Metals Removal Performance by Three Proprietary Technologies for Stormwater from Boatyard Maintenance Facilities

Boatyards, Ports, and other public and private shore-side facilities typically hold National Pollutant Discharge Elimination System (NPDES) stormwater permits. These facilities are increasingly being evaluated by regulators for their ability to reduce pollutant concentrations in their stormwater discharges. High stormwater metals concentrations in particular can be produced from a variety of shoreside facilities, and in Washington State private boat yard facilities were sued to require assessment of stormwater treatment technologies for use at their facilities.Controlled stormwater monitoring was conducted for the inflow and outflow of three different proprietary stormwater treatment technologies to evaluate reduction of metals concentrations from small boat yard operations. To evaluate available stormwater treatment systems, three stormwater treatment technologies were installed at three boatyards in the Puget Sound area. These three technologies include (1) the StormwateRx Aquip™ (Aquip) installed at the Port of Edmonds Boat Workyard, (2) the Siemens Water Technologies Wastewater Ion Exchange (WWIX) Services installed at the Canal Boatyard, and (3) the Water Tectonics, Inc. Wave Ionics™ Electro-Coagulation System Treatment (Wave Ionics) installed at CSR Marine. Each technology was installed to treat runoff from approximately one to two acres of predominately impervious surfaces where boats are maintained and serviced. Inflowing metals concentrations were relatively high (up to 2000 μg/l).Results of inflow and outflow sampling of multiple discharge events are completed, and showed each of the treatment technologies were able to substantially reduce quite high concentrations of metals (copper, lead, and zinc), but did not always meet the low regulatory discharge criteria. Regardless of inflowing concentrations, discharge concentrations appeared to be limited to approximately 10 – 20 μg/l.These results show even some of the most advanced treatment technologies available can get close to, but cannot quite reach, the very lowest metals concentrations proposed by regulatory agencies. Additionally, maintenance and cost for each of the technologies are quite different, with some being relatively simple, and others more complex and costly. Treatment cost comparison between the technologies following a “common basis of costing” will be presented. The results from this study provided the technical basis for determination of AKART for the Washington State Boatyard Sector NPDES General Permit, and can provide guidance for feasibility and costs to reduce high metals concentrations to very low levels for similar facilities.