RCRA Wastewater Treatment Unit Exemption: A Hazardous Waste Inspector’s Perspective

RCRA Wastewater Treatment Unit Exemption: A Hazardous Waste Inspector’s Perspective

Your facility has gone through the proper channels to obtain a Clean Water Act (CWA) wastewater discharge permit.  Did you ever think that a Resource Conservation and Recovery Act (RCRA) hazardous waste inspection could challenge the status of your CWA permit? The answer is yes and we’ve seen this firsthand.

The U.S. Environmental Protection Agency (EPA) recognized that sometimes more than one environmental program applies to a single waste stream at a facility.  For example, a characteristically hazardous wastewater that would be subject to RCRA regulation from its point of generation onward can also be subject to the CWA when discharged.  Thus, on November 17, 1980 (45 Federal Register 76074), the EPA promulgated the wastewater treatment unit (WWTU) exemption from RCRA requirements under Title 40 Code of Federal Regulations (CFR), Part 260.10.  The exemption was designed specifically to avoid duplicative requirements under RCRA and the CWA for the management of certain hazardous wastes.  The exemption excludes qualifying equipment used to treat hazardous wastewater and wastewater treatment sludge from: (1) the RCRA permitting requirements of 40 CFR Part 270, (2) general facility standards in 40 CFR Parts 264 and 265, and (3) specific tank design and operating requirements in 40 CFR Parts 264 and 265, Subpart J.

Criteria for WWTU Exemption

For the WWTU exemption to apply to a piece of equipment, it must meet the following three criteria:

  1. The equipment is part of a wastewater treatment facility that is subject to regulation under either Section 402 (i.e., the National Pollutant Discharge Elimination System [NPDES]) permitting program or 307(b) of the CWA (the national pretreatment program for facilities that discharge to publicly-owned treatment works [POTWs]).
  2. The equipment receives and treats or stores an influent wastewater that is a hazardous waste as defined in 40 CFR 261.3; or generates and accumulates a wastewater treatment sludge that is a hazardous waste as defined in 40 CFR 261.3; or treats or stores a wastewater treatment sludge which is a hazardous waste as defined in 40 CFR 261.3 of this chapter.
  3. The equipment meets the definition of a tank or tank system in Section 260.10.

Wastewater Management Challenged During a Hazardous Waste Inspection

During a hazardous waste inspection by a regulatory agency, EHS Support observed the unanticipated consequence of managing hazardous wastewater in the context of the WWTU exemption.  While reviewing the waste determination documents for a hazardous waste generator (i.e., laboratory data, safety data sheets, etc.), required per 40 CFR 262.11, an inspector with the hazardous waste section of a state agency questioned how hazardous wastewater or wastewater treatment sludge was managed in an on-site WWTU.  Based on the analytical results, the inspector challenged the concentration of hazardous constituents in the waste stream and whether it met the definition of wastewater, even though it was acceptable to the receiving treatment works that issued the pretreatment permit. The question was:

“How does hazardous wastewater or wastewater treatment sludge meet the criteria of the WWTU exemption?”

What is “wastewater” under RCRA?

The EPA has not promulgated a definition of wastewater under RCRA; however, the EPA has noted that states have the option to define it.  However, EPA has provided guidance on what wastewater is.  Per guidance from 1981 and 2000, EPA states wastewater is waste that, “…is substantially water with contaminants amounting to a few percent at most.”  EPA has not issued any more guidance on their definition of wastewater since the 2000 memorandum.

Pointers for Managing Wastewater Under WWTU Exemption

Per the federal guidelines, it is critical for generators to be able to demonstrate compliance with all three criteria for the WWTU exemption of 40 CFR 260.10.  A generator should consider the following pointers to fully document its compliance with the criteria WWTU exemption:

  1. Maintain a copy of the current NPDES or other Clean Water Act Permit.
  2. Maintain documentation such as a flow diagram, engineering drawings, and a description of the wastewater treatment system including tanks, tank systems, and other containers.
  3. Maintain documentation of any local or state definitions of wastewater.
  4. Maintain documentation of the waste determination for the influent wastewater being treated in the on-site WWTU including laboratory analysis, safety data sheets, and any other information used to characterize the waste stream(s).
  5. Review these documents at least annually for any operational changes that may warrant revisions to any or all the documentation.

Note: It is recommended that facilities looking for coverage under the WWTU exemption of 40 CFR 260.10 consult with local and state guidance.


While your facility may be taking advantage of managing hazardous wastewater under the RCRA WWTU exemption, which was designed to avoid duplicative environmental program standards, the reality is that the line in the sand is not always clearly drawn between regulatory program standards. The best way to manage the risk associated with a regulatory inspection is to be prepared with documentation that can be shared with an inspector who has jurisdiction under any environmental program.
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