Explain the National Primary Drinking Water Standards

Safe Drinking Water Act (SDWA, 1974) required EPA to establish maximum contaminant levels (MCLs) for public water systems (any water supply facility (public or private) that provides water for human consumption and has at least 15 service connections or regularly serves at least 25 people daily at least 60 days in a year.

SDWA (amended in 1986) required EPA to set maximum contaminant level goals (MCLGs) and MCLs for 83 specific substances. MCL is the enforceable level that water supplier must not exceed and MCLGs is a goal that equal to the maximum contaminant level that is not expected to cause any adverse health effects over a lifetime of exposure. The typical contaminants found in water and the treatment methods used are listed in the table below. A typical treatment flow chart for surface water is shown also.