PracticalWastewaterTreatment
SecondEdition
DavidL.Russell,PE
Lilburn,Georgia
GlobalEnvironmentalOperationsInc.
Thiseditionfirstpublished2019
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Names:Russell,DavidL.(DavidLloyd),1943-author.
Title:Practicalwastewatertreatment/DavidL.Russell,PE,Lilburn, Georgia,GlobalEnvironmentalOperationsInc.
Description:Secondedition.|Hoboken,NJ,USA:Wiley,2019.|Includes index.|
Identifiers:LCCN2018035677(print)|LCCN2018036545(ebook)|ISBN 9781119527053(AdobePDF)|ISBN9781119527121(ePub)|ISBN9781119100850 (hardcover)
Subjects:LCSH:Watertreatmentplants.|Sewage–Purification. Classification:LCCTD434(ebook)|LCCTD434.R872019(print)|DDC 628.1/683–dc23
LCrecordavailableathttps://lccn.loc.gov/2018035677
CoverdesignbyWiley
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Setin10/12ptWarnockProbySPiGlobal,Chennai,India
PrintedintheUnitedStatesofAmerica 10987654321
Iwanttothankseveralpeoplefortheirinspiration.Asecondeditionofabook isharderthanwritingafirstedition,andalotmoreworktoensurethatone hassomethingtosay.
Thefollowingpeopleprovidedmotivationforthiseffort: ElizabethAnnEason MarianneRussell(1942–2007)
Mygirls:LauraRussellandJenniferRussell and theirgirls:Edda,ZolaandMiriam
AlsoaspecialnoteofthankstoDrBenitoJoseMarinas,Distinguished ProfessorandcurrentheadoftheCollegeofCivilandEnvironmental EngineeringattheUniversityofIllinois,Urbana,Illinois,forrecognition.
Andfinally,BobEspositoofWileyforpatiencewithanauthor.
Contents
Acknowledgments xvii
Preface xix
1Composition,Chemistry,andRegulatoryFramework 1
1.1WaterComposition 1
1.2WaterCharacteristicsandPhysicalProperties 2
1.2.1SolubilityofGasesinWater 4
1.2.1.1Nitrogen 4
1.2.2Henry’sLaw 6
1.3SolutionChemistry:SaltsandIonsinWater 10
1.4DisassociationConstantsforWeakAcidandBases 12
1.4.1CommonMineralsDissolvedinFreshwaterandSeawater 15
1.5SourcesofWater 16
1.5.1Groundwater 16
1.5.2GroundwaterQuality 17
1.5.3OtherPrincipalContaminantsinGroundwater 18
1.5.4MovementofGroundwater 19
1.6AnalyticalMethods 19
1.7LaboratoryGuidance 22
1.8RegulatoryFrameworkofWaterRegulations 24
1.8.1WhatIsQualityWater? 24
1.8.2WaterQualityStandards 25
1.8.3WaterQualityStandardsintheUnitedStates 26
1.8.4EstablishingWaterQualityStandards 26
1.8.5EffluentStandardsandGuidance 26
1.8.6MixingZones 27
1.8.7DischargePermits 28
1.8.8USPenaltyPolicies–EnforcementofPermitConditions 28
1.8.9WaterQualityDischargeBasicsintheUS 29
1.8.10HowWaterQualityStandardsAreEstablished 32
1.8.11UKWaterEffluentQualityStandard 37
1.8.12EUWaterQualityStandardsandEffluentLimits 39
vii
1.8.13OtherWaterQualityRequirements 40
1.8.13.1USPrimaryandSecondaryDrinkingWaterStandards 40
1.8.13.2WHODrinkingWaterQualityGuidelines 43
1.8.13.3EUDrinkingWaterDirectives 43
1.8.13.4UKDrinkingWaterStandards 43
1.9WaterUseDataandSomeDischargeCharacteristics 43
1.9.1WaterUsebyMunicipalities 45
1.9.2AgriculturalWater 47
1.9.3CoolingWater 47
1.9.4BoilerWater 48
1.9.5OtherIndustrialWaterQualityRequirements 49
1.9.5.1SteelIndustry 50
1.9.5.2PaperIndustry 50
1.9.5.3PetrochemicalIndustry 50
1.9.5.4PetroleumExplorationandProductionOperations 51 Notes 52
2WhatisWaterPollution? 59
2.1PollutionDefined 59
2.2ChemicalIndustry 60
2.3CoolingTowers 63
2.4Boilers 64
2.5IronandSteelIndustry 66
2.6MiningIndustries 67
2.7FrackingforOilandGas 68
2.8PetroleumExploration 71
2.9PetroleumRefining 73
2.10AgriculturalandFoodProcessing 75
