristics and the type of service.

1.1.3 Summary of Vendors for UOG Extraction Wastewater

Table B-4 lists vendors of sedimentation, filtration, and floatation technologies that offer 

treatment systems designed specifically for UOG extraction wastewater.

Table B-4. Filtration/Flotation Technology Vendors for UOG Extraction Wastewater

Vendor Technology Technology Name

Surface 

Footprint (ft2)

a

Capacity

(bpd)

Reference 

ID

Anguil Aqua 

Systems Sedimentationb NR NR NR 177

FilterSure Media Filtration NR Trailer mounted 5,000 120

Purestream Gas Flotation IGF and IGF+ Trailer mounted 2,500 183

NR—Not reported; IGF—induced gas flotation separator; IGF+— induced gas flotation separator plus; bpd—

barrels per day; ft2—square feet.

a—Only includes the primary treatment unit, not storage for wastewater, chemicals, or sludge (solid waste).

b—This vendor offers a chemical precipitation treatment technology that incorporates tube settlers into the process.
Part B

22

1.2 Chemical Precipitation

Chemical precipitation uses chemical addition to precipitate targeted constituents, 

followed by solids removal to remove the precipitate. It reduces metals, hardness, TSS, and other 

constituents, but does not remove TDS (sodium chloride or other salts). Chemical precipitation is 

most often used to treat UOG extraction wastewater prior to reuse in fracturing, or to pretreat 

wastewater prior to TDS-removal treatment. Both of these management strategies typically 

require removal of these types of constituents.

This section describes the chemical precipitation process, treatment capabilities and 

limitations, treatment cost, and vendors that the EPA is currently aware of that market the 

technology for UOG extraction wastewater treatment.

1.2.1 How Chemical Precipitation Works

This subsection describes chemical precipitation operating principles and how the process 

has been used to treat UOG extraction wastewater.

Principle

In chemical precipitation, chemicals are added to wastewater to change the physical 

properties of dissolved and suspended constituents so they can be removed by settling or 

filtration. Chemical precipitation works by destabilizing colloids and by converting soluble 

constituents to insoluble forms. This is accomplished by adding a treatment chemical 

(precipitant) to the wastewater that reacts with the target constituent and forms an insoluble solid

(precipitate). The insoluble solids are suspended in the wastewater, and then removed through 

solids removal such as settling or filtration.

Equation 1 and Figure B-3 illustrate the principle of chemical precipitation. Constituent B 

(which is soluble in water) is targeted for removal. Chemical A is added to the solution and 

reacts with B to form a new chemical, AB, which is insoluble; unable to dissolve, AB becomes a 

suspended solid. Chemical C represents a constituent unaffected by these reactions, illustrating 

that chemical precipitation does not remove all constituents.

Equation 1

A (additive chemical) + B (soluble constituent) → AB (insoluble constituent)
Part B

23

Figure B-3. Flow Diagram of Chemical Precipitation Principle

Table B-5 shows different additive chemicals and the constituents they remove. In UOG 

extraction wastewater applications, the targeted constituents include TSS, multivalent cations, 

and metals (e.g., iron) (DCN SGE01188). Therefore, the most commonly used chemicals include 

calcium hydroxide (i.e., lime) and sodium hydroxide (i.e., caustic soda). Because different 

constituents have different solubilities at different levels of pH, it may not be possible to remove 

all constituents in a one-step precipitation process. To maximize constituents removed, multiple 

stages of precipitation may be necessary, using different pH levels and additive chemicals (DCN 

SGE00127).

Table B-5. Common Additive Chemicals and Targeted Constituents for UOG Extraction 

Wastewater

Additive Chemical Targeted Constituents Reference ID

Sodium hydroxide (caustic soda) Noncarbonate hardness and TSS 44

Hydrogen peroxide Iron, TSS 172

Calcium hydroxide (lime) Carbonate hardness and TSS 3; 44

Manganate Barium, strontium, calcium 170

Sodium sulfate Barium, strontium, radium 44

One of the underlying principles dictating chemical precipitation design and operation is 

that a constituent’s solubility is correlated to pH. Each constituent has a different solubility at 

different pH ranges (DCN SGE00167). As a result, a chemical precipitation operation involves 

careful control of pH to maximize constituent removal. Figure B-4 shows how pH affects the 

solubility of different metals. The minimum of each curve represents the minimum solubility and 
Part B

24

optimum pH for chemical precipitation of that metal. Constituents shown in Figure B-4 most 

relevant to UOG extraction wastewater include iron, calcium, and magnesium.

Source: DCN SGE00133.

Figure B-4. pH Versus Concentration of Constituents

Process Description

Figure B-5 is a flow diagram of a typical chemical precipitation process to remove 

dissolved and suspended constituents from wastewater. 

1. First, wastewater enters a mixing tank where the treatment chemical is added.

Typical times required for proper mixing range from less than one second to 30 

seconds.

2. The wastewater enters a flocculation tank, where an organic polymer is added. 

Flocculation is used to increase the size of precipitated solids, thus increasing the 

rate of settling (DCN SGE00167).

3. Finally, the wastewater flows into a settling tank where the heavy suspended 

constituents fall to the bottom and are collected as sludge. The treated wastewater 

(decant water) is removed from the top of the tank.

4. Sludge is typically routed to a dewatering unit (e.g., filter press). Decant water is 

recycled to the head of the treatment system, and the solid waste that is generated 

is disposed of or otherwise managed. 

1.E-11

1.E-08

1.E-05

1.E-02

1.E+01

1.E+04

1.E+07

1.E+10

1.E+13

0 2 4 6 8 10 12 14

Concentration, Log (mg/L)

pH

Calcium (Ca(OH)2) Iron (Fe(OH)2) Iron (Fe(OH)3)

Magnesium (Mg(OH)2) Manganese (Mn(OH)2) Lead (Pb(OH)2)
Part B

25

Figure B-5. Flow Diagram of Chemical Precipitation and Settling Principle

1.2.2 Capabilities and Limitations

This subsection describes the targeted constituents and effectiveness, design and 

operation considerations, residuals, and energy use of chemical precipitation. 

Targeted Constituents and Treatment Effectiveness

The primary constituents removed by chemical precipitation in UOG extraction 

wastewater applications include hardness, TSS, and metals (DCN SGE00167). When these 

constituents are removed, TDS concentrations are only slightly reduced, if reduced at all.19 This 

is because TDS in UOG extraction wastewater is primarily sodium chloride, a dissolved solid 

that is not removed by chemical precipitation. 

Table B-6 shows chemical precipitation performance data in UOG extraction wastewater

applications. The table includes untreated influent constituent concentrations, effluent constituent

concentrations, and the resulting constituent removal efficiencies. Data in Table B-6 indicates 

that the removal of TDS from UOG extraction wastewater from chemical precipitation is low. In 

general, chemical precipitation is effective at any influent TDS concentration. 

 

19 It is also possible that TDS increases using chemical precipitation due to the addition of treatment chemicals.
Part B

26

Table B-6. Chemical Precipitation Removal Efficiency in UOG Extraction Wastewater 

Applications

Constituent

Typical Influent 

Range

(mg/L)

Typical Effluent 

Range

(mg/L)

Calculated 

Removal 

Efficiency (%) a,b

Chemical 

Additive Used Reference ID

TDS 33,000 – 47,000 31,000 – 48,000 −6 to +5 Lime, NaOH 3; 68; 60

Chloride 13,000 – 22,000 13,000 – 21,000 2 to 3 NR 5; 3

Sodium 7,100 – 17,000 6,800 – 17,000 –13 to +4 NR 5; 3; 60

Metals

Barium 7 – 600 0.1– 43 14 to >99 Lime, NaOH 60; 3; 5

Boron 18 – 25 16 – 23 7 to 11 Lime, NaOH 60; 3

Calcium 740 – 2,600 37 – 2,700 –5 to +97 Lime, NaOH 60; 3; 5

Iron 8 – 180 ND – 2 >87 Lime, NaOH 5; 60; 3; 68

Lithium 11 11 0 NaOH 60

Magnesium 130 – 1,200 49 – 520 –2 to +61 Lime, NaOH 5; 3; 60

Manganese 0.6 – 1.5 ND – 0.1 >83 Lime 3; 68

Nickel 0.11 0.1 11 Lime 3

Phosphorous 3 2 33 NaOH 60

Potassium 36 – 560 35 – 350 –18 to +43 Lime, NaOH 5; 60; 3

Strontium 150 – 470 6 – 480 –3 to +96 Lime, NaOH 5; 3; 60

Organics

BTEX 2.9 2.1 28 NaOH 60

HEM 2,100 6 >99 Lime 3

TOC 12 – 18 6 – 9 25 to 67 Lime, NaOH 60; 3

TPH 19 4 79 NaOH 60

Other

Alkalinity 240 – 750 4 – 330 39 to >99 Lime, NaOH 3; 68; 5; 60

Ammonia 84 84 0 NaOH 60

Hardness 301 – 2,400 560 – 1,600 –87 to +41 Lime, NaOH 3; 68; 60

Silica 150 – 190 18 – 40 78 to 89 Lime; NR 68; 3

Sulfates 10 – 320 27 – 210 –170 to +35 Lime, NaOH 5; 3; 60

TSS 120 – 780 18 – 130 48 to 98 NaOH; Lime 5; 68; 60; 3

Turbidity 44 – 100 3 93 to 97 NR 68

NR—Not reported; mg/L—milligrams per liter; NaOH—sodium hydroxide; TDS—total dissolved solids; BTEX—

benzene, toluene, ethylbenzene, and xylenes; HEM—hexane extractable material; TOC—total organic carbon; 

TPH—total petroleum hydrocarbons; TSS—total suspended solids.

a—The EPA calculated all removal efficiencies using paired influent and effluent concentrations reported in 

literature. Attachment 1 (DCN SGE01186.A01) presents these removal efficiency calculations. The number of data 

points that these removal efficiencies are based on are also presented in Attachment 1.

b—Occasionally, literature reported higher constituent concentrations after treatment than before treatment. These 

instances are indicated by negative removal efficiencies. The following are potential reasons for these negative 

values: inaccuracy of reported paired influent and effluent samples, addition of chemicals, or the technology does 

not remove the constituent.
Part B

27

Design and Operation Considerations for UOG Extraction Wastewater

In UOG extraction wastewater applications, chemical precipitation is typically utilized at 

CWT facilities where there is sufficient area for setup. A typical system, as shown in Figure B-5, 

will fit inside one to three trailers, depending on flow and the vendor. However, this does not 

include storage (e.g., impoundments, fracturing tanks) for influent and treated wastewater or a 

staging area for chemicals. One UOG operator the EPA visited owned a CWT facility designed 

for treating UOG extraction wastewater for reuse, using chemical precipitation as the primary 

treatment. The entire treatment system required a site that was approximately the same size as a 

well pad. It included (DCN SGE00635):

 Chemical storage area

 Two trailer-sized treatment units and a separate filter press

 Multiple sludge storage bins

 Multiple 500-barrel fracturing tanks for untreated and treated wastewater 

storage20

To improve chemical precipitation reliability, advanced systems to monitor

concentrations, pH, and flow rates may be installed (DCN SGE00127). The appropriate quantity 

and type of treatment chemical are determined based on influent wastewater characteristics. 

Testing wastewater prior to treatment is required because constituent concentrations in UOG 

extraction wastewater can vary greatly over time (DCN SGE00299; DCN SGE00300; DCN 

SGE00245). Important parameters include the influent pH, TDS, hydrocarbons, and TSS (DCN 

SGE00245). 

Residuals

In addition to treated wastewater, chemical precipitation processes generate sludge that is 

typically dewatered before landfill disposal. Table B-7 shows estimated sludge generation from 

chemical precipitation units processing UOG extraction wastewater. In general, higher influent 

TDS and TSS results in higher sludge generation (DCN SGE00285). Most of these units 

associated with the data in Table B-7 are operated to remove barium, strontium, magnesium, 

calcium, and TSS from UOG extraction wastewater. 

 

20 The number of 500-barrel fracturing tanks was not reported, but varies depending on the treatment rate and ability 

to move wastewater to and from the site.
Part B

28

Table B-7. Sludge Generated by Chemical Precipitation of UOG Extraction Wastewater

Type of Precipitation

Influent TDS 

(mg/L)

Influent Flow 

Rate (bpd)

Total Waste 

Generation (tons 

per day)

Waste Generation 

(pounds per 

influent barrel)

Reference 

ID

Caustic (NaOH) 

Addition 45,000 – 80,000 4,000 – 6,000 5 – 6 1.7 – 3 60

Lime-soda 34,000 – 59,000 N/A N/A 3.7 – 7.8 3

Sulfate Precipitation 130,000 N/A N/A 3.7 – 8.2 44; 51

Lime-soda 130,000 N/A N/A 14 51

Modified Lime-soda 130,000 N/A N/A 1.5 – 8.2 44; 51

Unknown 100,000 4,000 10 – 30 5 – 15 49

N/A—Not applicable; mg/L—milligrams per liter; bpd—barrels per day; NaOH— sodium hydroxide.

Note: Data in this table are as-reported in literature.

Energy Use

EPA has not quantified energy requirements for chemical precipitation. Energy is 

required to operate low-pressure pumps, mixers, equipment such as filter presses and any 

electrical monitoring devices.

1.2.3 Costs

Capital costs of chemical precipitation typically include costs for a precipitation tank, 

mixing tanks, a settling tank (clarifier) and/or filtration system, piping, low-pressure pumps, and 

monitoring equipment. Advanced monitoring equipment may be necessary to improve system 

reliability. In addition, using chemical precipitation will also require investment for wastewater 

storage to provide a relatively constant, homogeneous influent (e.g., impoundments, tanks) and 

sludge dewatering equipment.

The operating costs associated with chemical precipitation include energy for lowpressure pumps and mixers, additive chemicals, and labor costs. Operating costs also depend on 

quality of influent wastewater, desired effluent quality of treated wastewater, and chemical costs 

(which depend on the type and quantity of the additive chemical). The largest operating cost is 

typically the cost of the additive chemical. 

Table B-8 shows approximate capital and operating costs for purchased or rented 

chemical precipitation treatment systems, as reported in the literature. Table B-9 shows 

approximate costs UOG operators pay CWT facilities to treat UOG extraction wastewater using 

chemical precipitation. One CWT facility stated that when influent TDS concentrations are 

higher than 150,000 mg/L, they surcharge UOG operators to cover the increased chemical 

demand (DCN SGE00300).
Part B

29

Table B-8. Chemical Precipitation Capital and O&M Costs for UOG Extraction 

Wastewater Applications

Vendor and 

Technology Name

System 

Description

Cost 

Basis

Capacity 

(MGD)

Capital 

Cost 

($ per gpd)

O&M Cost 

($ per bbl)

Rental or 

Effective 

Cost ($ per 

bbl)a

Reference 

ID

Fountain Quail Water 

Management, LLC’s 

Rover

Mobile 

system Rental 0.29 NR NR 1.00 – 4.00c 60; 36

JS Meyer Engineering, 

JSM

Mobile 

system NR NR NR 2.10 NR 170

Not specified Plant Purchase 1.2 5.00 to 6.00

NR N/A 38

Not specified Plant Purchase 0.40 8.80

Not specified

Unit Purchase 

0.022 21.00

NR 0.50 –

3.00b 4

0.72 1.40

N/A—Not applicable; NR—Not reported; MGD—million gallons per day; gpd—gallons per day; bbl—barrels.

a—Represents rental cost if the cost basis was rental and is inclusive of O&M. Represents total effective cost when 

cost basis is purchase, which includes amortized capital costs and O&M costs combined if reported by the source

unless otherwise noted. 

b—This cost range represents a unit designed for UOG extraction wastewater treatment but has not been 

implemented. Amortization assumptions were not reported with this source.

c—SGE00415 (60) reported a general cost range of less than $1 per barrel for this treatment unit but the original 

source of the information is unknown. SGE00239 (36) reported $2 to $4 based on personal communication with the 

vendor.

Table B-9. Chemical Precipitation Costs to UOG Operators at CWT Facilities

CWT Facility Nameb

Type of 

UOG 

Typical 

Influent 

TDS 

(mg/L)

Type of 

Service

Cost to UOG 

Operator at 

CWT Facilities 

($ per bbl)a

Reference 

ID

Eureka Resources, LLC Shale gas 100,000

Reuse only

3.25b 49

Clean Streams, LLC Shale gas 100,000 3.60c 48

Reserved Environmental Services, LLC Shale gas NR 4.00d 38; 177

Hart Resource Technologies, Inc. Shale gas NR Discharge to 

surface water

2.20 1

Pennsylvania Brine Treatment, Inc. Shale gas NR 2.30 1

NR—Not reported; mg/L—milligrams per liter; bbl—barrels

a—Data in this table are as-reported in literature or to EPA. Cost ranges do not include transportation and may vary 

based on wastewater characteristics and the type of service. All facilities listed are located in the Appalachian Basin 

where Marcellus and Utica gas are produced.

b—A cost of $10 per barrel is charged if a load of treated wastewater is not taken by the operator in which case the 

wastewater is treated using evaporation/condensation and then stored until another operator can take it. Surcharges 

may apply for flowback and long-term produced water with TDS greater than 150,000 mg/L. The cost shown is for 

treatment of flowback and long-term produced water but the CWT facility also accepts UOG drilling wastewater. 

The cost ranges from $7 to $16 for treatment of UOG drilling wastewater due to high TSS. 

c—A cost range of $7.98 to $8.25 is charged if a load of treated wastewater is not taken by the operator in which 

case the wastewater is treated using evaporation/condensation and then stored until another operator can take it. The 

cost shown is for treatment of flowback and long-term produced water but the CWT facility also accepts UOG 
Part B

30

drilling wastewater. The cost ranges from $9.20 to $9.50 per barrel for chemical precipitation treatment of UOG 

drilling wastewater due to high TSS. 

d—A cost of $7.00 per barrel is charged if a load of treated wastewater is not taken by the operator in which case the 

wastewater is treated using chemical precipitation and stored until another operator can take it.

1.2.4 Summary of Vendors for UOG Extraction Wastewater

Table B-10 lists vendors that offer chemical precipitation treatment systems designed 

specifically for UOG extraction wastewater.

Table B-10. Chemical Precipitation Technology Vendors for UOG Extraction Wastewater

Vendor Technology Name

System 

Description

Surface 

Footprint 

(ft2)

a Capacity (bpd)

Reference 

ID

Fountain Quail Water 

Management, LLC Rover Mobile system 1,100 10,000 60

Anguil Aqua Systems NR NR NR NR 177

AquaTech International 

Corporation MoTreat Mobile system Unit fits on mobile trailer 1,700 – 6,900 74

MI-SWACO Frac Water 

Reclamation System Mobile system NR 3,000 111

JS Meyer Engineering JSM Mobile system NR NR 170

CoilChem, LLC CoilChem Mobile system 640 20,000 172

Gradiant Corporation Selective Chemical 

Extraction Fixed system NR 12,000 173

NR—Not reported; ft2—square feet; bpd—barrels per day.

a—Only includes the primary treatment unit, not storage for wastewater, chemicals, or sludge (solid waste).

1.3 Electrocoagulation

Electrocoagulation is used to remove suspended solids, metals, microbial contaminants, 

and colloids (organic and inorganic) in UOG extraction wastewater (DCN SGE00358; DCN 

SGE00638.A12; DCN SGE00653). It does not remove TDS (sodium chloride or other salts). 

Instead of using chemical additives to facilitate removal of constituents (as in chemical 

precipitation), electrocoagulation uses electrical current. Because it is able to reduce microbial 

contaminants, oils, suspended solids, and metals, this technology is primarily used to treat UOG 

extraction wastewater prior to reuse and as pretreatment before TDS removal treatment 

technologies. 

This section describes the electrocoagulation process, treatment capabilities and 

limitations, treatment cost, and vendors that the EPA is currently aware of that market the 

technology for UOG extraction wastewater treatment.

1.3.1 How Electrocoagulation Works

This subsection describes electrocoagulation operating principles and how the process 

has been used to treat UOG extraction wastewater.
Part B

31

Principle 

Electrocoagulation uses electrical current to destabilize and precipitate suspended, 

emulsified, or dissolved contaminants (as compared to chemical precipitation, which uses 

chemical additives). The particulates are then removed by settling, flotation, and/or filtration.

In a typical reactor, wastewater passes between pairs of electrode plates (usually 

aluminum or iron). One electrode is the anode and the other electrode is the cathode. Figure B-6

shows a simplified set up of an electrocoagulation reactor with aluminum electrodes and a 

constituent (B) in the wastewater. The reactions depicted in Figure B-6 are described below 

(DCN SGE00653):

1. At the anode, the electrical current creates metal ions, freeing them from the 

surface of the electrode. This reaction is shown in Equation 2.

2. At the cathode, the electrolysis of water forms hydrogen and hydroxyl radicals. 

This reaction is shown in Equation 3.

3. Some of the hydroxyl radicals react with the metal ions to form metal hydroxides 

(coagulants). This reaction is shown in Equation 4. 

4. The metal hydroxides formed in step 3 react with constituent B causing it to 

destabilize and precipitate. This reaction is shown in Equation 5.

5. Some of the hydroxyl radicals formed in step 2 skip step 3, reacting directly with 

constituent B to destabilize it causing it to precipitate. This reaction is shown in 

Equation 6.

Equation 2 (anode)

Al → 3e

− + Al3+

Equation 3 (cathode)

2H2O + 2e

− → H2 + 2OH−

Equation 4 (in solution)

Al3+ + 3OH− → Al(OH)3

Equation 5 (in solution)

B + Al(OH)3 → B(Al(OH)3)

Equation 6 (in solution)

B + 3OH− → B(OH)
Part B

32

Figure B-6. Principle of Electrocoagulation

The remaining steps in electrocoagulation treatment are the same as in chemical 

precipitation (described in Part B.1.1). Constituents are attracted to hydroxyl radicals and metal 

hydroxides (e.g., Al(OH)3), which cause them to become destabilized colloids. The colloids are 

dense enough to be separated from the wastewater by settling or a mechanical method (e.g., 

induced gas flotation or mechanical skimmer). The hydrogen gas produced during the hydrolysis 

reaction (step 2 above) assists in raising coagulated particles to the surface of the wastewater 

(DCN SGE00653).

Process Description

One UOG operator that uses electrocoagulation treatment systems described a typical 

process at their own CWT facility, shown in Figure B-7 (DCN SGE00638.A12). 

1. Influent wastewater enters the main electrocoagulation reactor where targeted 

constituents are destabilized, coagulated, and precipitated.

2. Wastewater flows to a weir tank where precipitated particles are removed, either 

by gas flotation or settling.

3. The sludge from the weir tank is dewatered, creating solid waste. 

4. The water from the weir tank and the decant water from the dewatering unit are 

filtered using a media filter (e.g., carbon filters, crushed glass) to further reduce 

suspended solids.
Part B

33

Source: Adapted from SGE00638.A12.

Figure B-7. Flow Diagram of Electrocoagulation

1.3.2 Capabilities and Limitations

This subsection describes the targeted constituents and effectiveness, design and 

operation considerations, residuals, and energy use of electrocoagulation. 

Targeted Constituents and Treatment Effectiveness

Electrocoagulation removes hardness, suspended solids, metals, and colloids (organic and 

inorganic) (DCN SGE00653). In electrocoagulation, TDS concentrations are only slightly 

reduced, if at all. This is because electrocoagulation does not destabilize or precipitate sodium or 

chloride, which are the primary dissolved ions that make up TDS in UOG extraction wastewater

(see Part A.1). UOG operators use electrocoagulation to remove targeted constituents that 

interfere with fracturing additives or cause formation damage and fouling and scaling down the 

well bore. The specific metals removed depend on the electrode material (e.g., iron, aluminum) 

and pH.
Part B

34

Table B-11 shows specific influent and effluent concentrations from electrocoagulation 

treatment of UOG extraction wastewater. The data shows how some of the multivalent cations 

are reduced in addition to sulfate reducing bacteria and suspended solids. Because 

electrocoagulation removes some dissolved constituents, TDS concentrations are slightly 

reduced. Electrocoagulation has been used to treat UOG extraction wastewater with TDS 

concentrations up to 300,000 mg/L with no adverse effect on operation (DCN SGE00638.A11). 

