Document

7TreatmentofSoapandDetergentIndustryWastesConstantineYapijakisTheCooperUnion,NewYork,NewYork,U.S.A.LawrenceK.WangZorexCorporation,Newtonville,NewYork,U.S.A.,andLenoxInstituteofWaterTechnology,Lenox,Massachusetts,U.S.A.7.1INTRODUCTIONNaturalsoapwasoneoftheearliestchemicalsproducedbyman.Historically,itsrstuseasacleaningcompounddatesbacktoAncientEgypt[14].Inmoderntimes,thesoapanddetergentindustry, although a major one, produces relatively small volumes of liquid wastes directly.However, it causes great public concern when its productsare discharged after use in homes,serviceestablishments,andfactories[522].AnumberofsoapsubstitutesweredevelopedforthersttimeduringWorldWarI,butthelarge-scale production of synthetic surface-active agents (surfactants) became commerciallyfeasible only after World War II. Since the early 1950s, surfactants have replaced soap incleaningandlaundryformulationsinvirtuallyallcountrieswithanindustrializedsociety.Overthepast40years,thetotalworldproductionofsyntheticdetergentsincreasedabout50-fold,butthisexpansioninusehasnotbeenparalleledbyasignicantincreaseinthedetectableamountsofsurfactantsinsoilsornaturalwaterbodiestowhichwastesurfactantshavebeendischarged[4].Thisisduetothefactthatthebiologicaldegradationofthesecompoundshasprimarilybeentakingplaceintheenvironmentorintreatmentplants.WaterpollutionresultingfromtheproductionoruseofdetergentsrepresentsatypicalcaseoftheproblemsthatfollowedtheveryrapidevolutionofindustrializationthatcontributedtotheimprovementofqualityoflifeafterWorldWarII.Priortothattime,thisproblemdidnotexist.Thecontinuingincreaseinconsumptionofdetergents(inparticular,theirdomesticuse)andthetremendousincreaseinproductionofsurfactantsaretheoriginofatypeofpollutionwhosemostsignicant impact is the formation of toxic or nuisance foams in rivers, lakes, and treatmentplants.7.1.1ClassicationofSurfactantsSoaps anddetergents are formulated productsdesigned to meet various cost andperformancestandards. The formulated products contain many components, such as surfactants to tie up323Copyright#2004by Marcel Dekker, Inc.All Rights Reserved.

unwantedmaterials(commercialdetergentsusuallycontainonly1030%surfactants),buildersor polyphosphate salts to improve surfactant processes and remove calcium and magnesiumions, and bleaches to increase reectance ofvisible light. They alsocontain various additivesdesignedtoremovestains(enzymes),preventsoilre-deposition,regulatefoam,reducewashingmachinecorrosion,brightencolors,giveanagreeableodor,preventcaking,andhelpprocessingoftheformulateddetergent[18].The classication of surfactants in common usage depends on their electrolyticdissociation, which allowsthe determination of the nature of the hydrophilic polar group, forexample,anionic,cationic,nonionic,andamphoteric.AsreportedbyGreek[18],thetotal1988U.S.productionofsurfactantsconsistedof62%anionic,10%cationic,27%nonionic,and1%amphoteric.AnionicSurfactantsAnionic surfactants produce a negatively charged surfactant ion in aqueous solution, usuallyderivedfromasulfate,carboxylate,orsulfonategrouping.Theusualtypesofthesecompoundsare carboxylic acids and derivatives (largely based on natural oils), sulfonic acid derivatives(alkylbenzene sulfonates LAS or ABS and other sulfonates), and sulfuric acid esters andsalts (largely sulfated alcohols and ethers). Alkyl sulfates are readily biodegradable, oftendisappearingwithin24hoursinriverwaterorsewageplants[23].Becauseoftheirinstabilityinacidic conditions, they were to a considerable extent replaced by ABS and LAS, which havebeen the most widely used of the surfactants because of their excellent cleaning properties,chemical stability, and low cost. Their biodegradation has been the subject of numerousinvestigations[24].CationicSurfactantsCationic surfactants produce a positively charged surfactant ion in solution and are mainlyquaternarynitrogencompoundssuchasaminesandderivativesandquaternaryammoniumsalts.Owingtotheirpoorcleaningproperties,theyarelittleusedasdetergents;rathertheiruseisaresult of their bacteriocidal qualities. Relatively little is known about the mechanisms ofbiodegradationofthesecompounds.NonionicSurfactantsNonionic surfactants are mainly carboxylic acid amides and esters and their derivatives, andethers (alkoxylated alcohols), and they have been gradually replacing ABS in detergentformulations (especially as an increasingly popular active ingredient of automatic washingmachineformulations)sincethe1960s.Therefore,theirremovalinwastewatertreatmentisofgreatsignicance,butalthoughitisknownthattheyreadilybiodegrade,manyfactsabouttheirmetabolism are unclear [25]. In nonionic surfactants, both the hydrophilic and hydrophobicgroupsareorganic,sothecumulativeeffectofthemultipleweakorganichydrophilsisthecauseof their surface-active qualities. These products are effective in hard water and are very lowfoamers.AmphotericSurfactantsAspreviouslymentioned,amphotericsurfactantspresentlyrepresentaminorfractionofthetotalsurfactants production with only specialty uses. They are compounds with both anionic andcationicpropertiesinaqueoussolutions,dependingonthepHofthesysteminwhichtheywork.Themaintypesofthesecompoundsareessentiallyanalogsoflinearalkanesulfonates,whichprovide numerous points for the initiation of biodegradation, and pyridinium compounds that324YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved.

also have a positively charged N-atom (but in the ring) and they are very resistant tobiodegradation[26].7.1.2SourcesofDetergentsinWatersandWastewatersTheconcentrationsofdetergentthatactuallyndtheirwayintowastewatersandsurfacewaterbodies have quite diverse origins: (a) Soaps and detergents, as well as their componentcompounds,areintroducedintowastewatersandwaterbodiesatthepointoftheirmanufacture,atstoragefacilitiesanddistributionwarehouses,andatpointsofaccidentalspillsontheirroutesof transportation (the origin of pollution is dealt with in this chapter). (b) The additionalindustrial origin of detergent pollution notably results from the use of surfactants in variousindustries, such as textiles, cosmetics, leather tanning and products, paper, metals, dyes andpaints, production of domestic soaps and detergents, and from the use of detergents incommercial/industrial laundries and dry cleaners. (c) The contribution from agriculturalactivities is due to the surface runoff transporting of surfactants that are included in theformulationofinsecticidesandfungicides[27].(d)Theoriginwiththemostrapidgrowthsincethe1950scomprisesthewastewatersfromurbanareasanditisduetotheincreaseddomesticusageofdetergentsand,equallyimportant,theiruseincleaningpublicspaces,sidewalks,andstreetsurfaces.7.1.3ProblemandBiodegradationNotable improvements in washingand cleaning resulted from the introduction and increasinguseofsyntheticdetergents.However,thisalsocauseddifcultiesinsewagetreatmentandledtoa new form of pollution, the main visible effect of which was the formation of objectionablequantitiesoffoamonrivers.Althoughbiodegradationofsurfactantsinsoilsandnaturalwaterswas inferred by the observation that they did not accumulate in the environment, there waswidespreadconcernthattheirmuchhigherconcentrationsintheefuentsfromlargeindustrialareas would have signicant local impacts. In agreement with public authorities, themanufacturersfairlyquicklyintroducedproductsofadifferenttype.The surface-active agents in these new products are biodegradable (called soft incontrast to the former hard ones). They are to a great extent eliminated by normal sewagetreatment,andtheself-puricationoccurringinwatercoursesalsohassomebenecialeffects[28]. However, the introduction of biodegradable products has not solved all the problemsconnectedtosurfactants(i.e.,sludgedigestion,toxicity,andinterferencewithoxygentransfer),butithasmadeasignicantimprovement.Studiesofsurfactantbiodegradationhaveshownthatthemoleculararchitectureofthesurfactantlargelydeterminesitsbiologicalcharacteristics[4].Nevertheless,oneofthelatermostpressingenvironmentalproblemswasnottheeffectsofthesurfactants themselves, but the eutrophication of natural water bodies by the polyphosphatebuildersthatgointodetergentformulations.Thisledmanylocalauthoritiestoenactrestrictionsinorevenprohibitionoftheuseofphosphatedetergents.7.2IMPACTS OF DETERGENT PRODUCTION AND USESurfactantsretaintheirfoamingpropertiesinnaturalwatersinconcentrationsaslowas1mg/L,and although such concentrations are nontoxic to humans [24], the presence of surfactants indrinkingwaterisestheticallyundesirable.Moreimportant,however,isthegenerationoflargevolumesoffoaminactivatedsludgeplantsandbelowweirsanddamsonrivers.TreatmentofSoapandDetergentIndustryWastes325Copyright#2004by Marcel Dekker, Inc.All Rights Reserved.

7.2.1ImpactsinRiversThe principal factorsthat inuence the formationand stability offoams in rivers [27]are thepresence of ABS-type detergents, the concentration of more or less degraded proteins andcolloidalparticles,thepresenceandconcentrationofmineralsalts,thetemperatureandpHofthewater.Additionalveryimportantfactorsarethebiochemicaloxygendemand(BOD)ofthewater,whichundergivenconditionsrepresentsthequantityofbiodegradablematerial,thetimeoftravelandtheconditionsinuencingthereactionsofthecompoundspresumedresponsibleforfoaming,betweenthepointofdischargeandthelocationoffoamappearance,andlastbutnotleast,theconcentrationofcalciumionthatisthemainconstituentofhardnessinmostnaturalwatersandmeritsparticularattentionwithregardtofoamdevelopment.The minimum concentrations of ABS or other detergents above which foam formationoccursvaryconsiderably,dependingonthewatermedium,thatis,riverorsewage,anditslevelofpollution(mineralororganic).Therefore,itisnotmerelytheconcentrationofdetergentsthatcontrolsfoamformation,butrathertheircombinedactionwithothersubstancespresentinthewaters. Various studies have shown [27] that the concentration of detergents measured inthefoamsisquitesignicantlyhigher,uptothreeordersofmagnitude,thanthatmeasuredatthesametimeinsolutionintheriverwaters.The formation of foam also constitutes trouble and worries for river navigation. Forinstance,intheareasofdamsandriverlocks,theturbulencecausedbytheintensivetrafcofbargesandbytheincessantopeningandclosingofthelockgatesresultsinfoamformationthatmaycoverentireboatsandleaveastickydepositonthedecksofbargesandpiers.Thisrendersthemextremelyslipperyandmaybethecauseofinjuries.Also,whenwindsarestrong,massesof foam are detached and transported to great distances in the neighboring areas, causingproblems in automobile trafc by deposition on car windshields and by rendering the roadsurfaces slippery. Finally, masses of foam oating on river waters represent an estheticallyobjectionablenuisanceandaproblemforthetourismindustry.7.2.2ImpactsonPublicHealthForalongtime,detergentswereutilizedinlaboratoriesfortheisolation,throughconcentrationinthefoam,ofmycobacteriasuchasthebacillusofKoch(tuberculosis),asreportedintheannalsof the Pasteur Institute [27]. This phenomenon of extraction by foam points to the dangerexisting in river waters where numerous such microorganisms may be present due to sewagepollution. The foam transported by wind could possibly serve as the source of a diseaseepidemic. In fact, this problem limits itself to the mycobacteria and viruses (such as those ofhepatitisandpolio),whicharetheonlymicroorganismsabletoresistthedisinfectingpowerofdetergents. Therefore, waterborne epidemics could also be spread through airborne detergentfoams.7.2.3ImpactsonBiodegradationofOrganicsSurfactant concentrations in polluted natural water bodies interfere with the self-puricationprocess in several ways. First, certain detergents such as ABS are refractory or difcult tobiodegradeandeventoxicorinhibitorytomicroorganisms,andinuencetheBODexhibitedbyorganicpollutioninsurfacewaters.Ontheotherhand,readilybiodegradabledetergentscouldimpose an extreme short-term burden on the self-purication capacity of a water course,possiblyintroducinganaerobicconditions.326YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved.