2.11CropWaterUse 75
2.12VegetableandFruitProcessing 76
2.13AnimalFarmingandConcentratedAnimalFeedingOperations 77
2.14LivestockandConcentratedAnimalFeedingOperations 78
2.15SlaughterhouseandMeatPackingandProcessingWastes 82
2.16DairyWastes 83
2.17MeasuringPollution 83
2.18TheSamplingPlan 85
2.19AnalyticalMethodsandtheRoleoftheLaboratory 87
2.19.1TheAnalyticalPlan 90
2.19.2TheEffectsofPollutionontheEnvironment 90
2.19.3OxygenDepletion–BiochemicalOxygenDemand 91
2.19.4OxygenUptakeinaStream—TheOxygenSagEquation 93
2.19.5BiologyofPollutedWater 95
2.19.6Nitrogen 96
viii Contents
2.19.7Phosphorus 97 Notes 98
3GroundwateranditsTreatment 103
3.1HydraulicsofGroundwater 104
3.2SoilParticlesandSurfaceAreas 106
3.3WellHydraulics 107
3.4WellPackingandScreens 109
3.5Trenches 109
3.5.1OrificesandPipeLosses 111
3.6CompressibleFlow 113
3.6.1CalculationofExpansionFactor 114
3.6.2GroundwaterHydraulics 115
3.7GroundwaterTreatment 117 Notes 123
4StatisticsofMeasurements 125
4.1IntroductiontoStatisticalMeasurements:Background 125
4.2SignificantFigures 126
4.3ProbableError 127
4.4RepeatMeasurements 128
4.5NetProcessMeasurements 129
4.5.1Calibration 129
4.5.2HowtoMeasureYourFlowAccurately 130
4.5.2.1GurleyCurrentMeter 130
4.6StatisticalDistributionsforEnvironmentalEvents 133
4.6.1WeibullDistributions 134
4.7BlackSwansandDataAnalysis 135
4.7.1BlackSwans 135
4.7.2DataAnalysis 136
4.7.3Outliers 136 Notes 137
5TheFlowofWaterandWastewater 139
5.1StatisticalBasisforErrorEstimation 139
5.2OpenChannelHydraulics 140
5.3FroudeNumber 147
5.4TypesofFlowmeters 150
5.5WeirPlates 155
5.6AlignmentErrors 156
5.7SamplesandSampling 158
5.8Conclusion 161 Notes 161
Contents ix
x Contents
6TroubleshootingandEmergencyPlanning 163
6.1FaultTreeAnalysis 163
6.2ReverseFaultTreeAnalysis 166
6.2.1BowTieAnalysis 166
6.3Analysis:TheFiveWhys 168
6.4RegulatoryRequirements 169
6.5SoftwareSolutions 169
6.6EmergencyResponsePlanning 170
Notes 170
7ChemistryandAnalyses 173
7.1AquaticTesting 173
7.2BacterialTesting 174
7.3DissolvedOrganicMaterials–BOD,COD,andTOC 175
7.3.1BODvsThOD 179
7.3.2ChemicalOxygenDemand 181
7.3.3TOC 183
7.4CommonIonSpecies 183
7.4.1MostImportantChemicalsintheWaterEnvironment 185
7.4.2pH 185
7.4.3CarbonateChemistry 186
7.4.4Alkalinity 186
7.5Hardness 189
7.6ChemicalWaterSoftening 192
7.6.1ExcessLimeProcess 193
7.7Nitrogen 194
7.8Phosphorus 197
7.9Sulfur 198
7.10Chlorine 198
7.11OtherHalogens 199
7.12Metals 199
7.13Solids 201
7.14OrganicChemicals 205 Notes 206
8BasicWaterandWastewaterTreatmentTechniques 209
8.1RemovalofMetals 209
8.2Chromium 211
8.2.1OtherChromiumReductionReactions 212
8.3Arsenic 213
8.4Cadmium 213
8.5Iron 214
8.6Zinc 214
8.7Mercury 214
8.8Radium 215
8.9Anions 218
8.9.1Cyanide 218
8.9.2NitratesandNitrites 219
8.10SolventsandOils 220
8.11ChlorinatedOrganics 221
8.11.1PCBs 222
8.11.2DDT 223 Notes 225
9BiologicalWastewaterTreatment 227
9.1TheMicrobialWorld 227
9.2OrderofTreatment 233
9.3TypesofOrganisms 234
9.4ChemistryandActivatedSludge 238
9.5GrowthConditionsandNitrification 239
9.6DenitrificationandPhosphateRemoval 240
9.7BiologicalGrowthEquation 241
9.7.1TheMonodEquation 242
9.7.2MicrobialDecay 243
9.7.3EffectofTemperatureandpHonRateofReactions 245
9.8PrinciplesofBiologicalTreatmentSystems 245
9.9ActivatedSludgeanditsVariations 248
9.10SubstrateRemovalDefinitions 250
9.11TricklingFiltersandVariations 252
