Pretreatment is the reduction of the amount of pollutants, the elimination of pollutants, or the alteration of the nature of pollutant properties in wastewater before or in lieu of discharging such pollutants into a Publicly-Owned Treatment Works (POTW). Since the mid-1980s, Missouri requires cities to have a state-approved pretreatment program when certain industries connect to the POTW. This pretreatment program requires industries to meet numeric limits on pollutants and to employ best management practices to control pollutants that discharge into city sewers.
In 1972, Congress passed the Federal Water Pollution Control Act, also known as the Clean Water Act (CWA) to restore and maintain the integrity of the nation’s water. The goals of the CWA are to eliminate the introduction of pollutants into the nation’s waters and to achieve fishable and swimmable water quality levels. The CWA’s National Pollutant Discharge Elimination System (NPDES) Permit Program generally requires direct discharges to obtain a NPDES permit. The Congress again revised the CWA in 1977 creating Section 307 (b) which established a program, the National Pretreatment Program, to address indirect discharges for industries that discharge to a POTW. The National Pretreatment Program under 40 C.F.R. Part 403 requires Significant Industrial Users to obtain an industrial user permit to discharge wastewater to the POTW. The pretreatment component of the POTW’s or municipal NPDES permit is part of the National Pretreatment Program.
Pretreatment standards protect the POTW from interference with the operation of the facility, prevent violations of the NPDES permit, protect the receiving waters, and improve opportunities to recycle the sewage sludge. Industrial processes may produce wastewater with pollutants not treated by the biological treatment systems used for conventional pollutants at a POTW. Alternatively, an industry may discharge conventional pollutants that are treatable, but are more concentrated or are a large volume.
In June 2017, EPA finalized technology-based pretreatment standards under the Clean Water Act to reduce discharges of mercury and other metals from dental offices into POTWs. Visit the dental amalgam rule page to learn more.