40 CFR 403: EPA General Pretreatment Regulations

Regulatory citation: 40 CFR Part 403, General Pretreatment Regulations for Existing and New Sources of Pollution

What Are the General Pretreatment Regulations?

40 CFR Part 403 controls what businesses send down the sewer to a publicly owned treatment works (POTW). Part 403 calls these businesses Industrial Users, meaning any source of indirect discharge. The rules apply to manufacturers, metal finishers, food processors and other facilities that discharge process wastewater to a municipal system rather than directly to a river or lake.

Most day-to-day oversight comes from the Control Authority. This is usually the POTW with an approved pretreatment program, or the state or EPA where no local program exists. The Control Authority issues permits or other control mechanisms and receives your reports.

Why Pretreatment Matters

POTWs are designed to treat domestic sewage. Industrial pollutants can upset treatment processes, contaminate sludge, pass untreated into rivers or create fire and fume hazards in sewers. Pretreatment keeps those pollutants out at the source.

Core Obligations

1. Do Not Cause Pass Through or Interference (403.5(a))

A user may not introduce any pollutant that causes Pass Through or Interference. Pass Through is a discharge that exits the POTW into waters of the United States and causes a violation of the POTW's NPDES permit. Interference is a discharge that inhibits or disrupts the POTW or its sludge processes and causes a permit violation or prevents lawful sludge use or disposal.

2. Follow the Specific Prohibitions (403.5(b))

Certain discharges are banned outright for every user. These include wastestreams with a closed cup flashpoint below 140 degrees Fahrenheit (60 degrees Celsius), discharges with a pH lower than 5.0 unless the works is specifically designed for them, and heat in amounts that raise the temperature at the treatment plant above 40 degrees Celsius (104 degrees Fahrenheit) unless alternate limits are approved.

3. Meet Categorical Standards and Permit Limits (403.6)

Categorical Pretreatment Standards are national limits for specific industries, set in the effluent guidelines in 40 CFR Chapter I, Subchapter N. Your permit or control mechanism may also contain local limits set by the POTW. You must meet whichever limits apply to your discharge.

4. Know If You Are a Significant Industrial User (403.3)

A Significant Industrial User includes any user subject to categorical standards. It also includes a user that discharges an average of 25,000 gallons per day or more of process wastewater, or contributes a process wastestream making up 5 percent or more of the POTW's average dry weather hydraulic or organic capacity. Significant users face closer oversight and regular reporting.

5. Submit Baseline and Compliance Reports (403.12(b) and (d))

Existing categorical users must submit a baseline monitoring report within 180 days after the effective date of a categorical standard, or of a final category determination, whichever is later. Within 90 days after the final compliance date, the user must report whether it is meeting the standard. These reports need the certification statement and signature of a responsible official under 403.12(l).

6. File Periodic Reports (403.12(e) and (h))

Categorical users report on continued compliance during June and December, unless the standard or Control Authority requires more often. Significant non-categorical users must report at least once every six months on the nature, concentration and flow of their pollutants.

7. Give Prompt Notices (403.12(f), (g), (j) and (p))

Notify the POTW immediately of discharges that could cause problems, including slug loadings. If sampling shows a violation, notify the Control Authority within 24 hours of becoming aware of it, repeat the sampling and submit the results within 30 days. Notify the Control Authority in advance of any substantial change in the volume or character of pollutants. A user that discharges a substance that would be a hazardous waste if otherwise disposed of must send a one-time written notice to the POTW, the EPA Regional Waste Management Division Director and state hazardous waste authorities within 180 days after the discharge starts. Users discharging 15 kilograms or less of non-acute hazardous waste in a calendar month are exempt, but any amount of acute hazardous waste needs a notice.

8. Control Bypasses and Keep Records (403.17 and 403.12(o))

Bypass, the intentional diversion of wastestreams from any part of your treatment system, is prohibited unless it was unavoidable to prevent loss of life, injury or severe property damage and there was no feasible alternative. Give notice at least 10 days ahead for an anticipated bypass where possible. For an unanticipated bypass that exceeds standards, give oral notice within 24 hours and a written submission within 5 days. Keep monitoring records for at least 3 years.

Common Compliance Approaches

Build a Reporting Calendar

List every report and sampling date from your permit, including the June and December reports, and assign an owner for each.

Write a Violation Response Procedure

Set out who calls the Control Authority within 24 hours, who arranges resampling and who tracks the 30-day deadline.

Example: Pretreatment Compliance in Practice

A metal finishing plant discharges about 40,000 gallons per day to the city sewer and holds a permit from the local POTW. Its pH neutralization system fails one night and a composite sample later shows a zinc result above the permit limit. The environmental manager phones the POTW the same morning, resamples that week and submits the new results within 30 days. The plant also schedules a bypass for a planned tank repair and sends notice two weeks ahead.

Related regulations: EPA Industrial Stormwater, EPA Hazardous Waste Generators, EPA Sewage Sludge Standards.

Note: This summary reflects federal EPA requirements. Many states run these programs under EPA authorization and may have additional or more stringent requirements. Always check the current regulation text and any state rules that apply to you.

Frequently Asked Questions

Who enforces my pretreatment permit?

Usually the local POTW acting as the Control Authority. Where there is no approved local program, the state or EPA takes that role.

How quickly must I report a permit exceedance?

Within 24 hours of becoming aware of the violation. You must then repeat the sampling and submit the results within 30 days.

Does Part 403 apply to direct discharges to a river?

No. Part 403 covers indirect discharges to a POTW. Direct discharges to waters of the United States need their own NPDES permit.