Publicly owned treatment works (POTWs)

Scope

POTWs are owned by states or municipalities and regulated under the Clean Water Act (CWA). POTWs are subject to the National Pollutant Discharge Elimination System (NPDES) permitting system as well as National Emission Standards for Hazardous Air Pollutants (NESHAP) permitting in some cases. They are required to develop and implement pretreatment programs and subject to certain reporting requirements.

Regulatory citations

• 40 CFR 63 Subpart VVV — National Emission Standards for Hazardous Air Pollutants: Publicly Owned Treatment Works
• 40 CFR 122 — EPA Administered Permit Programs: The National Pollutant Discharge Elimination System
• 40 CFR 133 — Secondary Treatment Regulation
• 40 CFR 136 — Guidelines Establishing Test Procedures for the Analysis of Pollutants
• 40 CFR 403 — General Pretreatment Regulations for Existing and New Sources of Pollution

Key definitions

• Affected source: The group of all equipment that comprise the POTW treatment plant.
• Combined sewer system (CSS): A wastewater collection system owned by a State or municipality which conveys sanitary wastewaters (domestic, commercial and industrial wastewaters) and storm water through a single-pipe system to a Publicly Owned Treatment Works (POTW) Treatment Plant.
• Effluent limitation: Any restriction on quantities, discharge rates, and concentrations of “pollutants” which are “discharged” from “point sources” into “waters of the United States,” shorelines, or the ocean.
• Effluent limitations guidelines: Regulations published by EPA to adopt or revise effluent limitations.
• General permit: An NPDES permit issued under 122.28 authorizing a category of discharges under the CWA within a geographical area.
• Group 1 POTW: A POTW that accepts a waste stream regulated by another NESHAP and provides treatment and controls as an agent for the industrial user. The industrial user complies with its NESHAP by using the treatment and controls located at the POTW. For example, an industry discharges its benzene-containing waste stream to the POTW for treatment to comply with 40 CFR part 61, subpart FF – National Emission Standard for Benzene Waste Operations. This definition does not include POTW treating waste streams not specifically regulated under another NESHAP.
• Group 2 POTW: A POTW that does not meet the definition of a Group 1 POTW. A Group 2 POTW can treat a waste stream that is either:
  1. Not specifically regulated by another NESHAP, or
  2. From an industrial user that complies with the specific wastewater requirements in their applicable NESHAP prior to discharging the waste stream to the POTW.
• Indirect discharge or Discharge: The introduction of pollutants into a POTW from any non-domestic source regulated under section 307(b), (c) or (d) of the CWA.
• National Pollutant Discharge Elimination System (NPDES): The national program for issuing, modifying, revoking and reissuing, terminating, monitoring and enforcing permits, and imposing and enforcing pretreatment requirements, under the CWA.
• Pass through: A discharge which exits the POTW into waters of the United States in quantities or concentrations which, 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 permit (including an increase in the magnitude or duration of a violation).
• Permit: An authorization, license, or equivalent control document issued by EPA or an approved state to meet effluent guidelines. The term includes a NPDES general permit, but does not include any permit which has not yet been the subject of final agency action, such as a draft permit or a proposed permit.
• Point source: Any discernible, confined, and discrete conveyance, including but not limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, landfill leachate collection system, vessel or other floating craft from which pollutants are or may be discharged. This term does not include return flows from irrigated agriculture or agricultural storm water runoff.
• Pollutant: Dredged spoil, solid waste, incinerator residue, filter backwash, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials (except those regulated under the Atomic Energy Act of 1954, as amended), heat, wrecked or discarded equipment, rock, sand, cellar dirt and industrial, municipal, and agricultural waste discharged into water.
• Pretreatment: The reduction of the amount of pollutants, the elimination of pollutants, or the alteration of the nature of pollutant properties in wastewater prior to or in lieu of discharging or otherwise introducing such pollutants into a POTW. The reduction or alteration may be obtained by physical, chemical or biological processes, process changes or by other means, except as prohibited.
• Publicly owned treatment works (POTW): A treatment works as defined by section 212 of the CWA, which is owned by a state or municipality (as defined by section 502(4) of the CWA). This definition includes any devices and systems used in the storage, treatment, recycling and reclamation of municipal sewage or industrial wastes of a liquid nature. It also includes sewers, pipes, and other conveyances only if they convey wastewater to a POTW Treatment Plant. The term also means the municipality as defined in section 502(4) of the CWA, which has jurisdiction over the indirect discharges to and the discharges from such a treatment works.

Summary of requirements

POTWs play an important role in ensuring water quality and pretreatment standards must be followed to prevent pass throughs or interference with POTW operations. To ensure compliance with pretreatment requirements, POTWs must:

• 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.