National Pollutant Discharge Elimination System (NPDES)

National Pretreatment Program

The national pretreatment program is a component of the NPDES program. It is a cooperative effort of federal, state, and local environmental regulatory agencies established to protect water quality. Similar to how EPA authorizes the NPDES permit program to state, tribal, and territorial governments to perform permitting, administrative, and enforcement tasks for discharges to surface waters (NPDES program), EPA and authorized NPDES state pretreatment programs approve local municipalities to perform permitting, administrative, and enforcement tasks for discharges into the municipalities’ publicly owned treatment worksHelppublicly owned treatment worksA treatment works (as defined by CWA section 212) that is owned by a state or municipality [as defined by CWA section 502(4)]. This definition includes any devices or systems used in the storage, treatment, recycling, and reclamation of municipal sewage or industrial wastes of a liquid nature. It also includes sewers, pipes, or other conveyances only if they convey wastewater to a POTW treatment plant. The term also means the municipality [as defined in CWA section 502(4)] that has jurisdiction over the indirect discharges to and the discharges from such a treatment works. [40 CFR 403.3(q)] (POTWs). The program is designed to:


The national pretreatment program requires nondomestic dischargers to comply with pretreatment standards to ensure the goals of the Clean Water Act (CWA) are attained.

The objectives of the program are to:

The national pretreatment program identifies specific discharge standards and requirements that apply to sources of nondomestic wastewater discharged to a POTW. By reducing or eliminating waste at the industries (“source reduction”), fewer toxic pollutants are discharged to and treated by the POTWs, providing benefits to both the POTWs and the industrial users.

  • general and specific prohibitions,
  • categorical pretreatment standards, and
  • local limits.


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Local municipalities are mostly responsible for implementing and enforcing the national pretreatment program requirements. The general pretreatment regulations at 40 CFR Part 403.8(a) require certain POTWs to establish a local pretreatment program to control discharges from nondomestic sources and to prevent pass through and interference at the treatment plant. There are approximately 1,600 POTWs that have local programs.
In a traditional pretreatment program, EPA approves a state’s NPDES authority to regulate the pretreatment program. Requirements for states to obtain NPDES state pretreatment authority are outlined in 40 CFR 403.10(3 pp, 188 K) — 36 states are authorized to act as the approval authorityHelpapproval authorityThe director in an NPDES Authorized State with an approved state pretreatment program, or the appropriate EPA regional administrator in a non-NPDES Authorized State or NPDES state without an approved state pretreatment program. [40 CFR 403.3(c)] for POTWs in their states.

The state includes conditions outlining pretreatment implementation requirements in NPDES permits issued to POTWs. For states not authorized to implement the pretreatment program, EPA serves as the approval authority. 

A POTW with an approved local pretreatment program is called the control authorityHelpcontrol authorityThe POTW, in the case of a POTW with an approved pretreatment program, or the Approval Authority, in the case of a POTW without an approved pretreatment program. [paraphrased from 40 CFR 403.3(f)] which regulates nondomestic facilities discharging to its system.

For the 40 CFR 403.10(e) (PDF) (3 pp, 188 K) states (Alabama, Connecticut, Mississippi, Nebraska, and Vermont), the state serves as the control authority.
An industrial user (IU)Helpindustrial userA source of indirect discharge. [40 CFR 403.3(j)] is a nondomestic source of indirect discharge into a POTW. An IU must comply with all applicable federal, state, and local pretreatment standards and requirements. Some federal requirements apply to all IUs and other requirements apply only to specific types of IUs. These federal requirements apply regardless of whether the IU has a control mechanism (e.g., permit or discharge authorization) from its control authority.

Regulatory History

EPA originally published the general pretreatment regulations in 1978. These regulations have been updated many times since then, but most recently in 2005 as the “Streamlining Rule.” The timeline below highlights key pretreatment regulatory changes and the significant events or publications that brought about those changes. Related documents and materials are also provided.

