Abstract:
The invention relates to the treatment of chemical process wastewaters and chemical waste landfill leachates containing obnoxious and hazardous halogenated organic chemicals by the use of a combination of physical, chemical and biological processes to produce a liquid discharge acceptable to the environment in an efficient and economical manner.

Description:
This application is a continuation of application Ser. No. 714,435, filed Mar. 21, 1985, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     Since World War II the chemical industry has grown to the point where there are over 35 million metric tons of hazardous wastes being generated. Large quantities of these wastes contain synthetic halogenated materials such as found in dielectric fluids, flame retardants, refrigerants, heat transfer fluids, lubricants, protective coatings, pesticides, and herbicides. Furthermore, it is well known that both the petroleum industry and the coal industry contribute many more millions of metric tons of hazardous chemical wastes to be disposed of which contain obnoxious organic compounds. Many of these materials are non biodegradable or recalcitrant, i.e., difficult to biodegrade. 
     In many cases, these materials and the by-products or residues from their manufacture have been accumulated in landfills or discharged (treated or partially treated) into the conduits of municipal sewer systems. In the case of landfills and over the course of time, and by a process of liquifaction, the contents of the landfill ultimately produces a leachate which must be disposed of. 
     In the case of disposing of chemical wastewaters into the municipal systems, the chemical wastewaters are mixed and diluted into the municipal wastes, and they become contaminants which are difficult or impossible for the municipal wastewater treatment plants to handle in a way which meets the standards of disposal of such wastewaters and the sludges produced, set up by the Federal and State governments. In some cases the toxic chemicals pass through the municipal wastewater treatment system and show up &#34;untreated&#34; in the waste sludge and final effluents. 
     All kinds of methods and techniques have been proposed and used for disposing of and/or treating these chemical wastes and their by-products to make them compatible with the environment. In spite of all the effort and money being spent, no technology has evolved which is economically and technically satisfactory. 
     The present state-of-the-art for treating chemical process wastewaters and chemical landfill leachates involves employing a series of process steps which are difficult to manage and/or operate economically with results that meet the stringent effluent restrictions imposed by Federal and State laws. 
     BRIEF DESCRIPTION OF THE INVENTION 
     This invention relates to an integrated biological-adsorption process for treating wastewaters containing halogenated organic compounds to render them acceptable in the natural environment without adverse effects and in an efficient and economical manner. More particularly, this invention relates to the method for treating chemical process wastewaters and chemical waste landfill leachates containing obnoxious and hazardous halogenated organic compounds, by a process which comprises: 
     1. introducing the wastewater to be treated into an equalization zone to produce a substantially uniform liquid phase composition and to allow for sedimentation of undissolved solids; 
     2. transferring the equalized wastewater to a pretreatment zone, subjecting the said liquid to neutralization and oxidation to cause precipitation of metal hydroxides, which metals are present in the wastewater, such as iron, which adsorbs a portion of organic pollutants, and separating the precipitate so formed from the treated liquid; 
     3. transferring the pretreated wastewater, produced in Step 2, to a biological treatment zone to remove substantially all biodegradable organic constituents of the wastewater; 
     4. transferring the bio-treated wastewater to a carbon adsorption treatment zone to remove the balance of organic pollutants and to produce a discharge acceptable to the natural environment. 
     We have now found that the suspended solids produced in the physiochemical treatment step of our process removes a significant proportion of the nonbiodegradable halogenated organic compounds so that the biotreatment process may be economically employed in accordance with our invention to remove virtually all organic compounds remaining in the wastewater which are biodegradable, thereby allowing for the efficient and economical use of the carbon adsorption system for removing the balance of organic pollutants to produce a liquid discharge acceptable to the environment without adverse effects. 
