Expected impacts of climate change on water and wastewater treatment in the Eastern Ontario region

Climate change impacts the hydrological cycle. The intensity of extreme precipitation events and droughts is expected to increase, creating stress on the water and wastewater infrastructure. The objective of this study is to assess the potential impacts of climate change on the existing water and wastewater treatment infrastructure in rural Eastern Ontario. In total, 13 municipal WTPs and 28 municipal wastewater treatment systems in the Eastern Ontario region were investigated. These facilities were characterized using existing data, questionnaires, and sites visits. On the basis of this information, potential impacts of climate change were identified. One conclusion of this analysis was the potential need to convert lagoon systems to mechanized WWTPs. Such a conversion would represent a significant financial burden for a small community. Therefore, a cost-estimation methodology was developed, based on the existing CAPDET software.; Dry periods, heavy rain events, heavy spring runoff and increased temperatures are the critical climate change phenomena that are expected to have the greatest impact on the water infrastructure of the study area. It was found that WTPs on the Ottawa River and the St. Lawrence River are not likely to exhibit water shortages, but those using smaller surface water sources are more vulnerable to water scarcity. Furthermore, this vulnerability to water scarcity will be exacerbated by and increase in water demand resulting from higher temperatures and more severe droughts.; Turbidity events typically occur during periods of heavy runoff, and it is expected that climate change will increase the intensity of heavy runoff events. Taste and odor problems due to algal growth during spring and summer are an existing concern for at least five facilities in the study area. It is expected that this phenomenon will increase as a consequence of increased temperatures, increased evaporation rates and longer dry periods during the spring, summer and fall.; Inflow and infiltration into the sewer system during spring runoff and rain events are typical problems in the study area, resulting in high peak flows at wastewater treatment facilities. Currently, certain WWTPs in the study area use bypass as a method to cope with extreme peak flows. It is expected that climate change will increase the intensity of spring runoff, and the intensity and frequency of rain events. Consequently, it is likely that there will be an increase in the frequency of bypass events, and an increase in the volume of bypassed wastewater.; In lagoon systems, intensified rain events will further swell the normal wastewater flow to several times the dry weather flow, likely causing incomplete treatment of the wastewater particularly at continuous discharge lagoons. During dry periods and warm weather, algal growth in lagoon systems will likely increase. The discharge of effluent containing high quantities of algae will degrade the receiving waters quality.; An increased frequency and intensity of periods of low streamflows will reduce the dilution capacity of receiving waters, particularly in small streams. This increased vulnerability may eventually be reflected in more stringent discharge criteria. A reduction in streamflows could also lead to more extensive algal growth, resulting in more turbidity, more taste and odor problems and possibly algal toxins contaminations.