Current Regulatory Activities

EPA develops and publishes new regulations and periodically updates existing regulations. There are current rulemaking activities expected to result in changes to the general pretreatment regulations at 40 CFR Part 403 (PDF)(43 pp, 372 K). The following will affect the implementation of the national pretreatment program:

Regulatory Timeline

Regulatory Activity

Related Materials




Availability of and Procedures for

Removal Credits

70 FR 60199 – 60202(4 pp, 173 K, About PDF)


EPA sought comment on two issues concerning the removal credits provisions in the General Pretreatment Regulations

  • Requested comments on whether to amend the list of pollutants for which removal credits are available to add certain pollutants
  • Comments were closed on December 13, 2005 and no rulemaking activities were initiated for these issues

Streamlining the General Pretreatment

Regulations for Existing and New Sources of Pollution (Streamlining Rule)

Streamlining Rule Fact Sheets

2006 - 2009

Fact sheet series outlining the changes made to the pretreatment program at 40 CFR Part 403 under the Pretreatment Streamlining Rule

  • 1: Summary of Changes Made Under the Streamlining Rule
  • 2: Required Changes
  • 3: Equivalent Mass Limits for Concentration Limits
  • 4: Equivalent Concentration-Based Limits for Flow-Based Standards
  • 5: New Classifications for Categorical Industrial Users
  • 6: Optional Sampling Waiver for Pollutants Not Present
  • 7: Best Management Practices
  • 8: Slug Control Plans
  • 9: General Control Mechanisms Option

70 FR 60134-60198(65 pp, 463 K, About PDF)


Changes to the General Pretreatment Regulations that address restrictions on and oversight of industrial users who introduce pollutants into publicly owned treatment works (POTWs) and modified certain program requirements to be consistent with National Pollutant Discharge Elimination System (NPDES) requirements

  • Authorized representative/duly-authorized employee
  • Best management practices
  • Concentration-based categorical pretreatment standards expressed as equivalent mass limits
  • Equivalent concentration limits in lieu of mass limits for certain categories of categorical industrial users (CIUs)
  • Flexibility in the use of certain sampling techniques
  • General control mechanisms
  • Middle-tier CIUs
  • Non-significant CIUs
  • Notification requirements
  • Reduced sampling for categorically regulated pollutants neither present nor expected to be present
  • Removal credits reference update
  • Representative samples
  • Significant noncompliance (SNC) criteria
  • Slug control requirements

64 FR 39564 - 39605(42 pp, 457 K, About PDF)


Project eXcellence and Leadership for Communities (Project XL)

63 FR 34170 - 34176(7 pp, 177 K, About PDF)


Solicitation of local pilot pretreatment program proposals under Project XL

  • Invited POTWs to propose alternative environmental performance-based pretreatment programs
  • Four POTWs conducted five experimental water regulatory projects
  • None of the pilot projects demonstrated pretreatment program alternatives that could be implemented at the national level

Streamlined Procedures for Modifying

Approved Publicly Owned Treatment

Works Pretreatment Programs

62 FR 38406-38415(10 pp, 155 K, About PDF)


  • Revised the procedures for modifying approved POTW Pretreatment Programs incorporated into NPDES permits issued to POTWs
  • Revisions designed to reduce the administrative burden and cost associated with maintaining approved pretreatment programs without affecting environmental protection

61 FR 39804-39810(7 pp, 137 K, About PDF)



Standards for the Disposal of Sewage Sludge

60 FR 54764-54770(7 pp, 215 K, About PDF)


EPA reconsidered issues remanded by the U.S. Court of Appeals for additional justification or modification

  • EPA amended 40 CFR Part 503 to delete the land application pollutant limits for chromium and to change the land application pollutant concentration limit for selenium
  • EPA also amended the list of pollutants (in Appendix G of 40 CFR Part 403) for which a removal credit may be available

58 FR 9248 – 9404


  • Leather Industries of America, Inc., (3/5/1993) and City of Pueblo, CO (6/17/1993) file petitions challenging the proposed rule, which are consolidated as the court case Leather Industries of America, Inc. v. Environmental Protection Agency, 40 F.3d 392, D.C. Cir., 1994 (11/15/1994)
  • Adds Appendix G to the Part 403 general pretreatment regulations
  • Appendix G—Section I lists the pollutants regulated in Part 503 and eligible for removal credit authorization
  • Appendix G–Section II lists additional pollutants that are eligible for a removal credit if the concentration of the pollutant in sewage sludge does not exceed a prescribed concentration
  • Appendix G—Section II lists the pollutants that EPA evaluated and opted not to regulate during development of the Part 503 regulation
  • Establishes 40 CFR Part 503
  • EPA promulgated regulation to protect public health and the environment from the reasonably anticipated adverse effects of certain pollutants in sewage sludge
  • Established requirements for the following final uses or disposal of sewage sludge: 1) land application either to condition the soil or to fertilize crops grown in the soil; 2) final disposal on the land; and 3) incineration

54 FR 5746 – 5902



Pretreatment Program and Domestic Sewage Exclusion Rulemaking (“Hazardous Solid Waste Amendments” [HSWA])

55 FR 30082 – 31033 Final Rule


Regulations to enhance control of toxic pollutants and hazardous waste discharges to POTWs