     Still further, we have found that the carbon consumption rate for the adsorption system which is required for treating wastewaters containing high concentrations of organic pollutants is reduced by more than 90 percent after treatment of wastewater in sequencing batch bioreactors in accordance with our invention. Furthermore, our process is sufficiently flexible to accommodate changes in wastewater characteristics and operating variables as will be disclosed more fully herein after. 
     We have also found that the sequencing batch reactor biological treatment systems are particularly effective when combined and integrated into the overall wastewater treatment systems of our invention. 
     THE PRIOR ART 
     Processes for treating chemical wastewater and chemical landfill leachates are of course known and practiced in industry in order to comply with the municipal, state and federal laws governing the discharge of wastes. The 1972 Water Pollution Control Act (PL 92-500) which was amended in 1977 as the Clean Water Act (PL 95-217) required the U.S. Environmental Protection Agency (EPA) to set standards in 1984 on the control of effluents for conventional parameters such as chemical oxygen demand (COD), biochemical oxygen demand (BOD) as well as for a large number of toxic priority pollutants including many halogenated organic compounds. Accordingly, many new technologies have been proposed for complying with these new standards. 
     The present state-of-the-art for treating chemical landfill leachates is described in W. J. McDougall, R. A. Fusco, and R. P. O&#39;Brien in &#34;Containment and Treatment of the Love Canal Landfill Leachate&#34; in Journal Water Pollution Control Federation, Vol. 52, pg. 2914-2924 (1980). 
     An overview and assessment of biological treatment systems relative to their overall applicability to industrial processing waste streams which discusses the various processes which may be considered including enzyme treatment, activated sludge, trickling filter, aerated lagoon, waste stabilization pond, anaerobic digestion and composting was given by Sandra L. Johnson in &#34;Unit Operations for Treatment of Hazardous Wastes&#34; (1978), pages 168 through 217 published by Noyes Data Corporation. 
     A review of physiochemical carbon adsorption process may be found in an article by Wei-chi Ying and Walter J. Weber, Jr. entitled &#34;Bio-physiochemical Adsorption Systems Model&#34;, Journal Water Pollution Control Federation, Vol. 51, pg. 2661-2677 (1979). 
     More specifically, several recent patents have been issued which address specific problems to be solved in safely disposing of process wastewater. 
     A recent development in the biological treatment of wastewater designated as Sequencing Batch Reactors (SBR) is reported by Robert L. Irvine, and Arthur W. Bush in &#34;Sequencing Batch Biological Reactors--An Overview&#34; in Journal Water Pollution Control Federation, Vol. 51, No. 2, pg. 235-304 (1980). 
     The SBR process consists of five sequential biotreatment steps. The wastewater is fed, during FILL, to a tank, which contains acclimated activated sludge from the previous cycle. Aeration and mechanical mixing are provided while feeding and/or subsequently during REACT, to enhance the rate of aerobic biodegradation. After the mixed liquor is biologically stabilized as indicated by small oxygen utilization rate, air and mixing are stopped, and clarification takes place in the SETTLE step. During DRAW, the clear supernatant is withdrawn from the reactor for carbon adsorption treatment. The SBR cycle was either repeated immediately or the reactor was kept in IDLE until the FILL time in the next cycle. 
     Most recently, U.S. Pat. No. 4,477,570 issued Oct. 16, 1984, which is owned by the common assignee of this application, discloses the biodegradation of halogenated organic chemicals employing new found life forms. 
     Copending application, Ser. No. 381,866 filed May 24, 1982 now U.S. Pat. No. 4,511,657 issued Apr. 16, 1985, which is also owned by the common assignee of this application and in which one of the present applicants is a co-inventor discloses the use of the new life forms described in U.S. Pat. No. 4,477,570 as innoculants in biological wastewater treatment systems. 
     These and many other processes have been proposed for treating chemical wastewaters and/or chemical landfill leachates to make them compatible with the natural environment; however, they involve expensive and/or complicated techniques. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     In order that our invention may be more readily understood, we shall describe it with respect to the following specific embodiments and examples; however, it shall be understood that we do not intend to be limited thereby, except as defined in the appended claims. 
