• Facilities that discharge to a POTW are known as indirect dischargers.
• The pretreatment program places much of the responsibility on local municipalities.

Another type of discharge that is regulated by the Clean Water Act (CWA) is one that goes to publicly owned treatment works (POTWs). The national pretreatment program (CWA 307(b)) controls the indirect discharge of pollutants to POTWs by “industrial users.” Facilities that discharge to a POTW are known as indirect dischargers.

The regulations establish responsibilities of government, industry, and the public to implement pretreatment standards to control pollutants from the industrial users which may pass through or interfere with POTW treatment processes or contaminate sewage sludge.

The Environmental Protection Agency (EPA) has developed technology-based standards for industrial users of POTWs. Different standards apply to existing and new sources within each category. EPA has also developed categorical pretreatment standards applicable to an industry on a nationwide basis. In addition, POTWs develop their own local limits, to assist in achieving the effluent limitations in their permits.

Regardless of whether a state is authorized to implement either the National Pollutant Discharge Elimination System (NPDES) or the pretreatment program, if it develops its own program, it may enforce requirements more stringent than federal standards.

Who’s the authority?

The pretreatment program places the majority of the responsibility on local municipalities. All large POTWs (i.e., those designed to treat flows of more than five million gallons per day) and smaller POTWs with significant industrial discharges establish local pretreatment programs.

These local programs enforce all national pretreatment standards and requirements in addition to any more stringent local requirements necessary to protect site-specific conditions at the POTW.

To ensure compliance with pretreatment requirements, POTWs:

• Identify and locate all industrial users (IUs) subject to the pretreatment program;
• Identify the character and volume of pollutants contributed by such users;
• Notify users of applicable pretreatment standards and requirements;
• Receive and analyze reports from IUs;
• Sample and analyze IU discharges and evaluate the need for IU slug control plans;
• Investigate instances of noncompliance; and
• Comply with public participation requirements.

Pretreatment defined

Pretreatment refers to the requirement that industrial sources discharging wastewater to POTWs control their discharges and meet limits 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:

• Pollution prevention techniques (product substitution recycle and reuse of materials); or
• Treatment of wastewater.