Table B-11. Electrocoagulation Removal Efficiency in UOG Extraction Wastewater 

Applications

Constituent

Typical Influent 

Range

(mg/L)

Typical Effluent 

Range

(mg/L)

Calculated 

Removal Efficiency 

(%)a,b Reference ID

TDS 39,000 – 270,000 27,000 – 270,000 –2 to +31 88; 94

Chloride 17,000 – 160,000 13,000 – 160,000 –1 to +26 56; 88; 94

Sodium 4,300 – 70,000 4,200 – 76,000 –7 to +42 56; 88; 94

Metals

Aluminum 1.4 2.3 –60c 94

Barium 5 – 1,300 1 – 740 10 to >99 56; 88; 94

Boron 20 – 71 17 – 66 7 to 18 56; 94

Calcium 440 – 29,000 39 – 29,000 1 to 92 56; 88; 94

Chromium 0.06 0.05 9 56

Iron 18 – 160 ND – 1 >92 56; 88; 94

Lead 0.020 0.015 33 56

Magnesium 37 – 4,300 17 – 3,100 22 to 85 56; 88; 94

Manganese 4.2 0.075 98 56

Potassium 35 – 1,700 31 – 1,700 –2 to +15 56; 88; 94

Strontium 75 – 2,200 24 – 2,000 3 to 79 56; 88; 94

Organics

Benzene 0.13 0.04 72 56

BTEX 3,500 3 >99 56

TOC 610 600 3 56

Toluene 0.03 0.01 55 56

TPH (all ranges) 4 – 54 ND – 6 59 to 92 56; 94
Part B

35

Table B-11. Electrocoagulation Removal Efficiency in UOG Extraction Wastewater 

Applications

Constituent

Typical Influent 

Range

(mg/L)

Typical Effluent 

Range

(mg/L)

Calculated 

Removal Efficiency 

(%)a,b Reference ID

Other

Alkalinity 710 580 18 56

BOD 100 – 26,000 81 – 210 20 – >99 56

Hardness 1,300 – 63,000 700 – 42,000 6 – 47 56; 88

Silica 17 – 66 0.27 – 13 80 – 99 56

SRB (cfu/100 mL) 1,200 – 450,000 200 – 4,200 84 – >99 56

Sulfates 28 – 410 13 – 88 5 – 79 88; 94

TSS 40 – 10,000 6 – 300 15 – 99 56; 88

Turbidity 180 15 92 94

ND—Not detected; mg/L—milligrams per liter; TDS—total dissolved solids; BTEX—benzene, toluene, 

ethylbenzene, and xylenes; TOC—total organic carbon; TPH—total petroleum hydrocarbons; BOD—biochemical 

oxygen demand; SRB—sulfate reducing bacteria; TSS—total suspended solids.

a—The EPA calculated all removal efficiencies using paired influent and effluent concentrations reported in 

literature. Attachment 1 (DCN SGE01186.A01) presents these removal efficiency calculations. The number of data 

points that these removal efficiencies are based on are also presented in Attachment 1.

b—Occasionally, literature reported higher constituent concentrations after treatment than before treatment. These 

instances are indicated by negative removal efficiencies. The following are potential reasons for these negative 

values: inaccuracy of reported paired influent and effluent samples, addition of chemicals, or the technology does 

not remove the constituent.

Design and Operation Considerations for UOG Extraction Wastewater

Electrocoagulation treatment systems, as shown in Figure B-7 above, can be configured 

to fit inside one to three trailers (depending on the vendor), not including storage for influent and 

treated wastewater. One UOG operator described a typical set up with a maximum treatment rate 

of 60,000 barrels (2,520,000 gallons) per month, consisting of the following units (DCN 

SGE00638.A12):

 Two trailers containing the electrocoagulation unit, filtration unit, and weir tank.

 Solid waste bin (trailer size).

 Multiple 500 barrel (210,000 gallon) fracturing tanks for untreated and treated 

wastewater, or an impoundment.21

Some vendors offer electrocoagulation units able to treat wastewater at rates up to 20 

barrels (840 gallons) per minute (see Part B.1.3.4). By using multiple treatment units in parallel, 

it is possible to treat wastewater on-the-fly with hydraulic fracturing (DCN SGE00638.A11). Onthe-fly treatment allows the UOG operator to reduce other costs, such as trucking and wastewater 

storage. These advantages are discussed in detail in Part B.1.4.2. Although these treatment rates 

 

21 The number of 500-barrel fracturing tanks was not reported, but varies depending on the treatment rate and ability 

to move wastewater to and from the site (Bosque, 2013).
Part B

36

are higher than most other UOG extraction wastewater treatment technologies, they are still 

much lower than AOP rates, which can reach 80 barrels (3,360 gallons) per minute in mobile 

applications. As a result, data available to the EPA indicates that electrocoagulation is not as 

frequently used on-the-fly with hydraulic fracturing as AOP.

Electrocoagulation does not require the purchase of chemical additives for precipitation. 

However, the electrodes in the main reactor must be periodically replaced, as metal ions are 

consumed by the electrochemical reactions. One vendor estimated approximately 500 pounds of 

anode material are required for every 100,000 barrels of UOG extraction wastewater treated 

(DCN SGE00638.A11).

Residuals

Electrocoagulation generates a sludge stream that is usually dewatered to form solid 

waste. However, electrocoagulation generates less waste than conventional chemical 

precipitation because no chemicals are added to the system, other than metal that dissolves from 

the anode (DCN SGE00638.A11; DCN SGE00311.A01; DCN SGE00653). One vendor 

estimated that the total volume of residual waste generated in UOG applications is less than five 

percent of the influent wastewater volume, compared to 20 percent for conventional chemical 

precipitation (DCN SGE00311.A01; DCN SGE00638.A11).

Most treatment operators haul the dewatered solids (sludge) to a landfill for disposal. 

Depending on the state and applicable permits, the operator may be required to screen the waste 

stream for radioactivity prior to transport to landfills (DCN SGE00299; DCN SGE00300; DCN 

SGE00245). The radioactivity of the waste correlates to the radioactive constituents in the 

untreated UOG extraction wastewater, and varies by location (DCN SGE01188). Furthermore, 

the level of radioactivity in the solid waste is dependent on the constituents removed from the 

wastewater. For example, one UOG operator reported they purposely do not remove barium or 

strontium in order to prevent precipitation of radioactive constituents, which typically coprecipitate with barium and strontium (DCN SGE00638.A12). 

Energy Use

Electrocoagulation treatment units require electricity to operate pumps and to apply 

electrical current through the wastewater. Units specifically designed to treat UOG extraction 

wastewater typically include a diesel generator for locations where connection to the electrical 

grid is not possible (DCN SGE00638.A11). 

Table B-12 reports energy use per barrel of influent wastewater specific to UOG 

applications. The EPA expects typical energy consumption to be more than conventional 

chemical precipitation, but less than TDS removal treatment technologies.
Part B

37

Table B-12. Electrocoagulation Energy Use in UOG Extraction Wastewater Applications

Vendor Technology Name

Influent TDS 

concentration (mg/L)

Energy Use

(kWh per bbl)

Reference 

ID

OriginOil® Clean-FracTM NR 0.84 98

Not specified Not specified 40,000 >0.25 85

NR—Not reported; mg/L—milligrams per liter; kWh per bbl—kilowatt-hours per barrel.

1.3.3 Costs

Capital costs of electrocoagulation typically include costs for the primary treatment unit, 

settling tank, filtration system, piping, low-pressure pumps, and monitoring equipment. The 

operating costs associated with electrocoagulation include energy for low-pressure pumps and 

mixers, periodic electrode replacement, and labor (DCN SGE00638.A12; DCN SGE00638.A11). 

Table B-13 shows approximate capital and operating costs for electrocoagulation when a 

treatment system is purchased or rented (as reported in the referenced literature).

Table B-13. Electrocoagulation Capital and O&M Costs for UOG Extraction Wastewater 

Applications

Vendor and 

Technology 

Name

System 

Descriptionb

Cost 

Basis

Capacity 

(MGD)

Capital 

Cost 

($ per gpd)

O&M Cost 

($ per bbl)

Rental or 

Effective Cost 

($ per bbl)a

Reference 

ID

Not specified Mobile system Purchase 0.063 12.00 NR NR 85

Not specified System Purchase 0.10 4.00 0.25 NR 88e

Not specified System Purchase 0.14 4.20 0.25 NR 88

Not specified System at 

centralized 

facility

Purchase 0.082 1.20 2.20 – 2.80 2.30 – 3.10c 72

Halliburton 

CleanWaveTM Mobile system Rental 1.0 NR NR 1.00 – 3.00d 53; 71

OriginOil 

CleanFracTM Mobile system Rental NR NR 0.52 – 1.10 NR 98

NR—Not reported; MGD—million gallons per day; gpd—gallons per day; bbl—barrel.

a—Represents rental cost if the cost basis was rental and is inclusive of O&M. Represents total effective cost when 

cost basis is purchase, which includes amortized capital costs and O&M costs combined if reported by the source 

unless otherwise noted.

b—All systems include pre- and post-treatment (e.g., filtration, sludge dewater).

c—The underlying source reported this range based on amortized capital costs but did not report the amortization 

rate.

d— The underlying source reported this as a generic range in chart format.

e— This cost range represents a unit designed for UOG extraction wastewater treatment but has not been 

implemented.

1.3.4 Summary of Vendors for UOG Extraction Wastewater

Table B-14 presents information on electrocoagulation units from vendors that the EPA is 

currently aware of that are producing and selling units specifically for treating UOG extraction 
Part B

38

wastewater. All of these systems can be trailer-mounted or installed permanently. Because these 

technologies can be used on-the-fly with fracturing, capacity is also presented in barrels per 

minute. 

Table B-14. Electrocoagulation Technology Vendors for UOG Extraction Wastewater

Vendor Technology Name

Surface 

Footprint (ft2)

a

Capacity 

(bpd)

Capacity 

(bpm)b

Reference 

ID

OriginOil, Inc. EWSTM Petro P160 Fits into a 40 foot 

shipping container 7,200 5 98; 97

Ecolotron, Inc. E-Floc© 500 11,000 7.5 56

Water Tectonics WaveIonics Trailer mounted NR NR 176

Halliburton Company CleanWaveTM Trailer mounted 29,000 20 53; 71

Bosque Systems, LLC Mobile Water 

Recycler 500 21,000 14 83

Baker Hughes, Inc. H2proTM Trailer mounted 8,500 6 82

NR—Not reported; ft2—square feet; bpd—barrels per day; bpm—barrels per minute.

a—Only includes the primary treatment unit, not storage for wastewater, chemicals, or sludge (solid waste).

b—For comparison, a typical fracturing job will inject fracturing fluid at approximately 60 to 120 barrels per 

minute.

1.4 Advanced Oxidation and Precipitation

Advanced oxidation and precipitation (AOP) is a non-TDS removal treatment technology 

that reduces microbial constituents and destabilizes and precipitates multivalent cations in UOG 

extraction wastewater (DCN SGE00331; DCN SGE00616). UOG operators began using AOP 

for treatment prior to reuse in 2008 (DCN SGE00333). To date, the EPA has identified AOP 

being utilized only in reuse applications. Most of these applications have been treatment on-thefly with hydraulic fracturing, a concept that Part B.1.4.1 describes in detail (DCN SGE00625; 

DCN SGE00705). 

Destroying microbial constituents and destabilizing and precipitating multivalent cations 

in UOG extraction wastewater reduces the potential for scaling and biological growth inside the 

well (DCN SGE00705; DCN SGE00331; DCN SGE00616; DCN SGE00625). The fact that 

UOG operators use this technology suggests that, in some cases, microbial and scale control is 

all that is necessary for treatment prior to reuse (DCN SGE00616). 

This section describes the AOP process, treatment capabilities and limitations, treatment 

cost, and vendors that the EPA is currently aware of that market the technology for UOG 

extraction wastewater treatment.

1.4.1 How Advanced Oxidation and Precipitation Works

This subsection describes AOP operating principles and how the process has been used to 

treat UOG extraction wastewater.
Part B

39

Principle

AOP generates highly reactive hydroxyl radicals (•OH) to oxidize targeted constituents. 

Hydroxyl radicals are produced in systems using processes including primary oxidants such as 

ozone (O3), an energy source such as ultraviolet (UV) light, or catalysts such as titanium dioxide 

(DCN SGE01048).

Process Description

AOP for UOG extraction wastewater treatment includes the addition of ozone to kill 

bacteria and the generation of hydroxyl radicals to destabilize targeted constituents and 

precipitate them out of the solution. The following sequence of processes occurs within an AOP 

treatment system (DCN SGE00705; DCN SGE00331):

1. Wastewater enters static mixers that homogenize the wastewater and initiate 

hydrodynamic cavitation whereby the velocity of the wastewater is increased and 

the pressure is simultaneously decreased, resulting in the creation of small vapor 

cavities (i.e., bubbles). These cavities quickly collapse, releasing energy sufficient 

to cause water molecules to break down into hydroxyl radicals, which kill bacteria 

and oxidize target constituents.

2. Ozone (O3), created by oxygen separators and ozone generators, is mixed with the 

wastewater in a flash reactor to kill bacteria. The treatment unit operator 

determines the appropriate dose of ozone by monitoring the oxidation reduction 

potential (ORP) in the UOG extraction wastewater.

3. The wastewater passes through an electrochemical oxidation unit, which uses 

electrical current to precipitate hardness and other target constituents and to 

convert water molecules into hydroxyl radicals to kill bacteria (see discussion of 

Electrocoagulation in Part B.1.3.1 above).

4. Next, the wastewater passes through ultrasonic transducers which generate sound 

waves with sufficient energy to initiate caustic cavitation to reduce the particle 

size of precipitated solids to less than one micron. 

According to AOP vendors, precipitated solids in the treated wastewater are reduced to 

less than one micron in size so they do not cause scale or formation damage during fracturing 

and therefore do not need to be separated from the treated wastewater (DCN SGE00331; DCN 

SGE00705). 

Operators most commonly use AOP to treat UOG extraction wastewater on-the-fly with 

hydraulic fracturing as shown in Figure B-8

22. On-the-fly treatment is only possible because 

mobile AOP units are capable of treating wastewater at relatively high rates.23 In on-the-fly 

 

22 UOG operators may store untreated wastewater in open pits or impoundments adjacent to the well pad depending 

on applicable regulations.

23 Treatment rates of 80 barrels per minute are typical for AOP treatment, but rates can be as high as 120 barrels per 

minute. For comparison, a typical fracturing job will inject fracturing fluid at approximately 60 to 120 barrels per 

minute. If needed, operators can use a second AOP system in parallel to meet the desired fracturing rate.
Part B

40

treatment, other source water (e.g., fresh water, ground water) and the untreated wastewaters are 

mixed together for treatment by AOP. One vendor explained that mixing other source water with 

the untreated UOG extraction wastewater provides better consistency for treatment and hydraulic 

fracturing (DCN SGE00705). Although not shown in Figure B-8, AOP typically requires 

pretreatment using bag filters to remove suspended solids (DCN SGE00705). 

Source: DCN SGE00705.

Figure B-8. Flow Diagram of AOP Treatment On-the-Fly with Hydraulic Fracturing in 

UOG Extraction Wastewater Applications

Figure B-9 shows an alternative use of AOP in UOG extraction wastewater applications. 

Units can be deployed at existing impoundments constructed at well sites to temporary store 

wastewater.

24 The treatment unit simply circulates the wastewater back into the impoundment 

after treatment. This use of AOP has many of the same advantages as on-the-fly (DCN

SGE00705). One additional advantage is that the AOP can operate continuously in this setup, 

 

24 Applicable regulations for storing UOG extraction wastewater in open impoundments vary by state and sometimes 

even within states. For example, at the time of writing, in Pennsylvania within the jurisdiction of the Susquehanna 

River Basin Commission (SRBC) UOG extraction wastewater cannot be stored in open impoundments. However, 

outside of the SRBC, UOG extraction wastewater may be stored in open impoundments in Pennsylvania (DCN 

SGE00635). 
Part B

41

whereas on-the-fly treatment requires periodic breaks while the fracturing job moves on to the 

next stage (DCN SGE00705). 

Source: DCN SGE00705.

Figure B-9. Flow Diagram of AOP Treatment at Wastewater Impoundments in UOG 

Extraction Wastewater Applications

1.4.2 Capabilities and Limitations

This subsection describes the targeted constituents and effectiveness, design and 

operation considerations, residuals, and energy use of AOP. 

Targeted Constituents and Treatment Effectiveness

UOG operators use AOP for treatment prior to reuse because it focuses on microbial 

control and scale control, two parameters that UOG operators consider prior to reuse (DCN 

SGE00331). Table B-15 shows specific influent and effluent concentrations from AOP treatment 

of UOG extraction wastewater from one vendor (Hydrozonix, LLC). Although AOP does not 

reduce TDS, the treatment also has no maximum limit on the influent TDS concentration. For 

example, AOP has successfully treated extraction wastewater from the Woodford shale with a 

TDS concentration of 170,000 mg/L TDS (DCN SGE00331).

Table B-15. AOP Removal Efficiency in UOG Extraction Wastewater Applications

Constituent

Typical Influent 

Range

(mg/L)

Typical Effluent 

Range

(mg/L)

Calculated 

Removal Efficiency 

(%)a Reference ID

Chlorides 18,000 – 19,000 17,000 – 19,000 0 to 2 114

Metals

Barium 56 – 290 42 – 250 12 to 25 114

Calcium 430 – 2,400 320 – 2,400 2 to 24 114

Iron 16 – 150 5.9 – 150 0 to 62 114

Magnesium 320 – 740 290 – 680 8 to 9 114
Part B

42

Table B-15. AOP Removal Efficiency in UOG Extraction Wastewater Applications

Constituent

Typical Influent 

Range

(mg/L)

Typical Effluent 

Range

(mg/L)

Calculated 

Removal Efficiency 

(%)a Reference ID

Other

Carbonate 4.5 – 92 2.8 – 58 37 to 38 114

Alkalinity 150 – 700 95 – 530 24 to 37 114

Hardness 2,100 – 7,300 2,000 – 7,100 3 to 5 114

Calcium hardness 1,800 – 6,000 1,700 – 5,900 2 to 8 114

SRB (mpn/mL) 13,000 – 140,000 92 – 450 99 to 100 116

Sulfates 100 – 860 85 – 660 15 to 23 114

mg/L—milligrams per liter; mpn/mL—most probable number per milliliter; SRB—sulfate reducing bacteria.

a—The EPA calculated all removal efficiencies using paired influent and effluent concentrations reported in 

literature. Attachment 1 (DCN SGE01186.A01) presents these removal efficiency calculations. The number of data 

points that these removal efficiencies are based on are also presented in Attachment 1.

Data in Table B-15 confirm that the concentrations of many multivalent cations are not 

reduced using AOP. As explained in Part B.1.4.1, AOP leaves the precipitated constituents 

suspended in the treated wastewater but reduces their size to less than 1 micron (DCN 

SGE00705). Results from UOG case studies (see Figure B-10) demonstrate how AOP is able to 

reduce scaling potential. This figure shows the results from dynamic tube block tests25 of treated 

UOG extraction wastewater (red) and the associated untreated UOG extraction wastewater 

(blue). The increase in pressure observed for the untreated UOG extraction wastewater indicates 

its higher potential to cause scale formation than the treated UOG extraction wastewater.

 

25 A dynamic tube block test is used by UOG operators to measure the scaling potential of a fluid. Operators use this 

test to determine the efficiency of chemical inhibitors that prevent scaling in the wellbore. This test measures the 

pressure change over time as a fluid (e.g., UOG extraction wastewater) flows through a tube apparatus. An increase 

in pressure indicates the buildup of scale within the apparatus. NACE International, The Corrosion Society, reports 

specific testing protocols in NACE 31105, Dynamic Scale Inhibitor Evaluation apparatus and Procedures in Oil and 

Gas Production.
Part B

43

psi—pounds per square inch

Source: DCN SGE00705.

Figure B-10. AOP Performance in Reducing Scaling Potential in the Eagle Ford Shale 

Formation

Design and Operation Considerations for UOG Extraction Wastewater

AOP typically requires bag filtration to reduce suspended solids prior to treatment, which 

AOP vendors may provide in an additional unit or UOG operators may provide (DCN 

SGE00264; DCN SGE00705). As residual ozone can potentially interfere with fracturing fluid 

chemicals, the treatment unit operator must carefully monitor ORP to determine the appropriate

dose of ozone. Mixing untreated wastewater with source water provides a more consistent water 

quality for providing an appropriate ozone dosage without ozone residual (DCN SGE00705).

Residuals

The most recent AOP designs for UOG extraction wastewater applications do not 

generate solid or liquid waste streams (DCN SGE00264; DCN SGE00331). Instead of removing 

the precipitated constituents, their particle size is reduced to less than 1 micron to mitigate the 

negative impacts of TSS in UOG extraction wastewater reuse (DCN SGE00705; DCN 

SGE00331).
Part B

44

Energy Use

AOP treatment units designed for UOG extraction wastewater applications require 

electricity from an on-site generator or from the electric grid, if available. Energy requirements 

to operate low-pressure pumps, ozone generators, and mixers account for approximately 18 

percent of the total operation and maintenance cost (DCN SGE00264). One vendor reported 

specific energy consumption of between 0.08 to 0.15 kWh per barrel of influent wastewater 

(DCN SGE00705). 

1.4.3 Costs

Table B-16 shows approximate costs for AOP when a treatment system is rented. The 

EPA did not identify any capital costs reported in the literature because available information 

indicates that UOG operators do not currently purchase AOP units. Even though they may not 

purchase the treatment units, UOG operators may still need to invest in storage for influent and 

treated extraction wastewater, depending on how the treatment system is used. However, when 

this technology is used on-the-fly with hydraulic fracturing, additional investment in storage is 

not necessary beyond that already required for reusing UOG extraction wastewater in hydraulic 

fracturing. One vendor estimated operational costs of under 25 cents per barrel (DCN 

SGE01249).

Table B-16. AOP Rental Costs for UOG Extraction Applications

Vendor and Technology 

Name

System 

Description Capacity (MGD) Rental Cost ($/bbl)a Reference ID

Hydrozonix, LLC Mobile system 4.8 0.50 – 0.75 114

EcoSphere OzonixTM Mobile system 4.8 0.60 – 1.30 54; 75

MGD—million gallons per day; bbl—barrel.

a—Represents rental cost and is inclusive of O&M. 

1.4.4 Summary of Vendors for UOG Extraction Wastewater

Vendors that offer AOP to UOG operators treat UOG extraction wastewater on a contract 

basis, mostly long-term. The approximate number of wells completed using AOP in several 

formations are noted below26 (DCN SGE00298.A23; DCN SGE00305.A07; DCN SGE00625; 

DCN SGE00616; DCN SGE00705; DCN SGE00331; DCN SGE00706):

 Woodford (shale oil and gas): 200 wells

 Eagle Ford (shale oil and gas): 7 wells

 Fayetteville (shale gas): 120 wells

 Marcellus (shale gas): 9 wells

 Permian (shale oil and gas and tight oil and gas): 430 wells

 

26 This only includes deployments reported by Ecosphere Energy Services, Inc and Hydrozonix, LLC. 
Part B

45

Table B-17 shows vendors that offer treatment systems designed specifically for UOG 

extraction wastewater. Because this technology is often used on-the-fly with hydraulic 

fracturing, capacity is also presented in barrels per minute. Treatment rates as high as 120 barrels 

per minute are possible, but with reduced treatment effectiveness. One vendor reported a typical 

flow rate of 80 barrels per minute to keep up with most fracturing jobs (DCN SGE00705).

Table B-17. AOP Technology Vendors for UOG Extraction Wastewater

Vendor

Technology 

Name

Surface 

Footprint (ft2)

a Capacity (bpd) Capacity (bpm)b

Reference 

ID

Hydrozonix, LLC OzonixTM 1 unit fits on a 53 

foot trailer 120,000 80 114

Ecosphere Technologies, 

Inc. OzonixTM 1 unit fits on a 53-foot trailer 120,000 80 54; 75

Terra Agua Resources, 

LLC

Mitton 

Cavitation 

Reactor

NR 170 – 25,000 0.12-17 169; 171

CoilChem, LLC CoilChem 640 20,000 NR 172

NR—Not reported; ft2—square feet; bpd—barrels per day; bpm—barrels per minute.

a—Only includes the primary treatment unit. One or two additional small trailers may be required for generators and 

miscellaneous equipment. Because this technology is typically used on-the-fly with hydraulic fracturing, there is no 

additional equipment required such as untreated and treated wastewater storage. The UOG operator must already 

have sufficient storage onsite for the fracturing job regardless of whether treatment is conducted on-the-fly or not.

b—For comparison, a typical fracturing job will inject fracturing fluid at approximately 60 to 120 barrels per 

minute.

1.5 Disinfection

Disinfection is a non-TDS removal treatment technology that destroys harmful bacteria 

and is used to treat freshwater, flowback, and produced water before they are used to make up 

fracturing fluids. Bacteria of concern in oil and gas extraction operations include bacteria that 

thrive in the low oxygen, anaerobic environments of the formation, chiefly sulfate reducing 

bacteria (SRB) and certain types of acid-forming bacteria (AFB). Also of concern are bacteria 

that live in higher oxygen, aerobic environments on the surface and in the wellbore, including 

slime-forming bacteria (SFB) and other types of AFB. Growth of SRB leads to generation of 

toxic hydrogen sulfide gas, which is a health and safety concern and may contribute to corrosion 

and formation damage. AFB and SFB may also impair oil and gas production (DCN SGE01118). 

Aerobic bacteria can degrade some fracturing fluid components (DCN SGE01119). 

