Designation:D4993−08(Reapproved2014)StandardPracticeforCalculationandAdjustmentofSilica(SiO2)ScalingforReverseOsmosis1ThisstandardisissuedunderthefixeddesignationD4993;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thispracticecoversthecalculationandadjustmentofsilica(SiO2)fortheconcentratestreamofareverseosmosissystem.Thecalculationsareusedtodeterminetheneedforscalecontrolintheoperationanddesignofreverseosmosisinstallations.Thispracticeisapplicableforalltypesofreverseosmosisdevices(tubular,spiralwound,andhollowfiber).1.2Thispracticeisapplicabletobothbrackishwatersandseawaters.1.3ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.4Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:D859TestMethodforSilicainWaterD1067TestMethodsforAcidityorAlkalinityofWaterD1129TerminologyRelatingtoWaterD1293TestMethodsforpHofWaterD3739PracticeforCalculationandAdjustmentoftheLangelierSaturationIndexforReverseOsmosisD4194TestMethodsforOperatingCharacteristicsofRe-verseOsmosisandNanofiltrationDevicesD6161TerminologyUsedforMicrofiltration,Ultrafiltration,NanofiltrationandReverseOsmosisMembraneProcesses3.Terminology3.1Definitions—Fordefinitionsoftermsrelatingtowaterusedinthispractice,refertoTerminologyD1129andD6161.4.SummaryofPractice4.1ThispracticeconsistsofcalculatingthepotentialforscalingbySiO2inareverseosmosisconcentratestreamfromtheconcentrationofSiO2inthefeedsolutionandtherecoveryofthereverseosmosissystem.4.2Thispracticealsopresentstechniquestoeliminatescalingbydecreasingtherecovery,decrea...
