Boatyard Stormwater Treatment Technology Study Executive Summary
Taylor Associates, Inc. Northwest Marine Trade Association; Puget Soundkeeper Alliance; Washington State Department of Ecology.
March 2008 Final Report
Project Overview. This report summarizes the methods and results of data collected from a study of three stormwater treatment technologies that were installed at three boatyards around Puget Sound. 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. The Northwest Marine Trade Association (NMTA), Puget Soundkeeper Alliance (PSA), and Washington State Department of Ecology (WSDOE) collaborated on the study to assess the ability of the different technologies to remove contaminants, especially metals and TSS, from the boatyards’ stormwater runoff. A steering committee comprised of members and representatives from the NMTA, PSA and Ecology was put together to oversee the study.
Technology Description. This section includes brief descriptions of the three technologies evaluated. More complete descriptions of each technology can be found at their respective websites which are listed below.
(1) StormwateRx® Aquip™ The Aquip is a passive adsorptive filtration technology designed specifically for reduction of stormwater pollutants such as turbidity and metals from industrial sites, including boatyards. The overall treatment capacity of the Aquip system installed in the Edmonds Boat Workyard was 5.4 gallons per minute (gpm).
(2) Siemens Water Technologies, Inc. Wastewater Ion Exchange Systems The WWIX utilizes ion exchange resins and other media to remove specific ionic contaminants such as metals from stormwater and
wastewater. The overall treatment capacity of the system installed at the Canal Boatyard was 10 gpm.
(3) Water Tectonics, Inc. Wave Ionics™ Electro-Coagulation System Treatment The Wave Ionics is an electro-coagulation system that uses electrical current to coagulate particles by forcing contaminated water to flow between closely spaced metal plates across which an electrical potential is applied. The overall treatment capacity of the system installed at CSR Marine was 50 gpm.
Sampling Approach. Rainfall and water quality data were collected for seven storm events for the Aquip and WWIX, and four storm events for the Wave Ionics between November 2007 and February 2008. Influent and effluent samples were collected at discrete flow rates of approximately 5.4 gpm for the Aquip, 13.5 gpm for the Wave Ionics, and 10 gpm for the WWIX using automated water quality samplers. Samplers were programmed to collect grab and time-paced composite samples, which were
submitted for total suspended solids (TSS) and total and dissolved copper (Cu), lead (Pb) and zinc (Zn) analysis.
Effluent Concentrations relative to discharge criteria. Effluent data for the three technologies were compared to discharge criteria set by the pilot study steering committee for total and dissolved copper, lead, and zinc. The steering committee did not establish a discharge criterion for TSS. The effluent results are summarized in the table below. The results generally indicate the technologies performed better in the removal of total and dissolved lead and zinc than total and dissolved copper.
Table I: Percent of effluent results that met the discharge criteria.
Pollutant reduction. Percent pollutant reduction for each parameter was calculated for the three technologies. Total inflow was equal to the total outflow for the Aquip and WWIX technologies due to the design of the technologies and the sampling approaches. As a result, the concentration reduction is equivalent to a mass loading reduction for these technologies on an event basis. Because of the large size, detention volume, and resulting sampling approach for the Wave Ionics the inflow was not equal to the outflow.
The average percent pollutant reduction for the grab and the composite samples for each technology are summarized in the table below. Overall removal rates ranged from 59.9 to 98.0 percent for Aquip, -92.6 to 97.8 percent for the Wave Ionics, and 75.8 to 99.0 percent for the WWIX.
Table II: Average percent pollutant reduction for grab and composite samples for each technology.
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