Biocides, chemicals intended to kill microbes, are a type of disinfectant added to 

fracturing fluid to inhibit bacterial growth and reduce the generation of hydrogen sulfide and to 

preserve the gelling agent integrity (DCN SGE01188). Commonly used biocides include 

quaternary ammonium compounds, aldehydes (e.g., glutaraldehyde), bronopol, and others. 

Tischler et al. (DCN SGE01118) note that limitations to using biocides in fracturing fluid include 

environmental toxicity, limited effectiveness in the pH and temperatures found in UOG wells, 

and high cost. Also, bacteria may become resistant to long half-life biocides, a particular concern 

when flowback is reused (DCN SGE01118).
Part B

46

Because of limitations to using biocide in fracturing fluid, operators use disinfection 

processes to reduce the concentrations of aerobic and anaerobic bacteria in make-up water. 

Disinfection reduces the potential for scaling, hydrogen sulfide souring, corrosion, plugging, and 

emulsion problems (DCN SGE01034; DCN SGE01035). In some cases, microbial and scale 

control is all that is necessary for treatment prior to reuse (DCN SGE00616). However, the level 

of treatment required for wastewater reuse varies depending on UOG formation, type of 

fracturing fluid design (e.g., gel, slickwater), and UOG operator preference (DCN SGE01188).

Disinfection is accomplished using physical agents, chemical agents, or combinations of 

the two. The chief physical agent used to disinfect UOG wastewater is UV light, which at the 

appropriate wavelength and intensity will kill bacteria. Chemical agents used in treating UOG 

wastewater are chiefly chlorine-containing chemicals such as calcium- and sodium hypochlorite 

and chlorine dioxide. Ozone is another chemical disinfectant. Ozone disinfection is a part of 

AOP where ozone is generated to kill bacteria and hydroxyl radicals are generated to destabilize 

and precipitate targeted constituents. See Part B.1.4 for more information on AOP. Disinfection 

with ozone and chlorine dioxide is known to produce regulated and unregulated byproducts 

associated with health concerns (DCN SGE01209). Additional processing may be needed prior 

to discharge or reuse as drinking water to remove these byproducts according to the EPA 

Microbial and Disinfection Byproducts rules (DCN SGE01126).

Additional treatment processes may be needed for effective disinfection. Aeration with 

sedimentation reduces the wastewater organic load, thus reducing the bacterial food supply, 

which drastically reduces bacterial population and makes effective disinfection easier. Also, 

aeration facilitates oxidation of reduced compounds which decreases chlorine demand, resulting 

in lower costs of chlorination disinfection (DCN SGE01118). The effectiveness of UV light for 

disinfection is dependent on how well the UV light penetrates the water to be treated. Because 

turbidity and TSS can impair UV effectiveness (DCN SGE01119), electro-coagulation (EC) 

pretreatment that removes TSS can improve UV disinfection performance (DCN SGE01120).

This section describes the disinfection process, treatment capabilities and limitations, 

treatment costs, and vendors that EPA is currently aware of that market the technology for UOG 

extraction wastewater treatment. Because UV disinfection and chemical disinfection differ in a 

number of ways, they will be discussed separately throughout the remainder of this section. 

How Disinfection Works

This subsection describes disinfection operating principles and how the process has been 

used to treat UOG extraction wastewater.

Principles

Disinfection inactivates bacteria in wastewater. UV light absorbed by a microbe damages

the DNA and/or RNA and renders the microbe non-viable (DCN SGE01034). The damaged 

microbe can no longer reproduce (DCN SGE01041). The optimal wavelength of UV light to 

damage a microbe is approximately 254 nm (DCN SGE01033).

Hypochlorites (calcium hypochlorite (Ca(OCl)2) or sodium hypochlorite (NaOCl)) 

dissociate to hypochlorous acid in water. This acid may kill bacteria through metabolic 
Part B

47

dysfunction or through DNA replication inhibition (DCN SGE01118). Chlorine dioxide (ClO2) is 

a strong oxidizer, highly reactive with certain amino acids, resulting in the destruction of cellular 

components (DCN SGE01118). In general, the mechanism of inactivation depends on the 

chemical disinfectant used. Non-oxidizing chemicals disrupt metabolic processes and are 

effective when microbes are active whereas oxidizing chemicals kill microbes by disrupting the 

flow of nutrients across the cell and are effective whether the microbe is active or dormant (DCN 

SGE01037). 

Disinfection effectiveness depends on the intensity of the UV light or the concentration 

of the disinfectant chemical, the time of exposure, and interfering substances (e.g., turbidity, 

TSS, organic material) in the wastewater.

Process Description

Operators may use disinfection to treat UOG extraction wastewater at centralized 

treatment facilities (DCN SGE01118). Operators also treat water as it is placed into storage tanks 

at the fracturing location. Because bacteria may regrow while the water is stored, operators 

increasingly treat water on-the-fly as it flows from the storage tanks to the fracturing blender 

(DCN SGE01119). On-the-fly treatment is described in Part B.1.4.1 (Figure B-8) (DCN 

SGE01058).

On-the-fly treatment requires mobile disinfection units capable of treating wastewater at 

relatively high rates. For example, one vendor described a mobile UV treatment unit that can 

disinfect wastewater at a rate of 50 to 75 bbl/min (DCN SGE01120). In on-the-fly treatment, 

other source water (e.g., fresh water, ground water) and the untreated wastewaters may be mixed 

together prior to treatment by disinfection to provide better consistency in the base fluid for 

hydraulic fracturing (DCN SGE00705). 

Capabilities and Limitations

This subsection describes the targeted constituents and effectiveness, design and 

operation considerations, residuals, and energy use of disinfection. 

Targeted Constituents and Treatment Effectiveness

Disinfection controls bacteria of concern in oil and gas extraction operations including 

SRB, AFB, and SFB (DCN SGE01118).

The efficacy of UV disinfection is dependent on the wastewater flow rate, UV intensity, 

and ability of the wastewater to allow light to pass through (the transmittance level) (DCN 

SGE01033). The transmittance level is impacted by TDS, the microbial concentration, suspended 

solids, humic acids, and minerals. Pretreatment may be needed to remove these constituents 

(DCN SGE01033). Vendors have demonstrated UV treatment effective at inactivating 96 –

100% of SRB present in UOG extraction wastewater of varying quality (DCN SGE00638.A11; 

DCN SGE01042; DCN SGE01057). 

The efficacy of hypochlorite disinfection depends on dose, contact time, and the 

wastewater concentration of chlorine-consuming materials such as ammonia, organic debris, and 
Part B

48

soluble iron (chlorine demand). Hypochlorite is extremely effective in killing bacteria once 

chlorine demand has been satisfied (DCN SGE01118). ClO2 is also a potent disinfectant, and is 

less reactive with ammonia and organic material. Because it is unstable, ClO2 must be generated 

at the point of use. One vendor demonstrated ClO2 treatment effective at inactivating 100% of 

SRB present in UOG extraction wastewater (DCN SGE01059). 

Design and Operation Considerations for UOG Extraction Wastewater

An advantage of UV disinfection is that it does not require the addition of chemicals. 

However, while biocides leave a disinfection residual that continues to kill microbes after 

treatment, UV disinfection only kills microbes during treatment (DCN SGE01033). In order to 

prevent re-growth of bacteria after UV disinfection, chemical biocides may be added. However,

because UV disinfection is commonly performed on-the-fly with hydraulic fracturing such that 

treated wastewater is immediately used in fracturing, chemical biocide addition may not be 

needed (DCN SGE01058).

Advantages of hypochlorite disinfection are that it is relatively inexpensive, extremely 

effective in killing bacteria once chlorine demand is satisfied, and it leaves a chlorine residual 

that helps to minimize recontamination (DCN SGE01118). Advantages of ClO2 disinfection are 

that it is a potent disinfectant and oxidizer and may facilitate other wastewater treatment 

processes such as emulsion breaking, sedimentation, and oil/water separation (DCN SGE01118). 

Also, unlike hypochlorite, ClO2 doesn’t react with ammonia and most organics and it is less 

corrosive (DCN SGE01121).

Residuals

Disinfection is not a separation process, that is, it is not designed to remove microbes 

from wastewater. Instead, light or chemicals are added to the wastewater to inactivate bacteria. 

For this reason, disinfection generates a minimum amount of treatment residuals. UV 

disinfection can result in the formation of salt (DCN SGE01058). In some cases, chlorine dioxide 

reacts with iron forming a precipitate that can be removed by processes such as flocculation and 

sedimentation (DCN SGE01046.A02). However, disinfection vendors for UOG applications 

appear to design their treatment units to operate in a way that does not result in a residual waste 

generation.

Energy Use

Both UV and chlorine dioxide disinfection systems designed for UOG extraction 

wastewater applications require electricity from an on-site generator or from the electric grid, if 

available. For UV disinfection, Halliburton’s CleanStream®system requires a generator prime 

power rating of 160 kW (DCN SGE01058).

Costs

The EPA did not identify any costs reported in the literature for disinfection treatment 

specific to UOG applications. 
Part B

49

Summary of Vendors for UOG Extraction Wastewater

Vendors that offer disinfection to UOG operators treat UOG extraction wastewater 

mostly on a contract basis. 

Table B-18 presents information on disinfection units from vendors that the EPA is 

currently aware of that are producing and selling units specifically for treating UOG extraction 

wastewater. All of these systems can be trailer-mounted or installed permanently. Because these 

technologies can be used on-the-fly with fracturing, capacity is also presented in barrels per 

minute. 

Table B-18. Disinfection Technology Vendors for UOG Extraction Wastewater

Vendor

Technology 

Name

Type of 

Disinfection

Surface 

Footprint (ft2)

a

Capacity 

(bpd)

Capacity 

(bpm)

b

Reference 

ID

Halliburton CleanStream® UV 380 170,000 120 142

Atg UV 

Technology NA UV NA 180,000 130 140

Bosque Systems 

LLC DIONIXTM ClO2 30-foot trailer 720,000 500 129

PureLine CG and Pure 3 

Seriesc ClO2 700c 7,500 5.2 135

Sabre Energy 

Services

DiKlor® and 

CHEMGEN ClO2 NA 160,000 110 143

Baker Hughes H2prO HD ClO2 NA 8,500 5.9 82

NA – Not available; ft2—square feet; bpd—barrels per day; bpm – barrels per minute; UV—ultraviolet; ClO2—

chlorine dioxide.

a—Only includes the primary treatment unit, not storage for wastewater, chemicals, or sludge (solid waste).

b—For comparison, a typical fracturing job will inject fracturing fluid at approximately 60 to 120 barrels per 

minute.

c—This footprint is for the entire coagulation, flocculation, sedimentation system. The CG and Pure 3 Series 

generators are much smaller (footprint of approximately 10 ft2).

2 TDS REMOVAL TREATMENT TECHNOLOGIES

TDS removal technologies are typically used to treat UOG extraction wastewater at CWT 

facilities. The treated wastewater is typically reused in fracturing, reused in other oil and gas 

extraction activities, or discharged from CWT facilities indirectly to POTWs or directly to 

surface waters. UOG industry use of TDS removal technologies has increased since UOG 

extraction began ramping up in the late 2000’s (DCN SGE01178). The EPA identified three TDS 

removal technologies currently used by UOG operators and CWT facilities:

 Evaporation followed by condensation (evaporation/condensation)

 Crystallization

 Reverse osmosis (RO)
Part B

50

When evaluating TDS removal treatment technologies, facilities consider not only costs 

and constituent removals, but also the “treated wastewater recovery percentage”. The treated 

wastewater recovery percentage is defined as the treated wastewater volume divided by the total 

influent wastewater volume (see Equation 7). The volume that is not recovered as treated 

wastewater is vented to the atmosphere or converted to concentrated brine and/or solid waste that 

must be managed at additional cost. Each TDS removal technology has a range of influent TDS 

concentrations at which the technology will perform optimally. At the maximum influent TDS 

concentration for each technology, treated wastewater recovery is lowest. As a result, as treated 

wastewater recovery percentage decreases, within the applicable range, the overall performance 

of the technology also decreases. 

Equation 7

Treated Wastewater Recovery =

Treated Wastewater Volume

Influent Wastewater Volume

Figure B-11 plots general ranges of costs associated with the three TDS removal 

technologies versus influent TDS concentrations. For comparison, this figure also shows the 

general range of TDS concentrations found in flowback and long-term produced water. 27

Though treatment costs generally increase as TDS increases, Figure B-11 represents each 

technology in the shape of a rectangle to illustrate that costs vary with other factors as well (e.g., 

residual waste disposal cost, availability of energy).

 

27 The range of TDS concentrations found in flowback and long-term produced water are from the EPA’s Technical 

Development Document for Effluent Limitations Guidelines and Standards for Oil and Gas Extraction (DCN 

SGE01188). The reported range represents the 25th to 75th percentiles of TDS concentrations for flowback and longterm produced water. 
Part B

51

RO—reverse osmosis

Figure B-11. Cost of TDS Removal Treatment Technologies versus Influent TDS

2.1 Evaporation/Condensation

Evaporation/condensation is the most commonly used TDS removal technology, 

converting high TDS wastewater into distilled water (low TDS) and concentrated brine (high 

TDS). Evaporation/condensation may be used when very low TDS treated water is desired (e.g., 

to meet requirements at CWT facilities discharging to surface waters or POTWs) (DCN 

SGE00167) or to reduce the volume of wastewater (brine) for transport and/or disposal (e.g., in 

the Marcellus where disposal costs are high because of a lack of disposal wells) (DCN 

SGE00300; DCN SGE00264; DCN SGE00625; DCN SGE00478). 

This section describes the evaporation/condensation process, treatment capabilities and 

limitations, treatment cost, and vendors that the EPA is currently aware of that market the 

technology for UOG extraction wastewater treatment.

2.1.1 How Evaporation/Condensation Works

This subsection describes evaporation/condensation operating principles and how the 

process has been used to treat UOG extraction wastewater.
Part B

52

Principle

The evaporation/condensation treatment process removes water from wastewater through 

evaporation (converting liquid to vapor), reducing the wastewater volume and concentrating 

wastewater constituents such as TDS in the resulting brine.

28 The evaporated water vapor is 

either vented to the atmosphere or condensed as clean distillate/condensate. As evaporation 

continues, the constituents in the brine become increasingly concentrated. When constituent

concentrations reach their solubility limits, dissolved material will precipitate out of the 

concentrated stream (which is not desired for normal operation).

Evaporation/condensation technologies differ in the method used for evaporation. Factors 

used to increase the rate of evaporation for wastewater treatment are listed below: 

 Pressure – As atmospheric pressure decreases, the rate of evaporation increases.

This can be accomplished by technologies operated under vacuum.

 Temperature – As temperature increases, the rate of evaporation increases. This 

can be accomplished using technologies that apply heat to wastewater.

 Surface area – As the surface area of the water that is in contact with the air 

increases, the rate of evaporation increases. This can be accomplished by spraying 

the wastewater into droplets.

 Air movement – As the flow rate of air at the liquid surface increases, the rate of 

evaporation increases. This can be accomplished using fans to push or pull air 

through the unit.

Figure B-12 is a flow diagram of evaporation/condensation used for wastewater 

treatment. The diagram shows vapor and atmospheric pressures, using arrows to show that 

pressures are forces with directions. Vapor pressure is the force exerted by the water on the 

atmosphere and the atmospheric pressure is the force exerted by the atmosphere on the water. In 

the process depicted in the figure, adding heat increases the vapor pressure, thus causing

evaporation. There are other ways to cause vapor pressure to be greater than atmospheric 

pressure, which are explained later in this subsection. The following steps are shown in the flow 

diagram.

1. Heat is added to the influent wastewater to increase the vapor pressure (Pvap) at 

the surface.

2. The liquid water vapor pressure (Pvap) becomes greater than atmospheric pressure 

(Patm), allowing the liquid water to evaporate into the vapor state (illustrated by 

the fact that the Pvap arrow is larger than the Patm arrow). 

3. The vapor comes into contact with a cool surface. As a result, the liquid water 

vapor pressure (Pvap) decreases and becomes lower than atmospheric pressure 

 

28 Some constituents, such as solvents and light hydrocarbons, may evaporate along with the water vapor. These may 

pass through the treatment or be recovered using a hydrocarbon recovery unit. Part B.2.1.2 provides more information 

on this limitation of evaporation/condensation.
Part B

53

(Patm), allowing the water vapor to condense into the liquid state (illustrated by the 

fact that the Patm arrow is larger than the Pvap arrow). 

4. The condensate, or treated wastewater, is collected in a collection pan as the 

liquid falls from the pipe.

Constituents (e.g., A+ ions) are unable to evaporate with the water and remain in the 

wastewater, creating a concentrated brine.

Figure B-12. Diagram of Evaporation/Condensation Principle

Process Description

Four types of evaporation/condensation processes are commonly used for wastewater 

treatment:

 Vapor compression (VC)

 Multiple stage flash (MSF)

 Multiple effect (ME)

 Rapid spray (RS)

Units deployed to treat UOG extraction wastewater operate on vapor compression, multiple stage 

flash, and multiple effect principles, with vapor compression being the most popular. The 

following subsections focus on these three evaporation processes. 

Vapor Compression (VC) Evaporation/Condensation

There are two types of vapor compression processes: mechanical vapor compression 

(MVC) and thermal vapor compression (TVC). The difference between these two types is how 
Part B

54

the water vapor pressure is increased. Mechanical vapor compression primarily uses a 

mechanical compressor29 to add energy into the system, while TVC uses a heat source to add 

energy, such as a gas burner. Although both types of vapor compression technologies are used in 

UOG extraction wastewater applications, mechanical vapor compression is more common 

because: 

 Mechanical compressors start up more quickly and are less expensive to run on 

electricity than thermal vapor compression (DCN SGE00300).

 Thermal vapor compression requires a closed loop system consisting of a working 

fluid (e.g., steam, oil) and boiler. This setup increases the overall size of the 

system.

Figure B-13 is a flow diagram, described by a CWT facility, of a MVC evaporator

designed specifically for UOG extraction wastewater applications. The steps below describe the 

process in Figure B-13. TVC evaporators use a similar process except that a heat exchanger with 

working fluid heated by a boiler is used to heat the water vapor, rather than a mechanical 

compressor.

1. Influent wastewater is preheated through a series of cross-flow heat exchangers 

referred to as the main, secondary, and tertiary heat exchangers. In these noncontact heat exchangers, energy is transferred from the downstream concentrated 

brine, distillate, and compressed water vapor to heat the influent wastewater. This 

transfer of energy greatly reduces the overall energy requirements of the system.

2. The wastewater enters the main vessel where water is evaporated from the 

wastewater. Constituents remain in the wastewater, resulting in concentrated 

brine. During startup, when concentrated brine, distillate, and compressed water 

vapor are not yet available to preheat the influent wastewater, the influent 

wastewater is instead heated in the main vessel by steam from a small boiler 

(usually fueled by natural gas). After start up, the boiler is shut off and operates 

only periodically to maintain the surface of the preheated wastewater at 

approximately 212o F. 

3. Water vapor from the main vessel is vented to a mechanical compressor. The 

compressor, which is powered by electricity, increases the vapor’s temperature 

and pressure. The compressed water vapor expands across the main heat 

exchanger, where its latent heat of condensation30 is transferred to influent 

wastewater to preheat it. At this point, the water vapor becomes condensed 

wastewater (i.e., distillate).

 

29 Mechanical vapor compression also typically includes a heat source (e.g., a gas-fired boiler) but it only operates 

during startup operations and then periodically during steady state operation. The boiler only runs approximately two 

percent of operational time, according to one CWT facility operator (DCN SGE00300). Because mechanical vapor 

compression does not rely on heat, it does not require steam or a boiler, making MVC more suitable for mobile 

treatment units than TVC.

30 Latent heat of condensation is the heat released by water vapor when it condenses from a gas to a liquid.
Part B

55

4. Concentrated brine from the main vessel enters the tertiary heat exchanger where 

its thermal energy is transferred to the influent wastewater to preheat it.

5. The distillate flows through the secondary heat exchanger where it provides 

sensible heat31 to preheat influent wastewater.

Source: DCN SGE00300.

Figure B-13. Evaporation/Condensation Mechanical Vapor Compression Process Flow 

Diagram

Multiple Stage Flash (MSF) and Multiple Effect (ME) Evaporation/Condensation

In MSF and ME evaporation/condensation, the main evaporation vessel operates at 

reduced pressure and higher temperature to facilitate evaporation. When the pressure is 

 

31 Sensible heat is the heat released or obtained by water during a change in temperature. 
Part B

56

decreased, preheated wastewater can be evaporated at temperatures lower than 212o F (DCN 

SGE00264). The primary difference between MSF and ME evaporation/condensation is that the 

reduced pressure and high temperatures are carried out in separate vessels in ME evaporation,

but in only one main vessel in MSF evaporation. Although decreasing the pressure requires

energy input, less energy is then required to increase the temperature of the influent wastewater. 

Figure B-14 is a flow diagram of a MSF evaporator, which includes the following steps: 

1. The cool influent wastewater is piped through the main vessel, which acts as a 

heat exchanger. Hot water vapor within the vessel preheats the influent 

wastewater as it passes through.

2. The preheated influent wastewater enters a second heat exchanger, where it is 

further heated by a hot working fluid (which is heated by a boiler or burner).

3. The heated wastewater then enters the first column in the main vessel. Because 

the pressure in this column is close to atmospheric, wastewater must be at high 

temperature to evaporate (Pvap>Patm).

4. Wastewater that does not evaporate in the first column enters a second column 

operated at lower atmospheric pressure than the first (achieved by a vacuum 

system). The vapor pressure again exceeds the reduced atmospheric pressure, 

causing further evaporation (Pvap>Patm). 

5. As water vapor rises in each column, it contacts pipes containing cool influent 

wastewater (step 1). Water vapor temperature decreases until the atmospheric 

pressure becomes greater than the vapor pressure, causing the vapor to condense 

(Pvap<Patm).

6. The condensate, or treated wastewater, is collected as the liquid falls from the 

pipe as it leaves the vessel.

7. Constituents are unable to evaporate with the wastewater, creating concentrated 

brine.
Part B

57

Figure B-14. Flow Diagram of a Multiple Stage Flash (MSF) Evaporator

Rapid Spray (RS) Evaporation/Condensation

In RS evaporation, wastewater is evaporated by spraying it in small droplets into a heated 

air stream. The evaporation generates water vapor and concentrated brine as with other 

evaporation technologies.

Figure B-15 and Figure B-16 are process flow diagrams of Heartland Technology 

Partners’ low momentum – high turbulence (LM-HT®) Concentrator (DCN SGE01047). Note 

that this technology uses one unit to accomplish both wastewater evaporation and crystallization 

(see discussion of Crystallization in Part B.2.2 below). At the Seneca facility in Covington, PA, 

waste exhaust from the compressor station’s reciprocating engines is collected into an exhaust 

manifold and pulled by vacuum (provided by an induced draft fan) downinto the evaporator. 

UOG extraction wastewater feed from storage tanks is injected into the evaporator where it 

comes into direct contact with the waste exhaust. In the evaporator, the wastewater feed is 

subjected to a tortuous path flow (Figure B-18), which breaks the liquid into small droplets, 

providing high interfacial surface area for heat transfer and evaporation.

Boiler Concentrated 

brine

Treated 

wastewater

Influent 

wastewater Condensation (Pvap< Patm)

Heat 

exchanger

Cool circulating 

fluid

Working 

fluid pump

6 3

2

1

Evaporation (Pvap > Patm) 

4

5

Pre-heated influent 

wastewater

Heated influent 

wastewater

7

Hot

circulating fluid

Vacuum system 
Part B

58

Source: DCN SGE01047.

Figure B-15. Heartland LM-® Concentrator Flow Diagram

Source: DCN SGE01047.

Figure B-16. Schematic of Heartland LM-® Evaporation Zone and Entrainment Separator
Part B

59

From the evaporator, the exhaust/brine mixture enters an entrainment separator where the 

concentrated brine is separated from the air and drains into a sump located under the separator. A 

sump pump transfers brine from the sump to a thickener tank, where salt solids/brine settle to the 

bottom and are removed, while the supernatant is recycled back to the evaporator. The 

supernatant recycle rate is adjusted to achieve the target brine salt concentration (DCN 

SGE01047).

Water vapor (steam) is typically released directly to the atmosphere. However, as an 

option, the steam can be routed to a shell and tube heat exchanger to condense it for reuse. 

Cooling water for the heat exchanger is provided by wastewater feed (DCN SGE01047).

2.1.2 Capabilities and Limitations

This subsection describes the targeted constituents and effectiveness, design and 

operation considerations, residuals, and energy use of evaporation/condensation. 

Targeted Constituents and Treatment Effectiveness

Evaporation/condensation technologies can remove a wide range of wastewater 

constituents, including suspended solids, dissolved organic matter, dissolved inorganic matter,

biological contaminants (e.g., bacteria and viruses), and radioactive elements (DCN SGE00264). 

