ASTM D7937-15

Standard Test Method for In-situ Determination of Turbidity Above 1 Turbidity Unit (TU) in Surface Water

SIGNIFICANCE AND USE
5.1 Turbidity is monitored to help control processes, monitor the health and biology of aquatic environments and to determine the impact of environmental events such as storms, floods, runoff, etc. Turbidity is undesirable in drinking water, plant-effluent waters, water for food and beverage production, and for a large number of other water-dependent manufacturing processes. Turbidity is often reduced by coagulation, sedimentation and water filtration. The measurement of turbidity may indicate the presence of particle-bound contaminants and is vital for monitoring the completion of a particle-waste settling process. Significant uses of turbidity measurements include:  
5.1.1 Compliance with permits, water-quality guidelines, and regulations;  
5.1.2 Determination of transport and fate of particles and associated contaminants in aquatic systems;  
5.1.3 Conservation, protection and restoration of surface waters;  
5.1.4 Measure performance of water and land-use management;  
5.1.5 Monitor waterside construction, mining, and dredging operations;  
5.1.6 Characterization of wastewater and energy-production effluents;  
5.1.7 Tracking water-well completion including development and use; and  
5.1.8 As a surrogate for other constituents in water including sediment and sediment-associated constituents.  
5.2 The calibration range of a turbidimeter shall exceed the expected range of TU values for an application but shall not exceed the measurement range specified by the manufacturer.  
5.3 Designs described in this standard detect and respond to a combination of relative absorption, intensity of light scattering, and transmittance. However, they do not measure these absolute physical units as defined in 3.2.15 and 3.2.19.  
5.4 Several different turbidimeter designs may be used for this test method and one design may be better suited for a specific type of sample or monitoring application than another. The selection flowchart in Annex A1 provides guidance for th...
SCOPE
1.1 This test method covers the in-situ field measurements of turbidity in surface water. The measurement range is greater than 1 TU and the lesser of 10 000 TU or the maximum measurable TU value specified by the turbidimeter manufacturer.  
1.1.1 Precision data was conducted on both real world and surrogate turbidity samples up to about 1000 TU. Many of the technologies listed in this test method are capable of measuring above that provided in the precision section (see Section 16).  
1.2 “In-situ measurement” refers in this test method to applications where the turbidimeter sensor is placed directly in the surface water in the field and does not require transport of a 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 designs covered in this test method are numerically equivalent in calibration when a common calibration standard is applied across those designs listed in Table 1. Measurement of a common calibration standard of a defined value will also produce equivalent results across these technologies. This test method prescribes the assignment of a determined turbidity values to the technology used to determine those values. Numerical equivalence to turbidity standards is observed between different technologies but is not expected across a common sample. Improved traceability beyond the scope of this test method may be practiced and would include the listing of the make and model number of the instrument used to determine the turbidity values.  
1.4 In this test method, calibration standards are often defined in NTU values, but the other assigned turbidity units, such as those in Table 1 are equivalent. For example, a 1 NTU formazin standard is also a 1 FNU, a 1 FAU, a 1 BU, and so forth.  
1.5 This test method was tested on different natural waters and with standards th...

General Information

• Status: Historical
• Publication Date: 31-Dec-2014
• ICS: 13.060.60 - Examination of physical properties of water
• Technical Committee: D19 - Water
• Drafting Committee: D19.07 - Sediments, Geomorphology, and Open-Channel Flow

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7937 − 15
Standard Test Method for
In-situ Determination of Turbidity Above 1 Turbidity Unit
1
(TU) in Surface Water
This standard is issued under the fixed designation D7937; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope such as those in Table 1 are equivalent. For example, a 1 NTU
formazin standard is also a 1 FNU, a 1 FAU, a 1 BU, and so
1.1 This test method covers the in-situ field measurements
forth.
of turbidity in surface water. The measurement range is greater
than 1 TU and the lesser of 10 000 TU or the maximum 1.5 This test method was tested on different natural waters
measurable TU value specified by the turbidimeter manufac- and with standards that served as surrogates for samples. It is
turer. recommended to validate the method response for waters of
1.1.1 Precision data was conducted on both real world and untested matrices.
surrogate turbidity samples up to about 1000 TU. Many of the
1.6 This standard does not purport to address all of the
technologies listed in this test method are capable of measuring
safety concerns, if any, associated with its use. It is the
above that provided in the precision section (see Section 16).
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1.2 “In-situ measurement” refers in this test method to
mine the applicability of regulatory limitations prior to use.
applications where the turbidimeter sensor is placed directly in
1.7 This international standard was developed in accor-
the surface water in the field and does not require transport of
dance with internationally recognized principles on standard-
a sample to or from the sensor. Surface water refers to springs,
ization established in the Decision on Principles for the
lakes, reservoirs, settling ponds, streams and rivers, estuaries,
Development of International Standards, Guides and Recom-
and the ocean.
mendations issued by the World Trade Organization Technical
1.3 Many of the turbidity units and instrument designs
Barriers to Trade (TBT) Committee.
covered in this test method are numerically equivalent in
calibration when a common calibration standard is applied
2. Referenced Documents
across those designs listed in Table 1. Measurement of a
2
2.1 ASTM Standards:
common calibration standard of a defined value will also
D1129 Terminology Relating to Water
produce equivalent results across these technologies. This test
D1193 Specification for Reagent Water
method prescribes the assignment of a determined turbidity
D2777 Practice for Determination of Precision and Bias of
values to the technology used to determine those values.
Applicable Test Methods of Committee D19 on Water
Numerical equivalence to turbidity standards is observed
D3864 Guide for On-Line Monitoring Systems for Water
between different technologies but is not expected across a
Analysis
common sample. Improved traceability beyond the scope of
D4411 Guide for Sampling Fluvial Sediment in Motion
this test method may be practiced and would include the listing
D7315 Test Method for Determination of Turbidity Above 1
of the make and model number of the instrument used to
Turbidity Unit (TU) in Static Mode
determine the turbidity values.
E177 Practice for Use of the Terms Precision and Bias in
1.4 In this test method, calibration standards are often
ASTM Test Methods
defined in NTU values, but the other assigned turbidity units,
E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1
This test method is under the jurisdiction of ASTM Committee D19 on Water
2
and is the direct responsibility of Subcommittee D19.07 on Sediments, For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Geomorphology, and Open-Channel Flow. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Current edition approved Jan. 1, 2015. Published February 2015. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D7937-15. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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D7937 − 15
TABLE 1 Summary of Known in-situ Instrument Designs, Applications, Ranges, and Reporting Units
Design and Reporting Unit Prominent Application Key Design Features Typical Instrument Range Suggested Application Ranges
Nephelometric Non-Ratio (NTU) White light turbidimeters Detector centered at 90° rela- 0.0–40 0.0–40 Regulatory
...