  • Expanded specific prohibitions on discharges into POTWs; established requirements regarding significant industrial user slug discharge control plans and POTW enforcement response plans; and strengthened and revised program implementation definitions and procedures

53 FR 47632 – 45656


Proposal to Implement the Recommendations of the Domestic Sewage Study (DSS)

52 FR 23477 – 23485


Response to comments on the Advanced Notice of Proposed Rulemaking

  • Agency summarized the comments received during three public meetings on DSS recommendations ANPR
  • Response to comments

51 FR 30166 – 30175


Preliminary Approaches to Implementing the Recommendations of the DSS

  • Based on DSS findings
  • Proposal to improve methods for controlling hazardous waste discharges to POTWs under the NPDES and general pretreatment programs.

Report to Congress on the Discharge of Hazardous Wastes to Publicly Owned Treatment Works (Domestic Sewage Study)


Response to the HSWA requirements to prepare a report to Congress

  • Contained information on 160,000 waste dischargers from 47 industrial categories and the residential sector
  • Provided information on the effectiveness of existing government controls for wastewater discharges, especially federal and local pretreatment programs and categorical pretreatment standards

Solid Waste Disposal Act(163 pp, 420 K, About PDF)


Congress enacts the Solid Waste Disposal Act

  • Section 3018(a)
  • Excluded coverage of solid and dissolved wastes in domestic sewage, meaning such wastes did not have to meet RCRA standards for hazardous waste treatment, storage, or disposal
  • Required EPA to prepare a report to Congress on the extent to which excluded wastes pass through POTWs

Pretreatment Implementation Review Task Force (PIRT)

53 FR 40561 – 40616


General Pretreatment Regulations for Existing and New Sources (PIRT Proposed and Final Rules)

  • Changes to 40 CFR Parts 122 and 403
  • Response to PIRT recommendations
  • Revisions included changes to local limits requirements, enforcement remedies, control authority and state program approvals, as well as industrial user and control authority monitoring and reporting requirements

51 FR 21454 – 21482


Pretreatment Review Task Force: Final Report to the Administrator


Task Force studied programs and recommended program improvements

  • Recommended ways to address day-to-day problems faced by POTWs, states, and industries in implementing the National Pretreatment Program
  • Included suggestions for simplifying and clarifying aspects of the program, on enforcement procedures, on the need for program resources, on the roles and relationships between program oversight authorities, and for regulatory updates

Amendments to the General Pretreatment Regulations

47 FR 42688 – 42689


EPA reinstated the January 1981 amendments

  • After Natural Resources Defense Council (NRDC) v. EPA (No. 81-2068) (7/8/1982) in which NRDC challenged EPA over the Agency’s deferral of the amendments to the General Pretreatment Regulations without having first given public notice
  • Court held that EPA’s suspension violated the Administrative Procedure Act
  • Court ordered EPA to reinstate all pretreatment amendments retroactive to March 30, 1981

46 FR 19936


EPA indefinitely postponed the 1981 Amendments' effective date

46 FR 11972


Deferral of Amendments to the General Pretreatment Regulations

  • Presidential memorandum temporarily deferring amendment to March 30, 1981

46 FR 9404 – 9460


  • Proposed changes to definitions, general prohibitions, determination of industrial subcategories, removal allowances, and implementation issues for local pretreatment programs
  • Scheduled to take effect on March 13, 1981

44 FR 62260 – 62275



Part 403 General Pretreatment Regulations for Existing and New Sources of Pollution

43 FR 27736 - 27773


EPA response to environmental groups (NRDC, Environmental Defense Fund (EDF), and Citizens For A Better Environment) bringing suit against EPA and the resulting consent decree

  • In the 1976, NRDC vs. Train Consent Decree (8ERC 2120, D.D.C. 1976), 21 industries are under consideration by EPA for national pretreatment standards pursuant to a settlement agreement between EPA and environmental groups filed in the U.S. District Court for the District of Columbia
  • Promulgation of General Pretreatment Regulations at 40 CFR Part 403, replacing the 40 CFR Part 128 requirements
  • EPA agreed to regulate the discharge of 65 categories of pollutants comprising the 126 priority pollutants from 21 industrial categories

42 FR 6476 – 6502


Pollutants in Publicly Owned Treatment Works Pretreatment Standards; 40 CFR Part 128 Pretreatment Standards

38 FR 30982 Final Rule


Original pretreatment regulations

  • Established 40 CFR Part 128
  • Defined: joint treatment works, major contributing industry; pretreatment
  • First proposal of pretreatment standards, prohibited discharges, pretreatment of compatible and incompatible pollutants, and timeline for compliance with pretreatment standards
38 FR 19236 -19237 Proposed Rule 7/19/1973

Laws and Regulations Related to Pretreatment

EPA and other federal agencies have laws and regulations that affect the implementation of the pretreatment program.

