An Initial Assessment of a Wetland-Reservoir Wastewater Treatment and Reuse System Receiving Agricultural Drainage Water in Nova Scotia

摘要

A wetland-reservoir wastewater treatment and reuse systems is an integrated water management system constructed on farms to conserve water and to help mitigate water pollution from agricultural drainage. This research assesses such a system in Nova Scotia and provides recommendations for adapting its location, design, construction, and operation to a cold climate. Water quality, hydraulic, and meteorological data was collected between November 2007 and January 2009. The system collected approximately15500 m3 (8700 m3 ha-1 of drained land) annually, potentially enough water to irrigate more than the drained area. A tracer study was conducted in the constructed treatment wetland to assess residence time. Little difference was observed between the actual residence time (15.0 d) and the nominal residence time (14.5 d). This is attributed to a high length to width ratio (10:1). Annual nitrate-nitrogen and E. coli reductions by the constructed treatment wetland were 52% and 33%, respectively. Significant monthly variation was observed, and is attributed to the dynamic hydraulic and pollutant loading of tile drainage water. Total phosphorus and soluble reactive phosphorus concentrations were typically below detectable levels (0.10 mg L-1 and 0.05 mg L-1respectively) at all sampling locations. Reservoir water quality exceeded irrigation water quality guidelines forE. coli (100 CFU 100 mL-1) during summer months and is attributed to environmental factors. At a cost of approximately $50,000 ha-1 the system may require economic incentives or drainage water disposal regulations before it can be adopted by farmers.