1、Designation: D7726 11 (Reapproved 2016)1Standard Guide forThe Use of Various Turbidimeter Technologies forMeasurement of Turbidity in Water1This standard is issued under the fixed designation D7726; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se 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.1NOTEEditorial corrections were made throughout in November 2016.1. Scope1.1 This guide covers the bes
3、t practices for use of variousturbidimeter designs for measurement of turbidity in watersincluding: drinking water, wastewater, industrial waters, andfor regulatory and environmental monitoring. This guide cov-ers both continuous and static measurements.1.1.1 In principle there are three basic appli
4、cations foron-line measurement set ups. The first is the bypass orslipstream technique; a portion of sample is transported fromthe process or sample stream and to the turbidimeter foranalysis. It is then either transported back to the sample streamor to waste. The second is the in-line measurement;
5、the sensoris submerged directly into the sample or process stream, whichis typically contained in a pipe. The third is in-situ where thesensor is directly inserted into the sample stream. The in-situprinciple is intended for the monitoring of water during anystep within a processing train, including
6、 immediately before orafter the process itself.1.1.2 Static covers both benchtop and portable designs forthe measurement of water samples that are captured into a celland then measured.1.2 Depending on the monitoring goals and desired datarequirements, certain technologies will deliver more desirabl
7、eresults for a given application. This guide will help the useralign a technology to a given application with respect to bestpractices for data collection.1.3 Some designs are applicable for either a lower or uppermeasurement range. This guide will help provide guidance tothe best-suited technologie
8、s based given range of turbidity.1.4 Modern electronic turbidimeters are comprised of manyparts that can cause them to produce different results onsamples. The wavelength of incident light used, detector type,detector angle, number of detectors (and angles), and opticalpathlength are all design crit
9、eria that may be different amonginstruments. When these sensors are all calibrated with thesample turbidity standards, they will all read the standards thesame. However, samples comprise of completely differentmatrices and may measure quite differently among thesedifferent technologies.1.4.1 This gu
10、ide does not provide calibration informationbut rather will defer the user to the appropriateASTM turbiditymethod and its calibration protocols. When calibrated ontraceable primary turbidity standards, the assigned turbidityunits such as those used in Table 1 are equivalent. For example,a 1 NTU form
11、azin standard is also equivalent in measurementmagnitude toa1FNU,a1FAU,anda1BUstandard and soforth.1.4.2 Improved traceability beyond the scope of this guidemay be practiced and would include the listing of the make andmodel number of the instrument used to determine the turbidityvalues.1.5 This gui
12、de does not purport to cover all availabletechnologies for high-level turbidity measurement.1.6 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 This standard does not purport to address all of thesafety concerns, if any, ass
13、ociated 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.1.8 This guide does not purport to address all of the safetyconcerns, if any, associated with its u
14、se. It is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatory1This guide is under the jurisdiction of ASTM Committee D19 on Water and isthe direct responsibility of Subcommittee D19.07 on Sediments, Geomorph
15、ology,and Open-Channel Flow.Current edition approved Nov. 1, 2016. Published November 2016. Originallyapproved in 2011. Last previous edition approved in 2011 as D7726 11. DOI:10.1520/D7726-11R16E01.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. U
16、nited States1limitations prior to use. Refer to the MSDSs for all chemicalsused in this procedure.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD3977 Test Methods for Determining Sediment Concentra-tion in Water SamplesD6698 Test Method for On-Line Measurement of Turb
17、idityBelow 5 NTU in WaterD6855 Test Method for Determination of Turbidity Below 5NTU in Static ModeD7315 Test Method for Determination of Turbidity Above 1Turbidity Unit (TU) in Static Mode2.2 Other References:USGS National Field Manual for the Collection of WaterQuality Data3Wagners Field Manual Gu
18、idelines and Standard Proceduresfor Continuous Water-Quality Monitors: StationOperation, Record Computation, and Data Reporting43. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer toTerminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 calib