     EXAMPLE I 
     Several batches of aqueous leachate from a chemical landfill in Niagara Falls, N.Y., having a composition which includes organic compounds and halogenated organic compounds as exemplified in Table 1 were introduced into our equalization zone consisting of a 2000-L storage vessel. The combined leachate is maintained in a quiescent condition until a substantially uniform aqueous phase is formed. The supernatant was analyzed and found to have characteristics as shown in Table 2. 
     400 liters of said leachate were introduced into a pretreatment zone consisting of a 500-L plastic tank equipped with inlets for air, and sludge, and a mechanical mixer. Concentrated sodium hydroxide solution was added to this 400 liters of leachate while the mixer was operating and until the pH was equal to 7.5, causing precipitates to be formed. Air was introduced through the air inlet to this body of leachate over the course of about two hours, and this caused oxidation and more precipitates to be formed. After the immediate chemical oxygen demand was satisfied, air and mixing were stopped, and separation of precipitates by sedimentation was allowed. The composition of the pretreated leachate is also given in Table 2. 
     The sludge produced in the pretreatment zone was periodically removed and disposed of in a secure landfill. The pretreated leachate was then transferred to the biological treatment zone consisting of three parallel 500-L SCR tanks, each equipped with inlets for pretreated leachate feed, air, and nutrients, and a mechanical mixer. 
     The wastewater was fed, and solution of nutrients (NH 4  Cl, KH 2  PO 4 ) were added during FILL, to each tank, which contained acclimated activated sludge from the previous cycle which was obtained originally from a nearby publicly owned treatment works (Wheatfield, N.Y., 14304). Aeration and mechanical mixing were provided while feeding and/or subsequently during REACT to enhance the rate of aerobic biodegradation. After the mixed liquor was biologically stabilized as indicated by reduced rate of oxygen utilization, air and mixing were stopped, and clarification took place in the SETTLE step. During DRAW, the clear supernatant was withdrawn from the reactor for carbon adsorption treatment. The SBR cycle was either repeated immediately or the reactor was kept in IDLE until the FILL time in the next cycle. The SBR operating and cycle schedules are described in Table 3. 
     The bio-treated leachate, the composition of which is given in Table 4, was then transferred to the adsorption zone consisting of two carbon adsorbers in series. Each adsorber had a diameter of 8.0 cm and a depth of 120 cm packed with 3 Kg of Calgon Service carbon. After a residence time of 40 minutes in the adsorber effluent was discharged. The final effluent met the existing discharge limits as given in Table 5. 
     EXAMPLE II 
     In adsorption treatment of a chemical landfill leachate the capacity of activated carbon for each of the several major organic constituents are much lower than the capacity for the same compound in pure water because of competitive adsorptive of other adsorbable constituents, as shown in Table 6. The residual organic compounds, especially halogenated organics in the bio-treated leachate, as produced in the process described of Example I, are well adsorbed on activated carbon. Table 7 shows that the carbon capacity for total organic carbon (TOC) in the bio-treated leachate was the same as in the untreated leachate; however, it shows that the carbon capacity for total organic halides (TOX) was improved very substantially. 
     Since the biotreatment in a SBR reduces the TOC of a leachate by more than 90 percent, it follows that the carbon consumption rate would be reduced by at least 90 percent if the biotreatment is placed before carbon adsorption in accordance with our invention. The expected cost savings over a ten year period in treating a chemical landfill leachate employling the process of this invention is given in Table 8. 
