ELSA is a publicly owned wastewater treatment facility serving the communities of Ewing and Lawrence Townships in New Jersey. The effluent from the wastewater treatment plant (WWTP) contains low levels of copper. However, due stringent water quality criteria for protection of aquatic life and minimal dilution of the ELSA effluent in the receiving water, the New Jersey Department of Environmental Protection (NJDEP) imposed copper effluent limitations in ELSA’s NPDES permit.
Treatment technologies for removal of copper from municipal wastewater treatment plants at the levels observed in this instance do not exist. Therefore, ELSA could not comply with the effluent limitations imposed in its NPDES permit. Kleinfelder was asked to examine the basis for these effluent limitations and to determine whether compliance with water quality criteria could be achieved without treatment for removal of copper.
Kleinfelder applied two innovative approaches to interpretation and application of the water quality criteria: dynamic modeling and the Water Effect Ratio (WER). Dynamic modeling showed that NJDEP’s traditional model for establishing effluent limitations (i.e., steady state critical low flow) results in unnecessarily stringent effluent limitations. Determination of a site-specific WER provided further relaxation of the numeric water quality criteria.
Kleinfelder’s application of state-of-the-art concepts to the determination of effluent limitations and site-specific numeric water quality criteria demonstrated that this WWTP discharge would not cause water quality criteria violations. Consequently, effluent limitations for copper are not necessary for this facility.