9.12ClarificationforBiologicalRemovals 254
9.13OtherSolidsRemovals 255
9.14BiologicalSynthesisandOxidation 255
9.15BiologicalTreatmentofToxicWastes 257
9.16ModelingtheBiologicalProcess 257
9.16.1ModelingNotesBeforeOneStarts 258
9.16.2FreeWastewaterTreatmentModelingPlatforms 261
9.16.2.1SSSP 261
9.16.2.2STEADY 261
9.16.2.3JASS 262
9.16.2.4Stoat 262
9.16.3CommerciallyAvailableModelingTools 263
9.16.3.1GPSX 263
9.16.3.2SUMO 264
9.16.3.3SIMBA 265
Contents xi
9.16.3.4Biowin 267
9.16.3.5WEST 268
9.16.4ModelingSummary 268 Notes 270
10AnaerobicTreatment 273
10.1BasicAnaerobicProcessesforWastewater 273
10.2PhosphorusRemoval 275
10.3BasicAnaerobicProcessesforDigestionandTreatment 276
10.4AnaerobicPretreatment 278
10.5UpflowAnaerobicSludgeBlanketReactors 281
10.6OtherDigesterConfigurations 283
10.7SiloxaneRemovals 283
10.8SludgeDigestion 284
10.9GasProductionEmphasis 286
10.10NewTechnologies 287
10.11SludgeTreatment 288
10.12AnaerobicDigesterModelADM1 288
10.13StruviteandAnaerobicProcesses 289 Notes 290
11PrecipitationandSedimentation 293
11.1TheoryofSedimentation 293
11.2ClarifiersandtheirDesign 294
11.2.1BulkVelocity–SurfaceLoadingRate 294
11.2.2HydraulicDetentionTime 296
11.3LamellasandSpecialtyDevices 298
11.3.1Lamellas 298
11.3.2MembraneFilters 299 Note 301
12GranularFiltrationTheoryandPractice 303
12.1GranularMediaFiltration 303
12.1.1SizingofFiltersbyFlowRate 303
12.1.2UniformityCoefficientandEffectiveGrainSize 306
12.2FiltrationHydraulics 306
12.3ParticleSizeRemovals 307
12.4BackwashHydraulics 307
12.4.1UseofAirintheBackwashofGranularFiltrationSystems 310 Notes 312
13SkinFiltration 313
13.1Introduction 313
13.2MicrostrainersandScreens 313
xii Contents
13.3BeltFilters 316
13.4PlateandFrameFilters 316
13.5Clothvs.PaperFilters 319
13.6Precoat 320
13.7HeadLossThroughClothFilters 322
13.8BagFilters 323 Notes 324
14MembraneFiltersandReverseOsmosis 325
14.1Introduction 325
14.2DesignValues 330
14.3ProcessSelection 330
14.3.1UltrafiltrationMembraneSelection 330
14.3.2CelluloseAcetateMembranes 331
14.3.3PolysulfoneMembranes 331
14.3.4PolyamideMembranes 331
14.3.5PolyacrylonitrileMembranes 331
14.3.6UltrafiltrationModules 332
14.4ReverseOsmosis 333
14.5MassTransferTheory 333
14.6MembraneDesignSoftware 334
14.7MembraneMaterials 336
14.8MembraneConfigurations 337
14.9RODesignConsiderations 338
14.9.1FeedwaterSupplyConsiderations 338
14.9.2PressurePumping 338
14.9.3MembraneConsiderations 341
14.9.4Post-treatment 341
14.10DesignParameters 341 Notes 344
15Disinfection 347
15.1Introduction 347
15.2RateofKill–DisinfectionParameters 347
15.2.1Chick’sLaw 347
15.2.2HarmfulOrganisms 348
15.3Chlorine 353
15.3.1Ammonia,Chlorine,andChloramines 354
15.3.2OtherTypesofChlorine 355
15.3.3OtherReactionswithChlorine 355
15.3.4ChlorineSafety 355
15.3.5ChlorineDioxide 356
15.4Ozone 357
Contents xiii
15.5UltravioletLight 358
15.5.1LEDLighting 360
15.6OtherDisinfectingCompounds 360
15.6.1PotassiumPermanganate 360
15.6.2HydrogenPeroxideandOzone 361
15.6.3PAA:PeraceticAcid 362
15.6.4Bromine 364
15.6.5Iodine 365
15.6.5.1TypesofIodinators 365
15.6.5.2CarefulUseofIodine 365
15.7DisinfectionbyUltraFiltration 366 Notes 367
16PhosphorusandNitrogenRemoval 369
16.1General 369
16.2BardenPho©Processes 373
16.3ChemicalPhosphorusRemoval 375
16.4NitrogenRemoval 378
16.4.1NitrogenChemistryandForms 378
16.4.2Ammonia 378
16.4.3Nitrate 379
16.4.4Nitrification 379