Surfactantconcentrations alsoexert anegativeinuence on the bio-oxidation of certainsubstances,asevidencedinstudieswithevenreadilybiodegradablesubstances[7].Itshouldbenoted that this protection of substances from bio-oxidation is only temporary and it slowlyreducesuntilitsvirtualdisappearanceinaboutaweekformostsubstances.Thisphenomenonservestoretardtheself-puricationprocessinorganicallypollutedrivers,eveninthepresenceofhighconcentrationsofdissolvedoxygen.An additional way in which detergent concentrations interfere with the self-puricationprocess in polluted rivers consists of their negative action on the oxygen rate of transfer anddissolutionintowaters.AccordingtoGameson[16],thepresenceofsurfactantsinawatercoursecouldreduceitsre-aerationcapacitybyasmuchas40%,dependingonotherparameterssuchasturbulence.Inrelativelycalmwaterssuchasestuaries,undercertainconditions,thereductionofre-aerationcouldbeasmuchas70%.Itistheanionicsurfactants,especiallytheABS,thathavetheoverallgreatestnegativeimpactonthenaturalself-puricationmechanismsofrivers.7.2.4ImpactsonWastewaterTreatmentProcessesDespite the initial apprehension over the possible extent of impacts of surfactants on thephysicochemicalor biological treatment processes of municipal and industrialwastewaters, itsoonbecameevidentthatnomajorinterferenceoccurred.Asmentionedpreviously,thegreatestproblemprovedtobethelayersoffoamthatnotonlyhinderednormalsewageplantoperation,butwhenwind-blownintourbanareas,alsoaidedtheprobabletransmissionoffecalpathogenspresentinsewage.Therstunitprocessinasewagetreatmentplantisprimarysedimentation,whichdependsonsimplesettlingofsolidspartiallyassistedbyocculationofthenerparticles.Thestability,nonocculatingproperty,ofaneparticledispersioncouldbeinuencedbythesurfacetensionof the liquid or by the solid/liquid interface tension hence, by the presence of surfactants.Depending on the conditions, primarily the size of the particles in suspension, a givenconcentrationofdetergentscouldeitherdecrease (nerparticles)orincrease (largerparticles)therateofsedimentation[23].Thesynergisticorantagonisticactionofcertaininorganicsalts,whichareincludedintheformulationofcommercialdetergentproducts,isalsoinuential.Theeffectofsurfactantsonwastewateroilsandgreasesdependsonthenatureofthelatter,aswellasonthestructureofthelipophilicgroupofthedetergentthatassistssolubilization.Asisthecase,emulsicationcouldbemoreorlesscomplete.Thisresultsinamoreorlesssignicantimpactontheefciencyofphysicaltreatmentdesignedfortheirremoval.Ontheotherhand,theemulsifying surfactants play a role in protecting the oil and grease molecules from attackingbacteriainabiologicalunitprocess.In water treatment plants, the coagulation/occulation process was found early to beaffectedbythepresenceofsurfactantsintherawwatersupply.Ingeneral,theanionicdetergentsstabilizecolloidalparticlesuspensionsorturbiditysolids,which,inmostcases,arenegativelycharged.Langelier[29]reportedproblemswithwaterclaricationduetosurfactants,althoughaccordingtoNicholsandKoepp[30]andTodd[31]concentrationsofsurfactantsontheorderof45ppm interfered with occulation. The oc, instead of settling to the bottom, oats to thesurfaceofsedimentationtanks.Otherstudies,suchasthoseconductedbySmithetal.[32]andCohen [10], indicated that this interference could be not so much due to the surfactantsthemselves,buttotheadditivesincludedintheirformulation,thatis,phosphatecomplexes.Suchinterference was observed both for alum and ferric sulfate coagulant, but the use of certainorganicpolymerocculantswasshowntoovercomethisproblem.Concentrations of detergents, such as those generally found in municipal wastewaters,have been shown to insignicantly impact on the treatment efciency of biological sewageTreatmentofSoapandDetergentIndustryWastes327Copyright#2004by Marcel Dekker, Inc.All Rights Reserved.

treatment plants [33]. Studiesindicated that signicant impacts onefciency canbeobservedonlyforconsiderableconcentrationsofdetergents,suchasthosethatcouldpossiblybefoundinundilutedindustrialwastewaters,ontheorderof30ppmandabove.Aspreviouslymentioned,it is through their inuence of water aeration that the surfactants impact the organicsbiodegradation process. As little as 0.1mg/L of surfactant reduces to nearly half the oxygenabsorptionrate inariver,butinsewage aerationunits thesystem could beeasilydesigned tocompensate.Thisisachievedthroughtheuseofthealphaandbetafactorsinthedesignequationofanaerationsystem.Surfactants are only partially biodegraded in a sewage treatment plant, so that aconsiderableproportionmaybedischargedintosurfacewaterbodieswiththenalefuent.Theshortertheoveralldetentiontimeofthetreatmentplant,thehigherthesurfactantconcentrationin the discharged efuent. By the early 1960s, the concentration of surfactants in the nalefuentsfromsewagetreatmentplantswasinthe510ppmrange,andwhiledilutionoccursatthe site of discharge, the resulting values of concentration were well above the threshold forfoaming. In more recent times, with the advent of more readily biodegradable surfactants,foaming within treatment plants and in natural water bodies is a much more rare and limitedphenomenon.Finally, according to Prat and Giraud [27], the process of anaerobic sludge digestion,commonlyusedtofurtherstabilizebiologicalsludgepriortodisposalandtoproducemethanegas,isnotaffectedbyconcentrationsofsurfactantsinthetreatedsludgeupto500ppmorwhenitdoesnotcontaintoohighanamountofphosphates.Theselevelsofconcentrationarenotfoundinmunicipalorindustrialefuents,butwithinthebiologicaltreatmentprocessesalargepartofthe detergents is passed to the sludge solids. By this, it could presumably build up toconcentrations (especially ofABS surfactants)that may affect somewhat the sludge digestionprocess,thatis,methanegasproduction.Also,itseemsthatanaerobicdigestion[34]doesnotdecomposesurfactantsand,therefore,theiraccumulationcouldposeproblemswiththeuseofthenalsludgeproductasafertilizer.Thephenomenarelatedtosurfacetensioningroundwaterinterferewiththemechanismsof water ow in the soil. The presence of detergents in wastewaters discharged on soil forgroundwater recharge or ltered through sand beds would cause an increase in headloss andleaveadepositofsurfactantlmontheltermedia,therebyaffectingpermeability.Surfactants,especially those resistant to biodegradation, constitute a pollutant that tends to accumulate ingroundwater and has been found to remain in the soil for a few years without appreciabledecomposition. Because surfactants modify the permeability of soil, their presence couldpossiblyfacilitatethepenetrationofotherpollutants,thatis,chemicalsormicroorganisms, todepths where they would not have reached due to the ltering action of the soil, therebyincreasinggroundwaterpollution[35].7.2.5ImpactsonDrinkingWaterFrom all the aforementioned, it is obvious that detergents nd their way into drinking watersuppliesinvariousways.Asfarasimpartingodortodrinkingwater,onlyheavydosesofanionicsurfactantsyieldanunpleasantodor[36],andsomeonehastohaveaverysensitivenosetosmelldetergent doses of 50mg/L or less. On the other hand, it seems that the impact of detergentdosesonthesenseoftasteofvariousindividualsvariesconsiderably.AsreportedbyCohen[10],theU.S.PublicHealthServiceconductedaseriesoftastetestswhichshowedthatalthough50%ofthepeopleinthetestgroupdetectedaconcentrationof60mg/LofABSindrinkingwater,only 5% of them detected a concentration of 16mg/L.Because tests like this have beenconductedusingcommercialdetergentformulations,mostprobablytheobservedtasteisnotdue328YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved.

to the surfactantsbutrather to the additives orperfumes added to the products.However, theactual limit for detergents in drinking water in the United States is a concentration of only0.5mg/L,lessthaneventhemostsensitivepalatescandiscern.7.2.6ToxicityofDetergentsThereisanupperlimitofsurfactantconcentrationinnaturalwatersabovewhichtheexistenceofaquatic life, particularly higher animal life, is endangered. Trout are particularly sensitive toconcentrationsaslowas1ppmandshowsymptomssimilartoasphyxia[4].Ontheotherhand,numerous studies,which extendedover aperiodofmonthsandrequiredtestanimals todrinksignicantlyhighdosesofsurfactants,showedabsolutelynoapparentilleffectsduetodigesteddetergents. Also, there are no instances in which the trace amounts of detergents present indrinkingwaterweredirectlyconnectedtoadverseeffectsonhumanhealth.Riverpollutionfromanionicsurfactants,theprimarilytoxicones,isoftwotypes:(a)acutetoxic pollution due to, for example, an accidental spill from a container of full-strengthsurfactant products, and (b) chronic pollution due to the daily discharges of municipal andindustrialwastewaters.Theinternationalliteraturecontainstheresultofnumerousstudiesthathaveestablisheddosagesforbothtypesofpollutionaltoxicityduetodetergents,formosttypesofaquaticlifesuchasspeciesofsh.7.3CURRENT PERSPECTIVE AND FUTURE OUTLOOKThis sectionsummarizes the main points of arecent productreport [18],which presented thenewproductsofthedetergentindustryanditsproposeddirectionintheforeseeablefuture.If recent product innovations sell successfully in test markets in the United States andothercountries,rapidgrowthcouldbeginagainfortheentiresoapanddetergentindustryandespeciallyforindividualsectors ofthat industry.Among these new productsare formulationsthatcombinebleachingmaterialsandothercomponents,anddetergentsandfabricsoftenerssoldin concentrated forms. These concentrated materials, so well accepted in Japan, are nowbecomingcommerciallysignicantinWesternEurope.Theirmorewidespreadusewillallowthe industry to store and transport signicantly smaller volumes of detergents, with theconsequentreductionofenvironmentalrisksfromhousecleaningandspills.Somecomponentsof detergents such as enzymes will very likely grow in use, although the use of phosphatesemployedasbuilderswillcontinuetodropforenvironmentalreasons.Consumersshifttoliquidformulations in areas where phosphate materials are banned from detergents, because theyperceivethattheliquiddetergentsperformbetterthanpowderedoneswithoutphosphates.Infuelmarkets,detergentformulationssuchasgasolineadditivesthatlimitthebuildupofdepositsincarenginesandfuelinjectorswillverylikelygrowfastfromasmallbase,withthelikelihoodofanincreaseinspillsanddischargesfromthisindustrialsource.Soap,ontheotherhand,hasnowbecomeasmallpart(17%)ofthetotaloutputofsurfactants,whereastheanionicforms (which include soaps) accounted for 62% of total U.S. production in 1988. Liquiddetergents(manyoftheLAStype),whicharegenerallyhigherinsurfactantconcentrationsthanpowdered ones, will continue to increase in production volume, therefore creating greatersurfactantpollutionproblemsduetohousecleaningandspills.(Also,apowdereddetergentspillcreateslessofaproblem,asitiseasiertojustscoopuporvacuum.)Changesin theuseofbuildersresultingfromenvironmentalconcernshavebeenpushingsurfactantproductiondemand.OutrightlegalbansorconsumerpressuresontheuseofinorganicphosphatesandothermaterialsasbuildersgenerallyhaveledformulatorstoraisethecontentsofTreatmentofSoapandDetergentIndustryWastes329Copyright#2004by Marcel Dekker, Inc.All Rights Reserved.