     The five SBR steps are often overlapped, and one or two steps may be omitted in a particular treatment cycle. The withdrawal of effluent may start as soon as a clear zone of supernatant is formed, and the wastewater feeding may being immediately after the completion of the DRAW step of the last SBR cycle. Many combinations of feeding, aeration, and mixing strategies are possible. The required nutrients are either supplemented to the feed or added directly to the bioreactor. The sludge wasting is accomplished by removing a portion of the settled sludge in the DRAW or IDLE step. The optimum SBR operating and cycle schedules must be experimentally established in accordance with the teachings given herein for a wastewater to achieve the specific treatment objectives. The hydraulic retention time (HRT) may be varied between 1 to 20 days, and the mixed liquor suspended solids (MLSS) may vary between 2000 and 15000 ppm. The SBR cycle time may also be varied from 8 hours to a few days. The excess biomass was also periodically removed and disposed of in a secure landfill. 
     The wastewaters which may be treated in accordance with our invention may vary widely in their composition and makeup. For example, the process of this invention allows for treating wastewaters from chemical landfills, such as the leachate specifically exemplified in the foregoing example. In addition, this invention allows for treatment of chemical wastewaters directly emanating from chemical manufacturing operations such as petroleum, food processing, and other industrial plants issuing waste pollutants. 
     The biological treatment techniques that may be employed in accordance with our invention, other than the SBR technique, include such variations as trickling filter, aeration pond, oxidation ditch, contact stabilization, rotating biological contactor, among others. 
     In the foregoing specific example of our invention which illustrates a preferred embodiment, we may employ several other adsorbents other than activated carbon, such as activated alumina, molecular sieves, etc. Furthermore, either virgin or regenerated adsorbents may be used to produce effluent within the discharge limits. 
     It should be understood that, although we have emphasized the treatment of wastewater containing significant quantity of halogenated organic compounds, our invention should not be construed as limited to these compounds because our integrated treatment process not only removes these recalcitrant and obnoxious compounds to acceptable limits, but also at the same time, eliminates less recalcitrant and undesirable compounds, such as oil, grease, fats, and hydrocarbons in general. 
     The foregoing detailed description has been given to enable an understanding of our invention; however, we do not intend to be limited to the exact details or the specific examples for many obvious modifications will occur to those skilled in art. 
     
                       