19、ration drift, nthe error that is the result of driftin the sensor reading from the last time the sensor wascalibrated and is determined by the difference betweencleaned-sensor readings in calibration standards and the true,temperature-compensated value of the calibration standards.3.2.2 calibration
20、turbidity standard, na turbidity standardthat is traceable and equivalent to the reference turbiditystandard to within statistical errors; calibration turbidity stan-dards include commercially prepared 4000 NTU Formazin,stabilized formazin, and styrenedivinylbenzene (SDVB).3.2.2.1 DiscussionThese st
21、andards may be used to cali-brate the instrument.3.2.3 calibration-verification standards, ndefined stan-dards used to verify the accuracy of a calibration in themeasurement range of interest.3.2.3.1 DiscussionThese standards may not be used toperform calibrations, only calibration verifications. In
22、cludedverification standards are opto-mechanical light-scatterdevices, gel-like standards, or any other type of stable-liquidstandard.3.2.4 continuous, adjthe type of automated measurementat a defined-time interval, where no human interaction isrequired to collect and log measurements.3.2.4.1 Discus
23、sionMeasurement intervals range from sec-onds to months, depending on monitoring goals of a given site.3.2.5 design, na more detailed technology description thatwill encompass all of the elements making up a technology,plus any inherent criteria used to generate a specific turbidityvalue.3.2.5.1 Dis
24、cussionThe design will typically translate intoa specific make or model of an instrument.3.2.6 detection angle, nthe angle formed with its apex atthe center of the analysis volume of the sample, and such thatone vector coincides with the centerline of the incident lightsources emitted radiation and
25、the second vector projects to thecenter of the primary detectors view.3.2.6.1 DiscussionThis angle is used for the differentia-tion of turbidity-measurement technologies that are used in thisguide.3.2.6.2 attenuation-detection angle, nthe angle that isformed between the incident light source and the
26、 primarydetector, and that is at exactly 0 degrees.(1) DiscussionThis is typically a transmission measure-ment.3.2.6.3 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 180degrees.3.2.6.4 nep
27、helometric-detection angle, nthe angle that isformed between the incident light source and the detector, andthat is at 90 degrees.3.2.6.5 forward-scatter-detection angle, nthe angle that isformed between the incident light source and the primarydetector, and that is greater than 0 degrees but less t
28、han 90degrees.(1) DiscussionMost designs will have an angle between135 degrees and 180 degrees.3.2.6.6 surface-scatter detection, na turbidity measure-ment that is determined through the detection of light scattercaused by particles within a defined volume beneath thesurface of a sample.(1) Discussi
29、onBoth the light source and detector arepositioned 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 turbidityreading.3.2.7 foul
30、ing, vthe measurement error that can result froma variety of sources and is determined by the differencebetween sensor measurements in the environment before andafter the sensors are cleaned.3.2.8 in-situ nephelometer, na turbidimeter that deter-mines the turbidity of a sample using a sensor that is
31、 placeddirectly in the sample.3.2.8.1 DiscussionThis turbidimeter does not requiretransport of the sample to or from the sensor.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informatio
32、n, refer to the standards Document Summary page onthe ASTM website.3Available from United States Geological Survey (USGS), USGS Headquarters,12201 Sunrise Valley Drive, Reston, VA 20192, http:/www.usgs.gov/FieldManual/Chapters6/6.7.htm.4Wagner, R. J., et al, Guidelines and Standard Procedures for Co
33、ntinuousWater-Quality Monitors: Station Operation, Record Computation, and DataReporting, USGS Enterprise Publishing Network, 2005, available from: http:/pubs.usgs.gov/tm/2006/tm1D3.D7726 11 (2016)123.2.9 metadata, nthe ancillary descriptive informationthat describes instrument, sample, and ambient
34、conditionsunder which data were collected.3.2.9.1 DiscussionMetadata provide information aboutdata sets. An example is the useful background informationregarding the sampling site, instrument setup, and calibrationand verification results for a given set of turbidity data(especially when data are cr
35、itically reviewed or comparedagainst another data set).3.2.10 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.3.2.10.1 DiscussionUnits are NTU (Nephelometric Tur-bidity Units).
