STORMWATER QUALITY ASSESSMENT AND UPGRADE TO REMOVE LOW-LEVEL METALS

Resulting from adoption of a General Permit for Discharge of Stormwater from Industrial Facilities in the State of Connecticut, this fuel cell manufacturer, International Fuel Cells of South Windsor, Connecticut, registered in the program and maintained a compliance level with the program that included annual monitoring of stormwater discharges to the receiving stream. Monitoring consisted of several conventional pollutants as well as certain transition metals and stormwater toxicity to the daphnid, Daphnia pulex. Increasingly, threshold guidelines (limits) in the general permit were used as attainment goals by the regulators and increasing scrutiny was put on stormwater quality from this and other facilities in the State. Stormwater results for copper, zinc and effluent toxicity exceeded the guideline criteria published by the Connecticut DEP. Resultantly, requests for assessment, upgrade and implementation at the facility were made by the DEP.Exhaustive studies at the facility were undertaken to determine the cause of copper and zinc, which were shown to result in stormwater toxicity from the facility. In this process, miles of exposed thin copper tubing were removed from the roof structure and, to the extent feasible, architectural copper and zinc were covered or removed. However, as with many facilities in the northeast United States, architectural metals, exposed to mildly acetic rainwaters, leached copper and zinc in unacceptable amounts relative to general permit threshold levels.Following isolation of the copper and zinc loads as well as removal, to the extent feasible, of exposed copper and galvanized materials, a stormwater treatment system was designed and installed in the fall of 2000. This treatment system consisted of soil and vegetative contact of the stormwater prior to discharge and was designed to remove metals or simulate metal toxicity to below stormwater threshold levels. The removal mechanism is one of biological uptake/sorption or cation exchange with soil contact in the treatment system. The treatment system, a modified version of the Howland Swale is growing out in spring 2001 and will be tested for removal efficiencies in the summer and fall of 2001. Design and construction of the treatment system are detailed in the following paper with preliminary results to be available in the future.