MCLG's allow for a margin of safety. Turbidity in excess of 5 NTU is just noticeable to the average person. A treatment technique is a required process intended to reduce the level of a contaminant in drinking water. In order to ensure that tap water is safe to drink, EPA prescribes regulations that limit the amount of certain contaminants in drinking water provided by public water systems. As water travels over the surface of the land or through the ground, it dissolves naturally occurring minerals and, in some cases, radioactive material.
Water can pick up substances resulting from the presence of animals or from human activity.
Inorganic contaminants, such as salts and metals, can be naturally occurring or result from urban storm water runoff, industrial or domestic wastewater discharges, mining or farming. Pesticides and herbicides, may come from agriculture, urban storm water runoff and residential uses. Organic chemical contaminants, including synthetic and volatile organics, are byproducts of industrial processes and can also come from gas stations, urban storm water runoff and septic systems. Radioactive contaminants can be naturally occurring or be the result of human activities. High nitrate can cause blue baby syndrome.