16.4.4.1AmmoniaStripping 388
16.4.4.2IonExchange 390
16.5Conclusions 392 Notes 392
17CarbonAdsorption 395
17.1Introduction 395
17.2TheFreundlichandLangmuirEquations 396
17.3CarbonAdsorptionPhysicalCoefficientsandEconomics 397
17.4OtherConsiderations 397
17.4.1CarbonRegeneration 397
17.4.2ThePACTTM Process 397
17.4.3WetAirRegenerationforPACTSystems 398 Note 401
18IonExchange 403
18.1Resins 403
18.2PhysicalCharacteristics 403
18.3ChemicalStructure 404
18.3.1Selectivity 404
18.3.2SelectivityCoefficient 405
xiv
Contents
18.4DesignConsiderations 406
18.4.1Pretreatment 406
19DissolvedAirFlotationandTechniques 409
19.1DesignBasicsforDAF 409
19.2OperatingParameters 410
19.3TheoryandDesign 411
19.4RangesofData 412
19.5Electroflotation 413
19.5.1ElectroflotationTheoryandDesign 414
19.6Electrocoagulation 415 Notes 416
20Coagulation,FlocculationandChemicalTreatment 419
20.1Introduction 419
20.2Sols 421
20.3FlocculationandMixing 422
20.4Practice 423
20.5Modeling 424 Notes 424
21HeatTransferProcesses:Boilers,HeatExchangersand CoolingTowers 425
21.1Boilers 425
21.2BoilerClassifications 426
21.2.1FireTubeBoilers 426
21.2.2WaterTubeBoilers 426
21.3BoilerWaterQualityRequirements 427
21.4CoolingTowers 430 Notes 431
22EvaluatinganExistingWastewaterTreatmentPlantDesign usingModelingSoftware 433
22.1Step1:InformationGathering 433
22.2Step2:ModelSelection 435
22.3Step3:LaboratoryandOtherDataOrganization 438
22.3.1GeneratingtheFlowsWithouttheData 439
22.3.2GettingtheHydraulicsandtheTankageCorrect 440
22.3.2.1WhenYouCannotDye-testYourTanks–aProcedure 441
22.4Step4:FlowSheetSetupandModelOrganization 443
22.5Step5:ModelCompilationandSetup 444
22.5.1InitialValuesversusDerivedValues 445
22.5.2IntegratorSettings 445
Contents xv
22.6Step6:InputandOutputFilePreparation 445
22.7Step7:InitializationoftheModelParametersandFirstRuns 445
22.7.1WhattoBalanceorAdjust 446
22.7.2WhattoKeyinonDuringYourModeling 446
22.8Step8:ParameterAdjustments 446
Notes 447
Index 449
xvi Contents
Acknowledgments
Ihavebeenprivilegedtohaveknownseveralgiantsintheenvironmentalfield. Manyofthemhavealreadypassedon,buttheircontributionoftimeandeffort tothefieldofenvironmentalengineeringcannotbeoverlooked.Standingon theshouldersofthesegiantshasgivenmeaplatformtobeabletolookoutatthe fieldandwriteaseriesofenvironmentalbooksonvarioustopics,includingthis work.Iwishtoacknowledgetheircontributionstothefieldofenvironmental engineeringatthispoint:
ProfessorRichardS.Englebrecht ,formerheadoftheEnvironmentalEngineeringDepartmentattheUniversityofIllinois,Urbana,forencouragementto followmydreams.
DrJohnAustin (UofI),forassistanceatadifficulttimeinmyacademiccareer.
DrBenjaminEwing (UofI),forinvaluableadviceoncareerselection.
DrV.T.Chow (UofI),forhisbodyofworkonopenchannelflowandhydrology.
Andsomereallygreatbossesovertheyears:
LeonMattioli and RichardSobel ofAlliedChemicalSpecialtyChemicals Division,Claymont,DE,andMorristown,NJ.
J.S.Lagarias,and DrLouisMcCabe ofResourcesResearch,Inc.(Divisionof HazeltonLaboratories,Reston,VA).
DrRobertIrvine,PhD,rediscovereroftheSequencingBatchReactor.
DrPieterVanRolleghem,mathematician,engineer,andcreatorofWEST software.
Andsomeverydearfriendsandprofessionalassociates:
DrCharlesCalmbacher,PhD,CIH
DavidR.Vaughn,PE
DrJeremyDudley,PEng
ThomasMcGowan,PE
DrDonaldRay,PE
LeroyStaska
Thankyouall.
DavidL.Russell,PE Lilburn,Georgia
xvii
GlobalEnvironmentalOperationsInc.