36、 When ISO 7027 technology is employed unitsare FNU (Formazin Nephelometric Units).3.2.11 pathlength, nThe greatest distance that the sum ofthe incident light and scattered light can travel within a samplevolume (cell or view volume).3.2.11.1 DiscussionThe pathlength is typically measuredalong the ce
37、nterline of the incident-light beam plus thescattered light. The pathlength includes only the distance thelight and scattered light travel within the sample itself.3.2.12 ratio-turbidity measurement, nthe measurementderived through the use of a nephelometric detector that servesas the primary detect
38、or, and one or more other detectors usedto compensate for variation in incidentlight fluctuation, straylight, instrument noise, or sample color.3.2.13 reference-turbidity standard, na standard that issynthesized reproducibly from traceable raw materials by theuser.3.2.13.1 DiscussionAll other standa
39、rds are traced back tothis standard. The reference standard for turbidity is formazin.3.2.14 seasoning, vthe process of conditioning labwarewith the standard that will be diluted to a lower value to reducecontamination and dilution errors.3.2.15 slipstream, nan on-line technique for analysis of asam
40、ple as it flows through a measurement chamber of aninstrument.3.2.15.1 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”
41、or “continuous monitoring instrument.”3.2.16 sonde, na monitoring instrument that contains twoor more measurement sensors that share common power,transmitting, and data logging.3.2.16.1 DiscussionA sonde usually has one end thatcontains the measurement sensors, which are in close proxim-ity to each
42、other and together are submerged in a sample.3.2.17 stray light, nall light reaching the detector otherthan that contributed by the sample.3.2.18 technology, na general classification of a turbidi-meter design that incorporates the type and wavelength of theincident-light source, detection angles, a
43、nd the number ofdetectors used to generate a turbidity measurement and itsdefined reporting unit.3.2.18.1 DiscussionIn ASTM turbidity test methods, thetechnology is based on type and number of light sources, andtheir respective wavelength, detector angle(s), and number ofdetectors used in the techno
44、logy to generate the turbidity value.3.2.19 turbidimeter, nan instrument that measures lightscatter caused by particulates within a sample and converts themeasurement to a turbidity value.3.2.19.1 DiscussionThe detected light is quantitativelyconverted to a numeric value that is traced to a light-sc
45、atterstandard. See Test Method D7315.3.2.20 turbidity, nan expression of the optical propertiesof a sample that causes light rays to be scattered and absorbedrather than transmitted in straight lines through the sample.3.2.20.1 DiscussionTurbidity of water is caused by thepresence of matter such as
46、clay, silt, finely divided organicmatter, plankton, other microscopic organisms, organic acids,and dyes.4. Summary of Practice4.1 This guide is to assist the user in meeting and under-standing the following criteria with respect to turbidity mea-surements:4.1.1 The selection of the appropriate techn
47、ology for mea-surement of a given sample with implied characteristics.4.1.2 Help in the selection of a measurement technologythat will help meet the scope of requirements (goals) for use ofthe data.4.1.3 Assist in the selection of a technology that is bestsuited to withstand the expected environment
48、al and sampledeviations over the course of data collection. Examples ofdeviations would be expected measurement range and interfer-ences.4.1.4 Understand both the general strengths and limitationsfor a given type (design) of technology in relation to overcom-ing known interferences in turbidity meas
49、urement.4.1.5 Provide general procedures that can be used to deter-mine whether a given technology is suitable for use in a givensample or a given application.4.1.6 Understand the need for the user to include criticalmetadata related to turbidity measurement.4.1.7 This guide will help the user select the appropriatetechnology for regulatory purposes.5. Significance and Use5.1 Turbidity is a measure of scattered light that results fromthe interaction between a beam of light and particulate materialin a liquid sample. Particulate ma