TABLE 1______________________________________Compilation of Organic Compounds TypicallyFound In Chemical Waste LandfillsEmpiricalFormula  Compound Name______________________________________C.sub.7 H.sub.7 Cl    Chloromethylbenzene (isomer)C.sub.9 H.sub.12    C-3 AlkylbenzeneC.sub.6 H.sub.4 Cl.sub.2    Dichlorobenzene isomerC.sub.8 H.sub.11    2,4-Dimethyl-3-HexanoneC.sub.10 H.sub.14    C-4 AlkylbenzeneC.sub.7 H.sub.6 Cl.sub.2    Dichlorotoluene isomerC.sub.7 H.sub.14 O    2,2-Dimethyl-3-PropyloxiraneC.sub.4 Cl.sub.6    HexachlorobutadieneC.sub.6 H.sub.3 Cl.sub.3    Trichlorobenzene isomerC.sub.11 H.sub.24 or    Saturated HydrocarbonC.sub.16 H.sub.34C.sub.12 H.sub.24 O.sub.2    Undecanoic Acid MethylesterC.sub.7 H.sub.5 Cl.sub.3    Trichlorotoluene isomerC.sub.8 H.sub.7 O.sub.2 Cl    Methylester Chlorobenzoic Acid isomerC.sub.6 H.sub.2 Cl.sub.4    Tetrachlorobenzene isomerC.sub.10 H.sub.23 ON    O--Decyl-HydroxylamineC.sub.7 H.sub.5 Cl.sub.2    Trichlorotoluene isomerC.sub.10 H.sub.21 Cl    1-ChlorodecaneC.sub.6 H.sub.2 Cl.sub.4    Tetrachlorobenzene isomerC.sub.12 H.sub.10    1,1-BiphenylC.sub.12 H.sub.10 O    1,1-Oxybis-BenzeneC.sub.11 H.sub.24    UndecaneC.sub.7 H.sub.4 Cl.sub.4    Tetrachlorotoluene isomerC-9 or C-12    Branched Saturated HydrocarbonC.sub.10 H.sub.10 O.sub.3    Beta-Oxo-Benzenepropanoic Acid MethylesterC.sub.8 H.sub.18 O.sub.2    1,3-Hexanediol-2-EthylC.sub.8 H.sub.18 O    1-PropoxypentaneC.sub.9 H.sub.18    3,4,5-Trimethyl-1-HexeneC.sub.14 H.sub.14    1,1-Ethylidenebis-BenzeneC.sub.14 H.sub.14    1,1-Biphenyl-2-EthylC.sub.10 H.sub.21 Cl    1-ChlorodecaneC.sub.15 H.sub.32    2,5-DimethyltridecaneC.sub.16 H.sub.34    HexadecaneC.sub.13 H.sub.16 O.sub.2    Cyclohexylbenzoic Acid EsterC.sub.12 H.sub.14 O.sub.4    Diethylester 1,2-Benzenedicarboxylic AcidC.sub.5 H.sub.2 Cl.sub.6    HexachlorocyclopentadieneC.sub.10 H.sub.11 OCl    1-(4-Chlorophenyl)-1-ButanoneC.sub.14 H.sub.29 Cl    1-ChlorotetradecaneC.sub.7 H.sub.14 O--50    3-MethylcyclohexanolC.sub.5 H.sub.10 O.sub.2    Tetrahydropyran-2-olC.sub.14 H.sub.10    PhenanthreneC.sub.10 H.sub.12 O.sub.2 S    3-Phenylmethylthio Propanoic AcidC.sub.20 H.sub.10 O    1-Ethenyloxy-OctadecaneC.sub.7 H.sub.2 Cl.sub.6    1,2,3,4,7,7-Hexchloro Bicyclo-2,2,1-hepta-2,5-dieneC.sub.14 H.sub.12    1,1-Ethenylidene bis benzeneC.sub.18 H.sub.37 Cl    1-ChlorooctadecaneC.sub.16 H.sub.22 O.sub.4    Butyl-2-Methylpropyl Ester 1,2-Benzene-    dicarboxylic AcidC.sub.7 H.sub.8 S    Benzene MethanethiolC.sub.14 H.sub.14 S    1,1-Thiobis(methylene)bis-BenzeneC.sub.14 H.sub.10 Cl.sub.2    1,2-Bis(p-Chlorophenyl)EthyleneC.sub.10 H.sub.22 O    2,2-Dimethyl-1-OctanolC.sub.6 H.sub.9 OCl    3-Chlorobenzene EthanolC.sub.14 H.sub.22 O.sub.3    2,2,2-Triethoxyethyl-BenzeneC.sub.24 H.sub.38 O.sub.4    Diisooctylester-1,2-Benzenedicarboxylic Acid______________________________________ 
    
     
                       TABLE 2______________________________________Characteristics of Typical Rawand Pretreated Hyde Park Leachates                          PretreatedParameter.sup.a   Raw Leachate Leachate.sup.b______________________________________pH                   4.3          7.5Total organic carbon (TOC)             3500         3200Chemical oxygen demand (COD)             10040        9200Biological oxygen demand             7500         7200Suspended solids (SS)             900           80Volatile suspended solids             300           40Total dissolved solids             25700        22400Orthophosphate phosphorus             &lt;1            &lt;1Acid-hydrolyzable phosphorus              3             3Total phosphorus  131           92Ammonia nitrogen  150           130Total kjeldahl nitrogen             180           160Nitrate nitrogen   20           20Nitrite nitrogen  &lt;5            &lt;5______________________________________ .sup.a All values, except pH, are given in mg/L. .sup.b Pretreatment consisted of neutralization with NaOH to a pH of 7.5, two hours of aeration, and two hours or longer of settling. 
