1、Designation: D6698 12D6698 14Standard Test Method forOn-Line Measurement of Turbidity Below 5 NTU in Water1This standard is issued under the fixed designation D6698; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、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 is applicable to the on-line measurement of turbidity under 5 nephelometric turbidity units (NTU) in water
3、.1.2 It is the users responsibility to ensure the validity of this test method for waters of untested matrices.1.3 In this test method calibration standards are defined in NTU values, but other assigned turbidity units are assumed to beequivalent.1.4 This test method assigns traceable reporting unit
4、s to the type of respective technology that was used to perform themeasurement. Units are numerically equivalent with respect to the calibration standard. For example, a 1 NTU formazin standardis also equal to a 1 FNU (formazin nephelometric units) standard, a 1 FNRU (formazin nephelometric ratio un
5、its) standard, andso forth.1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of t
6、his standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and
7、 Bias of Applicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD3864 Guide for On-Line Monitoring Systems for Water AnalysisD7315 Test Method for Determination of Turbidity Above 1 Turbidity Unit (TU) in Static Mode2.2 Other Standards:EPA 180.1 Metho
8、ds for Chemical Analysis of Water and Wastes, Turbidity3GLI Method 24Hach Method 8195 Determination of Turbidity by Nephelometry EMMC Format4ISO 7027 Determination of Turbidity5Standard Method 2130B62.3 Other Documents:U.S. Patent 4,283,143 Patterson, JamesA. 1981. Optical Characterization of a Susp
9、ension. United States Patent 4,283,143, filedNovember 19, 1979, and issued August 11, 1981.71 This test method is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.03 on Sampling Water andWater-Formed Deposits, Analysis of Water for Power Gene
10、ration and Process Use, On-Line Water Analysis, and Surveillance of Water.Current edition approved June 1, 2012March 15, 2014. Published August 2013April 2014. Originally approved in 2001. Last previous edition approved in 20072012 asD6698 07.D6698 12. DOI: 10.1520/D6698-12.10.1520/D6698-14.2 For re
11、ferencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from United States Environmental ProtectionAssociation (E
12、PA),Ariel Rios Bldg., 1200 PennsylvaniaAve., NW, Washington, DC 20460, http:/www.epa.gov.4 Available from Hach Company, P.O. Box 389, Loveland, CO, 80539-0389, http:/.5 Available from International Organization for Standardization (ISO), 1 rue de Varemb, Case postale 56, CH-1211, Geneva 20, Switzerl
13、and, http:/www.iso.ch.6 Available from Standard Methods for the Examination of Water and Wastewater, 21st Edition, American Public Health Association, Washington, DC, 2005,http:/www.standardmethods.org.7 Available from AMCO Clear, P.O. Box 245, Powell, OH, 43065, http:/.This document is not an ASTM
14、standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all
15、cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1U.S. Patent 4,291,980 Patterson, James A. 1981. Styrene-Divinylbenzene Copoly
16、mer and Method of Manufacturer. UnitedStates Patent 4,291,980, filed August 14, 1978, and issued September 29, 1981.7U.S. Patent 5,777,011 Sadar, Michael J. 1998. Stabilized Formazin Composition. United States Patent 5,777,011, filed December1, 1995, and issued July 7, 1998.4,83. Terminology3.1 Defi
17、nitionsFor definitions of terms used in this test method, refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibration turbidity standard, na turbidity standard that is traceable and equivalent to the reference turbidity standardto within statistical errors; calibr
18、ation turbidity standardstandards include commercially prepared 4000 NTU formazin, stabilizedformazin, and styrenedivinylbenzene (SDVB).3.2.1.1 DiscussionThese standards may be used to calibrate the instrument. Calibration standards may be instrument specific.3.2.2 calibration verification standards
19、, ndefined standards used to verify the accuracy of a calibration in the measurementrange of interest.3.2.2.1 DiscussionThese standards may not be used to perform calibrations, only calibration verifications. Included verification standards areopto-mechanical light scatter light-scatter devices, gel
20、-like standards, or any other type of stable liquid stable-liquid standard.Calibration verification standards may be instrument specific.3.2.3 in-situ nephelometer, na turbidimeter that determines the turbidity of a sample using a sensor that is placed directly inthe sample.3.2.3.1 DiscussionThis tu
21、rbidimeter does not require transport of the sample to or from the sensor.3.2.4 nephelometric turbidity measurement, nthe measurement of light scatter from a sample in a direction that is at 90 withrespect to the centerline of the incident light incident-light path.3.2.4.1 DiscussionUnits are NTU (n
22、ephelometric turbidity units); when(Nephelometric Turbidity Units). When ISO 7027 technology is employed,units are FNU (formazin nephelometric units).(Formazin Nephelometric Units).3.2.5 ratio turbidity measurement, nthe measurement derived through the use of a nephelometric detector that serves as
23、theprimary detector, and one or more other detectors used to compensate for variation in incident light incident-light fluctuation, straylight, instrument noise, or sample color.3.2.6 reference turbidity standard, na standard that is synthesized reproducibly from traceable raw materials by the user.
