Designation:D5120−90(Reapproved2009)StandardTestMethodforInhibitionofRespirationinMicrobialCulturesintheActivatedSludgeProcess1ThisstandardisissuedunderthefixeddesignationD5120;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoversabatchprocedurethatevaluatestheimpactofselectedwastewaters,materials,orspecificcompoundsontherespirationrateofanaqueousmicrobialculture,suchasactivatedsludge.1.2Alternativeproceduresformeasurementofmicrobialactivity,suchasadenosine5'triphosphate(ATP),specificsubstrateutilization,etc.arenotwithinthescopeofthistestmethod.1.3Theresultsobtainedarebasedoncomparisonsinaspecifictestseriesthatexaminesarangeofconcentrationsofthepotentiallyinhibitorytestcandidateusingbatchmethodsinalaboratory.Resultsarecompletedinashorttimeframe(afewhours).1.4Thetestresultsarespecifictothemicrobialcultureused.Microbialculturefromdifferentwastewatertreatmentplantswilldifferinkindsandnumbersoforganisms,andperformancecapability.Thus,thereisnobasisforcomparingresultsformicrobialculturesfromdifferenttreatmentfacilities.1.5ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.6Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2D4478TestMethodsforOxygenUptake(Withdrawn1994)33.Terminology3.1Definitions:3.1.1respirationrate—thequantitativeconsumptionofoxygenbyanaqueousmicrobialsystem.TheconsumptionisgenerallyexpressedasmgO2/L/h.3.1.2EC50—theconcentrationofthetestcandidateinthisprocedure(volumepercentormg/L)thatresultsinareductionofrespirationrateto50%ofthatobservedforth...
