Sodium hypochlorite as a disinfectant - Lenntech

Sodium hypochlorite (NaOCl) is a compound that can be effectively used for water purification. It is used on a large scale for surface purification, bleaching, ... 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csoda(NaOH).Whenthisisdone,sodiumhypochlorite,water(H2O)andsalt(NaCl)areproducedaccordingtothefollowingreaction:Cl2+2NaOH+→NaOCl+NaCl+H2OWhataretheapplicationsofsodiumhypochlorite?Sodiumhypochloriteisusedonalargescale.Forexampleinagriculture,chemicalindustries,paint-andlimeindustries,foodindustries,glassindustries,paperindustries,pharmaceuticalindustries,syntheticsindustriesandwastedisposalindustries.Inthetextileindustrysodiumhypochloriteisusedtobleachtextile.Itissometimesaddedtoindustrialwastewater.Thisisdonetoreduceodors.Hypochloriteneutralizessulphurhydrogengas(SH)andammonia(NH3).Itisalsousedtodetoxifycyanidebathsinmetalindustries.Hypochloritecanbeusedtopreventalgaeandshellfishgrowthincoolingtowers.Inwatertreatment,hypochloriteisusedtodisinfectwater.Inhouseholds,hypochloriteisusedfrequentlyforthepurificationanddisinfectionofthehouse.Howdoessodiumhypochloritedisinfectionwork?Byaddinghypochloritetowater,hypochlorousacid(HOCl)isformed:NaOCl+H2O→HOCl+NaOH-Hypochlorousacidisdividedintohydrochloricacid(HCl)andoxygen(O).Theoxygenatomisaverystrongoxidator.Sodiumhypochloriteiseffectiveagainstbacteria,virusesandfungi.Sodiumhypochloritedisinfectsthesamewayaschlorinedoes.Howissodiumhypochloriteappliedinswimmingpools?Sodiumhypochloriteisappliedinswimmingpoolsforwaterdisinfectionandoxidation.Ithastheadvantagethatmicroorganismscannotbuildupanyresistancetoit.SodiumhypochloriteiseffectiveagainstLegionellabacteriaandbiofilm,inwhichLegionellabacteriacanmultiply.Hypochlorousacidisproducedbythereactionofsodiumhydroxidewithchlorinegas.Inwater,theso-called'activechlorine'isformed.Therearevariouswaystousesodiumhypochlorite.Foron-sitesaltelectrolysis,asolutionofsalt(NaCl)inwaterisapplied.Sodium(Na+)andchloride(Cl-)ionsareproduced.4NaCl-→4Na++4Cl-Byleadingthesaltysolutionoveranelectrolysiscell,thefollowingreactionstakeplaceattheelectrodes:2Cl-→Cl2+2e-2H2O+2e-→H2+20H-2H20→O2+4H++4e-Subsequently,chlorineandhydroxidereacttoformhypochlorite:OH-+Cl2→HOCl+Cl-Theadvantageofthesaltelectrolysissystemisthatnotransportorstorageofsodiumhypochloriteisrequired.Whensodiumhypochloriteisstoredforalongtime,itbecomesinactive.AnotheradvantageoftheonsiteprocessisthatchlorinelowersthepHandnootheracidisrequiredtolowerpH.Thehydrogengasthatisproducedisexplosiveandasaresultventilationisrequiredforexpolsionprevention.Thissystemisslowandabufferofextrahypochlorousacidneedstobeused.Themaintenanceandpurchaseoftheelectrolysissystemismuchmoreexpensivethansodiumhypochlorite.Whensodiumhypochloriteisused,aceticorsulphuricacidareaddedtothewater.Anoverdosecanproducepoisonousgasses.Ifthedosageistoolow,thepHbecomestohighandcanirritatetheeyes.Becausesodiumhypochloriteisusedbothtooxidizepollutions(urine,sweat,cosmetics)andtoremovepathogenicmicroorganisms,therequiredconcentrationofsodiumhypochloritedependsontheconcentrationsofthesepollutions.Especiallytheamountoforganicpollutiondeterminestherequiredconcentration.Ifthewaterisfilteredbeforesodiumhypochloriteisapplied,lesssodiumhypochloriteisneeded.Whatarethehealtheffectsofsodiumhypochlorite?ExposureThereisnothresholdvaluefortosodiumhypochloriteexposure.Varioushealtheffectsoccurafterexposuretosodiumhypochlorite.Peopleareexposedtosodiumhypochloritebyinhalationofaerosols.Thiscausescoughingandasorethroat.Afterswallowingsodiumhypochloritetheeffectsarestomachache,aburningsensation,coughing,diarrhea,asorethroatandvomiting.Sodiumhypochloriteonskinoreyescausesrednessandpain.Afterprolongedexposure,theskincanbecomesensitive.Sodiumhypochloriteispoisonousforwaterorganisms.Itismutagenicandverytoxicwhenitcomesincontactwithammoniumsalts.SodiumhypochloriteinswimmingpoolsTheconcentrationofsodiumhypochloritethatisfoundinswimmingpoolsisgenerallynotharmfultopeople.Whenthereistoomuchchlorineinthewater,thisburnsthebodytissues,whichcausesdamagetoairtracts,thestomachandtheintestines,theeyesandtheskin.Whensodiumhypochloriteisusedinswimmingpools,itsometimescausesredeyesanditgivesoffatypicalchlorineodor.Whenthereisalotofureum(amixtureofurineandsweat)present,hypochlorousacidandureumreacttoformchloramines.Thesechloraminesirritatemucousmembranesandcausetheso-called'chlorinesmell'.Inmostswimmingpools,theseproblemsarepreventedbywaterpurificationandventilation.Eyesirritationdisappearsafterawhile.Whataretheadvantagesanddisadvantagesofsodiumhypochloriteuse?AdvantagesSodiumhypochloriteasadisinfectanthasthefollowingadvantages:Itcaneasilyandbestoredandtransportedwhenitisproducedon-site.Dosageissimple.Transportandstorageofsodiumhypochloritearesafe.Sodiumhypochloriteisaseffectiveaschlorinegasfordisinfection.Sodiumhypochloriteproducesresidualdisinfectant.DisadvantagesSodiumhypochloriteisadangerousandcorrosivesubstance.Whileworkingwithsodiumhypochlorite,safetymeasureshavetobetakentoprotectworkersandtheenvironment.Sodiumhypochloriteshouldnotcomeincontactwithair,becausethatwillcauseittodisintegrate.BothsodiumhypochloriteandchlorinedonotdeactivateGiardiaLambiaandCryptosporidium.Whatisthelegislationforsodiumhypochlorite?Theregulationforsodiumhypochloriteisthesameastheregulationconsideringchlorine.DischargedemandsWhencoolingtowerwateristappedfromariverorlake,andmustbedischargedintothesamewaterbodyafterithasbeenused,itmustmeetcertaindischargedemands.Additionally,thewatertemperaturemaynotbetoohigh,becausewarmwaterhasalowoxygencontent,whichpromotesalgalgrowth.Thiscancausefishmortalityandadecreaseinwaterbiodiversity.UnitedStatesDischargedemandsforcoolingtowerwaterintheUSAarementionedintheCleanWaterAct(CWA)andareestablishedbytheEnvironmentalProtectionAgency(EPA).Moreinformationonwaterdisinfection?:IntroductionwaterdisinfectionNecessitywatertreatmentHistoryofdrinkingwatertreatmentWhatiswaterdisinfection?NecessityofdrinkingwaterdisinfectionHistoryofwaterdisinfectionWaterbornediseasesFactorsthatinfluencedisinfectionConditionsofwaterdisinfectionRegulationdrinkingwaterdisinfectionEUUSASwimmingpooltreatmentSwimmingpoolpollutionsSwimmingpooldisinfectionSwimmingpooldisinfection&healthCoolingtowerwaterCoolingtowerwaterpollutionsCoolingtowerwaterdisinfectionCoolingtowerwaterlegislationChemicaldisinfectantsChlorineSodiumhypochloriteChloraminesChlorinedioxideCoppersilverionizationHydrogenperoxideBrominePeroxonePeraceticacidDisinfectionbyproductsTypesofdisinfectionbyproductsResearchonhealtheffectsofdisinfectionbyproductsChlorinatorsystemMorefrom'Chemicaldisinfectants'ChlorineChloraminesChlorinedioxideCoppersilverionizationHydrogenperoxideBrominePeroxonePeraceticacidAboutLenntechLenntech(EuropeanHeadOffice)Distributieweg32645EGDelfgauwTheNetherlandsPhone:+31152610900fax:+31152616289e-mail:[email protected](Americas)5975SunsetDriveSouthMiami,FL33143USAPhone:+18774538095e-mail:[email protected](MiddleEast)Level6-OFFICE#101-OneJLTTowerJumeirahLakeTowersDubai-U.A.E.Phone:+97144295853e-mail:[email protected]©1998-2022LenntechB.V.Allrightsreservedbacktotop