Preface
ThefirsteditionofthisbookwasdevelopedfromacourseItaughtforthe AmericanInstituteofChemicalEngineers.Itwasafirstattempttointroduce industrialwastewatertreatmenttheory,practices,andissuesintotheChemical Engineeringcommunityasastand-alonediscipline.Itultimatelyledtothefirst editionofthisbook.
Thereisanaturalseparationbetweenindustryandacademia,andconsequentlytheacademicsteachthebasicsofengineering,butmoreandmorethe separationbetweenthewaythesubjectmaterialistaughtandthewayitispracticedisgrowing.Historically,muchofthewastewatertreatmentfieldhasbeen theprovenanceofthecivilengineeringcommunitybecauseofitsassociation withsanitaryengineering.MuchofthetimeIspentinconsulting,designing, andsupervisingtheconstructionofmunicipalwastewatertreatmentplantswas profoundlyformulaic,andalargelymechanicalexerciserequiringlittleimaginationandpresentingfewnewchallenges.Thetreatmentofindustrialwastes wasfarmoreinterestingbecausethewastesvariedsogreatly,andtheirtreatmentrequiredimaginationandresearch.
Myintroductiontoindustrialwastewatertreatmentcamethrougha Philadelphia-basedconsultingcompany,andthensubsequentworkassignmentsforcompaniesspecializinginindustrialwastewatertreatment,and ultimatelyintothechemicalindustry.Atonepoint,alongtheway,Irealized thatIwasmuchmoreathomewiththechemicalengineersthanwiththecivil engineers,andIstillam.
Thisbookwasdevelopedtogivethestudentandtheexperiencedpractitioner someinformationandbalancewithregardtoindustrialpracticesandgoals,and todescribehowthewaterindustryworks,andwhatisimportantinit.Ihave triedtocoverawiderangeoftopicstodumpthemorethan40yearsofmy experienceintothisbriefvolumetohelpthereaderinvestigatethetopics,and pointoutusefultoolsforfurtherstudyandmasteryofthesubjects.Idonottry tosolveproblemsforthereader,buthaveprovidedafewproblemsontopicsof interest.
xix
xx Preface
Mistakesinthisvolumeareminealone.Incompilingthiswork,Ihave amassedawidelistofreferencematerials,andhaveattemptedtodownloada copyofthereferencesformyownuse,andtomakethemavailabletoothers. TheInternetisfullofbothpermanentandtemporaryinformation.Someofthe informationIhaveprovidedthroughlinkswillundoubtedlybeobsoletebythe timethisbookispublishedorhasafewyearsofageonit.So,ifinresearching thetopicsinthebook,onefindsthatakeytopicorpaperismissing,contact me,andIwillsendyouacopyoftheindividualpaper,ortheentiresetof referencesforyourdigitallibrary.
DaveRussell,PE (dlr@mindspring.com)
Composition,Chemistry,andRegulatoryFramework
Muchwatergoethbythemill
Thatthemillerknowethnotof.
1.1WaterComposition
JohnHeywood(1497–1580)
Wateriscomposedoftwopartshydrogenandonepartoxygen.Itisnotthe materialsofthewaterbutthecontaminantsinitthatmakeitimportant.If welookatachemicalreaction,wewouldbeextremelysatisfiedwithareactionyieldof99%purity,asmanyreactionsareinthe70–90%range.However, forwater,evena1%levelofimpurityisunacceptable.Thelevelsofcontaminantsthatweoftenconsiderinsignificantinmanyproductsandfoodscan preventusfromusingwater.Impuritiesinwateratthe1%levelareequivalent to10000ppmormgl 1 .Atthatlevel,eventhingslikesodiumchloride,table salt,inthewaterwillrenderitundrinkableorharmfulifconsumed.Inother instances,evenafewmilligramsoftherightcompoundcanrenderthewater unpalatableorunusableformanyaquaticpurposes.
Fromanotherstandpoint,thechallengesthatarepresentedtoawastewatertreatmentplantcanbeformidable.Fromaprocessstandpoint,thereactionyieldswelookforproduceatreatedeffluentwithcontaminationlevelsof lessthan10mgl 1 ,andinanumberofinstancesunder2mgl 1 ofparticular contaminants.Thatisprettygoodforawastestreamwhichmaystartoutat 500mgl 1 ormore–itrepresentsa99.6%removalefficiency.