Typical influent TDS concentrations for cost effective operation can range from 20,000 mg/L to 

125,000 mg/L, and effluent concentrations can be less than 10 mg/L (DCN SGE00300; DCN 

SGE00625; DCN SGE00144; DCN SGE00264; DCN SGE00110).

Influent TDS concentrations, in theory, can be as high as the supersaturation 

concentration for TDS (approximately 250,000 to 300,000 mg/L),32 but at the expense of higher 

energy input and lower distilled water recovery. One CWT facility that uses 

evaporation/condensation suggested the economics become unfavorable when TDS reaches 

125,000 mg/L (DCN SGE00300). Case studies in the literature demonstrate that 

evaporation/condensation units can operate with TDS concentrations as high as 195,000 mg/L

(DCN SGE00110). Heartland’s LM-HT® Concentrator is able to treat water with TDS up to 

235,000 mg/L (DCN SGE01047).

Constituents with evaporation temperatures lower than water will evaporate and exit the 

system in the water vapor stream. Examples include ammonia (DCN SGE00625) and light 

hydrocarbons (DCN SGE00244). Light hydrocarbons can be separated from the evaporated 

wastewater using a dedicated recovery unit prior to condensation. The hydrocarbons recovered 

from this add-on unit can be sold (DCN SGE00244). 

Table B-19 shows performance data for evaporation/condensation used in UOG 

extraction wastewater applications. The table includes untreated influent constituent

concentrations, effluent constituent concentrations (distillate), and the resulting constituent

 

32 This is the approximate supersaturation concentration for sodium chloride, the primary TDS found in UOG 

extraction wastewater. Several vendors indicated that supersaturation occurs at approximately 300,000 mg/L TDS 

(DCN SGE00227; DCN SGE00228; DCN SGE00230).
Part B

60

removal efficiencies for flowback and produced waters. Table B-19 demonstrates that 

evaporation/condensation is effective at treating wastewater with a wide range of TDS. 

Table B-19. Performance Data of Evaporation/Condensation in UOG Extraction 

Wastewater Application

Constituent

Flowback Long-term Produced Water

Reference 

ID

Influent 

(mg/L)

Effluent

(Distillate) 

(mg/L)

Calculated 

Removal 

Efficiency 

(%)a

Influent 

(mg/L)

Effluent

(Distillate) 

(mg/L)

Calculated 

Removal 

Efficiency 

(%)a

TDS 41,000 – 47,000 76 – 100 >99 200,000 88 >99 8; 60

Chloride 20,000 35 >99 110,000 45 >99 8

Sodium 10,000 – 12,000 3.6 – 19 >99 21,000 25 >99 8; 60

Metals

Aluminum 2 0.1 95 2 0.1 95 8

Barium 6 – 160 0.1 >99 – – – 8; 60

Calcium 2,500 – 2,700 0.8 – 3.8 >99 15,460 5.1 >99 8; 60

Copper 0.52 0.08 85 0.8 0.02 98 8

Iron 2 – 8.3 0.02 – 0.1 >95 68 0.02 >99 8; 60

Lithium 11 0.1 99 – – – 60

Magnesium 220 – 300 0.1 – 0.4 >99 1,400 0.47 >99 8; 60

Manganese 2 0.02 99 5.2 0.02 >99 8

Phosphorous 2 0.1 95 – – – 60

Potassium 350 0.1 >99 – – – 60

Strontium 270 – 480 0.47 – 0.1 >99 2,200 0.7 >99 8; 60

Sulfate 160 – 210 2.2 – 5 >98 130 3.1 >98 8; 60

Zinc 0.4 0.16 60 0.4 ND >99c 8

Organics

Benzene 0.055 0.001 98 0.76 ND >99 8

BTEX 2.1 0.1 95 – – – 60

Toluene 0.085 0.0022 97 0.95 ND >99 8

TPH 4 4 0 – – – 60

Other

Alkalinity 200 48 76 94 9 90 8

Ammonia 84 64 24 – – – 60

Bicarbonate 200 24 88 – – – 8

Boron 6.4 – 16 0.02 – 0.4 >98 11 0.02 >99 8; 60

Fluoride 9.5 0.15 98 8.5 0.16 98 8

Hardness 4,000 11 >99 44,000 15 >99 8

Silica 49 1 >99 52 ND >99 8

Sulfates 160 – 210 2.2 – 5 98 to 99 130 3.1 98 8; 60

TSS 22 – 130 3 – 4 86 to 97 35 3 91 8; 60
Part B

61

Table B-19. Performance Data of Evaporation/Condensation in UOG Extraction 

Wastewater Application

Constituent

Flowback Long-term Produced Water

Reference 

ID

Influent 

(mg/L)

Effluent

(Distillate) 

(mg/L)

Calculated 

Removal 

Efficiency 

(%)a

Influent 

(mg/L)

Effluent

(Distillate) 

(mg/L)

Calculated 

Removal 

Efficiency 

(%)a

Radioactives (all units are pCi/L)

Gross alpha 76 ND >99 3,000 0.69 >99 8

Gross beta 240 ND >99 420 0.43 >99 8

Radium-226 33 ND >99 1,400 0.23 >99 8

Radium-228 27 ND >99 720 0.43 >99 8

Thorium-228 1.2 0.14 88 31 0.18 99 8

ND—Not detected; mg/L—milligrams per liter; TDS—total dissolved solids; BTEX—benzene, toluene, 

ethylbenzene, and xylenes; TPH—total petroleum hydrocarbons; TSS—total suspended solids.

a—The EPA calculated all removal efficiencies using paired influent and effluent concentrations reported in 

literature. Attachment 1 (DCN SGE01186.A01) presents these removal efficiency calculations. The number of data 

points that these removal efficiencies are based on are also presented in Attachment 1.

c—If effluent concentration was reported as not detected, the EPA reported greater than 99 percent removal 

efficiency for the purpose of this table.

Design and Operation Considerations for UOG Extraction Wastewater

One of the challenges with evaporation/condensation is the tendency for heat exchange 

surfaces (e.g., piping) to lose their heat transfer quality due to scaling. When these surfaces have 

diminished heat transfer capabilities, the overall heat exchanger efficiency decreases. As heat 

exchanger efficiency decreases, more energy input is required, making the overall process less 

energy efficient. Scaling occurs when high-temperature environments cause inorganic salts to 

precipitate onto pipes. Constituents that cause scaling include salts of multivalent cations (e.g., 

calcium, barium, magnesium).

Prior to evaporation/condensation, UOG extraction wastewater is typically pretreated 

using chemical precipitation and filtration to remove scale-causing constituents. Rigorous 

pretreatment requirements can be avoided if the evaporation/condensation unit is operated at 

higher than atmospheric pressures. Increasing the pressure allows inorganic salts to remain 

dissolved in the water at higher temperatures, reducing the tendency for scaling (DCN 

SGE00227; DCN SGE00095). One exception is the Heartland LM-HT® technology that is 

designed to operate at supersaturated concentrations without the need for pretreatment, or for 

operating under pressure (DCN SGE01047).

As previously explained, higher influent TDS concentrations decrease overall 

performance of evaporation/condensation because the water solubility limit is reached more 

quickly within the evaporator (DCN SGE00238; DCN SGE00300). If the influent TDS is near 

the TDS solubility limit (approximately 250,000 to 300,000 mg/L), crystals can grow in the 

concentrated brine, causing significant fouling and plugging problems. For reference, some UOG 

extraction wastewater, particularly long-term produced water, can have TDS concentrations as 

high as nearly 400,000 mg/L (DCN SGE01188). As a result, treatment unit operators must 
Part B

62

monitor influent TDS to ensure the solubility limit of the least soluble salt is not reached. CWT 

facilities using evaporation/condensation often test every influent truckload for TDS (DCN 

SGE00299; DCN SGE00300). Wastewater with excessive TDS may be rejected or subject to a 

surcharge.

Residuals 

Evaporation/condensation processes produce a concentrated brine stream. If evaporated 

water is vented to the atmosphere, organic compounds removed from the wastewater may also be 

released to the atmosphere. Where chemical precipitation is used for pretreatment in UOG 

applications, a solid waste stream will also be generated (see Part B.1.1 for solid waste 

generation from chemical precipitation). Table B-20 shows sample constituent concentrations in 

the concentrated brine generated by one evaporation/condensation unit. The concentrated brine 

stream contains all of the salt products contained in the influent water, but at higher 

concentrations than the influent. This includes any present radioactive elements in the influent 

wastewater. However, literature and industry do not discuss issues related to elevated levels of 

radioactive elements in the concentrated brine. According to literature and communication with 

industry, brine can be managed in several ways, including (DCN SGE00300; DCN SGE00299; 

DCN SGE00095):

 Injected into a disposal well

 Used as kill fluid33

 Used as additive for drilling fluid

 Further concentrated via crystallization 

Treated wastewater recovery is highly dependent on the influent TDS concentration. For 

economical operation in UOG operations, evaporation/condensation typically has a water 

recovery percentage between 60 to 95 percent (DCN SGE00264; DCN SGE00144; DCN 

SGE00300). The recovery is inversely proportional to the influent TDS concentration, as 

illustrated in Figure B-17. Figure B-17 is based on Equation 8, which the EPA derived from 

actual operating data of an MVC evaporator/condensation system treating Barnett shale 

wastewater (DCN SGE00300; DCN SGE00415).34 At higher influent TDS concentrations, water 

recovery decreases, resulting in a larger volume of concentrated brine and higher disposal costs 

(DCN SGE00299; DCN SGE00300; DCN SGE0095; DCN SGE00109). The relationship 

between influent TDS and recovery is specific to each type of evaporator (e.g., MVC, ME).

Equation 8

Percent Recovery = -0.0005 * (Influent TDS Concentration in mg/L) + 100

 

33 Kill fluid is the high density fluid injected into a well to eliminate the fluid flow from the reservoir through the 

wellbore.

34 Underlying data are based on data from SGE00415. Equation was confirmed by a CWT facility that operates the 

same treatment system in Pennsylvania (DCN SGE00300).
Part B

63

Figure B-17. Typical Distillate Recovery versus Influent TDS Concentration for MVC 

Technology35

Table B-20. Concentrated Brine Composition Evaporation/Condensation

Constituent

Marcellus Shale Long-Term Produced 

Watera Marcellus Shale Flowback Waterb

Influent to 

Unit (mg/L)

Treated 

Wastewater 

(Distillate) 

(mg/L)

Concentrated 

Brine (mg/L)

Influent to 

Unit

(mg/L)

Treated 

Wastewater 

(Distillate) 

(mg/L)

Concentrated 

Brine 

(mg/L)

TDS 200,000 88 350,000 41,000 76 110,000

Chloride 110,000 45 210,000 20,000 35 65,000

Sodium 21,000 25 86,000 10,000 19 32,000

Metals

Barium 160 <0.10 150 53 0.1 45

Arsenic <0.5 <0.5 <1.0 <0.5 <0.5 <5.0

Iron 68 <0.02 2.4 8.3 0.02 17

Zinc <0.4 <0.02 <0.4 <0.4 0.16 <0.4

 

35 Distillate recovery data shown in Figure B-17 may not agree with data presented in Table B-20 because the two 

tables represent two different evaporation/condensation technologies. Figure B-17 represents MVC and Table B-20

represents ME.
Part B

64

Table B-20. Concentrated Brine Composition Evaporation/Condensation

Constituent

Marcellus Shale Long-Term Produced 

Watera Marcellus Shale Flowback Waterb

Influent to 

Unit (mg/L)

Treated 

Wastewater 

(Distillate) 

(mg/L)

Concentrated 

Brine (mg/L)

Influent to 

Unit

(mg/L)

Treated 

Wastewater 

(Distillate) 

(mg/L)

Concentrated 

Brine 

(mg/L)

Aluminum <2.0 <0.10 <2.0 <2.0 <0.1 <2

Copper 0.8 <0.02 0.8 0.52 0.08 0.8

Calcium 15,000 5.1 30,000 2,500 3.8 6,800

Strontium 2,200 0.70 5,000 270 0.47 790

Sulfates 130 3.1 550 160 2.2 280

Magnesium 1,400 0.47 3,100 220 0.36 660

Potassium 470 0.35 1,300 95 0.19 360

Manganese 5.2 <0.02 8.2 2 0.02 2.6

Organics

Benzene 0.76 ND 1.2 0.055 ND ND

Toluene 0.95 ND 0.0030 0.085 0.0022 0.0013

Ethyl benzene 27 ND ND ND ND ND

Other

Bicarbonate NR NR NR 200 24 150

BOD >78 >75 63 >74 >75 >380

Total hardness 44,000 15 87,000 4,000 11 20,000

Fluoride 8.5 0.16 11 9.5 0.15 12

Boron 11 <0.02 17 6.4 <0.02 17

TSS 35–400 <3 180 22 <3 32

Alkalinity 94 30 32 200 48 150

Radioactives

Gross beta (pCi/L) 420 0.43 530 240 ND 87

Gross alpha (pCi/L) 3,000 0.69 1,900 76 ND 16

Thorium 228 (pCi/L) 31 0.18 23 1.2 0.14 5.3

Radium 226 (pCi/L) 1,400 0.23 1,500 33 ND 47

Radium 228 (pCi/L) 720 0.43 750 27 ND 18

ND—Not detected; mg/L—milligrams per liter; TDS—total dissolved solids; BOD—biochemical oxygen demand; TSS—

total suspended solids.

a—Source: DCN SGE00110. Treated wastewater recovery of the long-term produced water was 55 percent. 

b—Source: DCN SGE00110. Treated wastewater recovery of the flowback was 72 percent.

Energy Use

Evaporation/condensation is an energy-intensive treatment technology. TVC systems 

require a burner or boiler that uses oil or natural gas (DCN SGE00264). MVC units require 

compressors that run on electricity (DCN SGE00230; DCN SGE00227); therefore, MVC designs
Part B

65

are more popular for mobile units.36 Mobile MVC systems also include auxiliary generators

(running on diesel fuel or wellhead gas) for use when connection to the electrical grid is not 

possible (DCN SGE00230; DCN SGE00227). However, treatment unit operators desire 

electricity from the grid over the use of generators because it is less expensive (DCN 

SGE00625).

Evaporation/condensation systems can be designed to use waste or low-grade energy. 

One example is a CWT facility near Mt. Jewett, Pennsylvania that treats UOG extraction 

wastewater. This facility is adjacent to the McKean County landfill and uses landfill gas37 to 

power specifically-designed boilers that run their treatment process. The facility can evaporate 

up to 100,000 gallons per day of Marcellus shale wastewater for reuse under its general permit 

WMGR123NW005, or for discharge into a nearby surface water under its NPDES discharge 

permit PA0102288 (DCN SGE00367; DCN SGE00616). Another source for low-grade energy in 

UOG extraction wastewater applications is waste heat from compressor stations.

Table B-21 reports energy use per barrel of influent wastewater for some pilot and full 

scale projects using evaporation/condensation to treat UOG extraction wastewater. Table B-21

includes the associated influent TDS concentrations and resulting water recovery percentages. 

Because many of the units require both electricity and some type of fuel, the energy requirement 

is presented in three columns: electrical (e.g., pumps, compressors), fuel (e.g., natural gas for a 

burner), and the total energy required, if reported. 

 

36Most mechanical vapor compression systems still require a small boiler or burner to assist in startup operations 

(DCN SGE00300).

37 Landfill gas is low-grade natural gas produced from decomposition of organic materials within the landfill.
Part B

66

Table B-21. Evaporation/Condensation Energy Use in UOG Applications

Pilot or 

Full Scale 

Project Vendor 

Technology 

Name

Evaporator 

Type

Influent TDS 

Concentration 

(mg/L)

Energy Consumption (kWh, unless 

otherwise noted, per bbl of influent 

wastewater)

Water 

Recovery 

(%) Power Source

Reference 

Electrical ID

Fuel 

Energy 

(MCF) Total

Full scale

Purestream AVARA Mechanical 

vapor

20,000 – 40,000 6 N/A 6 80 Electrical 69

212 Resources Vacom Multiple 

effect ~30,000 1.3 NR 1.3 90

Electricity or 

wellhead natural gas

40; 32

Fountain Quail 

Water 

Management, 

LLC

Nomad Mechanical 

vapor

60,000 – 80,000 NR 0.07 4.6 60–90

50 kW generatora

33; 60

Pilot 

project

Altela Inc. AltelaRainTM Multiple 

effectb 25,000 – 200,000 2–2.5 5–10 NR 45–90

Electricity, natural 

gas, onsite waste heat, 

solar panels

8

GE Water & 

Process 

Technologies

NR Mechanical 

vapor

<130,000 NR NR 2.1–2.9 60–95

Electricity or natural 

gas

34; 40

Technology 

in general N/A N/A N/A 110,000 –130,000 NR NR 6.5–7.5 50 Wellhead gas generator 35

TBD—To be determined.

N/A—Not available; NR—Not reported; TDS—Total dissolved solids; mg/L—milligrams per liter; MCF—million cubic feet; kWh— kilowatt-hour; bbl— barrel.

a—Generator powered by natural gas directly from well head or electricity.

b—This vendor uses multiple effect technology in combination with membrane distillation.
Part B

67

2.1.3 Costs

Capital costs of evaporation/condensation typically include costs for the pretreatment

system, the evaporation/condensation unit, low-pressure pumps, and monitoring equipment. 

Operating costs include energy for low-pressure pumps and energy for evaporation, and labor

(DCN SGE00638.A12; DCN SGE00638.A11). Because the technology is energy-intensive, its

operating cost is relatively high compared to treatment technologies that do not remove TDS. 

However, several studies concluded that if waste heat (e.g., low-grade steam or low-grade 

natural gas) is used, the technology remains effective and cost is significantly reduced (DCN 

SGE00124; DCN SGE00264; DCN SGE00110). 

Table B-22 shows approximate capital and operating costs for evaporation/condensation 

reported in the literature for purchased and rented treatment systems. Costs include pretreatment 

systems such as chemical precipitation and/or filtration units. Table B-23 shows approximate 

costs UOG operators pay CWT facilities to treat UOG extraction wastewater using 

evaporation/condensation (including pretreatment). 

Table B-22. Evaporation/Condensation Capital and O&M Costs for UOG Extraction 

Wastewater Applications

Vendor and 

Technology 

Name

System 

Description

Influent 

TDS 

(mg/L)

Capacity 

(MGD)

Cost 

Basis

Capital 

Cost 

($ per gpd)

O&M Cost 

($ per bbl)

Rental or 

Effective 

Cost ($ per 

bbl) a

Reference 

ID

Altela

Rain Plant 25,000 –200,000 NR Rental NR 0.14 – 0.89 5.20 40; 8

f

212 

Resources Plant ~20,000 0.17 Purchase 30.00 0.30 – 0.50b NR 73; 37; 32

AquaPure 

NOMAD

Plant 45,000 –

80,000 0.32 Unknown

NR 2.60 5.00 – 6.00 60; 68; 61

Mobile 

system

45,000 –

80,000 0.11 Purchase 38.00 0.94 4.00 – 6.00 36

General Mobile 

system

110,000 

–

130,000

0.060 Purchase 

or Rental 100.00 2.40 5.40 35e

Purestream Mobile 

System

40,000 –

100,000 0.053

Purchase 22.00 to 

44.00 1.30 NR 100; 183

Rental NR NR 2.00 – 3.00 183

GE Mobile 

system

<130,000 NR NR NR NR 2.50 –

6.50d 34; 102e

NR 0.072 Purchase 34.00 NR NR 100

NR—Not reported; TDS—Total dissolved solids; mg/L—milligrams per liter; MGD—million gallons per day; 

gpd—gallons per day; bbl—barrel.

a—Represents rental cost if the cost basis was rental and is inclusive of O&M. Represents total effective cost when 

cost basis is purchase, which includes amortized capital costs and O&M costs combined if reported by the source 

unless otherwise noted.

b—Electricity costs only.

c—Cost for the entire plant and all treatment onsite.

d—Cost range was reported as a “ballpark” and does not include pretreatment that may be required.
Part B

68

e— This cost range represents a unit designed for UOG extraction wastewater treatment but has not been 

implemented.

f—Cost based on pilot project in the Marcellus region.

Table B-23. Evaporation/Condensation Costs to UOG Operators at CWT Facilities

CWT Facility Name

Treated 

Wastewater

Influent TDS 

concentration 

(mg/L) Type of Service

Cost to UOG 

Operator at 

CWT Facilities 

($ per bbl)a

Reference 

ID

Clean Streams, LLC Shale gas 100,000 Reuse 6.30 – 8.30 48

212 Resources Tight gas ~20,000 Discharge to surface 

water or reuse 3.00 – 4.00b

32; 37; 40

Eureka Resources, LLC Shale gas 100,000 Discharge to POTW or 

reuse

6.50 – 10.00 49

mg/L—milligrams per liter; bbl—barrel.

a—Data in this table are as-reported in literature or to EPA. Cost ranges do not include transportation and may vary 

based on wastewater characteristics and the type of service.

b—This cost range was reported as a “ballpark” number.

2.1.4 Summary of Vendors for UOG Extraction Wastewater

EPA identified permanent deployments of evaporation/condensation treatment systems in 

the following UOG formations:

 Marcellus (shale gas)

 Barnett (shale gas)

 Eagle Ford (shale oil)

 Fayetteville (shale gas)

 Mesaverde/Lance (tight gas)38

 Permian (shale oil and gas and tight oil and gas)

Table B-24 provides information about some evaporation/condensation units marketed

for treating UOG extraction wastewater. All of these systems can be trailer-mounted or installed 

permanently.

Table B-24. Evaporation/Condensation Technology Vendors for UOG Extraction 

Wastewater

Vendor

Technology 

Name

Surface 

Footprint (ft2)

a Capacity (bpd) Reference ID

212 Resources Vacom 2,400 2,500 – 3,000 32; 37; 73

AquaTech International Corporation MoVap 420 1,000 – 1,700 110; 74

Fountain Quail Water Management, LLC NOMAD 2,500 2,500 100; 60

 

38 This area is commonly referred to as the Pinedale field, which includes the Mesaverde and Lance tight gas 

formations.
Part B

69

Table B-24. Evaporation/Condensation Technology Vendors for UOG Extraction 

Wastewater

Vendor

Technology 

Name

Surface 

Footprint (ft2)

a Capacity (bpd) Reference ID

GE Water & Process Technologies NR NR 1,700 100; 34

Purestream AVARA Trailer mounted 1,000 – 2,500 100

AltelaRain, Inc. AltelaRainTM NR 100 – 600 106; 8

Gradiant Corporation Carrier Gas 

Extraction NR 12,000 173

NR—Not reported; ft2—square feet; bpd—barrels per day.

a—Only includes the primary treatment unit, not storage for wastewater, chemicals, or sludge (solid waste).
Part B

70

2.2 Crystallization

Crystallization is a TDS removal technology that converts high TDS wastewater into 

distilled water (low TDS) and solid salt crystals. To date, this technology has been used in full 

scale projects at CWT facilities and has also been pilot tested by UOG operators in the field. 

Industry has explored using crystallization at well pads, CWT facilities, and locations with lowgrade waste heat, such as compressor stations (DNC SGE01047). Unlike 

evaporation/condensation (which always generates a treated wastewater stream), crystallization 

can be operated such that all evaporated wastewater is vented to the atmosphere if desired. 

Similar to evaporation/condensation, this technology may be used for treating UOG extraction 

wastewater when low TDS treated water is desired (e.g., to meet requirements for discharging to 

surface waters or POTWs) (DCN SGE00177), or when costs for alternative disposal are high 

(e.g., lack of disposal wells in the Marcellus) (DCN SGE00300; DCN SGE00264; DCN 

SGE00625; DCN SGE00478; DCN SGE01047). 

This section describes the crystallization process, treatment capabilities and limitations, 

treatment cost, and vendors that the EPA is currently aware of that market the technology for 

UOG extraction wastewater treatment.

2.2.1 How Crystallization Works

This subsection describes crystallization operating principles and how the process has 

been used to treat UOG extraction wastewater.

Principle

Crystallization is very similar to evaporation/condensation in that both technologies rely 

on evaporation. They operate by changing temperature and pressure to evaporate water. 

Crystallization differs from evaporation/condensation in that so much water is evaporated that 

the brine stream becomes “supersaturated” with salts. This occurs when the constituents 

dissolved in a supersaturated solution have reached their maximum concentrations. Evaporating 

water beyond this point causes the constituents to precipitate out of the solution, forming solid 

crystals (DCN SGE00264).

Process Description

In crystallization systems designed for UOG extraction wastewater treatment, the 

evaporated water vapor is either recovered through condensation or emitted into the atmosphere. 

According to the literature, both MVC and TVC technologies are used. The EPA is also aware of 

one CWT facility that uses RS technology for both evaporation and crystallization (see Section 

2.1.1).

