STORMWATER METALS REMOVAL BY MEDIA FILTRATION: FIELD ASSESSMENT CASE STUDY
Abstract:In 2003, the Port installed eight Downspout Stormfilter units and began testing them for removing zinc in runoff from a 1-acre Galvalume metal-roofed cargo building. This approach examined runoff treatment by three media as an alternative to source controls for the associated zinc such as re-roofing or painting. A total of 7 storms were sampled between August 2003 and January 2004, ranging from 0.03“ to 0.38” total rainfall. Zinc, DOC, hardness and nutrient concentrations in the roof runoff varied over an order of magnitude during the study and decreased with rainfall volumes and possibly seasonal factors. Zinc in the roof runoff ranged from 0.42 mg/l to 14.7 mg/l and averaged 86% dissolved. The peat and leaf compost removed dissolved zinc at similar rates averaging 81% and 76%, respectively, though they fell short of achieving consistent effluent quality. The soy bean hull medium experienced subsidence that lead to short circuiting of the filter unit with unsuccessful attempts to correct it. The supplier is expected to rectify the physical properties of the soybean hulls for future testing. Potential collateral effects of each medium appeared to be positive in raising the pH of the slightly acidic runoff and providing nominal levels of DOC (an aid to reducing dissolved metal bioavailability). Each medium released nominal levels of nitrogen and phosphorus that dropped to insignificant concentrations after the first few storms sampled. Further testing will be carried out during 2004.
Document Type: Research Article
Publication date: 2004-01-01
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