    
     
                       TABLE 3______________________________________Examples of SBR Operating and Cycle Schedules            Sequencing Batch ReactorOperating Schedule A       B       C______________________________________Wastewater feed    (pretreated leachate)Sterilization of feed              (no)Bacterial supplementation              (no)SBR cycle time, hour              (24)Working volume, liter              (300)Feeding, % working volume               20       20      50Hydraulic retention time, day                5       5       2Mixed liquor suspended solids,              5000    10000   10000mg/LTime per SBR cycle, hourFILL (air &amp; mixing)              (6)REACT (air &amp; mixing)              (10)SETTLE             (2)DRAW               (5)IDLE               (1)______________________________________ 
    
     
                                           TABLE 4__________________________________________________________________________Results of SBR Biological Treatment of Leachate.sup.aSBR   TOC COD TOX.sup.b             SS HET acid                      Phenol                          Benzoic acid                                 o-CBA.sup.c                                      m-CBA                                           p-CBAsample (mg/L)__________________________________________________________________________Feed  2000     5300         325    260   530 730    350  110  110A effluent 140  510         110 114                170   6   6      12   25   3B effluent 120  400         105 100                150   1   2       2    3   2C effluent 536 1700         235 400                175   12  6      20   25   3__________________________________________________________________________ .sup.a Samples were taken at the end of the program. .sup.b TOX = total organic halides .sup.c CBA = chlorobenzoic acid. 
    
     
                       TABLE 5______________________________________Discharge Limits of Final Effluent                 MAXIMUMPARAMETERS            CONCENTRATION.sup.a______________________________________pH                    5-10Phenol                1        mg/LTOC (excluding Methanol) or                 300      mg/LTOC (total)           1000     mg/LTrichloroethylene     10       μg/LTetrachloroethylene   10       μg/LMonochlorobenzene     10       μg/LMonochlorotolene      10       μg/LBenzene               10       μg/LTrichlorobenzenes     10       μg/LTetrachlorobenzenes   10       μg/LMonochlorbenzotrifluoride                 10       μg/L(chloro-2,2,2-trichlorotoluene)Hexachlorocyclobutandiene (C-46)                 10       μg/LHexachlorocylopentadiene (C-56)                 10       μg/LHexachlorocyclohexanes (C-66)                 10       μg/L2,4,5-Trichlorophenol 10       μg/LEndosulfan            10       μg/LMirex                 1        μg/L2,3,7,8-Tetrachlorodibenzo-p-dioxin                 Not Dectectable______________________________________ .sup.a Except for pH 
    
     
                                           TABLE 6__________________________________________________________________________Adsorptive Capacities of Carbon for Major Leachate Constituents        Concentration   Adsorptive Capacity        (mg/L)          (mg adsorbed/g carbon)             combined.sup.a       pure.sup.e        raw  waste adsorber.sup.b                        carbon.sup.c                             leachate.sup.d                                  compoundConcentration Parameter        leachate             feed  effluent                        loading                             isotherm                                  isotherm__________________________________________________________________________pH              5.3             5.5-6.4                   5.5-6.4                        5.5-6.4                             4.9-5.5                                  5.0-6.0Phenol       981  780    ND.sub.0.1.sup.f                        41.0 74.9 174Benzoic acid 830  910   0.8  48.0 74.1 171o-chlorobenzoic acid        562  372   7.4  19.6 22.9 109m-chlorobenzoic acid         61  120   ND.sub.0.5                         6.4 23.0 160p-chlorobenzoic acid         40   80   ND.sub.0.1                         4.2 15.7 171TOC          3080 2618  318  137  143TOX          264  299   2.7  15.8 11.7__________________________________________________________________________ .sup.a Average concentrations for the adsorber feed during an adsorption service cycle. .sup.b Concentrations were measured at the end of an adsorption cycle. .sup.c Total removal of the compound at the end of an adsorption cycle. .sup.d Capacities were estimated at the feed concentration from the raw leachate isotherms. .sup.e Capacities were estimated at the feed concentration from the pure compound isotherms. .sup.f ND.sub.x = not detected at a detection limit of x mg/L. 
