ASTM_D_7937_-_15.pdf

Designation:D793715Standard Test Method forIn-situ Determination of Turbidity Above 1 Turbidity Unit(TU)in Surface Water1This standard is issued under the fixed designation D7937;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the in-situ field measurementsof turbidity in surface water.The measurement range is greaterthan 1 TU and the lesser of 10 000 TU or the maximummeasurable TU value specified by the turbidimeter manufac-turer.1.1.1 Precision data was conducted on both real world andsurrogate turbidity samples up to about 1000 TU.Many of thetechnologies listed in this test method are capable of measuringabove that provided in the precision section(see Section 16).1.2“In-situ measurement”refers in this test method toapplications where the turbidimeter sensor is placed directly inthe surface water in the field and does not require transport ofa sample to or from the sensor.Surface water refers to springs,lakes,reservoirs,settling ponds,streams and rivers,estuaries,and the ocean.1.3 Many of the turbidity units and instrument designscovered in this test method are numerically equivalent incalibration when a common calibration standard is appliedacross those designs listed in Table 1.Measurement of acommon calibration standard of a defined value will alsoproduce equivalent results across these technologies.This testmethod prescribes the assignment of a determined turbidityvalues to the technology used to determine those values.Numerical equivalence to turbidity standards is observedbetween different technologies but is not expected across acommon sample.Improved traceability beyond the scope ofthis test method may be practiced and would include the listingof the make and model number of the instrument used todetermine the turbidity values.1.4 In this test method,calibration standards are oftendefined in NTU values,but the other assigned turbidity units,such as those in Table 1 are equivalent.For example,a 1 NTUformazin standard is also a 1 FNU,a 1 FAU,a 1 BU,and soforth.1.5 This test method was tested on different natural watersand with standards that served as surrogates for samples.It isrecommended to validate the method response for waters ofuntested matrices.1.6 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3864 Guide for On-Line Monitoring Systems for WaterAnalysisD4411 Guide for Sampling Fluvial Sediment in MotionD7315 Test Method for Determination of Turbidity Above 1Turbidity Unit(TU)in Static ModeE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.07 on Sediments,Geomorphology,and Open-Channel Flow.Current edition approved Jan.1,2015.Published February 2015.DOI:10.1520/D7937-15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 TABLE 1 Summary of Known in-situ Instrument Designs,Applications,Ranges,and Reporting UnitsDesign and Reporting UnitProminent ApplicationKey Design FeaturesTypical Instrument RangeSuggested Application RangesNephelometric Non-Ratio(NTU)White light turbidimetersComply with EPA 180.1 for lowlevel turbidity monitoring.Detector centered at 90 rela-tive to the incident light beam.Uses a white light spectralsource.0.0400.040 RegulatoryRatio White Light Turbidimeters(NTRU)Complies with U.S.EPA regula-tions and EPA 2130B.Can beused for both low and high levelmeasurement.Used a white light spectralsource.Primary detector cen-tered at 90.Other detectorslocated at other angles.An in-strument algorithm uses a com-bination of detector readings togenerate the turbidity reading.010 000040 Regulatory010 000 otherNephelometric,Near-IRTurbidimeters,Non-Ratiometric(FNU)Complies with ISO 7027.Thewavelength is less susceptibleto color interferences.Appli-cable for samples with colorand good for low level monitor-ing.Detector centered at 90 rela-tive t