ASTM D6698 - 14

    Standard Test Method for On-Line Measurement of Turbidity Below 5 NTU in Water

    Active Standard ASTM D6698 | Developed by Subcommittee: D19.03

    Book of Standards Volume: 11.01


      Format Pages Price  
    PDF 11 $48.00   ADD TO CART
    Hardcopy (shipping and handling) 11 $48.00   ADD TO CART
    Standard + Redline PDF Bundle 22 $57.60   ADD TO CART


    Significance and Use

    5.1 Turbidity is undesirable in drinking water, plant effluent waters, water for food and beverage processing, and for a large number of other water-dependent manufacturing processes. Removal of suspended matter is accomplished by coagulation, settling, and filtration. Measurement of turbidity provides a rapid means of process control to determine when, how, and to what extent the water 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, and high purity industrial waters.

    5.3 The instrumentation 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 technology used to generate the result, 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 of measurement prescribed in this test method are mentioned, though others may come available.

    5.4.2 For 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.

    1. Scope

    1.1 This test method is applicable to the on-line measurement of turbidity under 5 nephelometric turbidity units (NTU) in water.

    1.2 It is the user's 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 be equivalent.

    1.4 This test method assigns traceable reporting units to the type of respective technology that was used to perform the measurement. Units are numerically equivalent with respect to the calibration standard. For example, a 1 NTU formazin standard is also equal to a 1 FNU (formazin nephelometric units) standard, a 1 FNRU (formazin nephelometric ratio units) standard, and so 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 responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D1129 Terminology Relating to Water

    D1193 Specification for Reagent Water

    D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water

    D3370 Practices for Sampling Water from Closed Conduits

    D3864 Guide for On-Line Monitoring Systems for Water Analysis

    D7315 Test Method for Determination of Turbidity Above 1 Turbidity Unit (TU) in Static Mode


    ICS Code

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

    UNSPSC Code

    UNSPSC Code 41113026(Nephelometers)


    DOI: 10.1520/D6698

    ASTM International is a member of CrossRef.

    ASTM D6698

    Citing ASTM Standards
    Back to Top