ASTM-D7725 2012

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D7725-12 Standard Test Method for the Continuous Measurement of Turbidity Above 1 Turbidity Unit (TU)

Published By	Publication Date	Number of Pages
ASTM	2012	24

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Categories: 13.060.60 - Examination of physical properties of water, ASTM

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Description

ASTM D7725-12

Historical Standard: Standard Test Method for the Continuous Measurement of Turbidity Above 1 Turbidity Unit (TU)

ASTM D7725

Scope

1.1 This test method covers the online and inline determination of high-level turbidity in water that is greater than 1.0 turbidity units (TU) in municipal, industrial and environmental usage.

1.2 In principle there are three basic applications for on-line measurement set ups. This first is the slipstream (bypass) sample technique. For the slipstream sample technique a portion of sample is transported out of the process and through the measurement apparatus. It is then either transported back to the process or to waste. The second is the in-line measurement where the sensor is brought directly into the process (see Figure 8). The third basic method is for in-situ monitoring of sample waters. This principle is based on the insertion of a sensor into the sample itself as the sample is being processed. The in-situ use in this method is intended for the monitoring of water during any step within a processing train, including immediately before or after the process itself.

1.3 This test method is applicable to the measurement of turbidities greater than 1.0 turbidity unit (TU). The absolute range is dictated by the technology that is employed.

1.4 The upper end of the measurement range is left undefined because different technologies described in this method can cover very different ranges of turbidity.

1.5 Many of the turbidity units and instrument designs covered in this 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 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 method may be practiced and would include the listing of the make and model number of the instrument used to determine the turbidity values.

1.5.1 In this 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.

1.6 This standard does not purport to cover all available technologies for high-level turbidity measurement.

1.7 This test method was tested on different waters, and with standards that will serve as surrogates to samples. It is the user’s responsibility to ensure the validity of this test method for waters of untested matrices.

1.8 Those samples with the highest particle densities typically prove to be the most difficult to measure. In these cases, the process monitoring method can be considered with adequate measurement protocols installed.

1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Refer to the MSDSs for all chemicals used in this procedure.

TABLE 1 Technologies for Measuring Turbidity Greater Than 1 TU that can be used for In-Line or On-Line Applications

Keywords

calibration; calibration verification; continuous; formazin; measurement; monitoring; nephelometer; nephelometric; on-line; standard; styrenedivinylbenzene; turbidimeter; turbidity; turbidity standards

ICS Code

ICS Number Code 13.060.60 (Examination of water for physical properties)

DOI: 10.1520/D7725-12

PDF Catalog

PDF Pages	PDF Title
1	Scope Referenced Documents
2	Terminology TABLE 1
3	Significance and Use Safety
4	Interferences Apparatus
5	FIG. 1
6	FIG. 2 FIG. 3 FIG. 4
7	Purity of Reagents Reagents FIG. 5
8	Instrument Installation, Sample Lines and Sampling FIG. 6
9	FIG. 7 FIG. 8
10	Calibration and Calibration Verification
11	Procedure
12	Results Quality Control/Quality Assurance Precision and Bias
13	Keywords X1. STABILITY OF FORMAZIN X1.1 TABLE X1.1
14	X2. PROCEDURE FOR SEASONING GLASSWARE WHEN PREPARING CALIBRATION STANDARDS X2.1 Introduction: X2.2 Procedure: X3. SELECTION CRITERIA FLOWCHART FOR TURBIDIMETERS. X3.1 Introduction X3.2 TABLE X1.2
15	X4. Examples Depicting the Demonstration of Capability for High Range Turbidity Measurement. X4.1 Example 1
16	FIG. 10
17	X4.2 Demonstration of On-Line Turbidity Data Usage to Confirm Water of Suitable Turbidity for Drinking Water Filtration Plant Applications FIG. 11
18	X4.3 Demonstration of Turbidity Data Usage to Monitoring or Drinking Water Filtration Plant Post Filtration Applications TABLE X4.1 TABLE X4.2 FIG. 12
19	X4.4 Continuous Monitoring of Turbidity in Southwestern Ohio Rivers Using a Modified On-Line Method FIG. 13
20	FIG. 14 FIG. 15 FIG. 16
21	FIG. 17 FIG. 18
22	X4.5 Demonstration of Turbidity Data Usage with a Backscatter Technology FIG. 19 FIG. 20
23	FIG. 21 FIG. 22
24	REFERENCES

Additional information

Formazin Attenuation Unit (FAU)	Compliance Reporting for ISO 7027 for samples that exceed 40 units
Forward Scatter Ratio Unit (FSRU)	The technology encompasses a single, light source and two detectors. Light sources can vary from single wavelength to polychromatic sources. The detection angle for the forward scatter detector is between 0 and 90- degrees relative to the centerline of the incident light beam.
Attenuation Unit (AU)	Not applicable for regulatory purposes. Best applied for samples with high level turbidity.
Nephelometric non- ratio (NTU)	White light turbidimeters Comply with EPA 180.1 for low level turbidity monitoring.
Ratio White Light tur bidimeters (NTRU)	Complies with ISWTR regulations and Standard Method 2130B. Can be used for both low and high level measurement.
Formazin Nephelometric, near- IR turbidimeters, non- ratiometric (FNU)	Complies with ISO 7027. The wavelengthis less susceptible to color interferences. Applicable for samples with color and good for low level monitoring.
Formazin Nephelometric near-IR turbidimeters, ratio metric(FNRU)	Complies with ISO 7027. Applicable for samples with high levels of color and for monitoring to high turbidity levels.
Formazin Back Scatter (FBU)	Not applicable for regulatory purposes. Best applied to high turbidity samples. Backscatter is common probe technology and is best applied in higher turbidity samples.
Surface Scatter Turbi dimeters (SSU)	Turbidity is determined through light scatter from a defined volume beneath the surface of a sample. Applicable for reporting for USEPA compliance monitoring.
Formazin Nephelometric Turbidity Multibeam Unit (FNMU)	Is applicable to EPA regulatory method GLI Method 2. Applicable to drinking water and wastewater monitoring applications.
ICS Codes	13.060.60 - Examination of physical properties of water