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

摘要

Boatyards, Ports, and other public and private shore-side facilities typically hold NationalrnPollutant Discharge Elimination System (NPDES) stormwater permits. These facilities arernincreasingly being evaluated by regulators for their ability to reduce pollutant concentrations inrntheir stormwater discharges. High stormwater metals concentrations in particular can bernproduced from a variety of shoreside facilities, and in Washington State private boat yardrnfacilities were sued to require assessment of stormwater treatment technologies for use at theirrnfacilities.rnControlled stormwater monitoring was conducted for the inflow and outflow of three differentrnproprietary stormwater treatment technologies to evaluate reduction of metals concentrationsrnfrom small boat yard operations. To evaluate available stormwater treatment systems, threernstormwater treatment technologies were installed at three boatyards in the Puget Sound area.rnThese three technologies include (1) the StormwateRx Aquip? (Aquip) installed at the Port ofrnEdmonds Boat Workyard, (2) the Siemens Water Technologies Wastewater Ion Exchangern(WWIX) Services installed at the Canal Boatyard, and (3) the Water Tectonics, Inc. WavernIonics? Electro-Coagulation System Treatment (Wave Ionics) installed at CSR Marine. Eachrntechnology was installed to treat runoff from approximately one to two acres of predominatelyrnimpervious surfaces where boats are maintained and serviced. Inflowing metals concentrationsrnwere relatively high (up to 2000 ug/l).rnResults of inflow and outflow sampling of multiple discharge events are completed, and showedrneach of the treatment technologies were able to substantially reduce quite high concentrations ofrnmetals (copper, lead, and zinc), but did not always meet the low regulatory discharge criteria.rnRegardless of inflowing concentrations, discharge concentrations appeared to be limited tornapproximately 10 – 20 μg/l.rnThese results show even some of the most advanced treatment technologies available can getrnclose to, but cannot quite reach, the very lowest metals concentrations proposed by regulatoryrnagencies. Additionally, maintenance and cost for each of the technologies are quite different,rnwith some being relatively simple, and others more complex and costly. Treatment costrncomparison between the technologies following a “common basis of costing” will be presented.rnThe results from this study provided the technical basis for determination of AKART for thernWashington State Boatyard Sector NPDES General Permit, and can provide guidance forrnfeasibility and costs to reduce high metals concentrations to very low levels for similar facilities.