Constructed wetlands (CW) have gained recognition as a management option for the treatment of various agricultural wastewaters. This study involved the design, construction, and initial evaluation of a wetland-reservoir-irrigation (WRI) system. The system was established in Truro, Nova Scotia, Canada, with the goal to capture, treat, and re-use agricultural sub-surface drainage water. It consisted of a 1.8-ha area of a cropped field that was systematically tile drained. Drainage water was directed through a 2-cell CW and then into a reservoir-irrigation pond. Flow rate hydraulics, residence time distributions, and treatment efficiencies for nitrate-nitrogen (NO 3 − -N) and Escherichia coli (E. coli) were monitored for 14 months. Mass reductions of NO 3 − -N and E. coli from the CW were 67.6% and 63.3%, respectively. However, average E. coli concentrations increased to 178 CFU 100 mL −1 in the reservoir during the warm season. It may therefore be best to use reservoir water for irrigation of crops that are not consumed raw. To aid in the future design of similar systems, mean first-order rate constants (k s ) for NO 3 − -N and E. coli were calculated to be 8.0 and 6.4 m y −1 , respectively. The volume of water collected in the reservoir exceeded typical irrigation requirements of the drained land and could therefore provide irrigation to additional land beyond the drainage area.

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 approximately 15500 m 3 (8700 m 3 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-1 respectively) at all sampling locations. Reservoir water quality exceeded irrigation water quality guidelines for E. 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.

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