surfactantsindetergents.Buildersprovideseveralfunctions,mostimportantofwhicharetoaidthedetergencyactionandtotieupandremovecalciumandmagnesiumfromthewashwater,dirt,andthefabricorothermaterialbeingcleaned.Besidessodiumandpotassiumphosphates,otherbuildersthatmaybeusedinvariousdetergentformulationsarecitricacidandderivatives,zeolites,andother alkalis.Citric acidcausescakingandisnotusedin powdereddetergents,butitndsconsiderableuseinliquiddetergents.Insomedetergentformulations,largerandlargeramountsofsodaash(sodiumcarbonate)arereplacinginertingredientsduetoitsfunctionalityasabuilder,anagglomeratingaid,acarrierforsurfactants,andasourceofalkalinity.Incorporating bleaching agents into detergent formulations for home laundry hasaccelerated,becauseitsperformanceallowsuserstocurtailtheneedtostoreaswellasadd(asa second step) bleaching material. Because U.S. home laundry requires shorter wash timesand lower temperatures than European home laundry, chlorine bleaches (mainly sodiumhypochlorite) have long dominated the U.S. market. Institutional and industrial laundrybleaching, when done, has also favored chlorine bleaches (often chlorinated isocyanurates)becauseoftheirrapidaction.Otherkindsofbleachingagentsusedinthedetergentmarketsarelargelysodiumperboratesandpercarbonatesotherthanhydrogenperoxideitself.Theperoxygenbleachesareforecasttogrowrapidly,forbothenvironmentalandtechnicalreasons,asregulatorypressuresdrivetheinstitutionalandindustrialmarketawayfromchlorinebleachesandtowardtheperoxygenones.TheCleanWaterActamendmentsarerequiringlowerlevels of trihalomethanes (products of reaction of organics and chlorine) in wastewaters.Expensive systems may be needed to clean up efuents, or the industrial users of chlorinebleacheswillhavetopayhigherandhighersurchargestomunicipalitiesforhandlingchlorine-containing wastewaters that are put into sewers. Current and expected changes in bleachingmaterials for various segments of the detergent industry are but part of sweeping changes tocomeduetoenvironmentalconcernsandresponsestoeffortstoimprovetheworldenvironment.Bothdetergentmanufacturersandtheirsupplierswillmakegreatereffortstodevelopmoreenvironmentallyfriendlyproducts.BASF,forexample,hasdevelopedanewbiodegradablestabilizerforperboratebleach,whichisnowbeingevaluatedforuseindetergents.Theexistingdetergentmaterial,suchasLASanditsprecursorlinearalkylbenzene,knowntobenontoxicandenvironmentally safe as well as effective, will continue to be widely used. It will be difcult,however, to gain approval for new materials to be used in detergent formulations until theirenvironmental performance has been shown to meet existing guidelines. Some countries, forexample, tend to favor a formal regulation or law (i.e., the EEC countries) prohibiting themanufacture,importation,oruseofdetergentsthatarenotsatisfactorilybiodegradable[28].7.4INDUSTRIAL OPERATION AND WASTEWATERThesoapanddetergentindustryisabasicchemicalmanufacturingindustryinwhichessentiallyboththemixingandchemicalreactionsofrawmaterialsareinvolvedinproduction.Also,short-and long-term chemicals storage and warehousing, as well as loading/unloading andtransportationofchemicals,areinvolvedintheoperation.7.4.1ManufactureandFormulationThis industry produces liquid and solid cleaning agents for domestic and industrial use,includinglaundry,dishwashing,barsoaps,specialtycleaners,andindustrialcleaningproducts.Itcanbebroadlydivided(Fig.1)intotwocategories:(a)soapmanufacturethatisbasedontheprocessing of natural fat; and (b) detergent manufacture that is based on the processing of330YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved. Figure 1Flowdiagramofsoapanddetergentmanufacture(fromRef.13).TreatmentofSoapandDetergentIndustryWastes331Copyright#2004byMarcelDekker,Inc.AllRightsReserved. petrochemicals. Theinformationpresentedhereincludesestablishmentsprimarilyinvolved inthe production of soap, synthetic organic detergents, inorganic alkaline detergents, or anycombinations of these, and plants producing crude and rened glycerine from vegetable andanimalfatsandoils.Typesoffacilitiesnotdiscussedhereincludeplantsprimarilyinvolvedintheproductionofshampooorshavingcreams/soaps,whetherfromsoaporsurfactants,andofsyntheticglycerineaswellasspecialtycleaners,polishingandsanitationpreparations.Numerous processing steps exist between basic raw materials for surfactants and othercomponentsthatareusedtoimproveperformanceanddesirability,andthenishedmarketableproductsofthesoapanddetergentindustry.Inorganicandorganiccompoundssuchasethylene,propylene,benzene,naturalfattyoils,ammonia,phosphaterock,trona,chlorine,peroxides,andsilicates are among the various basic raw materials being used by the industry. The nalformulationoftheindustrysnumerousmarketableproductsinvolvesbothsimplemixingofandchemicalreactionsamongcompoundssuchastheabove.Thecategorizationsystemofthevariousmainproductionstreamsandtheirdescriptionsistakenfromfederalguidelines[13]pertainingtostateandlocalindustrialpretreatmentprograms.It will be used in the discussion that ensues to identify process ows and to characterize theresulting raw waste. Figure 1 shows a ow diagram for the production streams of the entireindustry.Manufacturingofsoapconsistsoftwomajoroperations:theproductionofneatsoap(6570%hotsoapsolution)andthepreparationandpackagingofnishedproductsintoakesandpowders(F),barsoaps(G),andliquidsoaps(H).Manyneatsoapmanufacturersalsorecoverglycerine as a byproduct for subsequent concentration (D) and distillation (E). Neat soap isgenerally produced in either of two processes: the batch kettle process (A) or the fatty acidneutralization process, which is preceded by the fat splitting process (B, C). (Note, letters inparenthesesrepresenttheprocessesdescribedinthefollowingsections.)BatchKettleProcess(A)This process consists of the following operations: (a) receiving and storage of raw materials,(b)fatreningandbleaching,and(c)soapboiling.Themajorwastewatersources,asshownintheprocessowdiagram(Fig.2),arethewashoutsofboththestorageandreningtanks,aswellasfromleaksandspillsoffatsandoilsaroundthesetanks.Thesestreamsareusuallyskimmedforfatrecoverypriortodischargetothesewer.The fat rening and bleaching operation is carried out to remove impurities that wouldcause color and odor in the nished soap. The wastewater from this source has a high soapconcentration,treatmentchemicals,fattyimpurities,emulsiedfats,andsulfuricacidsolutionsof fatty acids. Where steam is used for heating, the condensate may contain low-molecular-weightfattyacids,whicharehighlyodorous,partiallysolublematerials.Thesoapboilingprocessproducestwoconcentratedwastestreams:sewerlyesthatresultfromthereclaimingofscrapsoapandthebrinefromNigreprocessing.Bothofthesewastesarelowvolume,highpH,withBODvaluesupto45,000mg/L.Soapmanufacturebytheneutralizationprocessisatwo-stepprocess:fatwater!fatty acidglycerine (fat splitting)(B)fatty acidcaustic!soap (fatty acid neutralization)(C)FatSplitting(B)Themanufactureoffattyacidfromfatiscalledfatsplitting(B),andtheprocessowdiagramisshowninFig.3.Washoutsfromthestorage,transfer,andpretreatmentstagesarethesameasthoseforprocess(A).Processcondensateandbarometriccondensatefromfatsplittingwillbecontaminatedwithfattyacidsandglycerinestreams,whicharesettledandskimmedtorecover332YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved. Figure 2Soapmanufacturebybatchkettle(A)(fromRef.13).TreatmentofSoapandDetergentIndustryWastes333Copyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 3Fattyacidmanufacturebyfatsplitting(B)(fromRef.13).334YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved. theinsolublefattyacidsthatareprocessedforsale.Thewaterwilltypicallycirculatethroughacoolingtowerandbereused.OccasionalpurgesofpartofthisstreamtothesewerreleasehighconcentrationsofBODandsomegreaseandoil.Inthefattyaciddistillationprocess,wastewaterisgeneratedasaresultofanacidicationprocess,whichbreakstheemulsion.Thiswastewaterisneutralizedandsenttothesewer.Itwillcontain salt from the neutralization, zinc and alkaline earth metal salts from the fat splittingcatalyst,andemulsiedfattyacidsandfattyacidpolymers.FattyAcidNeutralization(C)Soapmakingbythismethodisafasterprocessthanthekettleboilprocess andgenerateslesswastewaterefuent(Fig.4).Becauseitisfaster,simpler,andcleanerthanthekettleboilprocess,itisthepreferredprocessamonglargeraswellassmallmanufacturers.Often, sodium carbonate is used in place of caustic. When liquid soaps (at roomtemperature)aredesired,themoresolublepotassiumsoapsaremadebysubstitutingpotassiumhydroxideforthesodiumhydroxide(lye).Thisprocessisrelativelysimpleandhigh-purityrawmaterialsareconvertedtosoapwithessentiallynobyproducts.Leaks,spills,stormrunoff,andwashouts are absent. There is only one wastewater of consequence: the sewer lyes fromreclaimingofscrap.Thesewerlyescontaintheexcesscausticsodaandsaltaddedtograinoutthesoap.Also,theycontainsomedirtandpapernotremovedinthestrainer.GlycerineRecoveryProcess(D,E)A process ow diagram for the glycerine recovery process uses the glycerine byproductsfrom kettle boiling (A) and fat splitting (B). The process consists of three steps (Fig. 5):(a)pretreatment to remove impurities, (b) concentration of glycerine by evaporation, and(c)distillationtoanishedproductof98%purity.There are three wastewaters of consequence from this process: two barometriccondensates, one from evaporation and one from distillation, plus the glycerine foots or stillbottoms.Contaminantsfromthecondensatesareessentiallyglycerinewithalittleentrainedsalt.In the distillation process, the glycerine foots or still bottoms leave a glassy dark brownamorphoussolidrichinsaltthatisdisposedofinthewastewaterstream.Itcontainsglycerine,glycerine polymers, and salt. The organics will contribute to BOD, COD (chemical oxygendemand), and dissolved solids. The sodium chloride will also contribute to dissolved solids.Littleornosuspendedsolids,oil,andgreaseorpHeffectshouldbeseen.Glycerine can also be puried by the use of ion-exchange resins to remove sodiumchloridesalt, followed byevaporationof thewater. This processputsadditional salts intothewastewaterbutresultsinlessorganiccontamination.7.4.3ProductionofFinishedSoapsandProcessWastesTheproductionofnishedsoapsutilizestheneatsoapproducedinprocessesAandCtoprepareandpackagenishedsoap.Thesenishedproductsaresoapakesandpowders(F),barsoaps(G),andliquidsoap(H).SeeFigures6,7,and8fortheirrespectiveowdiagrams.FlakesandPowders(F)Neat soap may or may not be blended with other products before aking or powdering. Neatsoapissometimeslteredtoremovegelparticles andrunintoareactor(crutcher) formixingwithbuilders.Afterthoroughmixing,thenishedformulationisrunthroughvariousmechanicaloperations toproduce akes and powders.Because allofthe evaporated moisture goes totheatmosphere,thereisnowastewaterefuent.TreatmentofSoapandDetergentIndustryWastes335Copyright#2004by Marcel Dekker, Inc.All Rights Reserved. Figure 4Soapfromfattyacidneutralization(C)(fromRef.13).336YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 5Glycerinerecoveryprocessowdiagram(D,E)(fromRef.13).TreatmentofSoapandDetergentIndustryWastes337Copyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 6Soapakeandpowdermanufacture(F)(fromRef.13).338YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 7Barsoapmanufacture(G)(fromRef.13).TreatmentofSoapandDetergentIndustryWastes339Copyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 8Liquidsoapprocessing(H)(fromRef.13).340YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved. Some operations will include a scrap soap reboil to recover reclaimed soap. The soapreboilissaltedoutforsoaprecoveryandthesaltwaterisrecycled.Afterfrequentrecycling,thesalt water becomes so contaminated that it must be discharged to the sewer. Occasionalwashdownofthecrutchermaybeneeded.Thetowerisusuallycleaneddowndry.Thereisalsosome gland water that ows over the pump shaft, picking up any minor leaks. This willcontributeaverysmall,butnite,efuentloading.ThereareanumberofpossibleefuentsshownontheowdiagramforprocessF(Fig.6).However, a survey of the industry showed that most operating plants either recycled anywastewater to extinction orused dry clean-up processes. Occasionally, water will be used forclean-up.BarSoaps(G)The procedure for bar soap manufacture (O) will vary signicantly from plant to plant,dependingontheparticularclienteleserved.AtypicalowdiagramforprocessOisshowninFigure7.Theamountofwaterusedinbarsoapmanufacturevariesgreatly.Inmanycases,theentire bar soap processing operation is carried out without generating a single wastewaterstream. The equipment is all cleaned dry, without any washups. In other cases, due tohousekeeping requirements associatedwith the particularbarsoapprocesses,thereare oneormorewastewaterstreamsfromairscrubbers.Themajorwastestreamsinbarsoapmanufacturearethelterbackwash,scrubberwaters,or condensate from a vacuum drier, and water from equipment washdown. The maincontaminant of all these streams is soap that will contribute primarily BOD and COD to thewastewater.LiquidSoap(H)Inthemakingofliquidsoap,neatsoap(oftenthepotassiumsoapoffattyacids)isblendedinamixingtankwithotheringredientssuchasalcoholsorglycolstoproduceanishedproduct,orthepineoilandkeroseneforaproductwithgreatersolvencyandversatility(Fig.8).Thenalblended product may be, and often is, ltered to achieve a sparkling clarity before beingdrummed.Inmakingliquidsoap,waterisusedtowashoutthelterpressandotherequipment.Accordingtomanufacturers,thereareveryfewefuentleaks.Spillscanberecycledorhandleddry.Washoutbetweenbatchesisusuallyunnecessaryorcanberecycledtoextinction.7.4.4DetergentManufactureandWasteStreamsDetergents,asmentionedpreviously,canbeformulatedwithavarietyoforganicandinorganicchemicals, depending on the cleaning characteristics desired. A nished, packaged detergentcustomarily consists of two main components: the active ingredient or surfactant, and thebuilder.Theprocessesdiscussedinthefollowingwillincludethemanufactureandprocessingofthesurfactant aswellasthepreparationofthenished,marketabledetergent.Theproductionof the surfactant (Fig. 1) is generally a two-step process: (a) sulfation or sulfonation, and(b)neutralization.7.4.5SurfactantManufactureandWasteStreamsOleumSulfonation/Sulfation(I)Oneofthemostimportantactiveingredientsofdetergentsisthesulfateorsulfonatecompoundsmade via the oleum route. A process ow diagram is shown in Figure 9. In most cases, thesulfonation/sulfation is carried out continuously in a reactor where the oleum (a solution ofsulfur trioxide in sulfuric acid) is brought into contact with the hydrocarbon or alcohol and aTreatmentofSoapandDetergentIndustryWastes341Copyright#2004by Marcel Dekker, Inc.All Rights Reserved. Figure 9Oleumsulfationandsulfonation(batchandcontinuous)(I)(fromRef.13).342YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved. rapidreactionensues.Thestreamisthenmixedwithwater,wherethesurfactantseparatesandisthensenttoasettler.Thespentacidisdrawnoffandusuallyforwardedforreprocessing,andthesulfonated/sulfatedmaterialsaresenttobeneutralized.Thisprocessisnormallyoperatedcontinuouslyandperformsindenitelywithoutneedofperiodiccleanout.Astreamofwaterisgenerally playedoverpumpshaftstopickupleaksaswellastocoolthepumps.Wastewaterowfromthissourceisquitemodest,butcontinual.AirSO Sulfation3/Sulfonation(J)Thisprocessforsurfactantmanufacturehasmanyadvantagesandisusedextensively.WithSO3sulfation,nowaterisgeneratedinthereaction.AprocessowdiagramisshowninFigure10.SO canbegeneratedattheplantbyburningsulfurorsulfurdioxidewithairinsteadofobtaining3it as a liquid. Because of this reactions particular tendency to char the product, the reactorsystem must be cleaned thoroughly on a regular basis. In addition, there are usually severalairbornesulfonic acid streams that must bescrubbed, with the wastewater going to the sewerduringsulfation.SO SolventandVacuumSulfonation(K)3UndilutedSO andorganicreactant are fedintothevacuum reactorthrough amixing nozzle.3AprocessowdiagramisshowninFigure11.Thissystemproducesahigh-qualityproduct,butoffsetting this is the high operating cost of maintaining the vacuum. Other than occasionalwashout,theprocessisessentiallyfreeofwastewatergeneration.SulfamicAcidSulfation(L)Sulfamicacidisamildsulfatingagentandisusedonlyinveryspecializedqualityareasbecauseofthehighreagentprice.AprocessowdiagramisshowninFigure12.Washoutsaretheonlywastewaterefuentsfromthisprocessaswell.ChlorosulfonicAcidSulfation(M)Forproductsrequiringhigh-qualitysulfates,chlorosulfonicacidisanexcellentcorrosiveagentthatgenerateshydrochloricacidasabyproduct.AprocessowdiagramisshowninFigure13.Theefuentwashoutsareminimal.NeutralizationofSulfuricAcidEstersandSulfonicAcids(N)Thisstepisessentialinthemanufactureofdetergentactiveingredientsasitconvertsthesulfonicacidsorsulfuricacidesters(productsproducedbyprocessesIM)intoneutralsurfactants.Itisapotential source of some oil and grease, but occasional leaks and spills around the pump andvalves are the only expected source of wastewater contamination. A process ow diagram isshowninFigure14.7.4.6DetergentFormulationandProcessWastesSpray-DriedDetergents(O)In this segment of the processing, the neutralized sulfonates and/or sulfates are rst blendedwithbuildersandadditivesinthecrutcher.Theslurryisthenpumpedtothetopofaspraytowerofabout4.56.1m(1520ft)indiameterby4561m(150200ft)inheight,wherenozzlessprayoutdetergentslurry.AlargevolumeofhotairentersthebottomofthetowerandrisestoTreatmentofSoapandDetergentIndustryWastes343Copyright#2004by Marcel Dekker, Inc.All Rights Reserved. Figure 10AirSO sulfationandsulfonation(batchandcontinuous)(J)(fromRef.13).3344YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 11SO solventandvacuumsulfonation(K)(fromRef.13).3TreatmentofSoapandDetergentIndustryWastes345Copyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 12Sulfamicacidsulfation(L)(fromRef.13).346YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 13Chlorosulfonicacidsulfation(M)(fromRef.13).TreatmentofSoapandDetergentIndustryWastes347Copyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 14Neutralizationofsulfuricacidestersandsulfonicacids(N)(fromRef.13).348YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved. meet the falling detergent. The design preparation of this step will determine the detergentparticles shape, size, and density, which in turn determine its solubility rate in the washingprocess.Theaircomingfromthetowerwillbecarryingdustparticlesthatmustbescrubbed,thusgeneratingawastewaterstream.Thespraytowersareperiodicallyshutdownandcleaned.Thetowerwallsarescrapedandthoroughlywasheddown.Thenalstepismandatorybecausethemanufacturersmustbecarefultoavoidcontaminationtothesubsequentformulation.Wastewaterstreamsarerathernumerous,asseenintheowdiagramofFigure15.Theyinclude many washouts of equipment from the crutchers to the spray tower itself. Onewastewaterowthathashighloadingsisthatoftheairscrubber,whichcleansandcoolsthehotgases exiting from thistower.All the plants recycle some ofthe wastewater generated, whilesome of the plants recycle all the ow generated. Owing to increasingly stringent air qualityrequirements,itcanbeexpectedthatfewerplantswillbeabletomaintainacompleterecyclesystemofallwaterowsinthespraytowerarea.Afterthepowdercomesfromthespraytower,itisfurtherblendedandthenpackaged.LiquidDetergents(P)Detergent actives are pumped into mixing tanks where they are blended with numerousingredients,rangingfromperfumestodyes.AprocessowdiagramisshowninFigure16.Fromhere, the fully formulated liquid detergent is run down to the lling line for lling, capping,labeling, and so on. Whenever the lling line is to change to a different product, the llingsystemmustbethoroughlycleanedouttoavoidcrosscontamination.DryDetergentBlending(Q)Fullydriedsurfactantmaterialsareblendedwithadditivesindrymixers.Normaloperationwillseemanysucceedingbatchesofdetergentmixed inthesameequipmentwithoutanything butdrycleaning.However,whenachangeinformulationoccurs,theequipmentmustbecompletelywasheddownandamodestamountofwastewaterisgenerated.AprocessowdiagramisshowninFigure17.Drum-DriedDetergent(R)Thisprocessisonemethodofconvertingliquidslurrytoapowderandshouldbeessentiallyfreeof the generation of wastewater discharge other than occasional washdown. A process owdiagramisshowninFigure18.DetergentBarsandCakes(S)Detergentbarsareeither100%syntheticdetergentorablendofdetergentandsoap.Theyareblendedinessentiallythesamemannerasconventionalsoap.Fairlyfrequentcleanupsgenerateawastewaterstream.AprocessowdiagramisshowninFigure19.7.4.7WastewaterCharacteristicsWastewatersfromthemanufacturing,processing,andformulationoforganicchemicalssuchassoaps and detergents cannot be exactly characterized. The wastewater streams are usuallyexpected to contain trace or larger concentrations of all raw materials used in the plant, allintermediate compounds produced during manufacture, all nal products, coproducts, andbyproducts, and the auxiliary or processing chemicals employed. It is desirable, from theTreatmentofSoapandDetergentIndustryWastes349Copyright#2004by Marcel Dekker, Inc.All Rights Reserved. Figure 15Spray-drieddetergentproduction(O)(fromRef.13).350YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 16Liquiddetergentmanufacture(P)(fromRef.13).TreatmentofSoapandDetergentIndustryWastes351Copyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 17Detergentmanufacturebydryblending(Q)(fromRef.13).352YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 18Drum-drieddetergentmanufacture(R)(fromRef.13).TreatmentofSoapandDetergentIndustryWastes353Copyright#2004byMarcelDekker,Inc.AllRightsReserved.