Figure B-18 presents a flow diagram of a MVC crystallizer that includes vapor recovery: 

1. Influent wastewater enters a pump, where it is pressurized. 

2. The influent wastewater is routed through a heat exchanger, where it is heated by 

downstream hot, pressurized water vapor from the crystallizer. 
Part B

71

3. The atmospheric pressure of the hot, pressured water suddenly drops as it enters 

the crystallizer. When this happens, the vapor pressure becomes greater than the 

atmospheric pressure on the water (Pvap>Patm), causing the wastewater to 

evaporate. 

4. As more wastewater evaporates, the remaining brine becomes supersaturated, 

causing dissolved solids to precipitate into solid crystals. The mixture leaves the 

vessel through a separator, which removes the solid crystals. After separation, the 

remaining brine is mixed with influent wastewater at step 1.

5. The water vapor from evaporation (step 3) is pulled into a compressor, which 

increases the pressure and temperature of the vapor.

6. The hot, pressurized vapor then enters the heat exchanger, where it is used to heat 

the incoming brine and influent wastewater mixture from step 4. Heat transferred 

from the water vapor to the wastewater mixture causes the atmospheric pressure 

of the vapor to become greater than the vapor pressure, causing it to condense 

(Pvap>Patm).

7. Finally, the condensed water exits the heat exchanger as treated wastewater

(condensate). 

Figure B-18. Mechanical Vapor Compression Crystallization Process

Crystal 

separator

Condensate 

(treated wastewater)

Cool influent 

wastewater

Evaporation (Pvap > Patm) 

Vapor 

compressor 

Heat 

exchanger

Solid crystals

4

3

2

1

5

6

7

Condensation (Pvap< Patm)

Hot, pressurized 

wastewater

Water vapor

Hot 

pressurized 

water vapor

Brine
Part B

72

INTEVRAS Technologies, LLC (INTEVRAS) crystallizer (EVRASTM) uses TVC and 

does not include vapor recovery. Instead, the water vapor is emitted to the atmosphere. Figure 

B-19 is a flow diagram for an EVRASTM unit (DCN SGE00149): 

1. First, influent wastewater enters a pump where it is pressurized. 

2. The influent wastewater is routed through a heat exchanger, where it is heated by 

downstream hot, pressurized vapor from the crystallizer. 

3. The atmospheric pressure of the heated, pressurized water suddenly drops as it 

enters the crystallizer. When this happens, the vapor pressure becomes greater 

than the atmospheric pressure on the water (Pvap>Patm), causing the wastewater to 

evaporate. 

4. As more wastewater evaporates, the remaining brine becomes supersaturated 

causing dissolved solids to precipitate into solid crystals. The mixture exits the 

vessel through a separator to remove the solid crystals. After separation, the 

remaining brine is mixed with influent wastewater at step 1.

5. This water vapor is either released in the atmosphere (typical for the EVRASTM) 

or may be sent to a condenser to recover the water. 

6. The working fluid is circulated between the heat exchanger (step 2) and a waste 

heat source or burner. 

Figure B-19. INTEVRA’s EVRASTM Crystallization Process

Crystal 

Separator

Cool influent 

wastewater

Heat exchanger

Solid crystals

Brine

4

3

2

1

5

Waste heat or 6

burner

Vapor to atmosphere 

or condenser

Cold circulating fluid

Evaporation (Pvap > Patm) 

Hot circulating fluid

Hot, pressurized 

wastewater
Part B

73

2.2.2 Capabilities and Limitations

This subsection describes the targeted constituents and effectiveness, design and 

operation considerations, residuals, and energy use of crystallization. 

Targeted Constituents and Treatment Effectiveness

Crystallizers are capable of treating wastewaters with extremely high TDS concentrations 

typical of some UOG extraction wastewater (DCN SGE00140). Crystallization treatment 

technologies operate most efficiently when the influent wastewater is already near its 

supersaturation concentration for TDS (250,000 to 300,000 mg/L). The EPA did not identify 

detailed data on constituent removal for crystallization. Given the similarity of the process to 

evaporation/condensation, constituent removal for crystallization is likely similar in effectiveness 

and efficiency to that of evaporation/condensation (see Part B.2.2.2). Evaporation/condensation 

typically produces effluent (condensate) TDS concentrations of less than 50 mg/L.

Design and Operation Considerations for UOG Extraction Wastewater

In UOG extraction wastewater applications, crystallizers have been added to existing 

evaporation/condensation treatment systems. In these designs, the concentrated brine produced 

by evaporation/condensation becomes the influent to the crystallization unit (DCN SGE00300).

However, some UOG operators have used stand-alone crystallization units. In either case, the 

influent wastewater is typically pretreated to reduce concentrations of multivalent cations (e.g., 

iron, calcium, magnesium, strontium, barium) (DCN SGE00238; DCN SGE00300). Removal of 

these cations has three benefits (DCN SGE00238):

 Reduced scaling and capital costs – Multivalent cations are corrosive to metals. 

Removing them reduces potential corrosion and scaling of metal equipment and 

piping. Pretreatment to reduce corrosion allows downstream equipment, such as 

the crystallization unit, to be constructed of less expensive materials of 

construction, reducing capital costs. 

 Reduced operating costs – Removing multivalent cations allows for a lower 

operating temperature, resulting in energy savings. This is because the solubility 

limit of concentrated brine that contains multivalent cations is higher than that of 

concentrated brine that does not contain multivalent cations.

 Purity of solid crystals – When all multivalent cations and other constituents are 

removed prior to crystallization, the salt crystal is very pure sodium chloride. One 

CWT facility suggested the solid crystals are 98 percent pure sodium chloride, 

which has potential value in industrial applications (DCN SGE00300).

An alternative to rigorously removing multivalent cations before crystallization is to 

operate the crystallization unit at reduced pressure using a vacuum and chilling system (DCN 

SGE00238). Reducing the operating pressure of the crystallizer significantly decreases the 

boiling temperature of the solution. Ultimately, the unit can still be constructed of less-expensive 

materials of construction, reducing capital costs, because the solubility limit of multivalent 

cations will not be reached. This alternative design eliminates the need to rigorously pretreat the 
Part B

74

influent wastewater to remove multivalent cations (DCN SGE00238). However, pretreatment 

may still be needed to remove other constituents (e.g., TSS, iron) (DCN SGE00160).

Regardless of the type of crystallizer used, equipment is affected by scaling and corrosion 

in the same way that evaporation/condensation units are affected (DCN SGE00140). Common 

pretreatment alternatives include settling, chemical precipitation, and filtration to remove 

suspended solids and other undesired constituents (e.g., iron) (DCN SGE00264; DCN 

SGE00160; DCN SGE00300).

Ambient temperature can be a design consideration. Because crystallization is a thermal 

technology, low winter temperatures increase energy requirements. A fixed heat exchange 

capacity and lower temperatures result in a lower rate of evaporation and capacity (i.e., barrels 

treated per day). For example, one vendor reported that capacity may be as low as 200 bpd in the 

winter and as high as 450 bpd in the summer for a specific mobile system (DCN SGE00160).

Residuals 

If the crystallization unit is operated so that the water vapor is collected and condensed,

recovered treated effluent (condensate) can be reused for hydraulic fracturing or other purposes

by UOG operators. When the influent wastewater is concentrated brine from an evaporator (TDS 

approximately 250,000 to 300,000 mg/L), crystallization recovers more than 80 percent of the 

influent wastewater (DCN SGE00300). 

Crystallization typically produces a solid crystal residue of high quality sodium chloride 

(up to 98 percent purity) (DCN SGE00300). A crystallizer treating 210,000 gallons per day of 

UOG extraction wastewater would generate approximately 120 tons per day of solid crystals39

(DCN SGE00300; DCN SGE00616). There are several practices used for managing the solid 

crystals which have been documented in the literature, including (DCN SGE00300):

 Hauling to landfill for disposal40

 Returning to UOG operators to use as an additive in drilling fluid41

 Sell for use as highway deicer

 Sell for use as a raw material for industrial processes

States may regulate the use of the crystallized solids. For example, Pennsylvania requires 

that all salts generated by oil and gas facilities that are used for deicing or as an industrial process 

raw material meet applicable standards in Pennsylvania Department of Environmental 

Protection’s (PA DEP) General Permit. This permit provides 21 specific quality standards for 

 

39 Actual waste generation will vary by influent TDS concentration. This estimation was based on Marcellus 

wastewater with a typical TDS concentration of 100,000 mg/L (DCN SGE00300). 

40 Because the water has been removed, transport and disposal of salt crystals is less expensive than transport and 

disposal of brine.

41 Salt may be used as an additive in drilling fluid to increase density and/or increase the fluid’s electrical conductivity 

(EC).
Part B

75

salt crystals, including maximum levels of two radioactive constituents: thorium 232 (2 pCi/kg) 

and uranium 238 (2 pCi/g). 

Crystallization may also generate a calcium chloride brine purge stream that must be 

managed. A crystallizer treating 210,000 gallons per day of UOG extraction wastewater would 

generate approximately 38,000 gallons per day of purge42 (DCN SGE00300; DCN SGE00616). 

This purge stream would consist of calcium chloride at concentrations lower than 35 percent 

(DCN SGE00300). One CWT facility with a crystallization treatment unit reported that if the 

calcium chloride concentration is at least 35 percent, the purge stream would have high value for 

other industrial applications (DCN SGE00300). As a result, this CWT facility is also considering 

additional purge treatment (e.g., flash evaporation and cooling to further concentrate the purge 

stream and increase the calcium chloride concentration) (DCN SGE00300; DCN SGE00616). In 

the absence of this flash evaporation system, the CWT facility plans to dispose of the calcium 

chloride by off-site underground injection, or by returning it to UOG operators to use as a 

drilling fluid additive (DCN SGE00300).

43

Since crystallization is an evaporative technology, organic compounds removed from the 

wastewater may be released to the atmosphere along with evaporated water vapor. Therefore, 

consideration of air emissions may be necessary.

Energy Use

Crystallization is an energy-intensive and expensive treatment technology. This is

because nearly all of the influent wastewater is evaporated to generate solid crystals (DCN 

SGE00095). Most units use natural gas burners as an energy source, but a variety of alternatives 

have been tested. 

Vendors attempt to offset energy demand by designing units that can use alternative 

energy sources, such as waste heat from compressor stations and solar energy (DCN SGE00160). 

For example, Epiphany Solar Water Systems offers a crystallizer treatment unit that uses

concentrated solar energy44 (DCN SGE00298.A21). When this report was written, Consol 

Energy, Inc. was pilot testing the system.

Table B-25 reports energy use per barrel of influent wastewater based on data reported by 

vendors. Table B-25 also includes associated influent TDS concentrations, and resulting water 

recovery percentages. Because many of the units require both electrical energy and fuels, the 

energy requirement is presented in three columns: electrical (e.g., pumps, compressors), fuel 

(e.g., natural gas for a burner), and the total energy required if reported. 

 

42 Actual waste generation will vary by influent TDS concentration. This estimation was based on Marcellus 

wastewater with a typical TDS concentration of 100,000 mg/L (DCN SGE00300). 

43 Calcium chloride may be added to drilling fluid to increase density and/or increase electrical conductivity.

44 In this technology, solar thermal energy is collected onto mirrors and reflected into a central point. A working fluid 

with high thermal energy capacity (e.g., antifreeze) is passed through this central point to be heated by the concentrated 

solar energy. This process essentially replaces step 6 in Figure B-19.
Part B

76

Table B-25. Energy Usage of Crystallization in UOG Extraction Wastewater Applications

Vendor 

Technology 

Name

Influent TDS concentration 

(mg/L)

Energy Consumption (kWh, unless 

otherwise noted, per bbl of influent 

wastewater) Water 

Recovery 

(%) Additional Notes

Reference 

Electrical Steam (tons)a Total ID

INTEVRAS EVRASTM Produced water TDS levels NR N/A 1.9 – 2.1b No recovery

Uses waste heat from 

compressor stations or 

powered by natural gas

19

Epiphany Solar Water 

Systems E3H Produced water TDS levels NR N/A NR NR Uses concentrated solar energy

45

Heartland Technology 

Partners, LLC LM-HT® Produced water TDS levels NR N/A NR NR

Uses waste heat from 

compressor stations or 

powered by natural gas

91

Not specified Not specified 130,000 0.5 – 1.7 ~14 NR NR Assuming waste steam is 

available 35

Not specified Not specified >40,000 NR NR 4.2 – 11 NR None 40

N/A—Not available; NR—Not reported; TDS—total dissolved solids; mg/L—milligrams per liter; kWh—kilowatt-hour; bbl—barrel.

a—Waste steam from other industrial processes may be used to improve economics.

b—Vendor reported the power requirement for the pumps and fans alone as 30 kW to treat 325 barrels per day, assuming waste heat is available. Assuming a 90 to 

95 percent capacity, electrical consumption is between 1.9 and 2.1 kWh per barrel of influent wastewater. Additional energy is required if waste heat is not 

available.
Part B

77

2.2.3 Costs

Capital costs of crystallization typically include costs for the pretreatment system, 

evaporation/condensation unit, low-pressure pumps, and monitoring equipment. The operating 

costs associated with crystallization include energy for low-pressure pumps and evaporation and 

labor costs (DCN SGE00638.A12; DCN SGE00638.A11). The energy costs are highest among 

all technologies used to treat UOG extraction wastewater, unless low-grade or waste energy is 

used (such as waste heat from compressor stations or solar energy) (DCN SGE00124; DCN 

SGE00264; DCN SGE00110). Factors that affect the costs for crystallization include feed water 

quality, energy source, and disposition of residuals. 

Table B-26 shows approximate capital and operating cost for crystallization when a 

treatment system is purchased or rented. Table B-27 shows approximate costs UOG operators 

pay CWT facilities to treat UOG extraction wastewater using crystallization (including 

pretreatment). One CWT facility the EPA visited (not listed in Table B-27) considered adding 

crystallization to their existing evaporation/condensation process. The company investigated at 

least eight different vendors and concluded that the technology was too expensive given the 

current price of gasoline. The biggest problem was the lack of market for the solid waste (i.e., 

salt). Through their research, the CWT facility estimated that the crystallization process, alone, 

would cost UOG operators $15 to $18 per barrel ($0.36 to $0.43 per gallon), including 

pretreatment (DCN SGE00299). However, other CWT facilities in the Marcellus have multiple 

facilities already permitted that will use crystallization (DCN SGE00300).

Table B-26. Crystallization Capital and O&M Costs for UOG Extraction Wastewater 

Applications

Vendor or 

Technology 

Name

System 

Description

Influent 

TDS 

(mg/L)

Cost 

Basis

Capacity 

(MGD)

Capital 

Cost 

($ per gpd)

O&M 

Cost 

($ per 

bbl)

Rental or 

Effective Cost 

($ per bbl)a

Reference 

ID

NR Unit 100,000b Purchase 0.21 33.00 NR NR 49

NR Plant 110,000 –

130,000 Purchase 0.25 120.00 3.50 11.00 to 22.00 35c

NR System 40,000 –

150,000 Purchase 0.25 45.00 3.70 NR 52c

GE Plant ~130,000 NR 1.0 NR NR 5.00 to 6.80 102c

NR System NR Rental NR N/A N/A

1.00 – 3.00 

more than 

evaporation/ 

condensation

32

N/A—Not available; NR—Not reported; TDS—Total dissolved solids; mg/L—milligrams per liter; MGD—million 

gallons per day; gpd—gallons per day; bbl—barrel.

a—Represents rental cost if the cost basis was rental and is inclusive of O&M. Represents total effective cost when 

cost basis is purchase, which includes amortized capital costs and O&M costs combined if reported by the source 

unless otherwise noted.

b—This represents the TDS of the untreated wastewater. The influent wastewater to crystallization is the effluent

concentrated brine from evaporator/condensation, which contains TDS concentrations close to the supersaturation 

concentration (250,000 to 300,000 mg/L).
Part B

78

c—This cost range represents a unit designed for UOG extraction wastewater treatment but has not been 

implemented.

Table B-27. Crystallization Costs to UOG Operators at CWT Facilities

CWT Facility 

Name

Treated 

Wastewater 

Typical Influent 

TDS 

concentration 

(mg/L)a Type of Service

Cost to UOG 

Operator at 

CWT Facilities 

($ per bbl)a

Reference 

ID

Fairmont Brine 

Processing Shale gas 250,000 to 300,000 Discharge to surface water or reuse 5.50 – 8.00 179; 153

Eureka Resources, 

LLC Shale gas

250,000 to 

300,000b

Discharge to POTW or 

reuse

10.80 – 11.00c 49

N/A N/A >100,000 Reuse only 5.00 – 6.80d 102

N/A—Not available; NR—Not reported; TDS—total dissolved solids; mg/L—milligrams per liter; bbl—barrel.

a—Data in this table are as-reported in literature or to EPA. Cost ranges do not include transportation and may vary 

based on wastewater characteristics and the type of service.

b—The typical influent to the plant has a TDS concentration around 100,000 mg/L. The TDS concentration 

presented is the assumed concentration for the actual influent to the crystallization unit, which is the effluent 

wastewater from an evaporator.

c—Cost may be as low as $7 per barrel to the UOG operator if the residuals can be sold for beneficial use to other 

industries.

d—Costs were reported assuming that the hypothetical CWT facility is owned and operated by the vendor, and that 

the UOG operator brings wastewater to the plant for treatment on a contractual basis.

2.2.4 Summary of Vendors for UOG Extraction Wastewater

Fairmont Brine Processing, LLC in Fairmont, West Virginia, is a CWT facility that 

accepts UOG extraction wastewater from Marcellus and Utica shale operators and treats it using 

a crystallizer. Fairmont’s process includes chemical pretreatment of the wastewater, which is 

then crystallized into sodium chloride crystals. The EPA identified a second company, Eureka 

Resources, LLC, that accepts UOG extraction wastewater from operators and is currently 

constructing a crystallizer as an add-on treatment unit to evaporation/condensation at their 

existing CWT facility in Williamsport, Pennsylvania. Eureka Resources, LLC is also 

constructing a second CWT facility in the Marcellus that will include crystallization (DCN 

SGE00523; DCN SGE00616). EPA also visited a UOG operator who uses a crystallization 

treatment unit at one of their compressor stations allowing them to utilize waste heat (DCN 

SGE01047).

EPA identified several vendors that offer these units, most of which have been pilot 

tested. Table B-28 summarizes data gathered from vendors offering crystallization units.
Part B

79

Table B-28. Crystallization Technologies for Treating UOG Extraction Wastewater

Vendor

Technology 

Name

System 

Description

Surface 

Footprint 

(ft2)

a

Capacity 

(bpd) Other Notes

Reference 

ID

INTVRAs 

Technologies, 

LLC.

EVRASTM Semi-mobile 820 200 – 400

Can be designed for lowgrade waste heat utilization. 78; 19; 18

Heartland 

Technology 

Partners, LLC

LM-HT®

Mobile NR 1,000 Can be designed for lowgrade waste heat utilization. 91; 136

Stationary NR 6,300

Epiphany Solar 

Water Systems E3H Non-mobile

NR, fits 

on well 

pad

10 – 100

Each unit is sized for one 

well, but can be scaled up 

for a multi-well pad. Uses 

concentrated solar energy in 

lieu of fuel.

45

NR—Not reported; ft2—square feet; bpd—barrels per day.

a—Only includes the primary treatment unit, not storage for wastewater, chemicals, or sludge (solid waste).

2.3 Reverse Osmosis

Application of reverse osmosis (RO) is limited to treatment of flowback or long-term 

produced water from formations where TDS is relatively low compared to typical 

concentrations. The typical upper limit of TDS concentration in the wastewater for cost-effective 

operation is 45,000 to 50,000 mg/L (DCN SGE00331; DCN SGE00683; DCN SGE00161).

This section describes the RO process, treatment capabilities and limitations, treatment 

cost, and vendors that the EPA is currently aware of that market the technology for UOG 

extraction wastewater treatment.

2.3.1 How RO Works

The following subsections describe reverse osmosis operating principles and how the 

process has been used to treat UOG extraction wastewater.

Principle

In RO, pressurized water is forced through a semi-permeable membrane to separate the 

water from dissolved solids. Semi-permeable membranes allow water but not dissolved solids to 

flow through (they are permeable to water but impermeable to dissolved solids). Like other 

filtration technologies, the RO membrane separates constituents from wastewater based on size 

differences. However, unlike other filtration technologies, RO membranes also separate 

constituents based on electrostatic charge. RO membranes will repel most charged particles

(ions), but allow neutral molecules like water to pass through. Because salts, such as sodium 

(Na+) and chloride (Cl-), are ions that are repelled by RO membranes, RO is well suited for 

desalination (DCN SGE00166). 

The name “reverse osmosis” derives from osmosis: the spontaneous flow of water from a 

dilute solution to a concentrated solution, which occurs when the two solutions are separated by 
Part B

80

a semi-permeable membrane (DCN SGE00166). In “reverse” osmosis, water flows from a 

concentrated solution to a dilute solution. This is accomplished when a pressure greater than the 

osmotic pressure is applied to the concentrated water. When the pressure applied to the 

concentrated water exceeds the osmotic pressure, the osmosis process reverses and the water is 

driven through the membrane to the dilute solution. The membrane prevents B+ ions from 

passing, leaving a concentrated solution behind (DCN SGE00167). Figure B-20 illustrates RO 

when a pressure greater than the osmotic pressure is applied to the concentrated water. Because 

the applied pressure must be greater than the osmotic pressure, higher concentrations require

higher applied pressure (DCN SGE00166). 

Figure B-20. Flow Diagram of Reverse Osmosis Principle

Process Description

In a typical wastewater treatment RO unit, hydraulic pumps apply pressure to the influent 

wastewater. The process requires pressures ranging from 250 to 1,180 psi, depending on the TDS

of the influent wastewater (DCN SGE00175). The applied pressure pushes the water through the 

membrane while the membrane blocks the ions and other dissolved material (TDS) from passing. 

The influent wastewater is separated into two separate streams: treated wastewater and 

concentrated brine. In the literature, the treated wastewater is referred to as permeate and the 

concentrated brine is referred to as concentrate (DCN SGE00264). 

RO membranes are made from man-made polymers, such as synthetic cellulose or 

polyamide (e.g., nylon). All membrane materials have a retention rating, which describes the size 

of materials retained by the membrane. The retention rating can be called the molecular weight 

cutoff (MWCO), based on the molecular weight of material retained by the membrane. The 

lower the cutoff, the smaller the molecules that will be retained by the membrane. The MWCO 

varies between membranes and can affect the performance of the RO process and operating costs 

(DCN SGE00167). A typical membrane pore size is between 0.0001 and 0.001 microns (4 to 40 

billionths of an inch) and have treatment rates of 8 to 12 gallons per square foot of membrane per 

B

+

B

+

B

+

B

+

B

+

B

+

B

+

B

+

Applied 

pressure

B

+

B

+

Diluted Concentrated
Part B

81

day. At these rates, a typical unit will require hundreds to thousands of square feet of membrane 

to treat typical desired rates of wastewater by the UOG industry. To reduce the space required by 

membrane systems, the membranes are often rolled into spirals (DCN SGE00167). 

During RO treatment, the influent wastewater first enters a hydraulic pump where it is 

pumped to the required pressure. The pressurized wastewater flows into the RO vessel, where the 

membrane separates the permeate from the concentrate. Figure B-21 illustrates how a spiralwound membrane separates the influent wastewater into permeate and concentrate streams. The 

pressurized influent wastewater enters one end of the wound membrane, which is wrapped 

around a permeate collection tube. The high pressure in the influent stream drives the water 

through the wound membrane and into the permeate collection tube. However, only the water is 

able to pass through the membrane, leaving the concentrate behind. The two streams exit the 

membrane device in parallel with the permeate in the collection tube and the concentrate outside. 

Figure B-21. Spiral-Wound Membrane Flow Diagram

2.3.2 Capabilities and Limitations

This subsection describes the targeted constituents and effectiveness, design and 

operation considerations, residuals, and energy use of RO. 

Targeted Constituents and Treatment Effectiveness

RO is used to remove dissolved organic and inorganic constituents, such as ions, acids, 

sugars, dyes, natural resins, salts, BOD, COD, and radioactive elements from wastewater (DCN 

SGE00264). The typical upper limit of TDS concentration in the wastewater for cost-effective 

Permeate 

collection tube

Permeate

Concentrate

Wound 

membranes

A

+

A

+

A

+

A

+

A

+

A

+

Permeate

Permeate flow across 

membrane

High pressure 

influent feed water

effluent High pressure 

influent
Part B

82

operation is 45,000 to 50,000 mg/L (DCN SGE00683; DCN SGE00161). Higher TDS 

concentrations increase osmotic pressure to the point where excessive energy is required to 

generate enough applied pressure to reverse the osmotic flow, making the process prohibitively 

expensive. RO can produce effluent TDS concentrations of 200 to 500 mg/L, depending on the 

composition of the influent wastewater (DCN SGE00095). Alexander, 2011 (DCN SGE00161) 

suggests that RO is the most cost-effective treatment for UOG extraction wastewater when TDS 

is less than 30,000 mg/L.

