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National Pollutant Discharge Elimination System (NPDES)

Pretreatment Standards and Requirements-General and Specific Prohibitions

Pretreatment standards are pollutant discharge limits which apply to industrial users (IUHelpIUA source of indirect discharge. [40 CFR 403.3(j)]s). Pretreatment requirements are substantive or procedural requirements applied to IUs.

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General and specific prohibitions are national standards. These standards apply to all nondomestic dischargers that discharge wastewater to a publicly owned treatment works (POTW). They apply whether or not the POTW has an approved pretreatment program and also whether or not the nondomestic discharger has been issued a control mechanism or permit. EPA developed these standards with the intent to provide protection for POTWs, which include a treatment plant’s collection system.

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General Prohibitions

The general prohibitions at 40 CFR Part 403.5(a) (PDF)(2 pp, 204 K) forbid the discharge of any pollutant(s) to a POTW that can cause pass through or interference:

Pass through (40 CFR Part 403.3(p)) (PDF)(4 pp, 192 K) – “A discharge that exits the POTW into waters of the United States in quantities or concentrations that, alone or in conjunction with a discharge or discharges from other sources, is a cause of a violation of any requirement of the POTW's NPDES [National Pollutant Discharge Elimination System] permit (including an increase in the magnitude or duration of a violation).”

Interference (40 CFR Part 403.3(k)) (PDF)(4 pp, 192 K) – “A discharge that, alone or in conjunction with a discharge or discharges from other sources, both (1) inhibits or disrupts the POTW, its treatment processes or operations, or its sludge processes, use, or disposal; and (2) therefore is a cause of a violation of any requirement of the POTW's NPDES permit (including an increase in the magnitude or duration of a violation) or of the prevention of sewage sludge use or disposal in compliance with the following statutory provisions and regulations or permits issued thereunder (or more stringent state or local regulations): Section 405 of the Clean Water Act, the Solid Waste Disposal Act (SWDA) (including title II, more commonly referred to as the Resource Conservation and Recovery Act (RCRA), and including state regulations contained in any state sludge management plan prepared pursuant to subtitle D of the SWDA), the Clean Air Act, the Toxic Substances Control Act, and the Marine Protection, Research and Sanctuaries Act.”

Specific Prohibitions

The specific prohibitions at 40 CFR Part 403.5(b) (PDF)(2 pp, 204 K) are intended to “enhance control of hazardous wastes entering POTWs.” (55 FR 30082) These provisions forbid eight categories of pollutant discharges:

(1) Pollutants which create a fire or explosion hazard in the POTW, including, but not limited to, wastestreams with a closed cup flashpoint of less than 140 degrees Fahrenheit or 60 degrees Centigrade using the test methods specified in 40 CFR Part 261.21 (PDF)(2 pp, 204 K).

(2) Pollutants which will cause corrosive structural damage to the POTW, but in no case discharges with pH lower than 5.0, unless the works is specifically designed to accommodate such discharges.

(3) Solid or viscous pollutants in amounts which will cause obstruction to the flow in the POTW resulting in interference.

(4) Any pollutant, including oxygen demanding pollutants (biochemical oxygen demand, etc.) released in a discharge at a flow rate and/or pollutant concentration which will cause Interference with the POTW.

(5) Heat in amounts which will inhibit biological activity in the POTW resulting in Interference, but in no case heat in such quantities that the temperature at the POTW treatment plant exceeds 40 °C (104 °F) unless the approval authority, upon request of the POTW, approves alternate temperature limits.

(6) Petroleum oil, nonbiodegradable cutting oil, or products of mineral oil origin in amounts that will cause interference or pass through.

(7) Pollutants which result in the presence of toxic gases, vapors, or fumes within the POTW in a quantity that may cause acute worker health and safety problems.

(8) Any trucked or hauled pollutants, except at discharge points designated by the POTW.”

Additional Information

Documents providing additional information on specific prohibitions of hazardous exposure to wastewater:

  • Guidance Manual for Preventing Interference at POTWs
  • Guidance Manual for the Identification of Hazardous Wastes Delivered to Publicly Owned Treatment Works by Truck, Rail, or Dedicated Pipe
  • Guidance To Protect POTW Workers From Toxic And Reactive Gases And Vapors
  • Occupational Safety and Health Administration Permissible Exposure Limits
  • Resource Conservation and Recovery Act

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