ASTM_D_7725_-_17.pdf

Designation:D772517Standard Test Method for theContinuous Measurement of Turbidity Above 1 TurbidityUnit(TU)1This standard is issued under the fixed designation D7725;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 on-line and in-line determi-nation of high-level turbidity in water that is greater than 1.0turbidity units(TU)in municipal,industrial and environmentalusage.1.2 In principle,there are three basic applications for on-linemeasurement set ups.This first is the slipstream(bypass)sample technique.For the slipstream sample technique aportion of sample is transported out of the process and throughthe measurement apparatus.It is then either transported back tothe process or to waste.The second is the in-line measurementwhere the sensor is brought directly into the process(see Fig.8).The third basic method is for in-situ monitoring of samplewaters.This principle is based on the insertion of a sensor intothe sample itself as the sample is being processed.The in-situuse in this test method is intended for the monitoring of waterduring any step within a processing train,including immedi-ately before or after the process itself.1.3 This test method is applicable to the measurement ofturbidities greater than 1.0 TU.The absolute range is dictatedby the technology that is employed.1.4 The upper end of the measurement range is left unde-fined because different technologies described in this testmethod can cover very different ranges of turbidity.1.5 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.1.5.1 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.1.6 This test method does not purport to cover all availabletechnologies for high-level turbidity measurement.1.7 This test method was tested on different waters,and withstandards that will serve as surrogates to samples.It is theusers responsibility to ensure the validity of this test methodfor waters of untested matrices.1.8 Those samples with the highest particle densities typi-cally prove to be the most difficult to measure.In these cases,the process monitoring method can be considered with ad-equate measurement protocols installed.1.9 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.10 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.Refer to the MSDSs for all chemicals used in this procedure.1.11 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.03 on Sampling Water andWater-Formed Deposits,Analysis of Water for Power Generation and Process Use,On-Line Water Analysis,and Surveillance of Water.Current edition approved Dec.15,2017.Published February 2018.Originallyapproved in 2012.Last previous edition approved in 2012 as D7725 12.DOI:10.1520/D7725-17.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 TABLE 1 Technologies for Measuring T