24、3.2.6.1 DiscussionAll other standards are traced back to this standard. The reference standard for turbidity is formazin.3.2.7 seasoning, nvthe process of conditioning labware with the standard that will be diluted to a lower value. value toreduce contamination and dilution errors. See Appendix X2 f
25、or suggested procedure.3.2.7.1 DiscussionThe process reduces contamination and dilution errors. See Appendix X2 for suggested procedure.3.2.8 slip stream nephelometer, nan on-line technique for analysis turbidimeter that determines the turbidity of a sample asit the sample flows through a measuremen
26、t chamber of an instrument.sampling chamber.8 This document is covered by a patent. Interested parties are invited to submit information regarding the identification of alternatives to the ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of the responsibl
27、e technical committee, which you may attend.D6698 1423.2.8.1 DiscussiontheThe sample is transporteddrawn from the source into the instrument (for example, a turbidimeter), analyzed, turbidimeter,analyzed and then transported to drain or back to the process stream. The term is synonymous with the ter
28、ms drain.on-lineinstrument or continuous monitoring instrument.3.2.9 stray light, nall light reaching the detector other than that contributed by the sample.3.2.9.1 DiscussionFor example: ambient light leakage and divergent light in optical systems.3.2.10 turbidimeter, nan instrument that measures l
29、ight scatter caused by particulates within a sample and converts themeasurement to a turbidity value.3.2.10.1 DiscussionThe detected light is quantitatively converted to a numeric value that is traced to a light scatter standard.light-scatter standard. SeeTest Method D7315.3.2.11 turbidity, nan expr
30、ession of the optical properties of a sample that causes light rays to be scattered and absorbed ratherthan transmitted in straight lines through the sample.3.2.11.1 DiscussionTurbidity of water is caused by the presence of suspended and dissolved matter such as clay, silt, finely divided organic ma
31、tter,plankton, other microscopic organisms, organic acids, and dyes.4. Summary of Test Method4.1 The optical property expressed as turbidity is measured by the scattering effect that suspended solids have on light; thehigher the intensity of scattered light, the higher the turbidity. In samples cont
32、aining particulate matter, the manner in which theparticulate matter interacts with light transmittance is related to the size, shape and composition of the particles in the water, andalso to the wavelength of the incident light.4.2 This test method is based upon a comparison of the intensity of lig
33、ht scattered by the sample with the intensity of lightscattered by a reference suspension. Turbidity values are determined by a nephelometer, which measures light scatter from asample in a direction that is at 90 degrees with respect to the centerline of the incident light path.5. Significance and U
34、se5.1 Turbidity is undesirable in drinking water, plant effluent waters, water for food and beverage processing, and for a largenumber of other water-dependent manufacturing processes. Removal of suspended matter is accomplished by coagulation, settling,and filtration. Measurement of turbidity provi
35、des a rapid means of process control to determine when, how, and to what extent thewater must be treated to meet specifications.5.2 This test method is suitable for the on-line monitoring of turbidity such as that found in drinking water, process water, andhigh purity industrial waters.5.3 The instr
36、umentation used must allow for the continuous on-line monitoring of a sample stream.NOTE 1See 8.2 for discussion on signal spikes resulting from bubbles.5.4 When reporting the measured result, appropriate units should also be reported. The units are reflective of the technologyused to generate the r