Figure 19Detergentbarandcakemanufacture(S)(fromRef.13).354YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved. viewpoint of economics, that these substances not be lost, but some losses and spills appearunavoidable and some intentional dumping does take place during housecleaning and vesselemptyingandpreparationoperations.According to a study by the USEPA [12], which presents estimates of industrialwastewater generation as well as related pollution parameter concentrations, the wastewatervolume discharged from soap and detergent manufacturing facilities per unit of productionrangesfrom0.3to2.8gal/lb(2.523.4L/kg)ofproduct.Thereportedrangesofconcentration(mg/L)forBOD,suspendedsolids,COD,andgreasewere5001200,4002100,4001800,and about 300, respectively. These data were based on a study of the literature and the eldexperience of governmental and private organizations. The values represent plant operatingexperience for several plants consisting of 24hour composite samples taken at frequentintervals.Therangesforowandotherparametersgenerallyrepresentvariationsinthelevelofplant technology or variations in ow and quality parameters from different subprocesses. Inparticular,themoreadvancedandmodern thelevelofproductiontechnology,the smaller thevolumeofwastewaterdischargedperunitofproduct.Thelargevariability(uptooneorderofmagnitude)intherangesisgenerallyduetotheheterogeneityofproductsandprocessesinthesoapanddetergentindustry.The federal guidelines [13] for state and local pretreatment programs reported the rawwastewater characteristics (Table 1) in mg/L concentration and the ows and water qualityparameters (Table 2) based on the production or 1ton of product manufactured for thesubcategoriesoftheindustry.MostsoapanddetergentmanufacturingplantscontaintwoormoreofthesubcategoriesshowninTable3,andtheirwastewatersareacompositeoftheseindividualunitprocesses.7.5U.S. CODE OF FEDERAL REGULATIONSThe information presented in this section has been taken from the U.S. Code of FederalRegulations(40CFR),containingdocumentsrelatedtotheprotectionoftheenvironment[14],in particular, the regulations contained in Part 417, Soap and Detergent Manufacturing PointSourceCategory,pertainingtoefuentlimitationsguidelinesandpretreatmentorperformancestandardsforeachofthe19subcategoriesshowninTable3.Theefuentguidelineregulationsandstandardsof40CFR,Part417,werepromulgatedonFebruary11,1975.AccordingtothemostrecentnoticeintheFederalRegister[15]regardingindustrial categories and regulations, no review is under way or planned and no revision isproposedforthesoapanddetergentindustry.Theefuentguidelinesandstandardsapplicabletothisindustrialcategoryinclude:(a)thebestpracticablecontroltechnologycurrentlyavailable(BPT); (b) the best available technology economically achievable (BAT); (c) pretreatmentstandards for existing sources (PSES); (d) standards of performance for new sources (NSPS);and(e)pretreatmentstandardsfornewsources(PSNS).For all 19 subcategories of the soap and detergent manufacture industry, there are nopretreatmentstandardsestablishingthequantityandqualityofpollutantsorpollutantpropertiesthat may be discharged to a publicly owned treatment works (POTW) by an existing or newpointsource.Ifthemajorcontributingindustryisanexistingpointsourcedischargingpollutantstonavigablewaters,itwillbesubjecttoSection301oftheFederalWaterPollutionControlActand to the provisions of 40 CFR, Part 128. However, practically all the soap and detergentmanufacturing plants in the United States discharge their wastewaters into municipal sewersystems.TheefuentlimitationsguidelinesforcertainsubcategoriesregardingBPT,BAT,andNSPSarepresentedinTables410.TreatmentofSoapandDetergentIndustryWastes355Copyright#2004by Marcel Dekker, Inc.All Rights Reserved. Table1SoapandDetergentIndustryRawWastewaterCharacteristicsParameterBatchkettle(A)Fatsplitting(B)Fattyacidneutralization(C)Glycerineconcentration(D)Glycerinedistillation(E)Flakesandpowders(F)Barsoap(G)Liquidsoap(H)BOD(mg/L)3600a603600a40016003000aCOD(mg/L)4267a1156000a1000TSS(mg/L)160064201156000775Oilandgrease(mg/L)250a13760a200apH513.5HighHighNeutralNeutralNeutralNeutralNeutralChlorides(mg/L)2047maZinc(mg/L)PresentNickel(mg/L)PresentParameterOleumsulfationandsulfonation(I)Airsulfationandsulfonation(J)SO solvent3andvacuum(K)Sulfamicacidsulfation(L)Chloro-sulfonic(M)Neutralsulfuric(N)Spray-dried(O)Liquiddetergent(P)Dryblend(Q)Drum-dried(R)Barsandcakes(S)BOD(mg/L)752000a3805208.56ma4819ma653400aNeg.COD(mg/L)2206000a9201589a24521ma15060ma64011maTSS(mg/L)1003000Oilandgrease(mg/L)1003000apH1a2aLowLowLowLowSurfactant(mg/L)2507000602mBoron(mg/L)PresentPresentPresentPresentPresentPresentPresentPresentPresentPresentPresentaIn high levels these parameters may be inhibitory to biological systems; mthousands; BOD, biochemical oxygen demand; COD, chemical oxygen demand; TSS, totalsuspendedsolids.Source:Ref.10.356YapijakisandWangCopyright#2004byMarcelDekker,Inc.AllRightsReserved.

