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Frequent Questions About The Revision of Wastewater Treatment Exemptions for Hazardous Waste Mixtures (‘‘Headworks Exemptions’’)
1. What is the scope of this rule?
This final rule revises the wastewater treatment exemptions for hazardous waste mixtures found in 40 CFR 261.3(a)(2)(iv)(A-G), also known as the headworks rule exemptions. This action is promulgated under the authority of sections 2002(a), 3001, 3002, 3004, and 3006 of the Solid Waste Disposal Act of 1970, as amended by both the Resource Conservation and Recovery Act of 1976 (RCRA) and the Hazardous and Solid Waste Amendments (HSWA) of 1984.2. What are the headworks rule exemptions?
The headworks rule exemptions are a part of the Resource Conservation and Recovery Act (RCRA) rules that define when wastes are considered to be hazardous and, therefore, subject to the more stringent Subtitle C hazardous waste regulations. The exemptions determine when management of hazardous waste mixtures in a wastewater treatment system would result in sludges or effluent discharges that could be safely handled under regulations governing non-hazardous wastes.3. What are the revisions being made to the headworks rule?The headworks rule exemptions are divided into five categories:
- Paragraphs (A) and (B) are concerned with concentrations of spent solvents that may be contained in wastewaters when going to treatment,
- Paragraph (C) is concerned with certain petroleum wastes,
- Paragraph (D) with de minimis quantities of commercial chemical products that are lost to the wastewater treatment system during normal handling operations,
- Paragraph (E) with laboratory wastes and/or wastewaters discharged to wastewater treatment, and
- Paragraphs (F) and (G) with certain carbamate pesticide wastes.
The reasoning behind each of these exemptions is that the wastewater treatment system receives many different kinds of wastes, and the solvents, commercial chemical products, lab wastes, and certain additional listed wastes are a minuscule and treatable part of the mix of wastewaters. The relatively small volumes of these organic constituents should be easily and effectively handled by the wastewater treatment system, so the risk to the environment would be negligible.
The promulgation of this rule finalizes the addition of benzene and 2-ethoxyethanol to the list of solvents whose mixtures are exempted from the definition of hazardous waste under RCRA, provided that certain conditions are met (benzene at or below 1 ppm with conditional management requirements and 2-ethoxyethanol at 25 ppm). In addition, scrubber waters derived from the incineration of the exempted solvents are included in the exemption. Facilities also now have the option to directly measure solvent chemical levels at the headworks of the wastewater treatment system to demonstrate compliance with the exemption in addition to the current requirement of performing mass balance calculations. Finally, this rule is broadening the scope of the de minimis exemption to include listed hazardous wastes (beyond discarded commercial chemical products) as well as eligible non-manufacturing facilities.
4. What are the results of the risk assessment performed for this rule?
The environmentally conservative risk assessment demonstrated that the 1 part per million (ppm) standard for benzene is protective for the indirect exposure of sludge to groundwater and for direct exposure of groundwater to wastewaters and sludge from aerated treatment trains (after secondary clarification). Scenarios from non-aerated systems and primary clarifier sludge from the aerated treatment scenario did result in some risks of concern. As a result, EPA is requiring that wastewaters containing benzene must be managed in aerated biological treatment units and that surface impoundments used prior to secondary clarification must be lined.5. What are the estimated monetized benefits associated with rule?In addition, the risk assessment performed on 2-ethoxyethanol demonstrated that this constituent at 25 ppm is not a risk of concern for direct air exposure or direct groundwater exposure.
EPA estimates that the annual cost savings for affected industrial entities range from $11.4 to $48.6 million.6. How many U.S. industrial entities will be affected?
EPA estimates that these revisions will affect 3,266 to 10,446 facilities.7. How many tons of hazardous waste will be affected?
EPA estimates that approximately 1.4 to 5.8 million tons/year of waste currently regulated as hazardous will be affected.8. Are states required to adopt these regulations?
No. This rulemaking is less stringent than the existing Resource Conservation and Recovery Act (RCRA) rules; therefore, states are not required to adopt the revisions.