37、esult, and if necessary, provide more adequate comparison to historical data sets.5.4.1 Table 1 describes technologies and reporting results. Those technologies listed are appropriate for the range ofmeasurement prescribed in this test method are mentioned, though others may come available.5.4.2 For
38、 a specific design that falls outside of the reporting ranges in Table 1, the turbidity should be reported in turbidity units(TU) with a subscripted wavelength value to characterize the light source that was used.6. Safety6.1 Wear appropriate personal protection equipment at all times.6.2 Follow all
39、 relevant safety guidelines.D6698 1436.3 Refer to instrument manuals for safety guidelines when installing, calibrating, measuring or performing maintenance withany of the respective instrumentation.6.4 Refer to all Material Safety Data Sheets (MSDSs) prior to preparing or using standards and before
40、 calibrating or performinginstrument maintenance.7. Interferences7.1 Bubbles, color, and large suspended particles may result in interferences. Bubbles cause positive interference and colorcauses negative interference. Dissolved material that imparts a color to the water may cause errors in pure pho
41、toelectricnephelometric readings (versus ratio photoelectric nephelometric readings) unless the instrument has special compensatingfeatures. Certain turbulent motions also create unstable reading conditions of nephelometers.7.2 Scratches, finger marks, or dirt on any part of an optical component thr
42、ough which light must travel to reach the sample,or through which scattered light leaves the sample to a detector, may give erroneous readings. Keep these surfaces scrupulouslyclean and replace damaged (etched or scratched) components.8. Apparatus8.1 The sensor used for the on-line monitoring of tur
43、bidity is designed for continuous monitoring of the turbidity of the samplestream.TABLE 1 Technologies and Reporting ResultsDesign and Reporting Unit Prominent Application Key Design Features Typical Instrument Range Suggested ApplicationNephelometric non- ratio(NTU)White light turbidimeterscomply w
44、ith EPA 180.1for low-levelturbidity monitoring.Detector centered at 90relative to the incidentlight beam. Uses a whitelight spectral source.0.020 to 40 Regulatory reportingof clean waterRatio White Lightturbidimeters (NTRU)Complies with ISWTRregulations and StandardMethod 2130B.Can be used forboth l
45、ow andhigh-level measurement.Used a white lightspectral source. Primarydetector centered at 90.Other detectors locatedat other angles.An instrument algorithmuses a combinationof detector readingsto generate theturbidity reading.0.020 to 10 000 Regulatory Reportingof clean waterNephelometric, near-IR
46、turbidimeters, non-ratiometric(FNU)Complies with ISO 7027.The wavelength isless susceptible tocolor interferences.Applicable for sampleswith color and goodfor low-level monitoring.Detector centered at90 relative to theincident light beam.Uses a near-IR(780-900 nm) monochromaticlight source.0.012 to
47、1000 040 ISO 7027Regulatory reportingNephelometric near-IRturbidimeters, ratio metric(FNRU)Complies with ISO 7027.Applicable for sampleswith high levelsof color andfor monitoring tohigh turbidity levels.Uses a near-IRmonochromatic light source(780900 nm).Primary detector centeredat 90. Other detecto
48、rslocated at other angles.An instrument algorithmuses a combination ofdetector readings togenerate the turbidityreading.0.012 to 10 000 040 ISO 7027Regulatory reportingFormazin NephelometricMultibeamUnit (FNMU)Is applicable toEPA regulatory method GLIMethod 2.Applicable to drinkingwater and wastewat
49、ermonitoring applications.Detectors are geometricallycentered at 0 and 90.Uses a near-IR light source(780900 nm)monochromatic light source.An instrument algorithmuses a combination ofdetector readings, whichmay differ forturbidities varying magnitude.0.012 to 4000 040 Reportingfor EPAand ISO compliancemNTU Is applicable toreporting of cleanwaters and filterperformance monitoring.Very sensitive toturbidity changes inlow turbidity samples.Nephelometric method involvinga laser-based light sourceat 660 nm anda
