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Drinking Water Standards And Testing Methods
Apr 22, 2017

Many things can affect the quality of drinking water, so government regulations set the level of turbidity that is permissible. In the United States, public drinking water systems that use flocculation or direct filtration for turbidity control cannot exceed 1.0 nephelometric turbidity unit (NTU) leaving the treatment plant. In the samples collected for turbidity measurement the turbidity should remain less than or equal to 0.3 NTU for at least 95 percent of those collected in any month. If a public drinking water system uses any filtration other than flocculation or direct filtration then they are subject to their individual state limit, but even these must not exceed a turbidity level of 5 NTU. Usually utilities will try to maintain a turbidity level of about 0.1 NTU.


Analytical methods

The published analytical test methods for turbidity include:

  • US EPA Method No. 180.1, "Turbidity"

  • ISO 7027 "Water Quality: Determination of Turbidity"

  • "Standard Methods," No. 2130B.

  • Numerous ASTM methods