PATHOGEN REMOVAL IN CONSTRUCTED WETLANDS FOCUSING ON BIOLOGICAL PREDATION AND MARINE RECREATIONAL WATER QUALITY
Abstract:Constructed wetlands can be extremely successful in removing a variety of pollutants from water which passes through them, including pathogenic bacteria, viruses, and protozoa. Removal mechanisms have been hypothesized but have rarely been quantified. Grazing experiments were performed to evaluate the potential contribution to pathogen consumption made by mussels (Mytilus edulis) and rotifers (Brachionus plicatilis) using fluorescent labeled enterococci and latex microspheres as food sources. Enterococcus bacteria were chosen due to their use as an indicator of marine recreational water quality. With mussel predation, enterococcus concentration was reduced by 90% (1-log removal) after 2 to 4 hours, and an average 97.2% reduction was seen after 24 hours. Rotifer average clearance rates ranged from 0.51 to 35.79 μL/individual*hour, and average ingestion rates ranged from 24 to 676 food particles/individual*hour. When compared to the pathogen removal rates observed in treatment wetlands, these clearance rates, consistent with those cited in the literature, illustrate the potential for grazing to make a substantial contribution to pathogen removal in wetlands containing these predatory organisms. These data were applied to a case study of Talbert Marsh, a restored wetland located in Huntington Beach, California that receives controlled stormwater discharges and acts an apparent source of enterococcus. While Talbert Marsh could be modified to enhance biological pathogen removal, alteration of the wetland flow patterns and substrate would probably have a more substantial impact in enhancing pathogen removal within the wetland.
Document Type: Research Article
Publication date: 2003-01-01
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