    
     
                       TABLE 7______________________________________Adsorptive Capacities of Carbon for TOC and TOXin Raw and SBR-treated Leachate Samples.sup.a                   SBR-treated         Raw Leachate.sup.b                   Leachate.sup.cActivated Carbon           TOC     TOX     TOC    TOXType            (mg adsorbed/g carbon)______________________________________Calgon F-300    133     11.7    152    127Calgon Service carbon           97.9    8.8     113    75.9Carborundum 30  173     19.6    268    172ICI Hydrodarco 3000           103     11.5    87.8   83.8Laboratory reactivated           148     18.3    115    91.6spent Calgon Service carbon______________________________________ .sup.a Adsorptive capacities were estimated from the Freundlich adsorptio isotherms. .sup.b Raw leachate: TOC = 3080 mg/L, TOX = 264 mg/L, pH = 5.3. The TOC capacities were estimated at TOC = 1500 mg/L, and the TOX capacities were estimated at TOX = 125 mg/L. .sup.c SBR-treated leachate: TOC = 400 mg/L, TOX = 334 mg/L, pH = 6.8. (The raw leachate had a TOC of 8100 mg/L and a TOX of 780 mg/L). The TOC capacities were estimated at TOC = 300 mg/L, and the TOX capacities were estimated at TOX =  125 mg/L. 
    
     
                       TABLE 8______________________________________Expected Saving in Treatment Cost withIntegrated SBR-Adsorption Process______________________________________                    Car-Time    Flow-   TOC.sup.a                    bon.sup.b                          Carbon.sup.c                                 Cost Saving.sup.dPeriod  rate    Loading  Usage Saving      $1000/(months)   (m.sup.3 /d)           (kg/d)            $/d  yr______________________________________ 1 thru 6    95     142       991   892   1475 538 7 thru 12   295     215      1442  1298   2146 78313 thru 18   250     202      1361  1225   2025 73919 thru 24   144     170      1170  1053   1742 63625 thru 30   144     170      1170  1053   1742 63631 thru 36   144     170      1170  1053   1742 63637 thru 120   144     170      1170  1053   1742 63610-year Average Saving                $643,600/year______________________________________ .sup.a The first 68 m.sup.3 /d at 1700 mg TOC/L; the next 45 m.sup.3 /d a 1000 mg TOC/L; the rest at 300 mg TOC/L. .sup.b 12 g/L for the first 68 m.sup.3 /d; 6.6 g/L for the next 45 m.sup. /d; 1.8 g/L for the rest. .sup.c 90% reduction in carbon exhaustion rate after biotreatment. .sup.d $1.65/kg carbon. All costs are in 1984 U.S. dollars.SBR Treatment System -design TOC loading = 181 kg/daverage TOC loading = 173 kg/d                $/year______________________________________1. Carbon saving     643,6002. Operating labor, misc. costs.sup.a                (0)  .sup.3. Maintenance.sup.a (50,000)  .sup.4. Electrical power.sup.b                (18,000)  .sup.5. Sludge disposal.sup.c                (21,300)  .sup.6. Analytical.sup.a  (23,000)  .sup.7. Nutrients and chemicals.sup.d                (4,600)  .sup.Net Saving           $526,700/year______________________________________ .sup.a Cost over the expanded adsorption operation required in the near future. .sup.b $0.06/kWh. .sup.c Total sludge production rate  1.02 g/g TOC; dewatered sludge  30% solid, disposal costs  $0.10/kg. .sup.d Supplementing NH.sub.3 and H.sub.3 PO.sub.4 to a TOC/N--NH.sub.4 /P--PO.sub.4 ratio of 150/10/2.