What is the maximum allowable NTUs before and after chemical addition at a treatment goal?

The correct answer of 10 NTUs refers to the guideline that is commonly applied in treatment processes, particularly in relation to the turbidity levels of water before and after chemical addition. Maintaining turbidity at or below this level is crucial for ensuring effective water treatment, particularly when considering clarity and the removal of contaminants.

In surface water treatment, turbidity is often measured in Nephelometric Turbidity Units (NTUs), and a limit of 10 NTUs is generally established to ensure that the water meets quality standards for safe consumption. This threshold helps in assessing the effectiveness of coagulation and sedimentation processes, where higher turbidity levels can indicate incomplete treatment and potential failure to remove pathogens and particle-bound contaminants.

Setting this limit before and after chemical addition ensures that the water treatment protocols adequately protect public health and the environment, aligning with regulations that are aimed at ensuring clear and safe drinking water. The rationale for this specific limit is based on research showing that levels above 10 NTUs may begin to pose risks in terms of pathogen viability and the overall quality of the treated water. Hence, the value of 10 NTUs serves as a standard that treatment facilities strive to maintain through their operational practices.