1、Designation: D7725 17Standard 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
2、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
3、.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
4、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
5、 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 meas
6、urement 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
7、 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 techn
8、ologies. 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
9、 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
10、equivalent. For example,a1NTUformazin standard is alsoa1FNU,a1FAU,a1BU,andsoforth.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 samp
11、les. 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 measu
12、rement 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 thi
13、s 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 reco
14、gnized 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 D
15、19 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
16、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 sta
17、ndardization 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.1TABLE 1 Technologies for Measuring Turbidity Greater Than 1 TU That Can be Used for In-
18、Line or On-Line ApplicationsDesign and ReportingUnitProminent Application Key Design Features Typical Instrument Range Suggested ApplicationNephelometric Non-Tatio(NTU)White light turbidimeters comply withEPA 180.1 for low-level turbiditymonitoring.Detector centered at 90 degreesrelative to the inci
19、dent light beam.Uses a white light spectral source.0.012 to 40 NTU Regulatory reporting ofclean waterRatio White Light Turbidi-meters (NTRU)Complies with Interim EnhancedSurface Water Treatment Rule(ISWTR) regulations and StandardMethod 2130B. Can be used forboth low- and high-level measure-ment.Use
20、d a white light spectral source.Primary detector centered at 90.Other detectors located at otherangles. An instrument algorithmuses a combination of detector read-ings to generate the turbidity read-ing.0.01210 000 NTRU Regulatory reporting ofclean waterFormazin Nephelometric,Near-IR Turbidimeters,N
21、on-Ratiometric (FNU)Complies with ISO 7027. The wave-lengthis less susceptible to color in-terferences. Applicable for sampleswith color and good for low-levelmonitoring.Detector centered at 90 degreesrelative to the incident light beam.Uses a near-IR (780900 nm)monochromatic light source.0.0121 000
22、 FNU 040 FNU ISO 7027 regu-latory reportingFormazin NephelometricNear-IR Turbidimeters,Ratio Metric (FNRU)Complies with ISO 7027. Applicablefor samples with high levels of colorand for monitoring to high turbiditylevels.Uses a near-IR monochromatic lightsource (780900 nm). Primary de-tector centered
23、 at 90. Other detec-tors located at other angles. An in-strument algorithm uses acombination of detector readings togenerate the turbidity reading.0.0121 000 FNU 040 FNRU ISO 7027 regu-latory reportingSurface Scatter Turbidi-meters (SSU)Turbidity is determined through lightscatter from a defined vol
24、ume be-neath the surface of a sample. Appli-cable for reporting for EPA compli-ance monitoring.Detector centered at 90 degreesrelative to the incident light beam.Uses a “white light” spectral source.0.01210 000 FNRU 1010 000 SSUFormazin NephelometricTurbidity Multibeam unit(FNMU)Is applicable to EPA
25、 regulatorymethod GLI Method 2. Applicable todrinking water and wastewater moni-toring applications.Detectors are geometrically centeredat 0 and 90. An instrument algo-rithm uses a combination of detectorreadings, which may differ for tur-bidities varying magnitude.0.012 to 4000 NTMU 0 to 40 NTMU Re
26、porting forEPA and ISO complianeFormazin Attenuation Unit(FAU)Compliance Reporting for ISO 7027for samples that exceed 40 units.Uses a near-IR light source at 860 30 nm and the detector is 0 degreesrelative to the centerline of the inci-dent light beam. The measurementis an attenuation measurement.1
27、010 000+ FAU 10010 000+ FAU Report-ing for ISO 7027 for levelsin excess of 40 unitsAttenuation Unit (AU) Not applicable for regulatory pur-poses. Best applied for samples withhigh-level turbidity.Uses a white light spectral source(400680 nm range). Detector ge-ometry is 0 relative to the incidentlig
28、ht beam.1010 000+ AU 10010 000+ AUFormazin Back Scatter(FBU)Not applicable for regulatory pur-poses. Best applied to high turbiditysamples. Backscatter is commonprobe technology and is best appliedin higher turbidity samples.Uses a near-IR monochromatic lightsource in the 780900 nm range.Detector ge
29、ometry is between 90and 180 relative to the incident lightbeam.10 000+ FBU 10 000 FBUForward Scatter RatioUnit (FSRU)The technology encompasses asingle, light source and two detec-tors. Light sources can vary fromsingle wavelength to polychromaticsources. The detection angle for theforward scatter d
30、etector is between0 and 90degrees relative to thecenterline of the incident light beam.The technology is sensitive to tur-bidities as low as 1 TU. The ratiotechnology helps to compensate forcolor interference and fouling.The measurement of ambientwaters such as streams,lakes, and rivers. The range i
31、stypically from about 1800FSRU, depending on themanufacturer.Forward Scatter Ratio Unit(FSRU)D7725 1722. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practice
