Trace Element Occurrence in Wastewater and Effects on Surface Water Quality in the Laurentian Great Lakes and the Grand River, Ontario
Wastewater , Geology , Surface Water , Geochemistry , Environmental Chemistry , Environmental Geology
Wastewater treatment plays an integral role in maintaining surface water quality in industrialized societies around the world. Wastewater effluent and sewage sludge can both be important vectors of contaminants that are not fully eliminated during treatment, and thus understanding effluent and sludge composition is key to preventing deleterious environmental impacts to receiving environments. Trace elements are one important class of contaminants in wastewater, as their increased use in industrialized societies is reflected in their growing occurrence in anthropogenic waste streams globally. Yet, the potential large-scale sources of trace elements to wastewater and their behavior during wastewater treatment remain poorly understood and potential environmental impacts on receiving environments therefore unclear. Because only a handful of specific parameters in wastewater and sludge are regulated in Canada, not including many trace elements, monitoring of their occurrence and potential impacts is crucial. In this thesis, >40 wastewater treatment facilities in the North American Great Lakes basin were screened for major and trace elements and a black-box approach was deployed to calculate representative estimates for average per-capita trace element loads and basin-scale effluent discharge rates, as well as trace element removal efficiencies across different wastewater treatment technologies. In addition, I report concentrations of major and trace elements in >30 riverine and effluent samples collected in the Grand River catchment, Ontario, in an attempt to assess imprints of effluent discharge on riverine trace element loads. The findings of this thesis demonstrate the effectiveness of wastewater surveillance for a quantitative exploration of anthropogenic versus geogenic trace element emissions and highlight its value to further the understanding of the current state of contaminants in wastewater and sewage sludge and their behavior during the wastewater treatment process.