Tables of Contents

•  Generalproper+esofwater•  Impuri+esinwater•  Hardnessandalkalinity•  Solubili+es•  pHandCyclesofconcentra+on•  Coolingwatertreatment

  CorrosionandScaleInhibitors  Biocides

•  Opera+onandtes+ng

General Properties of Water

•  Someoftheproper+esofwaterwhichmakeitidealforindustrialcoolingprocessesarelistedbelow:

  Waterhasthecapacitytostoreandtransportheat

  Waterabsorbsmoreheatperpoundthananyotherinorganicsubstance

  Waterhasthefollowingphysicalproper+es:

  Onepoundofwatergivesup144BTU’suponfreezing  Atatmosphericpressure,waterfreezesat32degFandboils

at212degF  Waterismostdenseat40degF  Onepoundofwater,whentransformedintosteam,releases

970BTU’s  Purewaterdoesnotexistinnature

General Properties of Water

•  Therearetwomainsourcesofwater,notegeneraldifferences

  Wellsandspringsareclassifiedasgroundwatersources−  Lowsuspendedsolidsanddissolvedoxygen,highdissolvedsolids

includingiron,hardness,andalkalinity,andalsohighcarbondioxide

  Riversandlakesareclassifiedassurfacewatersources−  Highsuspendedsolidsanddissolvedoxygen,lowdissolvedsolids

includingiron,hardness,andalkalinity,andalsolowcarbondioxide

Types of Impurities in Water

•  Suspendedsolids

  Turbidity  FinelydividedsuspendedorcolloidalmaWer

(clay,silt,dirt,organicmaWer)

  Color  Anarbitrarystandardscaleusedtomeasure

solubleorganicmaterialsinwater

CATIONSCaMgKNaFe,Al,CuZn,Si

ANIONSClHCO3

CO3

SO4PO4

NO3

Types of Impurities in Water (cont.)

•  Dissolvedsolids

  Dissolvedmineralsolids  Whenrainfalls,itscrubstheatmosphereofcarbondioxide  Carbondioxidemixeswithwatertoformaweakacidcalled

carbonicacid  Thecarbonicaciddissolvesmineralsolidscontainedinnature,

suchas:−  Limestone(calciumcarbonate),dolomite(magnesiumcarbonate),

epsomsalt(magnesiumsulfate),gypsum(calciumsulfate),sand(silica),andcommonsalt(sodiumchloride).

  Mineralscontainingsodiumhavearela+velyhighsolubilityinwater

  Mineralscontainingcalciumandmagnesiumhavearela+velylowsolubilityinwater

Types of Impurities in Water (cont.)

•  DissolvedGases

  Oxygen  Corrosivetometalatelevatedconcentra+ons  Solubilityinwaterdependsontemperature,surfacearea

andpressure

  CarbonDioxide  Willformcarbonicacid,aweakacid,whendissolvedinwater  Carbonicaciddissociatestoformbicarbonateandcarbonate

alkalinitywhichispHdependent  Solubilityinwaterdependsontemperature,surfacearea

andpressure

Types of Impurities in Water (cont.)

•  MiscellaneousImpuri+es

  Bacteriathatrequireoxygenandproducecarbondioxideareaerobicbacteria

  Bacteriathatdonotrequireoxygenandproducehydrogensulfideareanaerobicbacteria

  Algaefavorsexposuretosunlight

  Fungifavorsdarksecludedareas

Hardness and Alkalinity

•  Hardness(calciumandmagnesium)andalkalinity(bicarbonateandcarbonate)bothplayamajorroleincoolingwatertreatment:

  Theweakacid,carbonicacid,thatisformedduringrainfallhastheabilitytodissolvemineralsintheearth’sstrata

  Theacidsolu+oniscomposedofhydrogen,theposi+velychargedpor+onofthesolu+on(acidicpor+on),andanega+velychargedcounterpart

  Iftheearth’sstratacontainsappreciablequan++esoflimestoneanddolomite,thentwooftheprimaryreac+onsbetweentheweakacidandthestratawillbewiththecalciumcarbonateandmagnesiumcarbonate

Hardness and Alkalinity (cont.)