Theusabilityofthewaterdependsuponthecompoundseitherdissolvedin itorsuspendedinit.Contaminantscanbeorganicorinorganic,solidsorliquids.Theusabilityofthewateralsodependsuponthepurposeoftheuse.For example,waterusedforcoolingdoesnotnecessarilyneedtobeofthesame quality(purity)asthatusedfordrinkingorfoodpreparation.Fecalandbacterialcontaminationofcoolingwaterisoftenunavoidableincoolingtowers,and
1 1
PracticalWastewaterTreatment, SecondEdition.DavidL.Russell. ©2019JohnWiley&Sons,Inc.Published2019byJohnWiley&Sons,Inc.
towerwateristreatedwithchemicalstoreducecorrosionandinhibitexcessive bacterialgrowth.Inallcases,thiswaterqualityisnotsuitableforfoodpreparation,norfordrinking.Thesterility,turbidity,anddissolvedconstituentsinthe waterareimportantqualitycontrolissues,butnotallthreearenecessaryfora specificuse.
Watercanalsobetoopureforaspecificuse.Asanexample,therearea numberoflocationsworldwidethathavetheirdrinkingwaterfromthermal desalinationsources.AtonespecificfacilityintheMiddleEast,thewateris slightlyabove43 ∘ C,whichisabituncomfortablefordrinking,butbecauseitis fromathermaldesalinationplant,itis distilled .Hencethewaterisaggressive becauseitissolowincarbonatesandmineralsthatithastheeffectofleachingthecalciumfromtheasbestos-cementpiping,thusweakeningit.Similarly, distilledwaterwillcorrodeironandsteelpiping,anddrinkingdistilledwater canalsocausehealthproblemssuchasdiuresis,andachangeintheelectrolyte concentrationinthebody1 .
1.2WaterCharacteristicsandPhysicalProperties
Water(H2 O)isdense,weighinginat999.972kgm 3 ,boilingat99.98 ∘ C (212.96 ∘ F),andmeltingat0.0 ∘ C.Itisthestandardforviscosity,at1centipoise (cp)at20 ∘ C,andhasavaporpressurewhichistemperature-dependent,from 611Pa(0.180in.ofHg)at0 ∘ Cto101901.3548Paat100 ∘ C.Theformulafor vaporpressureofwaterinthatrangeis
Pw = 10A B∕(C+T )
whereA = 8.07131,B = 1730.63,andC = 233.426andthetemperature T isin Celsiusbetween0 ∘ Cand100 ∘ C. P w isinpascals;forreference,1atmosphere is101325Pa,or764.2602mmofHg,and1mmofHgisequalto133.333Pa.
Purewaterisanexcellentinsulator,butwaterisseldom,ifever,pure,andcontainssmallquantitiesofdissolvedsaltsandmanymaterials.Theknownmaximumresistivityofpurewateris182KΩ m 1 at25 ∘ C,(or5.4945 × 10 6 Sm 1 or 0.054945 μScm 1 ).2 Verysmalllevelsofcontaminants,sometimesintheparts pertrillion(ppt)range(10 12 gl 1 ),cancauselargeincreasesinitsconductivity. Theconductivityofwaterisdependentnotonlyonthequantityofcontaminant, butonthetypeofcontaminant.Ifthecontaminanthasaninteractionwiththe water,andasecondaryand/ortertiaryionizationconstant,itismuchharderto relateconductivitytoconcentration.
Whenwaterhassalts(ionicmaterial)init,itcanbecomeanexcellentconductor.Theelectricalconductivityofwatercanbeusedtoestimatethedissolved
2 PracticalWastewaterTreatment
Table1.1 Approximateconductivityofvariouschemicalsinwaterwherethe substanceistheprincipalcontaminant.
SaltConductivityequivalentTDS/conductivity
Sodiumchloride1.00ppmTDS
solidsconcentrationinwaterifthatvalueislessthanabout1500mgl 1 .Above thatpoint,theconductivitytodissolvedsolidscurveflattensoutandbecomes unreliable.Mostconductivitymetersuseaformulaof:
Totaldissolvedsolids, TDS (mg∕l)= C × 1000 × conductivityin microsiemens∕cm
Dependinguponthewatersourceandcomponents,thevalueofCcanvary anywherefrom0.51to0.83.3 Athigherlevelsofdissolvedsolids,thecoefficient changes.Table1.1illustratesthedifferenceinconductivityofcertainsoluble materialsinwater.Itshouldbenotedthattheconductivityisafunctionofthe molecularstructureofthesolidorgas,andinsomecases,substancesthathave secondionizationconstantsorwhichreactwithwaterhavesubstantiallydifferentvaluesforconductivitywhichwillnotfollowtheformulashownabove. Multipleionsinsolutionwillhaveanonlinearrelationshiptothevaluesgiven inthetable.
Conductivitycanalsobeusedtomeasuretheamountofcalciumcarbonatein water,ifthatistheprincipaldissolvedsalt.Calciumcarbonateanditsformsare referredtoashardness,andrepresenttheabilityofthewatertoleaveCaCO3 depositsinpiping,onheatexchangers,coolingtowers,andsoon.Wewillcover hardnessinlaterchapters.