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To access the Code of Federal Regulations (CFR) since 1994, visit the Government Printing Office site.

Analytical Methods

Industries and municipalities must use approved analytical methods to analyze the chemical and biological components of wastewater, drinking water, sediment, and other environmental samples required by the Clean Water Act (CWA) and Safe Drinking Water Act. The regulations at 40 CFR Part 403.12 (PDF)(10 pp, 216 K) and 40 CFR Part 136 (PDF)(374 pp, 4 MB) state the sampling and analysis requirements. EPA promulgates changes to the list of approved at 40 CFR Part 136 via the Methods Update Rule.

Learn more about the CWA Analytical Methods.

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Biosolids - Sewage Sludge

Biosolids are treated sewage sludge and regulated by 40 CFR Part 503 (PDF)(33 pp, 332 K). The general pretreatment regulations, 40 CFR Part 403 (PDF)(49 pp, 372 K) establish standards and mechanisms for responsible entities to control pollutants that might pass through or interfere with publicly owned treatment works (POTW) treatment processes or contaminate sewage sludge. Land-applied biosolids must meet strict regulations and quality standards.

The regulations for the use and disposal of biosolids (40 CFR Part 503) specify:

  • numerical limits for metals,
  • pathogen reduction standards,
  • site restriction,
  • crop harvesting restrictions and monitoring requirements,
  • record keeping and reporting requirements for land-applied biosolids, and
  • similar requirements for surface-disposed or incinerated biosolids

Learn more about the use and disposal of biosolids.

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Cross Media Electronic Reporting Regulation

EPA's Cross Media Electronic Reporting Regulation (CROMERR) sets standards for systems that oversight authorities (e.g., EPA, states, tribes, and local governments) use to receive electronic reports from facilities they regulate under EPA-authorized programs (e.g., the National Pretreatment Program). CROMERR also requires program modifications to incorporate electronic reporting (e.g., legal authorities, standard operating procedures). In pretreatment, CROMERR governs electronic submission of required reports from:

  • regulated industrial users to control authorities and
  • control authorities to approval authorities.

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Laws Affecting the NPDES Program

The regulations at 40 CFR Part 122.49 (PDF)(2 pp, 160 K) briefly discuss how certain laws relate to the NPDES program. These laws can apply to the NPDES permit program and therefore affect the national pretreatment program.

Learn more about how certain laws might affect NPDES implementation.

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Occupational Safety and Health Administration Permissible Exposure Limits

The Occupational Safety and Health Administration (OSHA) establishes permissible exposure limits to certain substances to ensure protection of worker health. These federal regulations at 29 CFR Part 1910.1000 (PDF)(13 pp, 268 K) address permissible exposures to toxic and hazardous air contaminants. For example, volatile organic compound (VOC) vapors can be toxic and carcinogenic, and might produce acute and chronic health effects after various periods of exposure.

Hazardous toxic gases can be produced when certain inorganic pollutants in wastewater discharges mix in the collection system. For example, acidic discharges can combine with nonvolatile substances such as sulfide and cyanide to produce toxic gases and vapors (hydrogen sulfide and hydrogen cyanide, respectively). POTWs can control this threat by establishing pretreatment standards (i.e., local limits) based on the maximum recommended levels of these VOC pollutants in air.

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Resource Conservation and Recovery Act

The Resource Conservation and Recovery Act (RCRA) authorizes EPA to control hazardous wastes, including the generation, transportation, treatment, storage, and disposal of hazardous waste. RCRA also provides EPA a framework for managing of non-hazardous wastes. POTWs and industrial users that generate hazardous waste and POTWs accepting hazardous waste must comply with both CWA and RCRA requirements.

The regulations at 40 CFR Part 270.60 (PDF)(2 pp, 184 KB) establish RCRA permit-by-rule requirements for facilities that treat, store, and dispose of hazardous waste. The Domestic Sewage Exclusion provision at 40 CFR Part 261.4(a)(1) (PDF)(25 pp, 268 K) identifies certain wastes under certain conditions, such as when the wastes mix with domestic sewage in a POTW’s collection system before reaching the boundary of the treatment works’ property, that may be excluded from RCRA regulations. The discharger of the waste is, however, required by 40 CFR Part 403 (PDF)(49 pp, 379 K) to notify the POTW of the discharge.

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Additional information