Evaluation of Treatment Potential and Feasibility of Constructed Wetlands receiving Municipal Wastewater in Nova Scotia

Abstract

The Canadian Council of Ministers of the Environment (CCME) is proposing Canada-wide municipal wastewater effluent regulations. This would put pressure on small communities to install wastewater collection systems and treatment facilities. Artificially constructed wetlands are cost-effective wastewater treatment systems that achieve secondary effluent standards in warmer climates. This study was conducted to assess the phosphorus and nitrogen removal of a constructed wetland during a typical Nova Scotian winter, compare the observed treatment ability to the proposed regulations, and estimate the cost-savings treatment wetlands could provide to the local community. The wetland system is located in Bible Hill and consists of a pond-marsh-pond system. The samples collected from the inlet and outlet of the system between October 2007 and February 2008 demonstrate an average phosphorus removal of 47.6% and an average nitrogen removal of 30.8%. The effluent concentrations were within the proposed regulatory limits for the parameters observed, however the CCME has proposed limits for numerous substances of concern that were not studied. The estimated cost for treatment wetlands for the village of Bible Hill over a 25-year period was $7.8 million, resulting in $6.3 million in savings over conventional facilities. These results provide insight into the range of nutrient removal efficiencies that can be expected from surface-flow wetland systems in Nova Scotia. The regulatory review shows that more research on the fate and transport of emerging contaminants of concern is needed to better understand the feasibility of installing treatment wetland systems.