Fate of Heavy Metals in Passive Wastewater Treatment Systems of the Northwest Territories
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Due to unique climatic, geologic, and biologic conditions of northern Canadian landscapes, wastewater management in this region is complex and geographically distinctive. Many regions of the Northwest Territories (NWT) employ passive, semi-engineered systems for municipal wastewater treatment as they are low-cost and require minimal maintenance; however, it is unclear if these natural systems are effective in treating effluent and improving water quality. A major lack of research exists surrounding heavy metals in passive treatment systems in northern environments. The current study distinguishes and quantifies the relationship between anthropogenic wastewater disturbances and ambient levels of heavy metals in receiving environments in the communities of Yellowknife, Hay River, and Fort Providence, NWT. Comparisons are made between federal environmental quality guidelines and levels of heavy metals found in wastewater system effluents. Water samples were collected during August of 2019 in wastewater lagoon, wetland, and reference sites for analysis of eight heavy metals. Data mining of water quality reporting from NWT databases and studies was conducted to compare ambient levels of heavy metals to samples collected form wastewater systems. A 2-way ANOVA analyzed variance between locations (Yellowknife, Hay River, and Fort Providence) and environments types (lagoon, wetland, and ambient) and found six of eight heavy metals indicated significant differences between locations while two metals exhibited significant differences between environment types. Generally, lagoons contained greater heavy metal samples above Canadian guidelines. However, there were fewer wetland samples above Canadian guidelines compared to ambient samples. The results suggest underlying geology and anthropogenic disturbances influence heavy metal occurrence in northern environments and passive systems may be improving water quality in wetlands by reducing heavy metal concentrations.