Ifanelectriccurrentispassedthroughwater,itwillgeneratehydrogenand oxygenintheratioof2:1byvolume.Iftherearesaltssuchassodiumchloride inthewater,aquantityofchlorinegas(Cl2 )willbegeneratedalongwiththe hydrogenandoxygen.Iflargeconcentrationsofhighpuritysaltaredissolved inthewater,andthepositiveandnegativeelectrodesareseparatedbyamembrane,theelectriccurrentbecomesthebasisforanelectrolyticcellusedinthe chemicalindustryforthegenerationofchlorinegasandcausticsoda(NaOH). Withwaterhavingaconductivitylessthan1200 μ℧,thevoltagerequirements increaseasthesaltconcentrationbecomesproportionallyless.
Composition,Chemistry,andRegulatoryFramework 3
= 2.04 μScm 1 0.49
Sodiumsulfate1.00ppmTDS = 1.49 μScm 1 0.67 Calciumsulfate1.00ppmTDS = 1.36 μScm 1 0.74
Sodiumbicarbonate1.00ppmTDS = 1.06 μScm 1 0.91
1.2.1SolubilityofGasesinWater
Themostimportantdissolvedgasisoxygen,andthesecondmostimportantgas isnitrogen,becauseitcomprisesapproximately79%ofouratmosphere,andis apotentialsourceofnutrientsforcertainaquaticplants.
Thesolubilityofvariousgasesinwaterisgiveninmanytablesfoundinchemicalandanalyticalhandbooks,andonmanycommercialwebsites,including www.engineeringtoolbox.com,andinhandbooksandanalyticalreference materials.4
Table1.2isalistingofthesolubilityofoxygeninwaterattemperatures between0 ∘ Cand30 ∘ C,forvariousvaluesofsaltsinthewater.Table1.2shows thesolubilityofselectedgasesinwater.
L.E.Geventmanpublishedaresearchpaperonthesolubilityofselectedgases inwater.5 Geventman’spaperstatesthatthesolubilityoftheselectedgasescan becalculatedbythefollowingformula: ln X1 = A + B∕T ∗ + Cln T ∗
where T * = T /100K,and X 1 isthesolubilityofthegas.A,B,andCaredeterminedexperimentallyfromchemicaldata.Hispaperprovidesalistofthecoefficients.Allvaluesrefertoapartialpressureofthegasof101.325kPa(1atm).
Theconcentrationofoxygeninwateratanytemperatureisgivenbythefollowingequationfoundin StandardMethods:6
=−139.34411 +(1.575701 × 105 ∕T2 )−(6.642308 × 107 ∕T2 ) +(1.243800 × 1010 ∕T3 )−(8.621949 × 1011 ∕T4 )
((3.1929 × 102 )−(1.9428 × 10∕T)+(3.8673 × 103 ∕T2 ))
whereChlisthechlorinitymeasuredingrams/kilogramandisdefinedaschlorinity = salinity/1.80655,andsalinityisapproximatelyequaltototalsolidsin wateraftercarbonateshavebeenconvertedtooxidesandafterallbromideand iodidehavebeenreplacedbychloride.
Figure1.1illustratesthesolubilityofoxygeninwateratvaryingtemperatures andvaluesofchlorinityofzeroand1000mgl 1 .
1.2.1.1Nitrogen
Nitrogenissolubleinwater,butinthegaseousorN2 formisessentiallyinert. Principalformsofnitrogeninwaterareammonia,nitrate,andnitrite.Theonly timeonehastoworryaboutthesolubilityofnitrogenisinitsionizedforms, asammonianitrite,ornitrate(tobediscussedlater)orwhenoneisdesigning apressureflotationsystem.
Figure1.2illustratesthesolubilityofnitrogengas(N2 )inwaterattemperaturesbetween0 ∘ Cand60 ∘ C.
4 PracticalWastewaterTreatment
LnO2
Chl
Table1.2 Solubilityofoxygeninmgl 1 inwaterexposedto water-saturatedairatatmosphericpressure(101.3kPa).