Table B-29 shows performance data for RO in UOG extraction wastewater applications. 

The table includes untreated influent constituent concentrations, effluent constituent

concentrations, and the resulting constituent removal efficiencies. 

Table B-29. RO Removal Efficiency in UOG Extraction Wastewater Applications

Constituent

Typical Influent 

Range

(mg/L)a

Typical Effluent 

Range

(mg/L)a

Calculated 

Removal Efficiency 

(%)b Reference ID

TDS 6500 – 31,000

41 – 400

95 to >99 55; 101; 3; 112; 

160

Chloride 3,300 – 21,000

18 – 240

97 to > 99 55; 101; 3; 112; 

160; 56

Sodium 2,300 – 17,000 37 – 220 97 to 99 112; 56; 3; 160

Metals

Aluminum 0.35 – 1 ND – 0.2 >80 56

Arsenic 0.037 ND >99c 55

Barium 0.15 – 35 ND – 0.1 32 to >99 55; 56; 3

Boron 15 – 30 ND – 17 39 to 98 3; 101; 160

Cadmium 0.014 ND >99 55

Calcium 37 – 350 ND – 5 87 to >99 55; 56; 3; 160

Chromium 0.068 ND >99 55

Copper 0.068 – 0.13 0.020 – 0.025 70 to 80 55; 56

Iron 0.4 – 13 ND – 0.5 >92 55; 56; 3; 160

Lead 0.015 0.003 80 56

Magnesium 0.1 – 520 ND – 8.2 80 to 98 55; 56; 3; 160

Manganese 0.075 – 0.10 ND – 0.10 80 56; 3; 160

Nickel 0.056 – 0.10 0.025 – 0.10 55 55; 3; 160

Phosphorous 1.2 ND >99 55

Potassium 53 – 320 0.1 – 5 96 to >99 56; 3; 160

Silver 0.087 0.001 99 55

Strontium 6 – 24 0.1 >98 56; 3

Thallium 0.038 ND >99 55
Part B

83

Table B-29. RO Removal Efficiency in UOG Extraction Wastewater Applications

Constituent

Typical Influent 

Range

(mg/L)a

Typical Effluent 

Range

(mg/L)a

Calculated 

Removal Efficiency 

(%)b Reference ID

Organics

Benzene (μg/L) 0.005 ND >99 55

Bis(2-

chloroethyl)ether 

(μg/L)

0.038 ND >99

55

BTEX (μg/L) 28,000 – 80,000 ND >99 101

Diesel range organics 

(μg/L) 77,000 – 1,100,000 ND >99 101

Ethylbenzene (μg/L) 0.004 ND >99 55

Gasoline range 

organics (μg/L) 88,000 – 420,000 ND >99 101

Oil and grease 14 – 2,400 ND – 1.1 >92 55; 101

Phenol (μg/L) 39 ND >99 55

TOC 6 – 77 1 – 18 76 to 95 3; 55; 160

Toluene (μg/L) 6 0. 97 83 55

Xylene (μg/L) 24 ND >99 55

Other

Alkalinity 330 – 1,000 31 – 81 86 to 97 56; 55; 3

Ammonia 40 – 53 1.1 – 1.9 >97 55; 3

Bicarbonate 

Alkalinity 528 90 83 160

BOD 200 9 95 55

COD 250 2 99 55

Electrical 

Conductivity 10,200 350 97 160

Fluoride 2 0 >99 55

Hardness 560 – 1,200 10 98 55; 3

Methanol 40 – 1,500 ND >99 101

Nitrate 7 ND >99 160

pH 7.7 6.7 13 160

Silica 14 – 40 0.43 – 5 >87 56; 3

Sodium Adsorption 

Ratio 73 39 49 160

Sulfates 10 – 100 ND – 1 97 to >99 101; 55; 3; 160

TSS 18 – 65 ND – 10 >44 – 97 3; 55

Radioactives

Gross Alpha (pCi/L) 270 ND >99 55

Gross Beta (pCi/L) 72 ND >99 55

Radium 226 (pCi/L) 82 ND >99 55
Part B

84

Table B-29. RO Removal Efficiency in UOG Extraction Wastewater Applications

Constituent

Typical Influent 

Range

(mg/L)a

Typical Effluent 

Range

(mg/L)a

Calculated 

Removal Efficiency 

(%)b Reference ID

Radium 228 (pCi/L) 7 ND >99 55

Uranium 234 (pCi/L) 1 ND >99 55

Uranium 238 (pCi/L) 1 ND >99 55

ND—Not detected; mg/L—milligrams per liter; μg/L—micrograms per liter; pCi/L—picocuries per liter; TDS—

total dissolved solids; BTEX—benzene, toluene, ethylbenzene, and xylenes; TOC—total organic carbon; BOD—

biochemical oxygen demand; COD—chemical oxygen demand; TSS—total suspended solids.

a—Units are in mg/L unless otherwise specified in the constituent column.

b—The EPA calculated all removal efficiencies using paired influent and effluent concentrations reported in 

literature. Attachment 1 (DCN SGE01186.A01) presents these removal efficiency calculations. The number of data 

points that these removal efficiencies are based on are also presented in Attachment 1.

c—If effluent concentration was reported as not detected, the EPA reported greater than 99 percent for removal 

efficiency for the purpose of this table.

Design and Operation Considerations for UOG Extraction Wastewater

Because RO is only efficient when treating wastewater with TDS concentrations less than 

50,000 mg/L, it is generally only used to treat flowback wastewater (which may have relatively 

low TDS), or long-term produced waters from UOG formations that generate relatively low TDS 

concentrations (DCN SGE00331). 

A number of other limitations must also be considered in the design and operation of RO 

units. The most challenging problem with RO is that, without proper pretreatment, membranes 

are subject to fouling.45 Constituents that cause fouling include metal hydroxides, colloidal and 

particulate foulants, precipitates or salts, organic materials (e.g., oil, humic acids), and 

biologicals (e.g., microbes, bacteria) (DCN SGE00161; DCN SGE00264). Membrane fouling 

can lead to reduced treatment efficiency and high volumes of concentrated brine.

To prevent scaling and reduce membrane fouling, pretreatment and chemical addition are 

typically required (DCN SGE00264; DCN SGE00683). Usually, scale control occurs first, and 

can include pH adjustment or antiscalant addition. After scale control, the wastewater is filtered

to remove particulate matter (TSS). Finally, wastewater should also be disinfected to reduce 

biofouling of the membrane (DCN SGE00167). Even with proper pretreatment, occasional 

chemical addition may be needed to clean buildup from the membrane. Cleaning chemicals 

include hydrochloric acid and sodium hydroxide (DCN SGE00264). Examples of pretreatment 

specifically used in UOG applications include AOP, induced gas flotation, filtration, and 

electrocoagulation.

 

45 Membrane fouling occurs when dissolved and suspended solids deposit onto a membrane surface, degrading overall 

performance. Specific declines in performance include a decrease in permeate quality and water recovery percentage.
Part B

85

Residuals

RO generates concentrated brine. At higher influent TDS concentrations, water recovery 

decreases, resulting in a larger proportion of concentrate and higher disposal costs (DCN 

SGE00095; DCN SGE00264; DCN SGE00109). High water recovery (75 to 90 percent) and 

reduced concentrated brine generation is possible if influent TDS is below approximately 25,000 

mg/L (DCN SGE00095). One vendor estimated that water recovery drops to 60 percent when 

TDS reaches 30,000 mg/L and to 25 percent when TDS reaches 50,000 mg/L (DCN SGE00161). 

For comparison, flowback from UOG wells typically contain TDS concentrations between 

30,000 mg/L and 120,000 mg/L and long-term produced water from UOG wells may have TDS 

concentrations as high as nearly 400,000 mg/L (DCN SGE01188)

46

.

Table B-30 shows results of RO water recovery as a function of influent TDS 

concentration using Woodford shale wastewater. As TDS concentrations increase above 

approximately 30,000 mg/L, the percent recovery decreases which results in higher operating 

costs (e.g., higher pressure required, increased brine disposal) (DCN SGE00070). 

Table B-30. Influent TDS Concentration Versus 

Water Recovery

Influent TDS to RO

(mg/L)

Water Recovery Percent

(%)

20,000 95

33,000 95

42,000 51

64,000 42

TDS—total dissolved solids; mg/L—milligrams per liter.

Source: DCN SGE00070.

The overall performance and treated wastewater recovery is also affected by the desired 

effluent TDS concentration. If the lowest TDS concentration possible is desired, treated 

wastewater recovery will decrease as illustrated in Figure B-22.

 

46 The reported flowback range represents the 25th to 75th percentiles of TDS concentrations.
Part B

86

Source: DCN SGE00166.

Figure B-22. TDS Concentration Versus Water Recovery Percent

In UOG applications, disposal methods used for concentrated brine include evaporation 

in ponds (DCN SGE00374; DCN SGE00298.A24; DCN SGE00369) and injection to a Class II 

disposal well (DCN SGE00298.A24; DCN SGE00369). 

Energy Use

RO requires electrical energy to run the pumps that pressurize the influent wastewater 

(DCN SGE00175). A general rule of thumb in industry is that for every 100 mg/L of influent 

TDS, an additional 1 psi of applied pressure is required (DCN SGE00161). For example, sodium 

chloride concentration of 13,000 mg/L results in an osmotic pressure of 150 psi. When the 

concentration increases to 35,000 mg/L, then the osmotic pressure increases to 398 psi (DCN 

SGE00166). When the required applied pressure increases, then energy requirements also 

increase. 

In general, RO pumps are powered by electricity purchased from off-site generation (i.e., 

the grid). Burnett, 2011 (DCN SGE00163) suggested alternative methods of powering RO units. 

These methods include microturbines (which require low grade gas), solar panels (if the system 

has low pressure requirements), and wind turbines. Burnett described a mobile wind turbine unit 

that is capable of providing enough power for pretreatment operations such as media filtration,

but not enough to run the high-pressure hydraulic pumps required for RO.

Table B-31 reports energy use per barrel of influent wastewater. Influent and effluent 

TDS concentrations are also included with the final water recovery percent. The reported data 

confirm the general trend that higher influent TDS concentrations result in higher energy 

requirements. The data also confirm that as influent TDS concentration increases, water recovery 

percentage decreases.
Part B

87

Table B-31. RO Energy Use in UOG Extraction Wastewater Applications

Vendor Technology Name

Influent TDS 

concentration 

(mg/L)

Energy Use

(kWh per bbl)

Water 

Recovery 

(%)

Reference 

ID

Ecosphere 

Technologies, Inc.

Ozonix TM, includes AOP for 

pretreatment 14,000 2.2 75 55; 40

Not specified N/A, includes filtration for 

pretreatment 500 – 25,000 0.02 – 0.4a 60 – 85 40; 7

Not specified Mobile unit designed by 

Chevron, includes 

electrocoagulation for 

pretreatment

45,000 1 NR 85

Not specified N/A, includes softening and 

filtration for pretreatment 20,000 – 47,000 0.5 – 1.6 30 – 60 40; 7

NR—Not reported; mg/L—milligrams per liter; kWh—kilowatt-hour; bbl—barrel; TDS—total dissolved solids.

2.3.3 Costs

The major capital costs associated with RO are the RO unit and reliable hydraulic pumps 

that can withstand the corrosivity of the high TDS in UOG extraction wastewater. The major 

operating costs associated with RO include membrane replacement, which is expected to occur 

every three to seven years for oil and gas wastewater applications according to Colorado School 

of Mines (CSM) (2009). According to Burnett, 2011 (DCN SGE00163), UOG extraction 

wastewater treatment requires annual membrane replacement. The second major cost is the 

energy required for the pumps (DCN SGE00264). 

Table B-32 shows approximate RO capital and operating costs. The reported data show 

that overall cost of RO units depends on influent wastewater quality. As influent TDS 

concentrations increase, the capital and operational costs increase. This is because larger and 

more robust pumps and vessels are required as the applied pressure increases (with the increase 

of TDS). Table B-33 shows approximate costs UOG operators pay CWT facilities to treat UOG 

extraction wastewater using RO (including pretreatment).

Table B-32. RO Capital and O&M Costs for UOG Extraction Wastewater Applications

Vendor and 

Technology 

Name

System 

Description

Influent 

TDS 

(mg/L)

Capacity 

(MGD)

Cost 

Basis

Capital 

Cost 

($ per gpd)

O&M 

Cost 

($ per 

bbl)

Rental or 

Effective 

Cost 

($/bbl)a

Reference 

ID

General Mobile system 

with EC and 

DAF

~50,000 0.063 Purchase 18.00 1.50 4.40 85b

Ecosphere 

Energy 

Services, Inc.

Mobile system 20,000 –

30,000 0.14 NR NR NR 3.50 –4.00 75

Siemens Mobile system ~30,000 NR Purchase 1 – 4 NR NR 20

General Mobile system 

with filtration

20,000 –

47,000 NR Purchase 3.00 – 7.00 0.08 NR 40
Part B

88

NR—Not reported; mg/L—milligrams per liter; MGD—million gallons per day; gpd—gallons per day; bbl—

barrels; TDS—total dissolved solids.

a—Represents rental cost if the cost basis was rental and is inclusive of O&M. Represents total effective cost when 

cost basis is purchase, which includes amortized capital costs and O&M costs combined if reported by the source 

unless otherwise noted.

b—This cost range represents a unit designed for UOG extraction wastewater treatment but has not been 

implemented. Amortization assumptions were not reported with this source.

Table B-33. RO Costs to UOG Operators at CWT Facilities

CWT Facility 

Name

Type of 

UOG

Influent TDS 

concentration 

(mg/L) Type of Service

Cost to UOG 

Operator at CWT 

Facilities ($ per 

bbl)a

Reference 

ID

Anticline 

Disposal, LLC Tight gas ~20,000

Reuse treated wastewater in 

fracturing or discharge treated 

wastewater to surface water

NR

161;13;

179; 180; 

181; 182

Red Desert 

Reclamation, LLC Tight gas ~20,000

Reuse treated wastewater in 

fracturing and evaporate 

concentrated brine in ponds

2.00 – 3.00 109

mg/L—milligrams per liter; bbl—barrel; TDS—total dissolved solids; NR—Not reported.

a—Cost ranges are as-reported in literature. Cost ranges do not include transportation and may vary based on 

wastewater characteristics and the type of service.

2.3.4 Summary of Vendors for UOG Extraction Wastewater

To date, the EPA has found that only CWT facilities are removing TDS from UOG 

extraction wastewater with reverse osmosis (RO) technology. However, RO has also been pilottested by UOG operators for reuse applications. The EPA identified full scale applications of 

reverse osmosis treatment systems in the Mesaverde and Lance tight gas formations at CWT 

facilities.47 In addition, the EPA identified several vendors offering mobile RO units that can be 

used by UOG operators, most of which have been pilot tested for UOG extraction wastewater. 

Table B-34 summarizes data gathered from vendors marketing RO units for treating UOG 

extraction wastewater.

Table B-34. RO Technology Vendors for UOG Extraction Wastewater

Vendor

Technology 

Name

System 

Description

Surface 

Footprint 

(ft2)

a

Capacity 

(bpd) Other Notes

Reference 

ID

GeoPure 

Hydrotechnologies NR NR NR 5,000 None 77

M-I SWACO GPRI 

DesignsTM NR NR 5,000 None 79

Veolia Water 

Solutions & 

Technologies

OPUSTM Mobile or 

stationary NR 10,000

Includes chemical 

softening, 

degasification, and 

media filtration

87; 80

 

47 This area is commonly referred to as the Pinedale field, which includes the Mesaverde and Lance tight gas 

formations.
Part B

89

Table B-34. RO Technology Vendors for UOG Extraction Wastewater

Vendor

Technology 

Name

System 

Description

Surface 

Footprint 

(ft2)

a

Capacity 

(bpd) Other Notes

Reference 

ID

Omni Water 

Solutions, Inc. HIPPO® Mobile NR 2,500 –10,000 Includes pretreatment 96

Siemens Water 

Technologies FracTreat Mobile NR NR Includes pretreatment 20; 6

Ecosphere 

Technologies, Inc. Ozonix TM Mobile 380 7,200 Includes AOP as pretreatment 75; 55

NR—Not reported; ft2—square feet; bpd—barrels per day.

a—Only includes the primary treatment unit, not storage for wastewater, chemicals, or sludge (solid waste)
Part C

90

Part C. POTENTIAL TECHNOLOGIES

In addition to the established technologies described above, the EPA identified the 

following treatment technologies not currently used to treat UOG extraction wastewater, but 

which may be applied in the future due to their use for other similar wastewaters, such as 

drinking water treatment of brackish or sea water: 

 Ion Exchange

 Electrodialysis Reversal (EDR)

 Capacitative Deionization (CDI)

 Membrane Distillation

 Forward Osmosis

Section C contains two parts: Section C.1 is a table documenting the potential of each 

technology for application in UOG extraction wastewater treatment and Section C.2 contains a 

detailed description of how each technology works.

1 POTENTIAL TECHNOLOGIES FOR APPLICATION IN UOG EXTRACTION WASTEWATER 

TREATMENT

Table C-1 presents technologies that the EPA identified as being potentially relevant for 

the treatment of UOG extraction wastewater. Table C-1 presents a summary of each technology, 

including the capabilities of the treatment technology, design and operation considerations, and 

residuals.
Part C

91

Table C-1. Potential Technologies for Application in UOG Extraction Wastewater Treatment

Treatment 

Technology

Potential Application for 

UOG Extraction 

Wastewater Treatment Design and Operation Considerations Residuals Reference ID

Ion Exchange Removes arsenic, metals, 

nitrates, radium, salts, and 

uranium.

Pretreatment to prevent resin fouling by TSS, oil and 

grease.

Use of scavenger exchange resins to selectively 

remove organic chemicals which compete with 

targeted constituents during ion exchange.

Concentration of mixed salts in produced water, 

requiring a two-stage process.

Regenerate containing 

TDS, metals, hardness, 

calcium, magnesium, 

sodium, sulfate, chloride, 

nitrates, and radioactive 

elements.

Expected water recovery 

less than 97 percent.

4; 21; 16; 23; 24; 26;

31; 41; 112; 138

Electrodialysis 

Reversal 

Removes dissolved charged

ions, including: TDS, 

chloride, sodium, calcium, 

magnesium, hardness, 

sulfate, bicarbonate, nitrate, 

fluoride, barium, potassium, 

iron, phosphate, total 

organic carbon (TOC), and 

SAR.

Pretreatment to reduce membrane fouling, including 

scaling control, filtration, or disinfection.

Membrane life expectancy is about ten years. Cathode 

membranes have a longer life expectancy than anode 

membranes.

Cathode and anode plates must be replaced every two 

to three years.

Low maintenance requirements.

Concentrated brine 

stream ranging from 10-

20 percent of the influent 

wastewater volume.

4; 7; 10; 25; 26; 39; 40

Capacitative 

Deionization

Removes dissolved charged 

ions, including: nitrates, 

ammonia, perchlorate, 

arsenic, fluoride, chromium, 

ion, and organic acids

Performance factors include: electrode thickness, 

spacer geometry, cell design, operational settings.

CDI modules operated in series can treat higher TDS 

concentrations while modules in parallel can treat at 

higher flow rates.

Pretreatment using microfiltration or other 

appropriate technologies to remove contaminants

such as particulates, biological matter, or organic 

constituents.

Long electrode life expectancy with little 

maintenance.

Regeneration time can be lengthy or incomplete with 

high salinity water.

Concentrated brine 

stream.

Expected water recovery 

of 75-90 percent.

147; 145; 40; 86
Part C

92

Table C-1. Potential Technologies for Application in UOG Extraction Wastewater Treatment

Treatment 

Technology

Potential Application for 

UOG Extraction 

Wastewater Treatment Design and Operation Considerations Residuals Reference ID

Membrane 

Distillation

Removes non-volatile 

constituents, including: 

ions, macromolecules, 

colloids, cells, and metals

Performance depends on membrane properties, design 

of the module, operating temperature and flow rate, 

and partial pressure established by condensate stream.

Minimal pretreatment is required to remove large 

particles and surfactants, and reduce membrane 

fouling.

Capable of treating wastewater with TDS > 50,000-

70,000 mg/L, up to 200,000 mg/L.

Flux through the membrane decreases significantly 

with increasing salinity. 

Membranes can be cleansed with citric or 

hydrochloric acid to remove deposits. A decline in 

maximum flux capacity may result if not properly 

cleansed.

Relatively low energy requirements. Optimal 

operating temperature > 68o F.

Low capital and maintenance costs, compared with 

costs for pressure-driven membrane processes.

Volatile organic 

compounds (VOCs) pass 

through the membrane 

with water vapor.

Expected water recovery 

rate of 60-95 percent.

146; 40; 84; 89; 90; 

93; 95; 103

Forward 

Osmosis

Removes TDS, ammonia, 

organic carbon, boron, 

barium, calcium, iron, 

magnesium, potassium, 

strontium, alkalinity, 

bromine, silica, sodium, 

sulfates, gross alpha, and 

gross beta.

Requires additional processes to produce a high 

quality effluent.

Requires little oversight, flexible with sensitivity to 

low and high pH streams, and operates semicontinuously, requiring little downtime for cleaning.

Operation at high pressure increases membrane 

fouling.

Operates at ambient temperature, reducing energy 

requirements and costs. Treatment unit operators must 

select the draw solution. Highly soluble solutes 

minimize scaling.

Concentrated brine and 

dilute draw solution.

40; 92; 104; 108
Part C

93

2 DESCRIPTION OF HOW EACH POTENTIAL TECHNOLOGY WORKS

2.1 Ion Exchange

Ion exchange treatment is used to remove ionic species from water using an ion exchange 

resin. Ion exchange is commonly used in water softening, where calcium (Ca+2) and magnesium 

(Mg+2) are the ions targeted for removal. Ion exchange has also been used to remove sodium 

(Na+) and bicarbonate (HCO3

-

) ions from coalbed methane (CBM) wastewater in the Powder 

River Basin (PRB). 

TDS in UOG extraction wastewater contains both cations and anions, primarily 

consisting of sodium (Na+), calcium (Ca+2), and chloride (Cl-) (DCN SGE01188) (see Part A.1); 

therefore, removing TDS from UOG extraction wastewater via ion exchange would require both 

cationic and anionic exchangers in a two-step process. Some UOG operators have also discussed 

removing select ions (e.g., boron) from UOG extraction wastewater using ion exchange (DCN 

SGE01067).

Ion exchange removes dissolved ions using an ion exchange resin. Ion exchange resins, 

also known as cation (positively charged) and anion (negatively charged) exchangers, contain 

charged and mobile ions (e.g., sodium, hydrogen) on the surface that are available for exchange 

with other charged ions. Ion exchange resins are chosen based on what ions are targeted for 

removal; positively or negatively charged ions present in water are replaced with similarly 

charged ions present in the ion exchange resin. The types of ion exchange resins used depend on 

the ions targeted for removal and the concentrations of anions and cations in the wastewater. 

Figure C-1 illustrates the ion exchange process. Specifically, dissolved ions (B+) are 

removed from wastewater by absorption to the resin surface; in exchange, the mobile ions (A+) 

from the resin transfer to the wastewater (see Figure C-1 (A)). The concentration of targeted ions 

differs from the concentration of ions present in the resin, creating a concentration gradient 

which drives the exchange of ions to and from the resin. This process continues until the 

concentration of A+is the same in the resin and solution, as shown in Figure C-1 (B) (DCN 

SGE00166). 

Figure C-1. Ion Exchange Process Using a Cation Exchange Resin
Part C

94

As more and more ions are exchanged, the resin eventually requires regeneration through 

a reverse chemical reaction with a regeneration solution (DCN SGE00167). Cation resin 

regeneration requires an acidic solution because acids provide free H+ cations. Anion resin 

regeneration requires a basic solution because bases provide free OH- anions (DCN SGE00166; 

DCN SGE00690). Table C-2 shows regeneration solutions for different types of resins.

Table C-2. Resin Type and Corresponding Regenerate Solutions

Resin Type

Strongly Acidic 

Cation Exchanger

Weakly Acidic Cation 

Exchanger

Strongly Basic Anion 

Exchanger

Weakly Basic Anion 

Exchanger

Form of resin Strong acid-H+ Weak acid-H+ Strong base-OH- Weak base-OHRegenerate HCl or H2SO4 HCl or H2SO4 NaOH NaOH, NH4OH, or 

Na2CO3

Source: DCN SGE00166; DCN SGE00690.

Figure C-2 illustrates how concentration gradients drive the regeneration process in 

reverse of the ion exchange process. If a resin with a low concentration of A+ cations is placed in 

a solution with a high concentration of A+, a driving force is established due to the concentration 

difference between A+ in the regeneration solution and on the resin and B+ in the solution and 

on the resin. B+ cations from the resin will exchange places with A+ cations in the solution, as 

shown in Figure C-2 (A). This process continues until the concentration of A+ is the same in the 

resin and solution, as shown in Figure C-2 (B) (DCN SGE00166). 

