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Frequently Asked Questions

The following is a list of Frequently Asked Questions for Pretreatment organized from general questions about the NPDES Program to more technical questions about Pretreatment. Click here to search for other program-specific FAQs or to display a list of all NPDES FAQs. Please check back periodically for updates!

When were the federal regulations governing pretreatment program requirements first promulgated and where can I find them?

The General Pretreatment Regulations were originally published in 1978, and have been updated several times (the latest changes were made on October 14, 2005) and can be found in the Code of Federal Regulations in 40 CFR Part 403.

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What is the National Pretreatment Program?

The National Pretreatment Program is a cooperative effort of federal, state, and local regulatory environmental agencies established to protect water quality. The program is designed to reduce the level of pollutants discharged by industry and other non-domestic wastewater sources into municipal sewer systems, and thereby, reduce the amount of pollutants released into the environment through wastewater. The objectives of the program are to protect the Publicly Owned Treatment Works (POTW) from pollutants that may interfere with plant operation, to prevent pollutants that may pass through untreated from being introduced into the POTW, and to improve opportunities for the POTW to reuse wastewater and sludges that are generated.

The term ""pretreatment"" refers to the requirement that nondomestic sources discharging wastewater to POTWs control their discharges, and meet limits established by EPA, the state or local authority on the amount of pollutants allowed to be discharged. The control of the pollutants may necessitate treatment prior to discharge to the POTW (therefore the term ""pretreatment""). Limits may be met by the nondomestic source through pollution prevention techniques (product substitution recycle and reuse of materials) or treatment of the wastewater.

Program objectives are:

  • To prevent industrial facilities' pollutant discharges from passing through municipal wastewater treatment plants untreated;
  • To protect treatment plants from the threat posed by untreated industrial wastewater, including explosion, fire, and interference with the treatment process
  • To improve the quality of effluents and sludges so that they can be used for beneficial purposes.

There are more than 1500 publicly owned treatment works that are required to implement local Pretreatment programs. By reducing the level of pollutants discharged by industry into municipal sewage systems, the program ensures the protection of America's multi-billion dollar public investment in treatment infrastructure.

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Under what Statutory Authority is the Pretreatment Program Administered?

The National Pretreatment Program's authority comes from section 307 of the Federal Water Pollution Control Act (more commonly referred to as the Clean Water Act). The federal government's role in pretreatment began with the passage of the Clean Water Act in 1972. The Act called for EPA to develop national pretreatment standards to control industrial discharges into sewerage systems.

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Are there any prescribed National Standards for Pretreatment?

There are two sets of standards: "categorical Pretreatment Standards" and "Prohibited Discharge Standards." These are uniform national requirements which restrict the level of pollutants that may be discharged by nondomestic sources to sanitary sewer systems. All POTWs that are required to implement a Pretreatment Program must enforce the federal standards.

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What are Categorical Pretreatment Standards?

These are technology-based limitations on pollutant discharges to POTWs promulgated by EPA in accordance with Section 307 of the Clean Water Act that apply to specified process wastewaters of particular industrial categories [see 40 CFR 403.6 and 40 CFR Parts 405- 471]. Go to and NPDES Regulations for more information.

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What are Prohibited Discharge Standards?

The Prohibited Discharge Standards are found in the regulations at 40 CFR 403.5. These are standards that prohibit the discharge of wastes that pass through or interfere with POTW operations (including sludge management). These are the general prohibitions. There are also specific prohibitions that prohibit the discharge from all nondomestic sources certain types of wastes that 1) create a fire or explosion hazard in the collection system or treatment plant, 2) are corrosive , including any discharge with a pH less than 5.0, unless the POTW is specifically designed to handle such wastes, 3) are solid or viscous pollutants in amounts that will obstruct the flow in the collection system and treatment plant, resulting in interference with operations, 4) any pollutant discharged in quantities sufficient to interfere with POTW operations, and 5) discharges with temperatures above 104 F (40 C) when they reach the treatment plant, or hot enough to interfere with biological processes.

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Last updated on January 24, 2013 1:31 PM