Seasonal and continuous loading and long-term phosphorus management of treatment in wetlands.

摘要

Two studies were carried out to further characterize the performance of agricultural constructed wetlands in Atlantic Canada. Research for both studies was conducted at the Bio-Environmental Engineering Center in Bible Hill, NS, where two similar surface flow constructed wetlands were built in the summer of 2000.;In the second study, a 5 year dataset from one of the wetlands located at BEEC was examined to determine the effects of continued loading on P treatment. The wetland was intensively monitored from November of 2000 through April of 2005 for TP and SRP. Liquid dairy wastewater was loaded at 1.5 +/- 1.0, and 1.0 +/- 0.9 kg ha-1 d-1 for TP and SRP, respectively. Mass reductions for the entire study were 53.7 and 52.7% for TP and SRP, respectively. Linear regression analyses of monthly TP and SRP mass reductions, and monthly outflow found mass reductions decreased as outflow increased. Mass reductions for both parameters were >50% when monthly outflow was 100 mm. When monthly outflow increased beyond 100 mm, mass reductions became more variable, making it difficult to predict system performance. It is recommended that management practices be adopted to prevent high external hydrological loadings.;A two year study compared seasonal and continuous loading of wetlands treating liquid dairy wastewater. One wetland was loaded seasonally (growing seasons only), while the other was loaded continuously (year-round), such that the same annual volume of wastewater was loaded into each system. Growing season mass removal rates for the seasonally loaded wetland were 1.3 to 2 times higher for TSS, TKN, (NH3+NH4 +)-N, TP, and E. coli, however, mass exports were 1.4 to 14.5 times higher than from the continuously loaded wetland. Annual mass removal rates were marginally higher for the continuously loaded wetland for nutrient parameters. There was variability in BOD5 and TSS treatment, with higher mass removal rates for the seasonally loaded wetland in year 1, while in year 2, rates were higher for the continuously loaded wetland. The continuously loaded wetland performed better during high flow events. Continuous loading is recommended due to economic benefits and better system performance during high flow events.