Table2RawWastewaterCharacteristicsBasedonProductionParameterBatchkettle(A)Fatsplitting(B)Fattyacidneutralization(C)Glycerineconcentration(D)Glycerinedistillation(E)Flakesandpowders(F)Barsoap(G)Liquidsoap(H)Flowrange(L/kkg)a623/25003.3M/1924M258Neg.Neg.FlowtypeBBBBBBBBBOD(kg/kkg)b6120.11550.13.40.1COD(kg/kkg)10220.2530100.35.70.3TSS(kg/kkg)4220.2220.15.80.1Oilandgrease(kg/kkg)0.92.50.05110.10.40.1ParameterOleumsulfationandsulfonation(I)SO3sulfationandsulfonation(J)SO3solventandvacuumsulfonation(K)Sulfamicacidsulfation(L)Chloro-sulfonic(M)Neutralsulfuricacidesters(N)Spray-dried(O)Liquiddetergent(P)Dryblend(Q)Drum-dried(R)Barsandcakes(S)Flowrange(L/kkg)a100/274024910/417041/2084625/6250FlowtypeCCBBBB&CBBBBBBOD(kg/kkg)b0.233330.100.10.8250.10.17COD(kg/kkg)0.699990.30.325470.50.322TSS(kg/kkg)0.30.30.30.30.30.30.11.00.10.12Oilandgrease(kg/kkg)0.30.50.50.50.50.1Nil0.30.10.2Chloride(kg/kkg)5Surfactant(kg/kkg)0.733330.20.21.51.33.30.15aL/kkg,L/1000kgproductproduced(lowerlimit/upperlimit).bkg/kkg,kg/1000kgproductproduced.BBatch;CContinuous;Neg.Negligible;MThousand.Source:Ref.13.TreatmentofSoapandDetergentIndustryWastes357Copyright#2004byMarcelDekker,Inc.AllRightsReserved. Table3SoapandDetergentCategorizationSource:Ref.10.CategorySubcategoryCodeSoapmanufactureBatchkettleandcontinuousAFattyacidmanufacturebyfatsplittingBSoapfromfattyacidneutralizationCGlycerinerecoveryGlycerineconcentrationDGlycerinedistillationESoapakesandpowdersFBarsoapsGLiquidsoapHDetergentmanufactureOleumsulfonationandsulfation(batchandcontinuous)IAirSO sulfationandsulfonation3(batchandcontinuous)JSO solventandvacuumsulfonation3KSulfamicacidsulfationLChlorosulfonicacidsulfationMNeutralizationofsulfuricacidestersandsulfonicacidsNSpray-drieddetergentsOLiquiddetergentmanufacturePDetergentmanufacturebydryblendingQDrum-drieddetergentsRDetergentbarsandcakesSSource:Ref.10. Table4EfuentLimitationsforSubpartA,BatchKettleEfuentlimitations[metricunits(kg/1000kgofanhydrousproduct)]EfuentcharacteristicMaximumforany1dayAverageofdailyvaluesfor30consecutivedaysshallnotexceed(a)BPTBOD51.800.60COD4.501.50TSS1.200.40Oilandgrease0.300.10pHaa(b)BATandNSPSBOD50.800.40COD2.101.05TSS0.800.40Oilandgrease0.100.05pHaaaWithintherange6.09.0.BAT, best available technology economically achievable; NSPS, standards ofperformancefornewsources.Source:Ref.14.358YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved.

7.6WASTEWATER CONTROL AND TREATMENTThe sources and characteristics of wastewater streams from the various subcategoriesin soapand detergent manufacturing, as well assomeofthe possibilities for recycling and treatment,have been discussed in Section 7.4. The pollution control and treatment methods and unitprocessesusedarediscussedinmoredetailinthefollowingsections.Thedetailsoftheprocessdesigncriteriafortheseunittreatmentprocessescanbefoundinanydesignhandbooks.7.6.1In-PlantControlandRecycleSignicantin-plantcontrolofbothwastequantityandqualityispossible,particularlyinthesoapmanufacturing subcategories where maximum ows may be 100 times the minimum.Considerablylessin-plantwaterconservationandrecyclearepossibleinthedetergentindustry,whereowsperunitofproductaresmaller.Thelargestin-plantmodicationthatcanbemadeisthechangingorreplacementofthebarometriccondensers(subcategoriesA,B,D,andE).Thewastewaterquantitydischargedfromtheseprocessescanbesignicantlyreducedbyrecyclingthebarometriccoolingwaterthroughfatskimmers,fromwhichvaluablefatsandoilscanberecovered,andthenthroughthecoolingtowers.Theonlywastewiththistypeofcoolingwouldbethecontinuoussmallblowdownfrom Table5EfuentLimitationsforSubpartC,SoapbyFattyAcidEfuentlimitations[metricunits(kg/1000kgofanhydrousproduct)]EfuentcharacteristicMaximumforany1dayAverageofdailyvaluesfor30consecutivedaysshallnotexceed(a)BPTBOD50.030.01COD0.150.05TSS0.060.02Oilandgrease0.030.01pHaa(b)BATBOD50.020.01COD0.100.05TSS0.040.02Oilandgrease0.020.01pHaa(c)NSPSBOD50.020.01COD0.100.05TSS0.040.02Oilandgrease0.020.01pHaaaWithintherange6.09.0.Source:Ref.14.TreatmentofSoapandDetergentIndustryWastes359Copyright#2004by Marcel Dekker, Inc.All Rights Reserved.

the skimmer. Replacement with surface condensers has been used in several plants to reduceboththewasteowandquantityoforganicswasted.Signicantreductionofwaterusageispossibleinthemanufactureofliquiddetergents(P)bytheinstallationofwaterrecyclepipingandtankageandbytheuseofairratherthanwatertoblowdownllinglines.Intheproductionofbarsoaps(G),thevolumeofdischargeandthelevelofcontaminationcanbereducedmateriallybyinstallationofanatmosphericashevaporatoraheadofthevacuumdrier.Finally,pollutantcarryoverfromdistillationcolumnssuchasthoseusedinglycerineconcentration(D)orfattyacidseparation(B)canbereducedbytheuseoftwoadditionalspecialtrays.In another document [37] presenting techniques adopted by the French for pollutionprevention,anewprocessofdetergentmanufacturingefuentrecycleisdescribed.AsshowninFigure20,thewashoutefuentsfromreactionand/ormixingvesselsandwashwaterleaksfromthepastepreparationandpulverizationpumpoperationsarecollectedandrecycledforuseinthepaste preparation process. The claim has been that pollution generation at such a plant issignicantlyreducedand,althoughthesavingsonwaterandrawmaterialsaresmall,thecapitalandoperatingcostsarelessthanthoseforbuildingawastewatertreatmentfacility.Besselievre[2]hasreportedinareviewofwaterreuseandrecyclingbytheindustrythatsoapanddetergentmanufacturingfacilitieshaveshownanaverageratioofreusedandrecycledwater to total wastewater efuent of about 2:1. That is, over two-thirds of the generatedwastewaterstreaminanaverageplanthasbeenreusedandrecycled.Ofthisvolume,about66%hasbeenusedascoolingwaterandtheremaining34%fortheprocessorotherpurposes. Table6EfuentLimitationsforSubpartD,GlycerineConcentrationEfuentlimitations[metricunits(kg/1000kgofanhydrousproduct)]EfuentcharacteristicMaximumforany1dayAverageofdailyvaluesfor30consecutivedaysshallnotexceed(a)BPTBOD54.501.50COD13.504.50TSS0.600.20Oilandgrease0.300.10pHaa(b)BATBOD50.800.40COD2.401.20TSS0.200.10Oilandgrease0.080.04pHaa(c)NSPSBOD50.800.40COD2.401.20TSS0.200.10Oilandgrease0.080.04pHaaaWithintherange6.09.0.Source:Ref.14.360YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved.