Figure C-2. Regeneration Process of a Cation Resin

Vendors currently offer ion exchange units to treat coal bed methane produced water. 

One such unit is the Higgins Loop offered by Severn Trent. (DCN SGE01140). 

2.2 Electrodialysis Reversal

Electrodialysis reversal (EDR) is an electrically driven membrane separation process with 

alternating stacks of cation and anion membranes that work to remove dissolved ions from the 

influent wastewater using an electrical current gradient. The current reversal facilitates 

A

+ Resin

A

+

A

+

A

+

A

+

A

+

A

+

A

+

B

+

A

+

B

+

A

+

A

+

B

+

B

+

B

+

B

+

A

+

A

+

A

+

A

+

A

+

A

+

A

+

A

+

A

+

A

+

A

+

A

+

A

+

A

+

Regeneration solution

B) Equilibrium
Part C

95

backwashing, which minimizes scale build-up on the anion and cation membranes. EDR operates 

at lower pressures than RO and can reduce TDS to less than 200 mg/L before internal resistance 

drives up power costs (DCN SGE01140).

EDR technologies have been used since the 1960s to generate drinking water by 

desalinating brackish water48 and seawater (DCN SGE00264; DCN SGE00261; DCN 

SGE00175). The EPA identified a few instances where EDR was used to treat CBM wastewater 

(DCN SGE00141), but did not identify any specific instances where EDR was used to treat UOG 

extraction wastewater. 

The principle of EDR builds on the principle of electrodialysis (ED). ED is an electrically 

driven membrane separation process. Electrical current is applied to a salty solution (e.g., UOG 

extraction wastewater) between two electrodes with opposite electrical charges (one positive and 

one negative), the positively- and negatively- charged ions in solution migrate to opposite 

electrodes. Between the positively and negatively charged electrodes lie ED membranes that are 

semi-permeable, meaning that they are impermeable to water, but are permeable to certain ions. 

Further, ED membranes are selective in what charged ions they allow to pass through. One type 

of ED membrane (cation membrane) allows only positively charged ions to pass; the second type 

(anion membrane) allows only negatively charged ions to pass. These two phenomena: charged 

electrodes and selective membranes are the basis for ED treatment.

Figure C-3 illustrates the principle of ED. The gray-shaded region in Figure C-3

represents a solution with the ionic constituents A+and B-. The water-tight compartments formed 

by the selective membranes are called cells. The following steps explain what occurs in ED, as 

shown in Figure C-3: 

1. A positive charge is applied to the anode and a negative charge is applied to the 

cathode; 

2. The negatively charged cathode attracts the A+ions while the positively charged 

anode repels the A+ions; 

3. As the A+ions move in the direction of the cathode, they pass through the cation 

membrane but are blocked by the anion membrane. As a result, the A+ions are

trapped in the central cell; 

4. The positively charged anode attracts the Bions while the negatively charged 

cathode repels the Bions;

5. As the Bions move toward the anode, they pass through the anion membrane but 

are blocked by the cation membrane. As a result, the Bions are trapped in the 

central cell; and

6. Ion concentrations decrease in the lower and upper cells, while ion concentrations 

in the central cell increase.

 

48 The TDS concentration of brackish water is between freshwater (500 mg/L) and seawater (35,000 mg/L). 
Part C

96

Figure C-3. Flow Diagram of Electrodialysis Principle

ED is effective at separating ions from water in principle, but in practice, operating with 

the flow of ions always in the same direction can result in membrane fouling. Membrane fouling 

can be minimized by using EDR, a process that uses the same principle as ED, but reverses the 

cathode and anode several times per hour. Reversing the cathode and anode changes the 

direction of ion flow, thus removing ions that have built up on the membranes (DCN SGE00264; 

DCN SGE00175). 

Figure C-4 shows the principle of EDR. Figure C-4(A) shows an ED unit equipped with 

four selective membranes, forming five cells, through which wastewater enters the unit. The 

arrangement of alternative anion and cation membranes traps the ions in cells 2 and 4 while 

treated wastewater flows out of cells 1, 3, and 5. Figure C-4(B) shows the charge reversal that 

occurs during EDR. The charge applied to the electrodes is reversed so that the cathode is on the 

left and anode is on the right. The process of reversing the electrode charges flushes out the brine 

cells by pulling away trapped ions from the membranes and preventing ions from building up in 

any particular cell. Cells 1, 3, and 5 accumulate the concentrated solution and cells 2 and 4 

accumulate the dilute solution.

A+

B

-

A+

A+

A+

+ -

B

-

B

-

B

-

Cathode Anode 

Cation 

membrane

Anion 

membrane

+ -
Part C

97

Figure C-4. Flow Diagram of Electrodialysis Reversal Principle

Figure C-5 is a flow diagram of EDR in a wastewater treatment application. Electricity is 

applied to the cathode and anode metal plates, creating opposite charges. Following any 

necessary pretreatment, the influent wastewater enters a low-pressure pump. The pressurized 

wastewater is split into separate streams as it enters the individual cells of the EDR unit. After 

the treatment is complete, the treated wastewater and concentrated brine exit the unit. 

Figure C-5. Flow Diagram of Electrodialysis Reversal

EDR units can run in either batch or continuous operation. In addition, multiple EDR 

units, or EDR “stacks”, can be operated in parallel or in series. Operating EDR stacks in parallel 

+ -

Pretreatment

+

_

Concentrated 

Brine

Treated 

Wastewater

Pump

DC Power Source

EDR Unit

Cathode

Anode
Part C

98

adds treatment capacity, while operating stacks in series improves treatment performance (e.g., 

TDS removal percentage). Figure C-6 shows a flow diagram of EDR stacks in parallel (see 

Figure C-6 (A)) and in series (see Figure C-6 (B)). The solid black lines represent wastewater 

and treated wastewater, while the dotted black lines represent the concentrated brine streams. 

EDR units require recycling a portion (typically 10 percent) of the concentrated brine stream to

the influent to maintain pressures and equal flow rates on both sides of the membranes.

Figure C-6. Flow Diagram of EDR Units in Parallel and in Series

2.3 Capacitive Deionization

Capacitive deionization (CDI) is an emerging treatment technology used to desalinate 

brackish water. CDI works by absorbing ions in porous electrodes and later releasing the ions

into a concentrated waste stream. CDI has been demonstrated to remove negatively charged ions 

such as chloride, nitrate, and silica, and positively charged ions such as calcium, magnesium, and 

sodium (DCN SGE01082). The technology has been pilot tested by vendors and various research 

institutions specifically for treatment of UOG extraction wastewaters, but the EPA has not 

identified its use by UOG operators or CWT facilities. 

A capacitor consists of two electric conductors, or electrodes, separated by an insulating 

material. In CDI, the electrodes of the capacitor are constructed of a porous carbon or metal and 

the insulating material is the wastewater to be treated. The basic CDI process consists of two 

phases: purification and regeneration. In the purification phase, a low electrical voltage potential, 

approximately 0.8 to 1.5 volts (DCN SGE00681), is applied, and ions move from the waste 

stream into the electrodes. The charged ions are pulled into electrodes with the opposite charge: 

the positive electrode (i.e., the anode) attracts particles with negative charges (anions) and the 

Treated 

Wastewater

Concentrated 

Brine

Pump Influent 

Wastewater

Concentrated Brine Collection

EDR Unit EDR Unit

EDR Unit EDR Unit

A

B
Part C

99

negative electrode (i.e., the cathode) attracts particles with positive charges (cations). After the 

ions are removed, treated effluent is discharged from the CDI channel. 

Typically, within 20 minutes, the electrodes become saturated with ions and must be 

regenerated. In the regeneration phase of the CDI process, the electrical voltage potential is 

reduced or reversed to release the ions from the electrodes (i.e., desorption). Desorption 

regenerates the absorption capacity of the electrodes to their initial uptake, and generates a waste 

stream with high ion concentrations (DCN SGE00673). The concentrated waste stream must be 

flushed from the cell and disposed of. When the electrode is completely regenerated, the original 

voltage potential is restored, and the cell is ready for use. According to the vendor Atlantis 

Technologies, typical cycle times for their Radial Deionization super capacitor technology 

platform (RDITM) range from 2 to 40 minutes, with 2 to 20 minutes for purification and 2 to 20 

minutes for regeneration (DCN SGE01082). 

The capacitor’s two electrodes may be protected by a membrane that selectively allows 

positive or negative ions to pass. Only positive ions can pass through the cationic membrane, 

which protects the cathode, and only negative ions can pass through the anionic membrane, 

which protects the anode (DCN SGE01051). Coating the electrodes with membranes also 

increases CDI’s removal efficiency by preventing ions from desorbing from the electrodes 

during purification and by promoting more complete desorption during regeneration (DCN 

SGE01086). The removal efficiency of CDI with a membrane is as high as 97%, whereas the 

removal efficiency of CDI without membrane is around 60% (DCN SGE01087). 

Figure C-7 and Figure C-8 are process flow diagrams for Atlantis Technologies RDITM, 

which has a selective membrane coating. Figure C-7 shows the purification process and Figure 

C-8 shows the regeneration process. 

Source: Compiled by the EPA using information from literature (DCN SGE01082).

Figure C-7. RDITM Purification Process Diagram

A+

B

-

A+

A+

+

-

B

-

B

-

Cathode

Anode 

Anionic 

membrane

Cationic 

membrane

-

+

Dielectric 

Flow 

Channel
Part C

100

Source: Compiled by the EPA using information from literature (DCN SGE01082).

Figure C-8. RDITM Regeneration Process Diagram

The porous carbon electrode is a key component in CDI. CDI performance depends on 

material properties of the carbon, such as total pore volume, pore size, pore connectivity, 

electronic conductivity, electrochemical stability and cost (DCN SGE00673). Ideal electrode 

material characteristics include a large ion-accessible surface area, high electro-chemical 

stability for the operating pH and voltage range, fast ion mobility within the pore network, high 

electric conductivity, low contact resistance between the electrode and the current collector, good 

wetting behavior, low costs and scalability, capable of being shaped into film electrodes, and low 

bio-fouling (DCN SGE00673). Currently, electrodes are most often made from a porous carbon 

material, such as activated carbon or carbon aerogel.

While CDI and EDR treatment processes are similar, the EPA identified the following 

differences:

 Constituents removed from wastewater in CDI collect within the porous 

electrodes, while constituents removed from wastewater in EDR collect in brine 

chambers separated from treated wastewater chambers by semi permeable ion 

selective membranes. 

 Performance of CDI is highly dependent upon the surface area and adsorption 

properties of the electrode (DCN SGE00264). EDR efficiency is highly dependent 

on membrane performance (DCN SGE00264). 

 CDI operates in cycles of purification and regeneration, generating intermittent 

streams of treated wastewater and concentrated brine. EDR operates continuously, 

generating treated wastewater and brine streams (DCN SGE01082).

A+

B

-

A+

A+

-

+

B

-

B

-

Anode

Cathode

Anionic 

membrane

Cationic 

membrane

+

-

A+

A+

B

-

B

-

B

-

Flow

Dielectric 

Flow 

Channel
Part C

101

2.4 Membrane Distillation

Membrane distillation (MD) is an emerging technology which uses heat to thermally 

drive vapor molecules through a hydrophobic porous membrane and into a permeate stream, 

leaving behind a waste stream concentrated in non-volatile and solid constituents. The EPA is 

not aware of any pilot scale testing of MD that has been performed for UOG extraction 

wastewater, but the technology is being developed and evaluated extensively. 

MD is based on the principles of vapor pressure and diffusion. In a basic MD unit, the 

feed stream (wastewater) is separated from the permeate stream (treated water) by a hydrophobic 

porous membrane. Vapor molecules diffuse across the membrane as a result of a difference in 

vapor pressure between the feed stream and the permeate stream. Liquid water cannot pass 

through the hydrophobic membrane’s pores, but water vapor and volatile vapors can. Nonvolatile solutes and suspended solids remain in the concentrated waste stream. Depending on the 

composition of the feed stream and the intended use for the permeate stream, additional 

treatment (e.g., air stripping) may be required to remove any volatile constituents from the 

permeate stream.

The vapor pressure of a liquid is directly related to temperature. For MD, the feed stream 

must be kept warmer than the permeate stream so that the vapor pressure of the feed stream is 

higher than that of the permeate stream. In other words, a temperature gradient causes a vapor 

pressure gradient across the membrane. Ultimately, water vapor and volatile vapors evaporate 

from the feed stream, diffuse through the membrane pores and condense upon contact with the 

cold permeate stream. Figure C-9 depicts the vapor pressure drop across the membrane and 

shows how water vapor would move through a pore.

Source: DCN SGE01083

Figure C-9. Membrane Distillation Pressure Gradient

The configuration shown in Figure C-9 is called Direct Contact Membrane Distillation 

(DCMD), and it’s the most basic and extensively studied configuration (DCN SGE01084). There 

are several other configurations, which are variations on DCMD. The following is an overview 

of a few different MD configurations (DCN SGE01081):

 Direct contact membrane distillation (DCMD) – The hot feed stream and cold 

permeate stream are both in direct contact with the membrane surface. 
Part C

102

Condensation takes place at the permeate-membrane interface. This method is the 

simplest configuration, but the main disadvantage is conductive heat loss across 

the membrane.

 Air gap membrane distillation (AGMD) – The feed stream is in contact with the 

membrane but the permeate stream is separated from the membrane by a gap 

filled with stagnant air. The vapor must cross the air gap before reaching the cold 

permeate stream and condensing. This configuration reduces the amount of heat 

lost by conduction, but the main disadvantage is that the air gap reduces mass 

transfer.

 Sweeping gas membrane distillation (SGMD) – The feed stream is in contact with 

the membrane but the permeate stream is separated from the membrane by a gap 

through which an inert gas flows. The flow, or sweep, of the inert gas carries the 

vapor out of the unit to an external condenser. The sweeping air reduces the heat 

lost by conduction, enhances mass transfer, and is useful for removing volatile 

constituents from the vapor. However, the disadvantage of this configuration is 

that a large volume of sweep gas is needed to generate a small amount of 

permeate, so a large condenser is required.

 Vacuum membrane distillation (VMD) – The feed stream is in contact with the 

membrane but the permeate stream is separated from the membrane by a vacuum, 

which pulls the vapor out of the unit and into an external condenser. This 

configuration enhances the vapor pressure gradient across the membrane and the 

heat lost by conduction is negligible.

 Thermostatic sweeping gas membrane distillation (TSGMD) – This configuration 

is the combination of AGMD and SGMD, where there is still a gas sweeping 

through the gap, but part of the vapor condenses in the permeate stream inside the 

unit, and the remainder condenses in an external condenser.

The hydrophobic porous membrane is typically constructed of polytetrafluoroethylene 

(PTFE), polyvinylidene fluoride (PVDF), or polypropylene (PP), but there is ongoing research 

investigating the use of novel membrane materials. Some qualities of an ideal membrane 

material include low resistance to mass transfer, low thermal conductivity, good thermal 

stability, and high resistance to chemical degradation (DCN SGE01081). The pore sizes usually 

range from 0.05 to 0.2 μm, but can be as large as 0.3 to 1.1 μm (DCN SGE00678). The mean 

pore size should be large enough to allow sufficient mass transfer, but small enough to prevent 

liquid penetration. Although the pores are larger than a water molecule, water does not flow 

through the pores due to its high surface tension and the effect of capillary action (DCN 

SGE00678). The membrane material and pore size distribution should be selected based on the 

specific wastewater feed composition and operating conditions.

Figure C-10 is a flow diagram showing the process for a vacuum membrane distillation 

(VMD) module from the startup vendor Refrakt. This system is designed to treat hydraulic 

fracturing wastewater. In this flow diagram, the wastewater stream is sent through three VMD 

units in series, and vapor is pulled out of the units and into an external condenser using a vacuum 

pump. More vapor is transferred from the wastewater feed stream into the permeate stream with 

each pass through the successive VMD units. The number of VMD units needed depends on the 

mass transfer efficiency of each unit and the level of treatment required for the operation.
Part C

103

Source: Compiled by the EPA using information from literature (DCN SGE01085).

Figure C-10. Process Flow Diagram from Refrakt Vacuum Membrane Distillation System

2.5 Forward Osmosis

Forward osmosis (FO), also referred to as engineered osmosis, is capable of reducing 

dissolved constituents commonly found in UOG extraction wastewater. FO has been bench and 

pilot tested for the treatment of UOG extraction wastewater, but there have not been full-scale

applications (DCN SGE00264; DCN SGE00684). 

Osmosis refers to the spontaneous flow of water from a dilute solution to a concentrated 

solution, which occurs when the two solutions are separated by a semi-permeable membrane 

(DCN SGE00166). FO uses osmotic pressure to draw water from a wastewater feed stream 

through a semi-permeable membrane, without the application of hydraulic pressure. The semipermeable membrane allows water to flow through while preventing target ions (e.g., B+

) from 

passing through. 

Figure C-11 shows a flow diagram of an FO unit consisting of two cells separated by a 

semi-permeable membrane. The right cell contains the draw solution, which has a high 

concentration of ions, and the left cell contains the influent waste stream, which has a lower 

concentration of ions than the draw solution. Osmotic pressure causes water to flow from the left 

cell to the right cell and as a result, the concentration of ions in the left cell increases and the 

concentration of ions in the right cell decreases (DCN SGE00167). The transfer of water from 

the left to right continues until the ion concentrations in the two cells are equal. Suspended solids 

and dissolved constituents in the influent waste stream remain in the left cell and exit the FO unit 

as a concentrated brine stream (DCN SGE00264). 

The FO wastewater treatment process shown in Figure C-11 uses the following steps: 

Wastewater 

Inflow

Pump

Flocculation 

Pretreatment 

(optional)

Settler

Brine

VMD Module

VMD Module

VMD Module

Added 

Heat

Condenser

Vacuum 

Pump

Treated 

Water
Part C

104

1. Wastewater is fed into the FO unit where it contacts the semi-permeable 

membrane.

2. The osmotic pressure gradient between the influent wastewater and the 

concentrated draw solution drives the transport of water molecules through the 

membrane, resulting in a diluted draw solution and concentrated brine.

3. The concentrated brine stream exits the FO unit for disposal. 

4. The diluted draw solution is circulated through a draw solution separation unit 

(e.g., reverse osmosis) where it is separated from water obtained from the influent 

wastewater. This separation process results in treated wastewater and a reusable 

concentrated draw solution. 

5. The reconcentrated draw solution is returned to the draw solution chamber to 

continue to drive the FO process.

Source: Compiled by the EPA using information from literature (DCN SGE00264).

Figure C-11. Flow Diagram of Forward Osmosis

As the ratio of ion concentrations in the draw solution relative to the concentration of 

ions in the waste stream decreases, the osmotic pressure decreases. When the ion concentrations 

in the left and right cells are equal, the draw solution needs to be regenerated to restore the 

osmotic pressure difference and recover the treated water. The draw solution is circulated out of 

the FO unit and into an external unit (draw solute separation) where it can be regenerated. 

Regeneration is typically achieved using reverse osmosis or distillation, but chemical 

precipitation or thermal methods can also be used. The regeneration process creates a clean water 

stream and a regenerated draw solution for recycle in the FO unit. In some industrial 

applications, including UOG extraction wastewater, the dilute draw solution may be reused, 

eliminating the need for the secondary draw solute separation process (DCN SGE00684). 

Saline Feed 

Water

Concentrated 

Brine

Draw Solute 

Separation

Diluted Draw Solution

Concentrated Draw 

Solution Recycle

Treated 

Water

Semipermeable 

membrane

Water 

Flow
Part D

105

Part D. REFERENCE LIST AND SOURCE FLAGS

The EPA reviewed existing data sources, including journal articles and technical papers, 

technical references, industry/vendor telephone queries, and vendor websites to gather 

information for this report. The EPA identified all of the information described in this report 

from the sources listed in Table D-1. EPA assigned one of the following data source quality flags 

to each of the sources referenced:

 Source quality flag “A”: Journal articles and documents prepared by or for a 

government agency (e.g., EPA site visit reports, industry meeting notes)

 Source quality flag “B”: Documents prepared by a verified49 source that include 

citation information (e.g., operator reports, vendor documents, university 

publications)

 Source quality flag “C”: Documents prepared by a verified source that do not 

include citation information (e.g., operator reports, vendor documents, conference 

presentations)

 Source quality flag “D”: Documents prepared by a source that could not be 

verified and that do not include citation information

Table D-1. Reference List

ID DCN Source Citation 

Source 

Flaga

1

SGE00011 Veil, John A. 2010. Water Mgmt Technologies Used by Marcellus Shale Gas 

Producers. Prepared by Argonne National Lab. Prepared for U.S. DOE NETL.

A

2

SGE00046 Abdalla, Charles W. et. al. 2011. Marcellus Shale Wastewater Issues in PACurrent & Emerging Treatment & Disposal Technologies. Penn State 

Cooperative

B

3

SGE00070 Acharya, Harish; Matis, Hope; Kommepalli, Hareesh; Moore, Brian; Wang, 

Hua. 2011. Cost Effective Recovery of Low-TDS Frac Flowback Water for 

Re-use. 

A

4

SGE00095 URS. 2011. Water-Related Issues Associated with Gas Production in the 

Marcellus Shale. (March 25).

B

5

SGE00105 Papso, John. 2010. Cabot Gas Well Treated with 100% Reused Frac Fluid. 

Cabot Oil and Gas Corp., Superior Well Services, Inc., Kroff Chemicals, Inc..

B

6 SGE00108 Siemens. 2011. Total Water Management for the Oil & Gas Industry. Siemens. C

7

SGE00109 Takashi Asano. 2007. Water Reuse: An Integrated Approach to Managing the 

World's Water Resources. 

A

8

SGE00110 Bruff, Matthew. 2011. An Integrated Water Treatment Technology Solution 

for Sustainable Water Resource Management in the Marcellus Shale.

A

9

SGE00124 James Beckman. 2008. Dewvaporation Desalination 5,000-Gallon-Per-Day 

Pilot Plant.

A

 

49 The EPA considered sources as “verified” if we were able to find information about the author outside of the 

reference document. The EPA primarily verified information by looking for company/organization websites that 

confirmed the author’s affiliation with the UOG industry
Part D

106

Table D-1. Reference List

ID DCN Source Citation 

Source 

Flaga

10 SGE00126 A. Joseph Reed. 2002. Application of Electrodialysis Reversal Process to 

Remediate a Brine-Impacted Aquifer. ARCADIS G&M Inc..

C

11 SGE00127 U.S. EPA. 2000. Wastewater Technology Fact Sheet: Chemical Precipitation. A

12 SGE00133 Brent Means. 2004. Comparison of Three Methods to Measure Acidity of 

Coal-Mine Drainage.

A

13 SGE00139 Puder, M.G.; Veil, J.A. 2006. Offsite Comm. Disposal of Oil and Gas 

Exploration and Prod. Waste: Availability, Options, and Costs.

A

14 SGE00140 ALL Consulting. 2011. Water Treatment Technology Fact Sheet: 

Crystallization.

B

15 SGE00141 ALL Consulting. 2011. Water Treatment Technology Fact Sheet: 

Electrodialysis.

B

16 SGE00142 ALL Consulting. 2011. Water Treatment Technology Fact Sheet: Ion 

Exchange.

B

17 SGE00144 ALL Consulting. 2011. Water Treatment Technology Fact Sheet: Thermal 

Evaporation Distillation.

B

18 SGE00149 Intervras Technologies, LLC. 2011. EVRAS Evaporation Reduction and 

Solidification.

C

19

SGE00160 Adams, Andy. 2011. Telephone Communication with Andy Adams, 

INTEVRAS, and Brent Ruminski, Eastern Research Group Inc. “EVRAS 

Evaporation Technology.”

A

20

SGE00161 Alexander, Jerry. 2011. Telephone Communication with J. Alexander, 

Siemens, S. Hays, ERG “Siemens Reverse Osmosis Technology.” (September 

28).

A

21

SGE00162 D. Beagle. 2011. Phone Communication with D. Beagle, Drake Water 

Technologies, and B. Ruminski, ERG. “Higgins Loop Technology.” 

(September 26).

A

22 SGE00163 Burnett, D. 2011. Telephone Communication with David Burnett, Global 

Petroleum Research Institute, and Sarah Hays, Eastern Research Group, Inc.

A

23 SGE00164 Dennis, Rich. 2011. Telephone Communication with Rich Dennis, Severn 

Trent, and Brent Ruminski, Eastern Research Group, Inc. 

A

24

SGE00165 Drake, Ron. 2011. Telephone Communication with Ron Drake, Drake Water 

Technologies, and Brent Ruminski, ERG. “Ionflo Technology.” (September 

26).

A

25 SGE00166 Walter Weber. 1972. Physiochemical Processes: For Water Quality Control. A

26 SGE00167 Metcalf and Eddy, Inc. 2002. Wastewater Engineering: Treatment and Reuse. 

Fourth edition. McGraw-Hill, Inc.

B

27 SGE00175 Tom Hayes. 2004. The Electrodialysis Alternative for Produced Water 

Management. Gas Technology Institute.

