December 16, 2022

Wastewater Treatment Unit Exemption Applicability

In recent guidance, EPA addressed a question on the applicability of the wastewater treatment unit (WWTU) exemption to a tank storing hazardous wastewater prior to offsite trucking to a publicly owned treatment works (POTW). [RO 14950] If the storage tank is eligible for the WWTU exemption, it would be exempt from RCRA tank requirements.

To determine applicability, EPA refers to the regulatory definition of a WWTU in §260.10:

Is part of a wastewater treatment facility that is subject to regulation under either section 402 or 307(b) of the Clean Water Act (CWA); and
Receives and treats or stores influent wastewater that is a hazardous waste as defined in §261.3 of this chapter, or that generates and accumulates a wastewater treatment sludge that is a hazardous waste as defined in §261.3 of this chapter, or treats or stores a wastewater treatment sludge which is a hazardous waste as defined in §261.3 of this chapter; and
Meets the definition of a tank or tank system in §260.10 of this chapter.

EPA also refers to the preamble of a final rule that clarified the scope of the WWTU exemption:

“However, any tank system that is employed in managing wastewater at a facility prior to its off-site transfer to another location, whether or not the off-site location is an NPDES-permitted wastewater treatment facility (or one that discharges to a POTW), is not covered by this exemption. EPA intends that this exemption apply to any tank system that manages hazardous wastewater and is dedicated for use with an on-site wastewater treatment facility. However, if a tank system, in addition to being used in conjunction with an on-site wastewater treatment facility, is used on a routine or occasional basis to store or treat hazardous wastewater prior to shipment off-site for treatment, storage, or disposal, it is not covered by this exemption. Unless the tank system qualifies for another exemption, it would be subject to the revised hazardous waste tank systems standards.” [53 FR 34080]

Based on the definition of a WWTU in §260.10 and the explanation in 53 FR 34080, the storage tank in question is not eligible for the WWTU exemption because the stored hazardous wastewater is being trucked offsite to the POTW. In fact, even if this happens just occasionally, and the wastewater is usually treated and discharged to the sewer, the occasional offsite trucking voids the exemption.

Regarding the status of the tank, the facility is a large quantity generator (LQG) of hazardous waste, and the tank is holding hazardous wastewater. The tank is not exempt, so it must either be RCRA-permitted or a 90-day tank, both subject to the RCRA tank standards in Part 265, Subpart J. As an LQG, the facility may manage the tank as a 90-day tank in compliance with §262.17 without the need for a RCRA permit

EPA also clarified and expanded on other guidance brought to its attention by the facility regarding the WWTU exemption:

The agency reiterated that a tank may qualify for the exemption regardless of whether wastewater is piped, trucked, or otherwise conveyed within the onsite boundaries of the facility generating the wastewater. [RO 13112]
EPA clarified that guidance in RO 13226 allows offsite shipment of WWTU sludges and tank bottoms from routine wastewater operations, but not the wastewater itself. Thus, these shipments do not void the exemption.
Finally, EPA noted that the guidance in RO 11519, regarding co-owned facilities discharging under the same CWA permit, does not apply in this case because the wastewater conveyance in that guidance was via pipeline, not transport vehicles.

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