CONTROLLING TOXICITY IN A MUNICIPAL TREATMENT PLANT– THE USE OF THE RTA AS A PRETREATMENT LIMIT

Under a 1992 administrative consent order (ACO) from the New Jersey Department of Environmental Protection (NJDEP), the Linden Roselle Sewerage Authority (LRSA) was required to reduce acute toxicity in the plant effluent and meet the statutory limit of LC50 ≥ 50% by the compliance deadline of May 1, 2000. In order to meet the acute toxicity limit, the LRSA had to greatly improve the quality of its discharge from single-digit LC50 values.A series of toxicity identification evaluation (TIE) studies identified ammonia as the primary source of toxicity, but also showed that there was a significant secondary cause of toxicity, which was designated as non-ammonia or refractory toxicity. While the source of ammonia was easily investigated and located, the identity of those sources contributing the refractory toxicity was difficult to determine. The solution to controlling the refractory toxicity consisted of performing refractory toxicity assessment (RTA) testing on industrial dischargers through the industrial pretreatment program (IPP). The IPP program required the development of a facility-specific RTA protocol, which was applied as a measurement tool and a toxicity limit.LRSA has taken a unique and equitable approach to solving a persistent toxicity problem. By using the RTA protocol since the adoption of the RTA limit in October 1997, there has been progressive improvement in the LRSA effluent toxicity levels.