ADEQ Water Treatment Grade 4 Practice Test

Which statement correctly describes the turbidity standard?

Turbidity must be greater than 0.3 NTU Turbidity must be zero NTU Turbidity must be ≤ 0.3 NTU in 95% of samples and never above 1 NTU Turbidity is not regulated

Correct Answer:

Turbidity must be ≤ 0.3 NTU in 95% of samples and never above 1 NTU

Explanation:

Turbidity levels show how clear the water is and reflect how well the filtration system is removing particles that could shield microbes from disinfectants. The standard requires finished water turbidity to be 0.3 NTU or less in at least 95% of monthly samples, and never exceed 1 NTU in any single measurement. This combination keeps water sufficiently clear most of the time while preventing any single sample from being too turbid. NTU stands for Nephelometric Turbidity Units, a measure of light scattering by suspended particles. The other statements aren’t correct because turbidity is not required to be greater than 0.3, nor must it be zero, and turbidity is regulated for drinking water.

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