Pathogen Removal by Agricultural Constructed Wetlands in Cold Climates

Constructed treatment wetlands have been found to remove fecal coliform (FC) through a variety of mechanisms. This research evaluated the removal of FC in both warm and cold seasons from surface flow treatment wetlands in Bible Hill, Nova Scotia. Two wetlands (100 m), of differing depths were monitored over a 17 month period. The wetlands were loaded with dairy wastewater (average inlet FC concentration of 7438 CFU) at a rate of 2.2×10 CFU had. Weekly samples were collected at the wetland inlet and outlet for FC using the MPN method. Removal rates and mass reductions ranged from 96.8 to 99.7% over the entire monitoring period. Fecal coliform discharge levels were below guidelines for recreation (< 200 CFU 100 mL) and irrigation (< 100 CFU 100 mL) purposes the majority of the time, indicating that removal of FC in these systems was sufficient in both warm and cold seasons, even when ice conditions existed.