•  Hardness(calciumandmagnesium)andalkalinity(bicarbonateandcarbonate)bothplayamajorroleincoolingwatertreatment:

  Asthemineraldissolves,boththecalciumandcarbonate(aswellasthemagnesiumandcarbonate),gointosolu+on

  Oncedissolved,boththecalciumandmagnesium(theposi+velychargedpor+onsofthemineral),tendtofavor“rever+ng”backtotheirnaturalinsolublestate

  Whencombinedwithothermineralimpuri+es,calciumandmagnesiumwillpreferen+allyprecipitateoutofsolu+onandformaninsolublesludge

  Thereac+onofcalciumandmagnesiuminwaterwithsoapsanddetergentscreatesanundesirablesludgewhichcanmakelaunderingdifficult.Thedifficultyor“hardtowashcondi+on”ledtothetheterminology“WaterHardness”

Solubilities •  Thecommonmineralsubstancescanbe

classifiedintofourcategoriesbasedonsolubility:

  Calciumandmagnesiumcompoundsrulesofthumb  Solubilitydecreaseswhentemperaturerises,

alkalinityincreases,andavailablecarbondioxidedecreases

  BoWomline:hardnesssaltsaremorelikelytodropoutathightemperaturesandpH

  Sodiumcompoundsrulesofthumb  Solubilityincreasesastemperatureincreases.Ifdeposits

withsodiumarefound,itcangenerallybeaWributedtoextremeconcentra+onsorevapora+ontodryness

  BoWomline:Sodiumcompoundsarerarelyaproblemcausedbywatertreatment)

CATIONSCaMgKNaFe,Al,CuZn,Si

ANIONSClHCO3

CO3

SO4PO4

NO3

Solubilities (cont.)

•  Thecommonmineralsubstancescanbeclassifiedintofourcategoriesbasedonsolubility(cont.):

  Silicadioxideruleofthumb  Solubilityincreasesasalkalinityincreases

  Ironandmanganesecompoundsruleofthumb  Solubilitydecreasesaswateralkalinityincreases

andasthedegreeofoxida+onincreases(i.e.oxygen,chlorine,bromine)

CATIONSCaMgKNaFe,Al,CuZn,Si

ANIONSClHCO3

CO3

SO4PO4

NO3

pH and Cycles of Concentration •  Definedexactly,pHisthelogarithmofthereciprocalofthe

hydrogenionconcentra+oninthereac+on

•  Amoresimpleexplana+onisthatpHisanumberbetween0and14thatdenotesvariousdegreesofacidityandalkalinity,withneutralwateratpH7.Below7becomesincreasinglyacidic,whileabove7becomesincreasinglyalkaline

pH and Cycles of Concentration (cont.)

•  pHisaveryimportantparameterinwatertreatment,especiallyincoolingwatertreatment.Aswateriscycled,alkalinityconcentrates,sosubsequentlypHincreases,example:

•  Wecallthisexampleasbeing2cyclesofconcentra+on,wheremineralconcentra+ons,aswellasconduc+vity,aredoubled

•  AtUPMCShadyside,towersaverage5cyclesofconcentra+on

Waterwith100ppmalkalinity Waterwith200ppm

alkalinity,pHincrease

Addheat,lose½thevolumeofwater

throughevapora+on

Langelier Saturation Index (LSI)

•  Anumericalvalueforthescalingpoten+alofcalciumcarbonate(CaCO3)

•  Theequa+onisanumericalcombina+onof:  Totaldissolvedsolids  Temperature  Calciumhardness  Alkalinity  pH

•  Aposi+veLSIisscaleforming,anega+veLSIiscorrosive,andzeroisperfectequilibrium

LSI/RSI Calculation

•  LSI=pH–pHs

•  pHs=9.3+TDS[F]+Temp[F]‐(Ca[F]+Alk[F])

Methods of Treatment for High LSI

•  AcidFeed  ByreducingpHincoolingwater,theequa+on

LSI=pH‐pHsmeansthatLSIwillbereduced,thereforecalciumcarbonatescalingpoten+alisreduced

  Properdilu+onofacidiscri+caltocontactallpointsofthesystem.Itisimportanttoequipthesystemwithsafeguardsifacidfeedislostorinefficient

