COMPREHENSIVE EVALUATION OF ALTERNATIVES FOR TOTAL DISSOLVED SOLIDS COMPLIANCE IN CHATHAM TOWNSHIP, NEW JERSEY

In the early 1990s the Township of Chatham's Main Water Pollution Control Plant (Plant) was expanded from 2,850 m3/d (0.75 mgd) to 3,800 m3/d (1.0 mgd) and upgraded for tertiary treatment. Subsequently, limitations on Total Dissolved Solids (TDS) monthly and weekly concentrations were added to the facilities NJPDES (discharge) permit. However, due to high drinking water TDS levels, especially during drought periods, and chemical addition necessary for meeting phosphorus effluent limitations, the discharge from the Plant does not reliably meet the TDS monthly and weekly effluent limitations of 500 mg/L and 750 mg/L, respectively. Consequently, the Township of Chatham (Township) has entered into an Administrative Consent Order (ACO) with the New Jersey Department of Environmental Protection (NJDEP) that establishes a schedule for attaining permanent compliance with the TDS limits. This presentation includes the results of the comprehensive analysis of alternatives for resolution of the TDS matter.The Township is located in central Northern New Jersey, approximately 48 km (30 mi) from Manhattan, New York City. The Plant discharges tertiary effluent to an unnamed intermittent tributary of the Black Brook, approximately 3.2 km (2 miles) upstream of the Great Swamp National Wildlife Refuge (Refuge). The U.S. Fish and Wildlife Service administers the approximate 26 km2 (10 mi2) refuge. Streams within the Refuge are classified as Category One antidegradation waters.The goal of this project is to provide the Township with a reliable and cost-effective mechanism for attaining compliance with its Plant TDS discharge limits. To that end, the following feasibility studies were performed:Permit/regulatory studies including: development of documentation in support of a petition to the NJDEP to remove certain receiving-water designated uses; a request for a variance from the TDS water quality-based effluent limitations; and/or participation in development of watershed-based water quality trading, including cross-pollutant trading options. A comprehensive social and economic impact analysis and the previously completed Black Brook TDS monitoring study were utilized as supporting documentation for this portion of the study.System modification evaluations (external to the Plant) including: relocation of the Plant outfall downstream of Category One waters (to the Passaic River) where stream dilution and therefore a higher TDS effluent limitation would be permitable; decrease of Plant flow to below 2,850 m3/d (0.75 mgd), thereby possibly eliminating the TDS limit; treating the drinking water such that the Plant effluent meets the TDS discharge limit.System modification evaluations (internal at the Plant) including: Plant process optimization for TDS and potential (foreseeable) other discharge limits; and/or the addition of new Plant unit process(s) such as reverse osmosis, strong acid ion exchange or electrodialysis.A screening level application of QUAL2E to the Passaic River was performed to evaluate water quality and antidegradation issues. The results of the modeling task indicated that relocation of the Plant outfall to the Passaic River is provisionally feasible. A detailed treatment process study resulted in the selection of reverse osmosis as the most feasible, though prohibitively expensive, option for meeting TDS effluent limitations at the existing discharge location. The study included an evaluation of options for disposal of the membrane reject. The cost and environmental impact of trucking the brine to an off-site disposal facility was considered prohibitive. A summary of technical options was provided, including the results of bench-scale testing for conceptual design of a reverse osmosis unit process, and consideration of other system modifications in the context of reasonably anticipated future discharge limits.Regulatory options for resolution of the TDS matter were then evaluated incorporating the results of the technical evaluation of alternative capital projects. The evaluations focused on determining the efficacy of petitioning for removal of a designated use of a stream or stream segment, or alternatively, requesting a variance from TDS effluent limitations. Based on the results of comprehensive social and economic evaluations, and of the technical alternative analyses, the highest-rated option for resolution of the matter was determined to be pursuing a petition for removal of certain designated uses. The Township is utilizing the results of this ongoing project as a basis for discussions with regulatory authorities and impacted stakeholders.