Tracking domestic wastewater and road de-icing salt in a municipal drinking water reservoir: Acesulfame and chloride as co-tracers

Developing strategies to identify the origins of contaminants in watersheds is crucial for source water protection. The use of multiple tracers improves the ability to identify contamination events originating from various land use activities. The objective of this study was to evaluate the use of acesulfame and chloride as co-tracers to represent the impact of pollution originating from wastewater and road de-icing on water quality in a municipal drinking water source. The study included a two-year sampling and water quality analysis program in numerous locations within a drinking water reservoir comprising a lake (upstream) and a river (downstream) which supply raw water to a municipal water treatment plant. Results showed that the spatial variability of acesulfame and chloride within the watershed of the lake-river systems depends on the location of contaminant sources, mainly municipal wastewater and septic tank discharges (for acesulfame) and the presence of small tributaries of the lake and river (for chloride). Temporal variability of the tracers under study differed according to the sampling location and was mainly affected by seasonal conditions. Correlation analyses between the two tracers in lake and river waters (in terms of concentrations and loads) made it possible to pinpoint the probable origins of contamination. The assessment of the spatio-temporal variability of these co-tracers within the lake-river watersheds allowed for the delineation of priority intervention zones as a decision-making tool for municipal authorities in improving drinking water source protection.