Methods of Treatment for High LSI #2

•  OrganicphosphonatescombinedwithpolymerscanwithstandLSIto+3.0

•  UsuallysafetomaintainLSIat+2.5

•  AnothermethodofcontrollingLSIissomenedmake‐up,butrequiresmanhoursforregenera+onandmaintenance

Cooling Water Treatment

•  Objec+veofacoolingwatertreatmentprogram:  Maintainop+mumheattransferinprocessequipmentand

heatexchangers  Insureequipmentreliabilityandavailability  Minimizeopera+ngcosts  Providepredic+vetreatmentrecommenda+onsforsystem

opera+ngchangesandtowercontamina+on  Maintainhealthyenvironmentinmoistareasaround

perimeteroftower  Assuresystemcircula+ontokeepallareaswith

freshflowonaregularbasis

Cooling Water Treatment (cont.) •  Majorconcernareas:

  Scale:Forma+onofinsolubledepositsonheattransfersurfaces,usuallyhardnesssaltsonthemostcri+cal(orhoWest)areas  Highpoten+alwithhightemperatures,highpH,excessive

alkalinity,highdissolvedsolids,andhighhardness

  Corrosion:Lossofmetalbyreac+onwiththeenvironment  Forma+onattheanodeorcathodeseongupan“electrical

circuit”,oroxida+onofbasemetal

  Fouling:Microbiologicalandsuspendedsolidsdeposi+on  Algae,fungi,orbacteriadependinguponloca+oninsystem,

canactas“thegluethatholdsdepositstogether”

Changing Chemistries Over the Years

•  ToxicNatureofChromate

•  DesiretoEliminateAcid

•  DesiretoOperateatHighCycles

•  EconomicPressure

•  MoreEffec+veInhibitors

Overview

•  CarbonSteelCorrosionProcess

•  HowChemicalTreatmentsWork

•  TreatmentPrograms:TheLast20Years

•  TheFuture

Corrosion Process

ANODEFe→Fe+2+2e‐

CATHODEH2O+½O2+2e‐→2OH‐

Rust Formation

Fe+2hydratedtoFe(OH)2

Fe(OH)2oxidizedtoFe(OH)3

Fe(OH)3precipitates

Anodic Inhibitors

Inhibitoxida+onofiron

Promotegamma‐Fe2O3

Precipitatesfillvoids

Anodic Inhibitors

•  Chromate

•  Nitrite

•  Molybdate

•  Orthophosphate

Cathodic Inhibitors

InhibitCathodicReac+on

FormBarrierFilms

HighsurfacepHcausesprecipitates

H2O+½O2+2e‐→2OH‐

Cathodic Inhibitors

•  Polyphosphates

•  Phosphonates

•  Zinc

•  CalciumCarbonate

Inorganic Phosphates

•  Orthophosphate

•  Pyrophosphate

•  Tripolyphosphate

•  Polyphosphate

Phosphates

•  1940’s:PolyphosphateGlasses

•  1950’s‐1960’s:Zinc/PolyGlasses

•  1970’s:PhosphateEsters

•  1980’s:StabilizedPhosphates

Stabilized Phosphate

1stStabilizedPhosphateProgramDianodicII™

1stAlkalineStabilizedPhosphateProgrampHreeGUARD™

Calcium Phosphate Inhibition

Inhibitors Ac2veDosage(mg/L)

PercentInhibi2on

70/30AA/AM 50 <25

AA/HPE 17 >90

1:1MA:SS 17 >90

PMA 50 <20

Polyaspar+cAcid(Green) 50 <20

Calcium Phosphate Inhibition

Inhibitors MinimumEffec2veDose(mg/L)

PercentInhibi2on

60/40AA/AMPS 7‐8 >90

(TRC‐233,AR‐546,CT‐40,Acumer2100,WB65‐37AS)

AA/AMPS/TBAM(Acumer3100) 7‐8 >90

AA/AMPS/SS(GoodriteK‐798) 7‐8 >90

AA/AHPSE 8 >90

75/25AA/AMPS 9‐10 >90

(TRC‐233i,AR‐545,Acumer2000,WB60‐45AS)

