Frequent Questions

May a tank be considered a wastewater treatment unit (WWTU) even though it does not discharge an effluent?

Yes, a tank may be considered a waste water treatment unit (WWTU), even though it does not discharge an effluent.  In order to meet the definition of a WWTU as defined in §260.10 (§§264.1(g)(6), 265.1(c)(10), 270.1(c)(2)), a unit must:

  • Have a discharge subject to Clean Water Act (CWA) pretreatment standards or permitting requirements under CWA §§402 or 307(b);
  • Manage hazardous wastewater or hazardous wastewater treatment sludge; and
  • Meet the definition of tank or tank system. 

The WWTU exemption also includes tank systems that are part of a wastewater treatment facility that produces no treated wastewater effluent as a direct result of the NPDES or pretreatment requirements of the CWA.  Therefore, as a direct result of CWA requirements, a tank that does not discharge an effluent is eligible for the exemption (Memo, White to Josephs; May 22, 1984 (RCRA Online 11036)) [PDF 6K].  Conversely, the WWTU exemption does not apply to tanks that are not required to obtain an NPDES permit because they do not discharge treated effluent (Memo, Lowrance to Wagoner; October 27, 1988 (RCRA Online 11374)). Additional guidance regarding the WWTU exemption is available in the following memos: 
Memo, Cotsworth to Brugge; July 17, 2002 (RCRA Online 14608) [PDF 26K]
Memo, Lowrance to Cervino; January 16, 1992 (RCRA Online 13526)
Memo, Lowrance to Elliott; March 20, 1989 (RCRA Online 11408)
Memo, Williams to Whittington and Elder; December 21, 1987 (RCRA Online 13112)
Memo, Lehman to Boynton; July 31, 1981 (RCRA Online 11020) [PDF 7K]

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