TemperatureChlorinity 0510152025
014.62113.72812.88812.09711.35510.657 114.21613.35612.54511.78311.06610.392 213.82913.00012.21811.48310.79010.139 313.46012.66011.90611.19510.5269.897 413.10712.33511.60710.92010.2739.664 512.77012.02411.32010.65610.0319.441 612.44711.72711.04610.4049.7999.228 712.13911.44210.78310.1629.5769.023 811.84311.16910.5319.9309.3628.826 911.55910.90710.2909.7079.1568.636 1011.28810.65610.0589.4938.9598.454 1111.02710.4159.8359.2878.7698.279 1210.77710.1839.6219.0898.5868.111 1310.5379.9619.4168.8998.4117.949 1410.3069.7479.2188.7168.2427.792 1510.0849.5419.0278.5408.0797.642 169.8709.3448.8448.3707.9227.496 179.6659.1538.6678.2077.7707.356 189.4678.9698.4978.0497.6247.221 199.2768.7928.3337.8967.4837.090 209.0928.6218.1747.7497.3466.964 218.9158.4568.0217.6077.2146.842 228.7438.2977.8737.4707.0876.723 238.5788.1437.7307.3376.9636.609 248.4187.9947.5917.2086.8446.498 258.2637.8507.4577.0836.7286.390 268.1137.7117.3276.9626.6156.285 277.9687.5757.2016.8456.5066.184 287.8277.4447.0796.7316.4006.085 297.6917.3176.9616.6216.2975.990 307.5597.1946.8456.5136.1975.896
Composition,Chemistry,andRegulatoryFramework 5
Figure1.1 Solubilityofoxygeninwateratvaryingtemperatures,andvaluesofchlorinityof zeroand1000mgl 1 .
Figure1.2 Solubilityofnitrogengas(N2 )inwaterattemperaturesbetween0 ∘ Cand60 ∘ C (litersperkgofwater).
OthercommongasessolubleinwaterareshowninTable1.3intermsofmillimols.Thisenablescalculationofthevolumeofthelistedgasesasafunction ofpressure.Thereisanexamplebelow.
1.2.2Henry’sLaw
Henry’slawgivesussomeideaofthesolubilityofothergases.In1803,William Henrystated:“Ataconstanttemperature,theamountofagivengasthatdissolvesinagiventypeandvolumeofliquidisdirectlyproportionaltothepartial pressureofthatgasinequilibriumwiththatliquid.” P = K′ C C
6 PracticalWastewaterTreatment 0 2 4 6 8 10 12 14 16 0510152025 DO in mg/L TemperatureDegreesCentigrade DOatzeroChlorinityDOat1000mg/LChlorinity
0.012 0.014 0.016 0.018 0.02 0.022 0.024 010203040506070
0.01
Table1.3 MolarHenry’slawconstantsforaqueoussolutions at25 ∘ C.
3 ) 1 )
where P isthepartialpressureofthegas, C isitsmolarconcentration,and K′ C istheHenry’slawconstant.Thisisuniversallytrueforalmostallliquids. However,astheconcentrationsandpartialpressuresincrease,deviationsfrom Henry’slawbecomenoticeable.Thisbehaviorisverysimilartothebehavior ofgases,whichdeviatefromtheidealgaslawaspressuresincreaseandtemperaturesdecrease.SolutionsthatobeyHenry’slawaresometimescalledideal dilutesolutions.ValuesoftheHenry’slawconstantsformanygasesinmany differentorganiccompoundsandgaseshavebeenmeasured.Theinverseof theHenry’slawconstant,multipliedbythepartialpressureofthegasabove thesolution,isthemolarsolubilityofthegas.
Henry’slawdoesnotholdforgasesthatreactwithwaterandwhichhavesecondaryandtertiaryionizationconstants.Someofthosegasesincludehydrogen sulfide,chlorine,andcarbondioxide.Thereactionsofthesegasesareoften pH-dependent,andthefreemolarformofthegasisdirectlyrelatedtothe inverseofthepHatwhichitismostsoluble.Forexample,ammoniatendsto formNH3 OHinwater,whichisammoniumhydroxide,andisastronglyionized base.AsthepHofthewaterincreases,theequilibriumreactionof:
shiftsleftward,releasingmorefreeammoniaintothesolution.AtavalueofpH 12,thereactionisessentiallycompleteandthereisessentiallynoionicammonialeftinaqueoussolution.ThisrelationshipisshowninFigure1.3.
ThevalueoftheHenry’slawconstantistemperature-dependent.Thevalue generallyincreaseswithincreasingtemperature.Asaconsequence,thesolubilityofgasesgenerallydecreaseswithincreasingtemperature.Oneexample ofthiscanbeseenwhenwaterisheatedonastove.Thegasbubblesappearingonthesidesofthepanwellbelowtheboilingpointofwaterarebubblesof air,whichevolveduetotheloweredsolubilityfromhotwater.Theadditionof boiledordistilledwatertoafishtankwillcausethefishtodieofsuffocation unlessthewaterhasbeenallowedtore-aeratebeforeaddition.
Composition,Chemistry,andRegulatoryFramework 7
Gas Constant (Pa(moldm
Constant (atm(moldm
He282.7
106 2865.0 O2 74.68
106 756.7 N2 155
106 1600.0 H2 121.2 × 106 1228.0 CO2 2.937 × 106 29.76 NH3 5.69 × 106 56.9
3 ) 1 )
×
×
×
NH3 + H2 O ↔ NH4 + + OH