32、s for Sampling Water from Closed ConduitsD3864 Guide for On-Line Monitoring Systems for WaterAnalysisD6698 Test Method for On-Line Measurement of TurbidityBelow 5 NTU in WaterD7315 Test Method for Determination of Turbidity Above 1Turbidity Unit (TU) in Static Mode2.2 Other Publications:EPA 180.1 Me
33、thods for Chemical Analysis of Water andWastes, Turbidity3GLI Method 2 Great Lakes Instruments (GLI) Turbidity4ISO 7027 Water Quality Determination of Turbidity5Standard Method 2130B Standard Methods for the Exami-nation of Water and Wastewater63. Terminology3.1 Definitions:3.1.1 For definitions of
34、terms used in this standard, refer toTerminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 attenuation-detection angle, nthe angle that isformed between the incident light source and the primarydetector, and that is at exactly 0-degrees.3.2.1.1 DiscussionThis is typically a tran
35、smission mea-surement.3.2.2 backscatter-detection angle, nthe angle that isformed between the incident light source and the primarydetector, and that is greater than 90-degrees and up to 180-degrees.3.2.3 calibration turbidity standard, na turbidity standardthat is traceable and equivalent to the re
36、ference turbiditystandard to within statistical errors; calibration turbidity stan-dards include commercially prepared 4000 NTU formazin,stabilized formazin, and styrenedivinylbenzene (SDVB).3.2.3.1 DiscussionThese standards may be used to cali-brate the instrument. Calibration turbidity standards m
37、ay beinstrument specific.3.2.4 calibration-verification standards, ndefined stan-dards used to verify the accuracy of a calibration in themeasurement range of interest.3.2.4.1 DiscussionThese standards may not be used toperform calibrations, only calibration verifications. Includedverification stand
38、ards are opto-mechanical lightscatter devices,gel-like standards, or any other type of stable-liquid standard.Calibration verification standards may be instrument specific.3.2.5 detection angle, nthe angle formed with its apex atthe center of the analysis volume of the sample, and such thatone vecto
39、r coincides with the centerline of the incident lightsources emitted radiation and the second vector projects to thecenter of the primary detectors view.3.2.5.1 DiscussionThis angle is used for the differentia-tion of turbidity-measurement technologies that are used in thistest method.3.2.6 forward-
40、scatter-detection angle, nthe angle that isformed between the incident light source and the primarydetector, and that is between 0 and 90-degrees.3.2.6.1 DiscussionMost designs will have an angle be-tween 10 and 45 degrees.3.2.7 nephelometric-detection angle, nthe angle that isformed between the inc
41、ident light source and the detector, andthat is at 90-degrees3.2.8 nephelometric-turbidity measurement, nthe mea-surement of light scatter from a sample in a direction that is at90 with respect to the centerline of the incident-light path.3.2.8.1 DiscussionUnits are NTU (nephelometric turbid-ity uni
42、ts). When ISO 7027 technology is employed units areFNU (formazin nephelometric units).3.2.9 ratio-turbidity measurement, nthe measurement de-rived through the use of a nephelometric detector that serves asthe primary detector, and one or more other detectors used tocompensate for variation in incide
43、nt-light fluctuation, straylight, instrument noise, or sample color.3.2.10 reference-turbidity standard, na standard that issynthesized reproducibly from traceable raw materials by theuser.3.2.10.1 DiscussionAll other standards are traced back tothis standard. The reference standard for turbidity is
44、 formazin.3.2.11 seasoning, nthe process of conditioning labwarewith the standard that will be diluted to a lower value.3.2.11.1 DiscussionThe process reduces contaminationand dilution errors. See Appendix X2 for suggested procedure.3.2.12 slipstream, nan on-line technique for analysis of asample as
45、 it flows through a measurement chamber of aninstrument.3.2.12.1 DiscussionThe sample is transported from thesource into the instrument (for example a turbidimeter),analyzed, and then transported to drain or back to the processstream. The term is synonymous with the terms “on-lineinstrument” or “con
46、tinuous-monitoring instrument.”3.2.13 stray light, nall light reaching the detector otherthan that contributed by the sample.3.2.14 surface-scatter detection, na turbidity measure-ment that is determined through the detection of light scattercaused by particles within a defined volume beneath thesur
47、face of a sample.3.2.14.1 DiscussionBoth the light source and detector are2For 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
48、ASTM website.3Available from United States Environmental ProtectionAgency (EPA), WilliamJefferson Clinton Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460,http:/www.epa.gov.4Available from Hach Company, P.O. Box 389, Loveland, Colorado 80539,https:/.5Available from International Organization
49、for Standardization (ISO), ISOCentral Secretariat, BIBC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,Geneva, Switzerland, http:/www.iso.org.6Available from American Public Health Association (APHA), 800 I St., NW,Washington, DC 20001, http:/www.apha.org.D7725 173positioned above the surface of the sample. The angle formedbetween the centerline of the light source and detector istypically at 90-degrees. Particles at the surface and in a volumebelow the surface of the sample contribute to the