7.6.2WastewaterTreatmentMethodsThesoapanddetergentmanufacturingindustrymakesroutineuseofvariousphysicochemicalandbiologicalpretreatmentmethodstocontrolthequalityofitsdischarges.Asurveyofthesetreatment processes is presented in Table 11 [13], which also shows the usual removalefcienciesofeach unitprocess on the various pollutantsofconcern. According to Nemerow[38]andWangandKrofta[39],theoriginofmajorwastesisinwashingandpurifyingsoapsanddetergentsandtheresultingmajorpollutantsarehighBODandcertainsoaps(oilyandgreasy,alkali, and high-temperature wastes), which are removed primarily through air otation andskimming,andprecipitationwiththeuseofCaCl asacoagulant.2Figure21presentsacompositeowdiagramdescribingacompletetreatmenttrainoftheunit processes that may be used in a large soap and detergent manufacturing plant to treat itswastes.Asaminimumrequirement,owequalizationtosmoothoutpeakdischargesshouldbeutilizedevenataproductionfacilitythathasasmall-volumebatchoperation.Largerplantswithintegrated product lines may require additional treatment of their wastewaters for bothsuspendedsolidsandorganicmaterialsreduction.Coagulationandsedimentationareusedbytheindustryforremovingthegreaterportionofthelargesolidparticlesinitswaste.Ontheotherhand,sandormixed-bedltersusedafterbiologicaltreatmentcanbeutilizedtoeliminateneparticles. One of the biological treatment processes or, alternatively, granular or powderedactivatedcarbonistheusualmethodemployedfortheremovalofparticulateorsolubleorganicsfromthewastestreams.Finally,asatertiarystepforremovingparticularionizedpollutantsor Table7EfuentLimitationsforSubpartG,BarSoapsEfuentlimitations[metricunits(kg/1000kgofanhydrousproduct)]EfuentcharacteristicMaximumforany1dayAverageofdailyvaluesfor30consecutivedaysshallnotexceed(a)BPTBOD51.020.34COD2.550.85TSS1.740.58Oilandgrease0.120.04pHaa(b)BATBOD50.400.20COD1.200.60TSS0.680.34Oilandgrease0.060.03pHaa(c)NSPSBOD50.400.20COD1.200.60TSS0.680.34Oilandgrease0.060.03pHaaaWithintherange6.09.0.Source:Ref.14.TreatmentofSoapandDetergentIndustryWastes361Copyright#2004by Marcel Dekker, Inc.All Rights Reserved.

totaldissolvedsolids(TDS),afewmanufacturingfacilitieshaveemployedeitherionexchangeorthereverseosmosisprocess.FlotationorFoamSeparationOne of the principal applications of vacuum and pressure (air) otation is in commercialinstallationswithcolloidalwastesfromsoapanddetergentfactories[20,4042].Wastewatersfrom soap production are collected in traps on skimming tanks, with subsequent recoveryoatingoffattyacids.Foamseparationorfractionation[40,41,4345]canbeusedtoextraadvantage:notonlydosurfactantscongregateattheair/liquidinterfaces,butothercolloidalmaterialsandionizedcompoundsthatformacomplexwiththesurfactantstendtoalsobeconcentratedbythismethod.Anincidental,butoftenimportant,advantageofairotationprocessesistheaerobicconditiondeveloped,whichtendstostabilizethesludgeandskimmingssothattheyarelesslikelytoturnseptic. However, disposal means for the foamate can be a serious problem in the use of thisprocedure[46].Ithasbeenreportedthatfoamseparationhasbeenabletoremove7080%ofsyntheticdetergents,atawiderangeofcosts[2].Gibbs[17]reportedthesuccessfuluseofnebubbleotationand40mmdetentionintreatingsoapmanufacturewastes,wheretheskimmedsludge was periodically returned to the soap factory for reprocessing. According to Wang[4749], the dissolved air otation process is both technically and economically feasible fortheremovalofdetergentsandsoaps(i.e.,surfactants)fromwater. Table8EfuentLimitationsforSubpartH,LiquidSoapsEfuentlimitations[metricunits(kg/1000kgofanhydrousproduct)]EfuentcharacteristicMaximumforany1dayAverageofdailyvaluesfor30consecutivedaysshallnotexceed(a)BPTBOD50.030.01COD0.150.05TSS0.030.01Oilandgrease0.030.01pHaa(b)BATBOD50.020.01COD0.100.05TSS0.020.01Oilandgrease0.020.01pHaa(c)NSPSBOD50.020.01COD0.100.05TSS0.020.01Oilandgrease0.020.01pHaaaWithintherange6.09.0.Source:Ref.14.362YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved.

ActivatedCarbonAdsorptionColloidalandsolubleorganicmaterialscanberemovedfromsolutionthroughadsorptionontogranular or powdered activated carbon, such as the particularly troublesome hard surfactants.Refractory substances resistant to biodegradation, such as ABS, are difcult or impossible toremovebyconventionalbiologicaltreatment,andsotheyarefrequentlyremovedbyactivatedcarbonadsorption[11].Theactivatedcarbonapplicationismadeeitherinmixed-batchcontacttanks with subsequent settling or ltration, or in ow-through GAC columns or contact beds.Obviously, becauseit isan expensive process, adsorption isbeing usedas apolishing stepofpretreated waste efuents. Nevertheless, according to Koziorowski and Kucharski [22] muchbetter results of surfactant removal have been achieved with adsorption than coagulation/settling.Wang[5052]usedbothpowderedactivatedcarbon(PAC)andcoagulation/settling/DAFforsuccessfulremovalofsurfactants.Coagulation/Flocculation/Settling/FlotationAsmentionedpreviouslyinSection7.2.4,thecoagulation/occulationprocesswasfoundtobeaffected bythe presence ofsurfactantsinthe raw water orwastewater. Suchinterference wasobserved for both alum and ferric sulfate coagulant, but the use of certain organic polymer Table9EfuentLimitationsforSubpartI,OleumSulfonationEfuentlimitations[metricunits(kg/1000kgofanhydrousproduct)]EfuentcharacteristicMaximumforany1dayAverageofdailyvaluesfor30consecutivedaysshallnotexceed(a)BPTBOD50.090.02COD0.400.09TSS0.150.03Surfactants0.150.03Oilandgrease0.250.07pHaa(b)BATBOD50.070.02COD0.270.09TSS0.090.03Surfactants0.090.03Oilandgrease0.210.07pHaa(c)NSPSBOD50.030.01COD0.090.03TSS0.060.02Surfactants0.030.01Oilandgrease0.120.04pHaaaWithintherange6.09.0.Source:Ref.14.TreatmentofSoapandDetergentIndustryWastes363Copyright#2004by Marcel Dekker, Inc.All Rights Reserved.

Table10EfuentLimitationsforSubpartP,LiquidDetergentsEfuentlimitations[metricunits(kg/1000kgofanhydrousproduct)]EfuentcharacteristicMaximumforany1dayAverageofdailyvaluesfor30consecutivedaysshallnotexceed(a)BPTaBOD50.600.20COD1.800.60TSS0.0150.005Surfactants0.390.13Oilandgrease0.0150.005pHcc(b)BPTbBOD50.05COD0.15TSS0.002Surfactants0.04Oilandgrease0.002pHc(c)BATaBOD50.100.05COD0.440.22TSS0.010.005Surfactants0.100.05Oilandgrease0.010.005pHcc(d)BATbBOD50.02COD0.07TSS0.002Surfactants0.02Oilandgrease0.002pHc(e)NSPSaBOD50.100.05COD0.440.22TSS0.010.005Surfactants0.100.05Oilandgrease0.010.005pHcc(f)NSPSbBOD50.02COD0.07TSS0.002Surfactants0.02Oilandgrease0.002pHcaFornormalliquiddetergentoperations.bForfastturnaroundoperationofautomatedlllines.cWithintherange6.09.0.Source:Ref.14.364YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved. Figure 20Processmodicationforwastewaterrecyclingindetergentmanufacture(fromRef.37).TreatmentofSoapandDetergentIndustryWastes365Copyright#2004byMarcelDekker,Inc.AllRightsReserved. occulants was shown to overcome this problem. However, chemical coagulation andocculation for settling may not prove to be very efcient for such wastewaters. Wastescontainingemulsiedoilscanbeclariedbycoagulation,iftheemulsionisbrokenthroughtheaddition of salts such as CaCl , the coagulant of choice for soap and detergent manufacture2wastewaters[11].Also,limeorothercalciumchemicalshavebeenusedinthetreatmentofsuchwasteswhosesoapyconstituentsareprecipitatedasinsolublecalciumsoapsoffairlysatisfactoryocculating (hardness scales) and settling properties. Treatment with CaCl can be used to2removepracticallyallgreaseandsuspendedsolidsandamajorpartofthesuspendedBOD[19].Using carbondioxide(carbonation)asanauxiliary precipitantreducestheamountofcalciumchloriderequiredandimprovestreatmentefciency.Thesludgefrom CaCl treatmentcan be2removedeitherbysedimentationorbydissolvedairotation[39,5356].Formonitoringandcontrol of chemical coagulation, occulation, sedimentation and otation processes, manyanalyticalproceduresandtestingprocedureshavebeendeveloped[5764].IonExchangeandExclusionTheion-exchange process has been usedeffectivelyinthe eldof waste disposal. Theuseofcontinuous ion exchange and resin regeneration systems has further improved the economicfeasibility of the applications over the xed-bed systems. One of the reported [1] special Table11TreatmentMethodsintheSoapandDetergentIndustryPollutantandmethodEfciency(percentageofpollutantremoved)OilandgreaseAPI-typeseparationUpto90%offreeoilsandgreases.Variableonemulsiedoil.CarbonadsorptionUpto95%ofbothfreeandemulsiedoils.FlotationWithouttheadditionofsolidphase,alum,oriron,7080%ofbothfreeandemulsiedoil.Withtheadditionofchemicals,90%.Mixed-medialtrationUpto95%offreeoils.Efciencyinremovingemulsiedoilsunknown.Coagulation/sedimentationwithiron,alum,orsolidphase(bentonite,etc.)Upto95%offreeoil.Upto90%ofemulsiedoil.SuspendedsolidsMixed-medialtration7080%Coagulation/sedimentation5080%BODandCODBioconversions(withnalclarier)6095%ormoreCarbonadsorptionUpto90%ResidualsuspendedsolidsSandormixed-medialtration5095%DissolvedsolidsIonexchangeorreverseosmosisUpto90%Source:Ref.13.366YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved. Figure 21Compositeowsheetofwastetreatmentinsoapanddetergentindustry(fromRef.13).TreatmentofSoapandDetergentIndustryWastes367Copyright#2004byMarcelDekker,Inc.AllRightsReserved. applications of the ion-exchange resins has been the removal of ABS by the use of a Type IIporousanionexchangerthatisastrongbaseanddependsonachloridecycle.ThisresinsystemisregeneratedbyremovingagreatpartoftheABSabsorbedontheresinbeadswiththehelpofamixture of hydrocarbons (HC) and acetone. Other organic pollutants can also be removed byion-exchangeresins,andthemainproblemiswhethertheorganicmaterialcanbeelutedfromtheresinusingnormalregenerationorwhetheritiseconomicallyadvisabletosimplydiscardtheused resin. Wang and Wood [65] and Wang [51,52,66] successfully used the ion-exchangeprocessfortheremovalofcationicsurfactantfromwater.The separation of ionic from nonionic substances can be effected by the use of ionexclusion[46].Ionexchangecanbeusedtopurifyglycerineforthenalproductofchemicallypureglycerineandreducelossestowaste,buttheconcentrationofdissolvedionizablesolidsorsalts(ash)largelyimpactsontheoveralloperatingcosts.Economically,whenthecrudeorsweetwatercontainsunder1.5%ash,straightionexchangeusingacationandanionmixedbedcanbeused,whereasforhigherpercentagesofdissolvedsolids,itiseconomicallyfeasibletofollowtheionexchangewithanion-exclusionsystem.Forinstance,wastestreamscontaining 0.20.5%ash and 35% glycerine may be economically treated by straight ion exchange, while wastestreams containing 510% ash and 35% glycerine have to be treated by the combinedion-exchangeandion-exclusionprocesses.BiologicalTreatmentRegarding biological destruction, as mentioned previously, surfactants are known to cause agreat deal of trouble due to foaming and toxicity [103] in municipal treatment plants. Thebehaviorofthesesubstancesdependsontheirtype[22],thatis,anionicandnonionicdetergentsincrease the amount of activated sludge, whereas cationic detergents reduce it, and also thevariouscompoundsdecomposetoadifferentdegree.Theactivatedsludgeprocessisfeasibleforthe treatment of soap and detergent industry wastes but, in general, not as satisfactory astrickling lters. The turbulence in the aeration tank induces frothing to occur, and also thepresence of soaps and detergents reduces the absorption efciency from air bubbles to liquidaerationbyincreasingtheresistanceoftheliquidlm.Ontheotherhand,detergentproductionwastewatershavebeentreatedwithappreciablesuccessonxed-lmprocessunitssuchastricklinglters[2].Also,processessuchaslagoons,oxidationorstabilizationponds,andaeratedlagoonshaveallbeenusedsuccessfullyintreatingsoap and detergent manufacturing wastewaters. Finally, Vath [102] demonstrated that bothlinearanionicandnonionicethoxylatedsurfactantsunderwentdegradation,asshownbyalossofsurfactantproperties,underanaerobictreatment.Wanget al.[42,67,68] have developed innovative biological process and sequencingbatch reactors (SBR) specically for removal of volatile organic compounds (VOCs) andsurfactants.Relatedanalyticalprocedures[5764,7191]availableforprocessmonitoringandcontrolareavailableintheliterature.7.7CASE STUDIES OF TREATMENT FACILITIESSoapanddetergentmanufactureandformulationplantsaresituatedinmanyareasintheUnitedStatesandothercountries.Atmost,ifnotalloftheselocations,thewastewatersfromproductionand cleanup activities are discharged to municipal sewer systems and treated together withdomestic,commercial,institutional,andotherindustrialwastewaters.FollowingtheprecipitousreductioninproductionanduseofhardsurfactantssuchasABS,nodiscernibleproblemsin368YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved.

