Constructed wetlands as a potential management practice for cold climate dairy effluent treatment - VT, USA

Four horizontal subsurface flow constructed wetlands (HSSF-CW) were monitored to determine their efficiency at reducing the concentrations of five-day biological oxygen demand (BOD<inf>5</inf>) and total suspended solids (TSS) from dairy farm effluents in cold climate in Vermont during the four year study period (between 2004 and 2007). This study evaluates effects of seasonal variations, wetland age, supplemental aeration and design connected in-series on BOD<inf>5</inf> and TSS treatment performances of CWs. Aerated CWs achieved higher BOD<inf>5</inf> and TSS treatment efficiencies by 8% and 5% respectively, compared with non-aerated ones. The performances of the CWs increased with increasing age, and in the best growing seasons (between April and September) of the plants. The utilization of in-series design increased BOD<inf>5</inf> and TSS removal efficiencies by 12% and 16%, respectively. In conclusions, the high treatment efficiency achieved by average 83% for BOD<inf>5</inf> and 90% for TSS presented that the CWs had a high potential as an appropriate technology for dairy farm effluents in cold climates.