A

28 SGE00177 John Crittenden. 2005. Water Treatment: Principles and Design. John Wiley & 

Sons, Inc..

A

29 SGE00178 American Water Works Association (AWWA). 2005. Water Quality & 

Treatment: A Handbook of community Water Supplies. McGraw-Hill.

A

30

SGE00195 U.S. EPA. 2000. Development Document for Effluent Limitation Guidelines 

and Standards for the Centralized Waste Treatment Industry EPA 821-R-00-

020.

A
Part D

107

Table D-1. Reference List

ID DCN Source Citation 

Source 

Flaga

31 SGE00197 U.S. EPA. 2004. Technical Support Document for the 2004 Effluent 

Guidelines Program Plan. U.S. EPA.

A

32 SGE00227 Mertz, Barry. 2011. Telephone Communication with Barry Mertz, 212 

Resource Corporation, and Brent Ruminski, Eastern Research Group, Inc.

A

33

SGE00228 Roman., Jaime. 2011. Telephone Communication with J. Roman, Fountain 

Quail, and B. Ruminski. ERG. “Fountain Quail Nomad Evaporator.” (October 

26)

A

34

SGE00230 Wilson, M. 2011. Telephone Communication with M. Wilson, GE, and B. 

Ruminski, ERG. “GE Power and Water: Wastewater Treatment Technologies.” 

Nov 10

A

35 SGE00238 William Shaw. 2011. The Real Cost of ZLD for Shale Gas Frac Water in the 

Marcellus Shale Play. HPD, LLC

C

36 SGE00239 Hefley, William, et al. 2011. The Economic Impact of the Value Chain of a 

Marcellus Shale Well. University of Pittsburgh. (August)

B

37 SGE00244 ERG. 2012. Camp, Meghan; Bicknell, Betsy; Ruminski, Brent. Notes on 

Conference Call with 212 Resources on 4 January 2012. (January 9)

A

38 SGE00245 ERG. 2012. Camp, Meghan et. al. Notes on Conference Call with Reserved 

Environmental Services, LLC on 5 January 2012. (February 1)

A

39 SGE00261 John Kiernan.1998. Selection of EDR Desalting Technology Rather Than 

MF/RO for the City of San Diego Water Reclamation Project. General Electric

B

40

SGE00264 CO School of Mines. 2009. An Integrated Framework for Treatment & Mgmt. 

of Produced Water: Technical Assessment of Produced Water Trtmnt 

Technologies

A

41 SGE00265 Hanson, Paul, P.E.. 2010. Memorandum to Public Record: Subject, Ion 

Exchange for Produced Water Treatment

A

42 SGE00275 U.S. EPA. 2012. Site Visit Report: Citrus Energy Corporation Marcellus Shale 

Gas Operations. (January 22).

A

43 SGE00276 U.S. EPA. 2012. Meeting with XTO Energy, Inc. about Unconventional Oil 

and Gas Sanitized.

A

44 SGE00285 Silva, 2012. Produced Water Pretreatment for Water Recovery and Salt 

Production. (January 26).

A

45 SGE00298.A21 Ron Pettengill. Innovative Water Management Strategies for Future Marcellus 

Development. Epiphany Solar Systems.

A

46 SGE00298.A23 Robie Cathey. 2012. Ecosphere. Ecosphere Tech. B

47

SGE00298.A24 Johan Themaat. 2012. Water Infrastructure Versus Mobile Options for 

Treating and Disposing Fracking and Produced Water. High Sierra Water 

Services.

C

48 SGE00299 U.S. EPA. 2012. Site Visit Report: US Gas Field Fluids Management 

(formerly Clean Streams) Marcellus Shale Gas Operations. (October 9).

A

49 SGE00300 U.S. EPA. 2012. Site Visit Report: Eureka Resources, LLC Marcellus Shale 

Gas Operations. (February 25).

A

50 SGE00305.A07 Aaron Horn. 2012. Comparing the Latest Innovations in Treatment 

Technology Based on Water Quality and Cost per Barrel. Hydrozonix.

C

51 SGE00306.A04 James Silva. 2012. Shale Gas Produced Water Pretreatment for Barium and 

Radium Removal. GE Global Research Center.

B
Part D

108

Table D-1. Reference List

ID DCN Source Citation 

Source 

Flaga

52 SGE00306.A06 Timothy Keister. 2012. Sequential Precipitation - Fractional Crystallization 

Treatment of Marcellus Shale Flowback and Production Wastewaters.

B

53 SGE00311.A01 Walter Dale. 2012. Sustainable Development of Completions. Haliburton 

Water Solutions.

C

54 SGE00331 Ely, John W., et al. 2011. Game Changing Technology for Treating and 

Recycling Frac Water. Society of Petroleum Engineering. SP SPE-214545-PP

A

55

SGE00333 Horn, A. 2009. Breakthrough Mobile Water Treatment Converts 75% of 

Fracturing Flowback Fluid to Fresh Water and Lowers CO2 Emissions. SPE121104-PP

B

56 SGE00358 Ecolotron Water Recovery Systems. 2011. Treatment of Flow Back and 

Produced Water from the Hydraulic Fracturing of Oil – Shale.

B

57 SGE00367 CARES. n.d. CARES McKean. Downloaded on 1/28/2013. C

58 SGE00369 Anticline Disposal, LLC. Unknown. Anticline Disposal, LLC. C

59 SGE00374 Red Desert. n.d. What Makes Our Water Treatment & Reclamation Facility So 

Advanced? Downloaded on 1/28/2013.

C

60 SGE00415 Thomas Hayes, et. al. 2012. Evaluation of the Aqua Pure Mechanical Vapor 

Recompression Sys. in the Trtmnt of Shale Gas Flowback Water. RPSEA.

B

61 SGE00421 Jay Ewing. 2008. Taking a Proactive Approach to Water Recycling in the

Barnett Shale. Devon Energy

B

62 SGE00478 Kasey, P. 2009. Gas Well Drilling Brine Treatment Facility Opens in 

Fairmont. The State Journal.

D

63 SGE00479 Kadramas, Lee & Jackson, Inc. 2012. Power Forecast 2012: Williston Basin 

Oil and Gas Related Electrical Load Growth Forecast.

B

64 SGE00523 Eureka Resources. 2013. The Technologies of Eureka Resources: Wastewater 

Distillation. May 30.

C

65 SGE00528 Gilmer, Ellen. 2013. Data Show More Marcellus Wastewater, More Injections. 

E&E News. (February 22).

C

66 SGE00601 U.S. EPA. 2001. Small Entity Compliance Guide: CWT Effluent Limitations 

Guidelines and Pretreatment Standards (40 CFR 437). EPA 821-B-01-003.

A

67 SGE00613 U.S. EPA. 2013. Meeting Summary: Meeting with Industry Representatives 

About the Unconventional Oil and Gas Effluent Guideline Rulemaking.

A

68 SGE00616 U.S. EPA. 2013. Summary of the Technical Workshop on Wastewater 

Treatment and Related Modeling. (April 18)

A

69 SGE00625 U.S. EPA. 2015. Site Visit Report: Southwestern Energy Fayetteville Shale 

Gas Operations. Sanitized.

A

70 SGE00635 U.S. EPA. 2012. Site Visit Report Chesapeake Energy Corporation Marcellus 

Shale Gas Operations Sanitized.

A

71 SGE00638.A11 Walter, Dale. 2013. H2OForward Service - Sustainable Development of 

Completions.

C

72 SGE00638.A12 Wilkerson, Tommy. 2013. Strategies for Sustainable Water Transport Lessons 

Learned in the Marcellus Applied to the Niobrara.

B

73 SGE00645 ALL Consulting. 2011. Vendor Profile: 212 Resources. C

74 SGE00646 ALL Consulting. 2011. Vendor Profile: AquaTech. C

75 SGE00647 ALL Consulting. 2011. Vendor Profile: Ecosphere Technologies, Inc. C
Part D

109

Table D-1. Reference List

ID DCN Source Citation 

Source 

Flaga

76 SGE00648 ALL Consulting. 2011. Vendor Profile: Fountain Quail. C

77 SGE00649 ALL Consulting. 2011. Vendor Profile: GeoPure Hydrotechnologies. C

78 SGE00650 ALL Consulting. 2011. Vendor Profile: INTEVRAS Technologies, LLC. C

79 SGE00651 ALL Consulting. 2011. Vendor Profile: MISWACO. C

80 SGE00652 ALL Consulting. 2011. Vendor Profile: Veolia. C

81 SGE00653 Ali, E., Yaakob, Z. 2012. Electro coagulation for Treatment of Industrial 

Effluents and Hydrogen Production. 

A

82 SGE00655 Baker Hughes. 2012. H2prO HMS Water Management Service. C

83

SGE00656 Bosque Systems, LLC. 2013. Water Trmt Solutions Using Electro 

Coagulation. http://www.bosquesystems.com/pdf/INSMWR06-13%20-

%20MWRU%20-%20Bosque.pdf

C

84 SGE00657 Brant , J. Unk. Oil and Gas Produced Water Treatment Technologies.

http://nexusgroupsolutions.com/TechnicalBrief_Produced%20Waters.pdf

B

85 SGE00658 Panu, Marc et al. 2013. Design of a Mobile Wastewater Treatment System for 

Hydraulic Fracturing Waste. Chevron Group. (April 19).

B

86 SGE00659 Christen, K. 2006. Desalination technology could clean up wastewater from 

coal-bed methane production. http://pubs.acs.org/doi/abs/10.1021/es062630s.

A

87

SGE00660 CO Department Of Public Health And Env. 2011. CDPS Fact Sheet To Permit 

Number Co0048739 Bopco, L.P., Yellow Creek Water Mgmt Facility Rio 

Blanco Co. 

A

88 SGE00661 Hause, Jennifer et al. 2010. Zero Discharge Water Management for Horizontal 

Shale Gas Well Development.

A

89 SGE00662 Emis. 2010. Membrane Distillation. Available online at: 

http://www.emis.vito.be/techniekfiche/membrane-distillation?language=en

C

90 SGE00663 Gryta, Marek. 2011. Water Desalination by Membrane Distillation. Available 

online at: http://www.intechopen.com/download/get/type/pdfs/id/13752

A

91 SGE00664 Heartland Technologies, LLC. 2013. Produced Water Treatment.

http://www.heartlandtechnologypartners.com/solutions/produced-watertreatment/

C

92 SGE00665 Hickenbottom, Kerri L. et al. 2013. Forward osmosis treatment of drilling mud 

and fracturing wastewater from oil and gas operations.

A

93 SGE00666 Kmx Corp. 2014. Membrane Distillation – Contaminated Water. C

94 SGE00667 Lord, R. LeBas; Luna, D.; Shahan, T. 2013. Development and Use of HighTDS Recycled Produced Water for Crosslinked-Gel-Based Hydraulic 

Fracturing. 

B

95 SGE00668 Mendez, Enrique. 2012. Sustainable desalination: Membrane distillation 

delivers greener clean water. 

B

96 SGE00670 Omni Water Solutions. 2014. Frac Water. Treating Flowback and Produced 

Water for Re-Use.

C

97 SGE00671 OriginOil. 2013. EWS Petro P160 "Clean-Frac: Process and Equipment 

Description. http://www.originoil.com/pdf/OriginOil-EWS-Petro-P160-DataSheet.pdf

C

98 SGE00672 OriginOil. 2013. Originoil’s Clean-Frac: An Overview. (June) C
Part D

110

Table D-1. Reference List

ID DCN Source Citation 

Source 

Flaga

99 SGE00673 Porada, S. 2013. Review on the science and technology of water desalination 

by capacitive deionization. 

A

100 SGE00674 Purestream. 2011. Welcome to Purestream. B

101 SGE00675 Shafer, Lee. 2010. A Working Model for Oil and Gas Produced Water 

Treatment. 

C

102 SGE00677 Tinto, Joseph, and Solomon, Robert. 2012. Water Recovery via Thermal 

Evaporative Processes for High Saline Frac Water Flowback.

C

103 SGE00678 Walton, J. 2004. Solar and Waste Heat Desalination by Membrane Distillation. 

http://www.usbr.gov/research/AWT/reportpdfs/report081.pdf

A

104 SGE00679 Wickramasinghe, R., Jones, S. 2013. Treating Hydraulic Fracturing Flowback 

Waters: Potential New Membrane Applications Webinar. (Dec 11).

C

105 SGE00681 Yukon College. 2012. Capacitative Deionization in Mine Water Recycling. C

106 SGE00682 ALL Consulting. 2011. Vendor Profile: Altela C

107 SGE00683 ALL Consulting. 2011. Water Treatment Technology Fact Sheet: Reverse 

Osmosis.

B

108 SGE00684 Coday, B.D. et al. 2014. The sweet spot of forward osmosis: Trmt of produced 

water, drilling ww, and other complex and difficult liquid streams. 

A

109 SGE00685 Global Water Intelligence. 2011. Produced Water Recycling Oasis flourishes 

in Wyoming. (February).

D

110 SGE00688 AquaTech International Corporation. 2011. Mobile Water Distillation System. C

111 SGE00689 M-I SWACO. 2009. Frac Water Reclamation System Reduces Operator’s 

Water Cost. 

C

112 SGE00690 ALL Consulting, LLC. 2006. A Guide to Practical Management of Produced 

Water from Onshore Oil and Gas Operations in the United States

B

113 SGE00691 U.S. EPA. 2013. Summary of the Technical Workshop on Water Acquisition 

Modeling: Assessing Impacts Through Modeling and Other Means. 

(September).

A

114 SGE00705 ERG. 2014. Ruminski, Brent. Notes on Call with Hydrozonix, LLC on 7 

February 2014. (March 7).

A

115 SGE00706 Ecosphere Energy Services, LLC. 2011. 100 percent Frac Water Recycling -

Strategy & Focus Ozonix®. (April 13).

B

116 SGE00707 Horn, A; Patton, M; Hu, J. 2013. Minimum Effective Dose: A Study of 

Flowback and Produced Fluid Treatment for Use as Hydraulic Fracturing 

Fluid.

B

117 SGE00708 Environmental Leader. 2013. Unconventional E&P “$8 Billion of US Water 

Services Market.” (November 11).

B

118 SGE00709 Natural Gas Europe. 2012. Flowback Water Driving Flurry of Activity in 

Water Treatment (May 22).

B

119 SGE00710 Slutz, J; Anderson, J; Broderick, R; Horner, P. 2012. Key Shale Gas Water 

Management Strategies: An Economic Assessment Tool. (September 11).

B

120 SGE00714 Ziemkiewicz, Paul et al. 2012. Zero Discharge Water Management for 

Horizontal Shale Gas Well Development. 

A

121 SGE00722 IHS. 2012. Water Management in Shale Gas Plays. (August) B
Part D

111

Table D-1. Reference List

ID DCN Source Citation 

Source 

Flaga

122 SGE00761 U.S. EPA. 1989. Letter from T.P. O'Farrell (EPA) to C.B. Harriman (Steptoe 

& Johnson) about applicability of 40 CFR 435 Subpart C to CBM operations. 

A

123 SGE00957 ERG. 2013. Environmental Engineering Support for Clean Water Regulations 

Programmatic Quality Assurance Project Plan (PQAPP).

A

124 SGE00958 ERG. 2014. Unconventional Oil and Gas (UOG) Supplemental Quality 

Assurance Project Plan (SQAPP).

A

125 SGE01192 U.S. Energy Information Administration. 2015. Annual Energy Outlook 2015

with Projections to 2040. 

A

126 SGE01033 ALL Consulting. Water Treatment Technology Fact Sheet: UV Light. 

http://www.all-llc.com/publicdownloads/UVLightFactSheet.pdf

B

127 SGE01034 Atg UV Technology. 2015. SRB Treatment. C

128 SGE01035 Bosque Systems, LLC. 2013. Case Study CSDIO001. C

129 SGE01036 Bosque Systems, LLC. 2013. Water Trmt Sol'n Using Chlorine Dioxide: 

DIONIX. http://www.bosquesystems.com/pdf/INSDIO06-13%20-

%20DIONIX%20-%20Bosque.pdf

C

130 SGE01037 PureLine. 2014. About ClO2. http://www.pureline.com/about-clo2/ C

131 SGE01041 U.S. EPA. 1999. Wastewater Technology Fact Sheet: Ultraviolet Disinfection. A

132 SGE01042 Wang, J. et al. 2005. Successfully Sterilizing the Sulfate Bacteria With 

Ultraviolet Radiation in Produced-Water Treatment in Daqing Oilfield.

B

133 SGE01044 Lee, D et al. 2007. Eff. of Oil/Water Sep. Ctrl by Gas Bub. Size & Fluid Dyn. 

w/in the Sep. Vessel. 

B

134 SGE01046.A02 Smith, D. 2014. Determining the Min. Treat. Levels Required for Prod. 

Efficiency.

B

135 SGE01046.A05 Wrenn, Brian A., 2014. Optimizing the Treatment of Produced Water and 

Flowback for Reuse or Disposal. 

B

136 SGE01047 U.S. EPA. 2015. Site Visit Report Seneca Resources Corporation, Covington, 

PA.

A

137 SGE01048 Zhou, H and D. Smith 2002. Advanced technologies in water and wastewater 

treatment. http://www.ozomax.com/pdf/Article_O3_treat_for_waste_water.pdf

B

138 SGE01050 Kimball, Bob. 2010. High Recovery Reverse Osmosis for Treatment of 

Produced Water.

B

139 SGE01051 Drewes, Jorg E; et al. 2009. Opportunities, Challenges, and Research Needs 

for Beneficial Use of CBM Produced Water

B

140 SGE01054 Atg UV Technology. Unconventional Gas (Fracking). B

141 SGE01057 Halliburton Multi-Chem. 2013. CleanStream® Service Capabilities. C

142 SGE01058 Halliburton Multi-Chem. 2014. CleanStream® Water Treatment Service 

Frequently Asked Questions. 

C

143 SGE01059 Sabre Energy Services, LLC. 2011. Oil Field Case Study: Disinfecting Water 

for Well Fracturing with Chlorine Dioxide. 

C

144 SGE01067 ERG. 2015. International Water Conference 2014. A

145 SGE01080 Fajt, James. 2012. Capacitive Deionization (CDI). M-I SWACO, A 

Schlumberger Co_CBI. (November 11).

C

146 SGE01081 Alkhudhiri, Abdullah. 2012. Membrane distillation: A comprehensive review. 

Desalination. (August 11).

B
Part D

112

Table D-1. Reference List

ID DCN Source Citation 

Source 

Flaga

147 SGE01082 Atlantis Technologies. 2012. Technical Summary Radial Deionization. 

http://www.deionizing.com/technology.html. Accessed on November 26, 2014.

B

148 SGE01083 Kim, A.S. 2012. A two-interface transport model with pore-size distribution 

for predicting the performance of direct contact membrane distillation. 

B

149 SGE01084 Shaffer et al. 2013. Desalination and Reuse of High-Salinity Shale Gas 

Produced Water: Drivers, Technologies, and Future Directions. (July 25).

B

150 SGE01085 Refrakt. 2012. Purifying oil and gas produced water with membrane 

distillation. https://angel.co/refrackt-1. Accessed on February 6, 2015.

B

151 SGE01086 Biesheuvel, P.M., A. van der Wal. 2010. Membrane capacitive deionization. 

Journal of Membrane Science. (September 18).

B

152 SGE01087 Li, Haibo, Linda Zou. 2011. Ion-exchange membrane capacitive deionization: 

A new strategy for brackish water desalination. (February 11).

B

153 SGE01111 Litvak, Anya. 2014. Engineering firm ventures into wastewater, LNG. 

Pittsburgh Post-Gazette.

D

154 SGE01118 Tischler, A, et al. 2010. Controlling Bacteria in Recycled Production Water for 

Completion and Workover Operations. Society of Petroleum Engineers.

A

155 SGE01119 Crane, B, et al. 2011. Improved Process Provides More Effective Ultraviolet 

Light Disinfection of Fracturing Fluids. Society of Petroleum Engineers.

A

156 SGE01120 Rodvelt, Gary, et al. 2011. Case History: Challenges Using UV Light to 

Control Bacteria in Marcellus Completions. Society of Petroleum Engineers.

A

157 SGE01121 McCutchan, Morgan. 2013. Water Management Overview, Chlorine Dioxide, 

Detail Case History. Baker Hughes.

B

158 SGE01126 U.S. EPA. 2015. Assessment of the Potential Impacts of Hydraulic Fracturing 

for Oil and Gas in Drinking Water Resources. ORD.

A

159 SGE01140 Veil, J. 2011. Produced Water Mgmt Options & Technologies. Chapter 29 of 

Produced Water: Environmental Risks and Advances in Mitigation 

Technologies.

A

160 SGE01168 Myers, J.E. 2014. Chevron San Ardo Facility Unit (SAFU) Beneficial 

Produced Warer Reuse for Irrigation. Chevron. Society of Petroleum 

Engineers.

A

161 SGE01178 ERG. 2016. Analysis of Centralized Waste Treatment Facilities (CWTs) 

Accepting UOG Extraction Wastewater.

A

162 SGE01179 ERG. 2016. Data Compilation Memorandum for the Technical Development 

Document (TDD).

A

163 SGE01181 ERG. 2016. Unconventional Oil and Gas (UOG) Drilling Wastewater 

Memorandum

A

164 SGE01184 ERG. 2016. Unconventional Oil and Gas (UOG) Produced Water Volumes and 

Characterization Data Compilation Memorandum

A

165 SGE01188 U.S. EPA. 2016. Technical Development Document for Effluent Limitations 

Guidelines and Standards for Oil and Gas Extraction.

A

166 SGE01193 Lester, Y., et al. 2013. Can We Treat Hydraulic Fracturing Flowback with a 

Conventional Biological Process? The Case of Guar Gum.

A

167 SGE01209 Krasner, S.W., et al. 2006. Occurrence of a New Generation of Disinfection 

Byproducts. Environmental Science & Technology.

A
Part D

113

Table D-1. Reference List

ID DCN Source Citation 

Source 

Flaga

168 SGE01228 Tipton, D.S. 2015. Assessment of Coilchem's Water Treatment Technology. 

ALL Consulting.

C

169 SGE01242 Ohio Department of Natural Resources (OH DNR). 2015. 2015 Quarterly 

Horizontal Shale Production: 2nd Quarter.

A

170 SGE01248.A01 JS Meyer Engineering. 2015. Public Comment EPA-HQ-OW-2014-0598-

0969: Oil and Gas Frack, Produced Flowback Water Processing Technology.

C

171 SGE01249 ERG. 2015. Terra Agua Call Notes. A

172 SGE01261 ERG. 2016. CoilChem, LLC Treatment Technology Memorandum. A

173 SGE01273 Gradiant. 2016. Gradiant: Operations. www.gradiant.com/operations. C

174 SGE01274 Talbot, D. 2014. How to Clean the Gas and Oil Industries’ Most Contaminated 

Water. MIT Technology Review.

D

175 SGE01342 Water Tectonics. 2016. Oil & Gas. C

176 SGE01343 Anguil Aqua Systems. 2016. Frac Water Reuse Technologies. C

177 SGE01065 ERG. 2015. Site Visit Report for Reserved Environmental Services, LLC

Mt. Pleasant, PA Centralized Waste Treatment.

A

178 SGE01346 ERG. 2016. 6th Annual Shale Plays Water Management Marcellus and Utica 

2016 Conference Notes.

A

179 SGE00298.A24 Johan Themaat. 2012. Water Infrastructure Versus Mobile Options for 

Treating and Disposing Fracking and Produced Water. High Sierra Water 

Services.

B

180 SGE00369 Anticline Disposal, LLC.. Unknown. Anticline Disposal, LLC. B

181 SGE00507 Boschee, Pam. 2012. Handling Produced Water from Hydraulic Fracturing. Oil 

& Gas Facilities.

A

182 SGE01264 WY DEQ. 2015. Permitted Commercial Oil Disposal Facilities. (September 1). B

183 SGE01354 U.S. EPA. 2013. Meeting with Purestream Technology about Treatment 

Technologies Relevant to the Unconventional Oil and Gas Industry. 

(November 8).

A

a—Source Flag A - Journal articles and documents prepared by or for a government agency (e.g., site visit reports, 

industry meeting notes); 

Source Flag B - Documents prepared by a verified source50 that include citation information (e.g., operator 

reports, vendor documents, university publications); 

Source Flag C - Documents prepared by a verified source that do not include citation information (e.g., operator 

reports, vendor documents, conference presentations); and 

Source Flag D - Documents prepared by a source that could not be verified and that do not include citation 

information.

 

50 The EPA considered sources as “verified” if we were able to find information about the author outside of the 

reference document. The EPA primarily verified information by looking for company/organization websites that 

confirmed the author’s affiliation with the UOG industry
Part E

114

Part E. ATTACHMENT
115

Attachment 1: UOG Extraction Wastewater Treatment Technology Costs & Performance 

Data 

(DCN SGE01186.A01)