Recommendations for the Use of Tundra Wetlands for Treatment of Municipal Wastewater in Canada’s Far North

Abstract

The treatment of domestic wastewater is logistically challenging in remote Arctic and sub-Arctic communities due to technical, economic and social factors. In some circumpolar countries, raw sewage with minimal to no treatment is released to marine or freshwater environments with the assumption that the wastewater constituents are quickly diluted to levels that are not harmful to environmental or human health. In many northern communities in Canada, primary treatment occurs in sewage lagoons before being intentionally decanted, or slowly released as wastewater leaks (by design or unintentional) through the berms of the lagoons (i.e., exfiltration) to the surrounding landscape, which is often covered by natural tundra wetlands. The tundra wetlands of northern Canada which are the focus of this chapter are unlike constructed wetlands which are engineered to treat wastewater under defined hydraulic conditions and loading regimes to meet specific treatment performance targets. These tundra wetlands should not be confused with constructed wetland (e.g., designed) technologies used within other cold climate regions. The work presented below is believed by the authors to be the first comprehensive review of natural tundra areas used for the treatment of domestic wastewaters and their use in Canada is thought to be unique within circumpolar regions. This work describes a series of studies undertaken by Fleming College and Dalhousie University which have demonstrated that in most cases the natural tundra wetlands provide ancillary treatment beyond what is often achieved in the sewage lagoons and in this manner provides a valued benefit to wastewater treatment within Canada’s far north and is a treatment strategy that may be appropriate in other circumpolar regions. The findings from this investigation show that the concentration reductions for 5-day carbonaceous biochemical oxygen demand (CBOD₅), total ammonia nitrogen (TAN), and total phosphorus (TP) typically range between 80 and 90% as the treated effluent leaves the wetland. The measure of total suspended solids (TSS) was not found to be a reliable indicator of treatment performance since some wetlands can generate TSS internally. Vegetation inventories were also conducted on tundra wetlands used for wastewater treatment and on control sites not exposed to wastewater. Findings indicate that a high abundance of Carex aquatilis was found in treatment wetlands. Laboratory studies illustrated that this sedge has an ability to enhance the reduction of organic nitrogen, ammonia and oxidized nitrogen even when temperatures were less than 5 °C. This chapter discusses key factors that influence the performance of tundra wetlands, with a focus on wastewater strength, hydrology, and seasonal variability. Monitoring of these remote wetlands presents unique challenges related to sample collection and analysis; the selection of representative collection sites; and the determination of seasonal and inter-annular variability, are two examples. We share insights into these challenges commenting on practical solutions, predictive tools related to treatment performance and the identification of knowledge gaps. The intent of this chapter is to provide readers an overview of what is currently known about tundra treatment wetlands in Canada’s Far North, and to present recommendations for how these sites, under certain conditions, can be used as a polishing component of the treatment train.

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