operation and treatment efciency due to the combined treatment of surfactant manufacturewastesatthesemunicipalsewagetreatmentplants(mostofwhichemploybiologicalprocesses)have been reported. In fact, there is a signicantly larger portion of surfactants and relatedcompounds being discharged to the municipal facilities from user sources. In most cases, theindustrialdischargeissimplysurchargedduetoitshigh-strengthBODconcentration.7.7.1ColgatePalmolivePlantPossiblythemostrepresentativetreatmentfacilitythathandleswastewatersfromtheproductionofsoaps,detergents,glycerines,andpersonalcareproductsisColgatePalmoliveCompanysplantatJeffersonville,IN[3].Theproductionwasteshadreceivedtreatmentsince1968[21]inacompletely mixed activated sludge plant with a 0.6MGD design ow and consisting of a0.5MG mixed equalization and storage basin, aeration basin, and nal clarier. The treatedefuent was discharged to the Ohio River, combined with rain drainage and cooling waters.During operation, it was observed that waste overloads to the plant caused a deterioration ofefuent quality and that the system recoveredvery slowly, particularly from surfactant short-term peaks. In addition, the fact that ABS had been eliminated and more LAS and nonionicsurfactantswerebeingproduced,aswellasthechangesinproductformulation,mayhavebeenthe reasons for the Colgate treatment plants generally less than acceptable efuent quality.(Notethat1MG3785m ,1MGD33785m3/day.)Owingtothefactthatthecompanyconsideredthetreatmentefciencyinneedofmoredependable results, in 19721973 several chemical pretreatment and biological treatmentstudies were undertaken in order to modify and improve the existing system. As a result, amodied treatment plant was designed, constructed, and placed in operation. A new 1.5MGmixedowandpollutantloadequalizationbasinisprovidedpriortochemicalpretreatment,andaashmixerwithlimeadditionprecedesaocculator/clarierunit.Aheadofthepre-existingequalizationandaerationbasins,thecapabilityforpHadjustmentandnutrientsupplementationwas added. Chemical sludge is wasted to two lagoons where thickening and dewatering(normally1530%solids)takeplace.Theintermediatestoragebasinhelpsequalizeupsetsinthechemicalpretreatmentsystem,providesneutralizationcontacttime,andallowsforstorageofpretreatedwastewatertosupplytothe biological treatment unit whenever a prolonged shutdown of the chemical pretreatmentoccurs. Such shutdowns are planned for part of the weekend and whenever manufacturingstoppage occurs in order to cutdownon costs. According to Brownell [3], waste loads to thepretreatment plant diminish during plantwide vacations and production shutdowns, andbypassingthechemicalpretreatmentallowsforamoreconstantloadingoftheaerationbasinsatthosetimes.Inthisway,thepreviouslyencounteredproblemsinthestart-upofthebiologicaltreatmentunitaftershutdownswerereduced.Thepollutantremovalefciencyofthisplantisnormallyquitehigh,withoverallMBAS(methylene blue active substances) removals at 9899% and monthly average overall BOD5removals ranging from 88 to 98% (most months averaging about 95%). The reported MBASremovalsachievedinthechemicalpretreatmentunitsnormallyaveraged6080%.Occasionalhigh MBAS concentrations in the efuent from the chemical pretreatment system werecontrolledthroughtheadditionofFeCl andanorganicpolymerthatsupplementedtheregular2doseoflimeandincreasedsuspendedsolidscapture.Also,highoilandgreaseconcentrationswere occasionally observed after spills of fatty acid, mineral oil, olen, and tallow, andhistoricallythiscausedproblemswiththebiologicalsystem.Inthechemicalpretreatmentunits,adequate oil and grease removals were obtained through the addition of FeCl . Finally, COD2TreatmentofSoapandDetergentIndustryWastes369Copyright#2004by Marcel Dekker, Inc.All Rights Reserved.

removalsinthechemicalsystemwerequiteconsistentandaveragedabout50%(CODwasabouttwicetheBOD ).5In the biological step of treatment, removal efciency for BOD was very good, often5averaging over 90%. During normal operating periods, the activated sludge system appearedincapable of treating MBAS levels of over 100lb/day (45.4kg/day) without signicantundesirablefoaming.TheBOD loadingwasnormallykeptat0.150.18g5/day/g(orlb/day/lb)MLVSS,butithadtobereducedwheneverincreasedfoamingoccurred.Finally,suspendedsolidsconcentrationsinthesecondaryclarierefuentwereoccasionallyquitehigh,althoughtheoverowrateaveragedonly510gal/day/ft andaslowas320gpd2/ft (1320.8m23/day/m ).Theuseofpolymerocculantsconsiderablyimprovedtheefuentturbidity,reducingitby25075%, and because higher efuent solids contribute to high efuent BOD , it was reduced5as well. Therefore, although the ColgatePalmolive waste treatment plant occasionallyexperiences operating problems, it generally achieves high levels of pollutant removalefciencies.ManyanalyticalprocedureshavebeendevelopedfordeterminationofMBAS[73,75]andCOD/DO [61,8991] concentrations in water and wastewater, in turn, for monitoring theefciencyoftreatmentprocesses.7.7.2CombinedTreatmentofIndustrialandMunicipalWastesMost soap and detergent manufacturing facilities, as mentioned previously, discharge theiruntreatedorpretreatedwastesintomunicipalsystems.Thecompositionsofthesewastewatersvarywidely,withsomebeingreadilybiodegradableandothersinhibitorytonormalbiologicaltreatmentprocesses.Inordertoallowandsurchargesuchanefuenttoamunicipaltreatmentplant,anevaluationofitstreatabilityisrequired.Suchadetailedassessmentofthewastewatersdischarged from a factory manufacturing detergents and cleaning materials in the vicinity ofPinxton,England,wasreportedbyShapland[92].Theaverageweeklyefuentdischargedfromasmallcollectionandequalizationtankwas119m3/day(21.8gpm),whichcontributesabout4%oftheowtothePinxtonsewagetreatmentplant.Monitoring of the diurnal variation in wastewater pollutant strengths on different daysshowedthatnoregulardiurnalpatternexistsandthedischargedwastewatersarechangeable.Inparticular, the pH value was observed to vary rapidly over a wide range and, therefore, pHcorrectionintheequalizationtankwouldbeaminimumrequiredpretreatmentpriortodischargeintothesewersinsuchcases.TheincreaseinorganicloadingcontributedtothePinxtonplantbythedetergentfactoryismuchhigherthanthehydraulicloading,representinganaverageof32%BODincreaseintherawinuentand60%BODincreaseintheprimarysettledefuent,butitdoesnotpresentaproblembecausetheplantisbiologicallyandhydraulicallyunderloaded.The treatability investigation of combined factory and municipal wastewaters involvedlaboratory-scaleactivatedsludgeplantsandrollingtubes(xed-lm)units.Theinuentfeedtothese units was settled industrial efuent (with its pH adjusted to 10) mixed in variousproportions with settled municipal efuent. The variation of hydraulic loading enabled therotating tubes to be operated at similar biological loadings. In the activated sludge units, themixed liquor suspended solids (MLSS) were maintained at about 3000mg/L, a difcult tasksince frothing and oe break-up caused solids loss. The overall results showed that moreconsistentremovalswereobtainedwiththexed-lmsystem,probablyduetothelossofsolidsfromtheaerationunits[93].At3and6%byvol.industrialwastecombination,slighttonobiologicalinhibitionwascausedeithertothexed-lmoractivatedsludgesystem.Theresultsofsampleanalysisfromtheinhibitoryrunsshowedthatintwoofthethreecases,thepossiblecauseofinhibitionwasthe370YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved.

presence of chloroxylenes and brominated compounds. The third case represented onlytemporary inhibition, since the rolling tubes provided adequate treatment after a period ofacclimation.Finally,thegeneralconclusionreachedintheinvestigationwasthatthedetergentfactory efuent may be accepted at 3% by vol. equalized ow to the municipal xed-lmtreatment plant, that is, up to 200m3/day (36.7gpm), without any noticeable efciencyreduction.7.7.3TreatabilityofOilyWastesfromSoapManufactureMcCarty[94]addressedthesubjectofthetreatabilityofanimalandvegetableoilsandfatsinmunicipal treatment systems. In general, certain reported treatment difculties in biologicalsystems are attributed to the presence of fats, oils, and other grease components inwastewaters.However,asopposedtomineral-typeoils,animalandvegetableoilsandfatssuchas those discharged by soap manufacture plants are readily biodegradable and generallynontoxic,althoughdifferencesexistastothedifcultiescauseddependingontheform(oatableoremulsied)andtype(hydrocarbons,fattyacids,glycerides,sterols,etc.).Ingeneral,shorter-chain-length fatty acids, unsaturated acids, and soluble acids are more readily degraded thanlonger-chain, saturated, and insolubleones. Themore insoluble and larger fatty acid particleshavebeenfoundtorequiregreatertimefordegradationthanthosewithoppositecharacteristics.It has also been reported that animal and vegetable oils, fats, and fatty acids are metabolizedquickly in anaerobic systems and generate the major portion of methane in regular anaerobicsludgedigestion.McCarty[94]alsoreportedontheresultsoflaboratoryinvestigationsinthetreatabilityofselectedindustrialoilywastesfromsoapmanufacturingandfoodprocessingbytheProcter&GambleCo.inCincinnati,OH,whencombinedwithmunicipalsewage orsludge.Thegreasecontentoftheindustrialwasteswashighinallcases,rangingfrom13to32%ofthewasteCOD,anditwasabout2.9gofCODpergramofgrease.ItwasfoundthatitispossibletotreataboutequalCODmixturesoftheindustrialwasteswithmunicipalsewageusingtheactivatedsludgeprocessandachieveremovalefcienciessimilartothoseformunicipalsewagealone.The grease components of the industrial wastes were readily degraded by anaerobictreatment, with removal efciencies ranging from 82 to 92%. Sludges from the anaerobicdigestion ofanindustrial/municipalmixturecouldbedewateredwithgenerallyhighdosesofchemicalconditioning(FeCl ),butthesestringentrequirementsseemedaresultofthehard-to-2dewatermunicipalwastesludge.Inconclusion,theProcter&GambleCo.industrialwasteswerereadilytreated whenmixedwithmunicipalsewagewithoutsignicantadverseimpacts,givensufcient plantdesign capacity to handle the combinedwasteshydraulicallyandbiologically.Also,therewasnoproblemwiththeanaerobicdigestionofcombinedwastes,ifadequatemixingfacilitiesareprovidedtopreventtheformationofscumlayers.For treatment process control, Wang [8587] has developed rapid methods fordeterminationofoilandgreaseanddissolvedproteinsinthewastewaters.7.7.4RemovalofNonionicSurfactantsbyAdsorptionNonionic surfactants, as mentioned previously, have been widely adopted due to theircharacteristics and properties and, in particular, because they do not require the presence ofundesirable phosphate or caustic builders in detergent formulation. However, the relativelylesser degree of biodegradability is an important disadvantage of the nonionic surfactantscomparedtotheionicones.Adsorptiononactivatedcarbonandvarioustypesofclayparticlesis,therefore, one of the processes that has been effective in removing heterodisperse nonionicTreatmentofSoapandDetergentIndustryWastes371Copyright#2004by Marcel Dekker, Inc.All Rights Reserved.

