Evaluation of a diffused air aeration system for a constructed wetland receiving dairy wastewater.

摘要

Treatment systems that utilize natural processes, such as constructed wetlands, offer a sustainable and economical alternative to conventional wastewater treatment. Dairy farm wastewater was loaded into two similar (~100 m2 each) surface flow treatment wetlands in Bible Hill, Nova Scotia, Canada, at an average rate of 65 kg BOD₅ ha-1 d-1. A diffused air aeration system was installed in one of the wetlands based on a design oxygen requirement of 3.52 kg O₂ d-1. Wetland treatment performance was evaluated over 20 months (September 2002 to April 2004), during which time the aeration system operated for 13 months. The wetlands were monitored intensively for dissolved oxygen (DO), five-day biochemical oxygen demand (BOD₅), total suspended solids (TSS), total Kjeldahl nitrogen (TKN), ammonia-nitrogen (NH₃-N), nitrate-nitrogen (NO₃--N), total phosphorus (TP), and Escherichia coli. Both the aerated and non-aerated wetlands provided effective year-round wastewater treatment. Artificial aeration significantly increased TKN and NH₃-N mass reductions (P<0.001). Aeration did not significantly affect the removal of BOD₅, TSS, NO₃--N, TP, and E. coli. The data suggest that the benefits of wetland aeration are not great enough to warrant its widespread adoption for small-scale agricultural systems.