Designation:D7725−17StandardTestMethodfortheContinuousMeasurementofTurbidityAbove1TurbidityUnit(TU)1ThisstandardisissuedunderthefixeddesignationD7725;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoverstheon-lineandin-linedetermi-nationofhigh-levelturbidityinwaterthatisgreaterthan1.0turbidityunits(TU)inmunicipal,industrialandenvironmentalusage.1.2Inprinciple,therearethreebasicapplicationsforon-linemeasurementsetups.Thisfirstistheslipstream(bypass)sampletechnique.Fortheslipstreamsampletechniqueaportionofsampleistransportedoutoftheprocessandthroughthemeasurementapparatus.Itistheneithertransportedbacktotheprocessortowaste.Thesecondisthein-linemeasurementwherethesensorisbroughtdirectlyintotheprocess(seeFig.8).Thethirdbasicmethodisforin-situmonitoringofsamplewaters.Thisprincipleisbasedontheinsertionofasensorintothesampleitselfasthesampleisbeingprocessed.Thein-situuseinthistestmethodisintendedforthemonitoringofwaterduringanystepwithinaprocessingtrain,includingimmedi-atelybeforeoraftertheprocessitself.1.3Thistestmethodisapplicabletothemeasurementofturbiditiesgreaterthan1.0TU.Theabsoluterangeisdictatedbythetechnologythatisemployed.1.4Theupperendofthemeasurementrangeisleftunde-finedbecausedifferenttechnologiesdescribedinthistestmethodcancoververydifferentrangesofturbidity.1.5ManyoftheturbidityunitsandinstrumentdesignscoveredinthistestmethodarenumericallyequivalentincalibrationwhenacommoncalibrationstandardisappliedacrossthosedesignslistedinTable1.Measurementofacommoncalibrationstandardofadefinedvaluewillalsoproduceequivalentresultsacrossthesetechnologies.Thistestmethodprescribestheassignmentofadeterminedturbidityvaluestothetechnologyusedtodeterminethosevalues.Numericalequivalencetoturbiditystandardsisobservedbetweendifferenttechnologiesbuti...