surfactants thosethatutilizeapolyhydroxylalcoholasalipophilicphase fromwastewaters[6].InanotherstudybyCarberryandGeyer[5],theadsorptivecapacitykineticsofpolydispersenonionicsurfactantsthosethatutilizeahydrocarbonspeciesasalipophilicbaseremovalbygranularactivatedcarbonandclaywereinvestigated. Bothclayparticulatesofdifferenttypesandvariousactivatedcarbonsweretestedandprovenefcientinadsorbingnonionicsurfactants.Ofalltheclaysandcarbonsstudied,Bentolite-Lappearedtobethesuperioradsorbent(9.95%mol/kg vs. 0.53mol/kg for Hydrodarco 400), but reaction rate constants for all adsorbentstestedappearedtobestrikinglysimilar.7.7.5RemovalofAnionicDetergentswithInorganicGelsInorganic gels exhibiting ion-exchange and sorption characteristics are more stable thansynthetic organic resins, which have also been used for the removal of detergents fromwastewaters[95].Thesorptionefciencyandnumberofcyclesforwhichinorganicgelscanbeused without much loss in sorption capacity would compensate the cost involved in theirpreparation. Zinc and copper ferrocyanide have been shown to possess promising sorptioncharacteristics for cationic and anionic surfactants. Of the two, copper ferrocyanide is abetter scavenger for anionic detergents, which have a relatively small rate and degree ofbiodegradation and their presence in raw water causes problems in coagulation andsedimentation.Thecation-exchangecapacityofthecopperferrocyanidegelusedwasfoundtobeabout2.60meq/ganditsanion-exchangecapacityabout0.21meq/g.Inallcasesofvariousdosesofgelusedandtypesofanionicsurfactantsbeingremoved,thetestsindicatedthatabatchcontacttime of about 12hours was sufcient for achieving maximum removals. Trials with variousfractions of particle size demonstrated that both uptake and desorption (important in materialregeneration)weremostconvenientandmaximizedon170200BSSmeshsizeparticles.Also,theadsorptionofanionicsurfactantswasfoundtobemaximumatpH4anddecreasedwithanincreaseinpH.ThepresenceofNaClandCaCl salts(monoandbivalentcations)insolutionwasshown2toincreasetheadsorptionofanionicsurfactantsinthepHrange47,whereasthepresenceofAlCl salt (trivalent cation) caused a greater increase in adsorption in the same pH range.3However,atsaltconcentrationsgreaterthanabout0.6M,theadsorptionofthestudiedanionicsurfactantsstarteddecreasing.Ontheotherhand,almostcompletedesorptioncouldbeobtainedbytheuseofK SO oramixtureofH SO andalcohol,bothofwhichwerefoundtobeequally2424effective.Inconclusion,althoughinthesestudiesthesorptioncapacityoftheadsorbentgelwasnot fully exploited, the anionic detergent uptake on copper ferrocyanide was found to becomparabletoyashandactivatedcarbon.7.7.6RemovalofCationicSurfactantsTherearefewdemonstratedmethodsfortheremovalofcationicsurfactantsfromwastewater,asmentionedpreviously,andionexchangeandultraltrationaretwoofthem.ChiangandEtzel[8]developed a procedure for selecting from these the optimum removal process for cationicsurfactantsfrom wastewaters. Preliminary batch-testinvestigationsled to the selection ofoneresin (Rohm & Haas Amberlite, Amb-200) with the best characteristics possible (i.e., highexchange capacity with a rapid reaction rate, not very ne mesh resin that would cause anexcessivepressuredropandotheroperationalproblems,macroporousresinthathasadvantagesover the gel structure resins for the exchange of large organic molecules) to be used inoptimizing removal factors in the column studies vs. the performance of ultraltration372YapijakisandWangCopyright#2004by Marcel Dekker, Inc.All Rights Reserved.

membranes (Sepa-97 CA RO/UF selected). The cyclic operation of the ion-exchange (H )column consisted of the following stops: backwash, regeneration, rinse, and exhaustion(service).Theion-exchangetestsindicatedthatthebreakthroughcapacityortotalamountadsorbedby the resin column was greater for low-molecular-weight rather than high-molecular-weightsurfactants. Furthermore, the breakthrough capacity for each cationic surfactant wassignicantly inuenced (capacity decreases as the inuent concentration increases) by thecorresponding relationship of the inuent concentration to the surfactant critical micelleconcentration(CMC).ANaCl/ethanol/water(10%NaClplus50%ethanol)solutionwasfoundtobeoptimuminregeneratingtheexhaustedresin.IntheseparationtestswiththeuseofaUFmembrane,therejectionefciencyfortheC16cationic surfactants was found to be in the range 9099%, whereas for the C12surfactants itranged from 72 to 86%, when the feed concentration of each surfactant was greater than itscorresponding CMC value. Therefore, UF rejection efciency seems to be dependent on therespectivehydratedmicellediameterandCMCvalue.Inconclusion,thestudyshowedthatforcationic surfactants removal, if the feed concentration of a surfactant is higher than its CMCvalue,thentheUFmembraneprocessisfoundtobethebest.However,ifthefeedconcentrationofasurfactantislessthanitsCMCvalue,thenionexchangeisthebestprocessforitsremoval.Initialandresidualcationicsurfactantconcentrationsinawaterorwastewatertreatmentsystemcanbedeterminedbytitrationmethods,colorimetricmethods,orUVmethod[6971,7779,81]. Additional references for cationic surfactant removal are available elsewhere[44,45,51,65,66].7.7.7AdsorptionofAnionicSurfactantbyRubberRemovalofanionicsurfactantshasbeenstudiedorreportedbymanyinvestigators[96101].Ithasbeenreported[101]thattheefciencyofrubbergranules,alow-costadsorbentmaterial,isefcientfortheremovalofsodiumdodecylsulfate(SDS),whichisarepresentativememberofanionicsurfactants(AS).PreviousstudiesontheabsorptionofASonvariousadsorbentssuchas alumina and activated carbon showed 8090% removals, while the sodium form of typeA Zeolite did not have a good efciency; however, these adsorbing materials are not cost-effective.Inthisstudy,averylow-costscraprubberintheformofgranules(thewasteproductoftireslocallypurchasedforUS$0.20perkg)wasusedtoremoveASfromthewaterenvironment.Tirescontain2530%byweightcarbonblackasreinforcingllerandhydroxyland/orcarboxylgroups; both the carbon black and carboxyl group are responsible for the high degree ofadsorption.Inadditiontotheabundanceandlowcostofthewastetirerubber,theadvantageisthepossibilityofreusingtheexhaustedrubbergranulesasanadditivetoasphaltasroadmaterial.Earlier, Shalaby and El-Feky [98] had reported successful adsorption of nonionicsurfactant from its aqueous solution onto commercial rubber. The average size of sievedadsorbent granules used was 75, 150, and 425m. Itwas observedthat within 1hour, with allthree sizes, the removal of AS was the same, about 78%. But after 5 hours, the removal wasfoundtobe90%forthe75maveragesize,whileitwasonlyabout85%fortheothertwolargersizes(adsorptionisasurfacephenomenonandasthesizedecreases,thesurfaceareaincreases).Testsperformedwithinitialadsorbate(SDS)concentrationsof2,4,and6mg/Landdosesofadsorbentvaryingbetween5and15g/Lshowedaremovalefciencyinallcasesof6575%within1hour,whichonlyincreasedtoabout80%after 7hours.Theeffectofsolution pHonadsorptionofASbyrubbergranuleswasalsostudiedoverapHrangeof313usinganinitialAS concentration and an adsorbent dose of 3mg/L and 10g/L, respectively. Over a 6 hourTreatmentofSoapandDetergentIndustryWastes373Copyright#2004by Marcel Dekker, Inc.All Rights Reserved.

contacttime,withincreaseofpH,theremovalofASdecreasedpracticallylinearlyfrom86to72%,probablyduetointerferenceofOH2ion,whichhassimilarchargetothatofAS.TheeffectofCa2ion,whichisverycommoninwaters,wasinvestigatedoverarangeof0170ppmcalciumanditwasshownthatabout8089%removalofASoccurredthroughoutthisrange.SimilarlyhighlevelsofASremoval(8793%)wereobservedforironconcentrationsfrom 20 to 207ppm, possibly due to formation of insoluble salt with the anionic part of thesurfactantcausingincreasedremoval.Ontheotherhand,theionicstrengthofthesolutionintheformofNO3concentrationrangingfrom150to1500ppmwasshowntoreduceSDSremovalefciencyto7177%,whiletheeffectofchlorideconcentration(intherange151200mg/L)onASremovalbyrubbergranuleswasfoundtobeadverse,downto3448%ofSDS,whichmightbeduetocompetitionforadsorbingsites.For treatment process control, initial and residual anionic surfactant concentrations in awater treatment system can be determined by titration methods or colorimetric methods[75,76,80,84,90]. The most recent technical information on management and treatment of thesoapanddetergentindustrywasteisavailablefromthestateofNewYork[104].REFERENCES1.Abrams,I.M.;Lewon,S.M.J.Am.WaterWorksAssoc.1962,54(5).2.Besselievre,E.B.TheTreatmentofIndustrialWastes;McGraw-Hill:NewYork,NY,1969.3.Brownell, R.P. Chemical-biological treatment of surfactant wastewater.Proceedings of the 30thIndustrialWasteConference,PurdueUniversity,Lafayette,IN,1975,Vol.30,1085.4.Callely,A.G.TreatmentofIndustrialEfuents;HaistedPress:NewYork,NY,1976.5.Carberry, J.B.; Geyer, A.T. Adsorption of non-ionic surfactants by activated carbon and clay.Proceedingsofthe32ndIndustrialWasteConference,PurdueUniversity,Lafayette,IN,1977,Vol.32,867.6.Carberry, J.B. Clay adsorption treatment of non-ionic surfactants in wastewater. J. Water Poll.ControlFed.1977,49,452.7.Chambon,M.;Giraud,A.Bull.Ac.Nt.Medecine(France)1960,144,623628.8.Chiang, P.C.; Etzel, J.E. Procedure for selecting the optimum removal process for cationic sur-factants.InToxicandHazardousWaste;LaGrega,Hendrian,Eds.;Butterworth:Boston,MA,1983.9.Cohen,J.M.TasteandOdorofABS;USDept.ofHealth,EducationandWelfareDept.:Cincinnati,OH,1962.10.Cohen,J.M.J.Am.WaterWorksAssoc.1959,51,12551266.11.Eckenfelder,W.W.IndustrialWaterPollutionControl;McGraw-Hill:NewYork,NY,1989.12.USEPA.DevelopmentDocumentonGuidelinesforSoapandDetergentManufacturing,EPA-440/1-74-018a;USGovernmentPrintingOfce:Washington,DC,ConstructionGrantsProgram,1974.13.USEPA