SulfonatedAAPolymer(AquatreatMPS) 9‐10 >90

All-Organic

•  HEDP/AMP

•  HEDP/PBTC

•  HEDP/ORTHO

•  HEDP/HPA

Halogen Stabilizers

•  CyanuricAcid

•  SulfamicAcid

•  Monoethanolamine

Chlorine Tolerant

•  BAYER:PBTC

•  RHODIA:PMAP

Zinc Products

•  Zinc/Polyphosphate

•  Zinc/Ortho

•  Zinc/AMP

•  Zinc/HEDP

•  Zinc/PBTC

•  WithPolymer

High Calcite Saturation: 240X (LSI=2.8)

Inhibitors %Inhini2on(ac2vedosagemg/L)

20mg/L 30mg/L

PEP 91 100

PBTC 72 76

HEDP 58 53

AMP ‐ 51

HPA 44

PMAP 46 39

PMA 51

Polyaspar+cAcid ‐ 39

Green Chemistry

•  Low/Non‐Zinc

•  Low/Non‐Phosphate

•  PMAP

Conclusion

•  MostImportantDevelopment:ImprovedPolymers

•  PolymerofChoice:60/40AA/AMPS

•  BestHighCalciteSatura+onInhibitor:NatcolenePEP

•  Future:MoreStudiesNeededforGreenChemistries

Oxidizing Biocides

•  Chlorinebased

  Notaseffec+veabovepH7.5

  Sodiumhypochlorite−  “Bleach”availableat14%

  HTH−  Calciumhypochloritepowder,rapiddissolving

  Chlorineisocyanuratetablets−  Organicchlorinerapiddissolvingtablets

  Chlorinedioxide−  Combina+onofsulfuricacidandhypochlorite

Oxidizing Biocides (cont.)

•  Brominebased

  Effec+veabovepH7.5

  Stabilizedbromine−  14%brominecombinedwithsodiumhypochlorite

  Brominehydantointablets−  Slowdissolvingfedviabrominator

  Bromineisocyanurate−  Rapiddissolvingbrominetablets

Non-Oxidizing Biocides

•  Liquidbiocidesusedtosupplementanoxidizingbiocideprogram

  Fedviapumpson7day+mer

  Actsasapoisontokillbacteria/algae/fungi/mold  WSCP(142L)‐algae,bacteria,fungi  Carbamate‐bacteria,sulfatereducers,fungi  MBT‐bacteria,sulfatereducers,fungi  Terbuthylazine‐algae  Isothiazoline‐bacteria,sulfatereducers,fungi  DBNPA‐bacteria  Glutaraldehyde‐bacteria,sulfatereducers,fungi  Thione‐bacteria,fungi  Triazine‐algae  DGH‐bacteria,sulfatereducers,fungi

Operation and Testing

•  MolybdateTest

1.  Add1.5mLoftowerwatertoeachviewingtube2.  Addtapwaterto1stmarkofeachviewingtube(5mLmark)3.  AddoneMolybdenum1ReagentPowderPillowtooneofthe

tubes4.  AddeightdropsofMolybdenum2Reagenttothesame

tubeusedinStep35.  InsertthetubefromStep4intotherightopeningof

thecolorcomparator6.  Placetheblankintothelemopening,andholdup

tonaturallight7.  Thecontroldisplayrangeis1.1mg/Lto1.8mg/L

Operation and Testing (cont.)

•  TotalandFreeHalogenTest

1.  Fillaviewingtubetothefirstline(5mL)withsamplewater2.  Addeithertotalorfreechlorinepowderpillowtothesample3.  Fortotalchlorinetest,allow3minutereac+on+mebefore

readingresult4.  Viewsampleincomparator,controlfreechlorine0.1‐0.3mg/Land

totalchlorine<1.0mg/L.

•  Conduc+vity  Control1600‐2000umhosconduc+vity

•  SanicheckTestKit  Control<105bacteria/mL

Review Quiz

•  Whatisthescalethatwearemostconcernedwithinrecircula+ngcoolingwatersystems?

•  Ifthemakeupwateris400conduc+vity,andthetowerwaterisat2000conduc+vity,whatarethecyclesofconcentra+on?

•  Whatarewaystocontrollegionellabacteriainacoolingtower?

•  Whereishardnessmostlikelytodropoutofthewatersolu+oninacoolingwatersystem?

•  Whatsafetyequipmentisnecessarywhenhandlingtreatmentchemicals?