Abstract
Sewage treatment studies at the watershed scale, compared to case-by-case community projects, ensures the most cost-efficient investment of funds commensurate with environmental requirements to sustain growth. A three-year environmental assessment study for the town of New Tecumseth, Ontario, examined all nutrient inputs to the Nottawasaga River watershed. Other challenging watershed constraints were investigated, such as stream and river flow takings for irrigation and sediment transport, prior to the selection of the master sewage treatment plan. The findings from the field research and computer modelling were used to (1) place a realistic perspective on nutrient impacts, present and future, attributable to treated sewage effluent; (2) design a master plan that could be used as an opportunity in terms of reusing the effluent locally for agricultural irrigation; (3) provide a real-time assurance of the plan’s performance/compliance, based on the actual carrying capacity of the aquatic ecosystem; (4) stage the construction of the plan in a cost-effective and environmentally sound manner; and (5) recommend a water resources management strategy to control other nutrient and sediment load sources within the watershed. The recommended master sewage treatment plan and water resources management strategy can restore the Ministry of Environment and Energy provincial water quality objective concentration for total phosphorus within the river during 7Q20 flow conditions.