National Pollutant Discharge Elimination System (NPDES) - Pretreatment Program


What is pretreatment?
Industrial wastewater is often contaminated by a variety of harmful substances (such as industrial process by-products, like copper, lead, nickel, and other heavy metals). Because sewage collection and treatment systems are not designed to remove these substances, industrial wastes can damage sewers and interfere with the operation of treatment plants; pass through the systems untreated, resulting in pollution of nearby waters; and increase the costs and environmental risks of sludge management. The practice of removing pollutants from industrial wastewaters before they are discharged into municipal sewage treatment systems is known as "pretreatment." In focusing on industrial sources, pretreatment differs from pollution prevention, which focuses on residential and commercial sources.

The General Pretreatment Regulations at 40 CFR 403.1 et seq. establish the responsibilities of government agencies, industries, and the public to implement pretreatment standards to control industrial pollutants that may pass through or interfere with publicly owned treatment works (POTWs) or contaminate sewage sludge.

What are pretreatment requirements?
In 1978, U.S. EPA promulgated extensive regulations requiring many POTWs to develop and implement local pretreatment programs. U.S. EPA delegated the responsibility to oversee these pretreatment programs to the State Water Board and Regional Water Boards in 1989. As a result, the State and Regional Water Boards are responsible for the review and approval of new and modified POTW pretreatment programs. The NPDES permits for these POTWs spell out the pretreatment program monitoring and reporting requirements.

POTWs are required to have pretreatment programs when their total design flows are greater than five million gallons per day (5 mgd) and they receive industrial pollutants that could pass through or interfere with POTW operations. POTWs with smaller flows (5 mgd or less) may also be required to implement a pretreatment program if they receive industrial waste and pretreatment is warranted.

What are the State Water Board responsibilities?
The State Water Board is responsible for supporting and providing general oversight of the Regional Water Boards’ management of the pretreatment programs in California. This responsibility includes the following:

  • Providing general oversight of the pretreatment program in California;
  • Providing technical and legal assistance to Regional Water Boards’ staff, POTWs, and industrial users;
  • Developing and maintaining a data management system;
  • Providing information to USEPA and other organizations as required and/or requested; and
  • Reviewing and ruling on petitions for review of Regional Water Board decisions.

What are the Regional Water Boards’ responsibilities?
The Regional Water Board's pretreatment program includes pretreatment compliance audits and inspections, annual and semiannual report reviews, program modifications, and enforcement activities.

Pretreatment compliance inspections verify the compliance status of POTWs, focusing on the POTW's own compliance monitoring and enforcement activities. Pretreatment compliance audits involve a comprehensive review of all elements of a POTW's pretreatment program. Audits take place every five years. Inspections usually occur every year, except when an audit is scheduled.

How can I get more information?
For more information about pretreatment, see Contacts.

The Federal Dental Amalgam Rule (Code of Federal Regulations, title 40, part 441)

The United States Environmental Protection Agency adopted Dental Effluent Guidelines and a new federal Dental Amalgam Rule to reduce the disposal of mercury-containing dental amalgam into public sewer systems. The Dental Amalgam Rule requires dental offices that place and/or remove amalgam to:

  1. Install and maintain amalgam separators;
  2. Implement further necessary industrial practices to eliminate disposal of amalgam into the local sewer system; and
  3. Submit a one-time compliance report to their Control Authority by October 12, 2020.

To determine your Control Authority, the State Water Resources Control Board requests dental offices to:

  1. Contact the local sanitation agency on your sewer bill.
  2. Ask your local sanitation agency if that agency, or another affiliated local sanitation agency, implements a federal Pretreatment Program for industrial discharges into the public sewer system.
    • a.  If a local sanitation agency implements a federal Pretreatment Program for its sewer system, that sanitation agency is your Control Authority.
      • Send your one-time compliance report to the identified local sanitation agency per their instructions.
    • b.  If a local sanitation agency does not implement a federal Pretreatment Program, the State Water Resources Control Board assumes the role of the Control Authority.

For more information regarding the Dental Amalgam Rule, please visit the United States Environmental Protection Agency website:


Pretreatment Federal, State, and Regional Information

Statewide Pretreatment Coordinator Contact Information

Erica Kalve
(916) 341-5484

Regional Water Boards Map