What turbidity limit is required for treated drinking water samples?

• A. ≤ 0.8 NTU in 95% of samples, never above 2 NTU
• B. ≤ 0.5 NTU in 95% of samples, never above 1 NTU
• C. ≤ 0.3 NTU in 95% of samples, never above 1 NTU
• D. ≤ 1.0 NTU in 95% of samples, never above 3 NTU

Answer: (C)

Turbidity shows how clear the water is and acts as a signal of how well the treatment process is removing suspended solids. For treated drinking water, the standard is very strict to keep disinfection effective and reduce anything that could shield microorganisms. The required limit is that turbidity must be 0.3 NTU or lower in 95% of samples, and no single sample may exceed 1 NTU. This means almost all measurements should be very clear water, with only rare peaks not allowed to go above 1 NTU. If turbidity creeps up toward these limits, operators would check filtration performance and related treatment steps to maintain water safety.