Investigation of High Surface Area Artificial Floating Wetlands for Removal of Pollutants in Nutrient-rich Waters
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Beneficial management practices for controlling and managing pollutant loadings from entering source waters are essential to preserving the natural habitat of lakes and rivers. Artificial Floating Wetlands (AFWs) are a promising technology, when applied with other beneficial management practices, for the removal of water borne contaminants in urban and agricultural runoff. To evaluate AFWs for their application for nutrient-rich water remediation, a pilot scale study was assessed at the Centre for Alternative Wastewater Treatment in Lindsay Ontario. Fifteen ponds, averaging in size from 7.2 m width to 9.7 m length to 3.8 m depth were divided into two controls and three treatments, each with three replicates. The controls were not covered with AFWs and were used for comparative purposes while the treatments had AFW coverage averaging 67% of the total surface area of each pond. The treatments and controls received varying inputs of simulated stormwater runoff during the study. This study was used to determine the effects of high surface area coverage of AFWs on temperature, pH, DO and ammonia. A lab scale study was designed to investigate the results obtained from the pilot study and to assess the effectiveness of 100% AFW coverage for nutrient-rich water treatment. The study consisted of twelve 150 L containers, with four of the containers covered with the AFW, four without coverage and the final four with coverage without vegetation. Water quality parameters including phosphorus, nitrogen, E.coli, pH and temperature were tested on a weekly basis for two five week retention periods. Results from these studies suggest that AFWs can provide a valuable method of treatment when combined with other beneficial management practices. The pilot scale study demonstrated that AFWs inhibit algae growth and create a cooler environment below the wetland surface. Results from the second study indicate AFWs have a much better and quicker removal of phosphorus and ammonia when compared to the treatment with coverage without vegetation. E.coli levels were completely reduced within the water column for all treatments during the testing period.