Chloramine transport and dissipation in Edmonton storm sewers

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To avert production of "disinfection by-products" that result from conventional chlorination processes and that carry significant human health risks, many municipalities in Canada and abroad chloraminate drinking water. The long-lasting disinfectant produced by chloramination is a key advantage of the process; however, its long lifetime also poses a risk to the environment when monochloramine is introduced from municipal water use into storm sewer systems and consequently downstream water sources. Chloramine dissipates naturally in pipe systems over time; however, little research has been undertaken to monitor and characterize chloramine decay and to study the impact of different environmental and biological parameters on its decomposition in storm sewer systems. Therefore, the proposed research aims to develop a deeper understanding of the physical, chemical, biological, and environmental factors that affect chloramine dissipation in storm sewer systems, and to refine decision-support tools for assessing the risks of specific chloraminated-water discharges. To these ends, the research will integrate field sample investigation, laboratory experiments, and simulation modelling to study chloramine decay mechanisms and to create a generally-applicable analytical framework to identify practical, cost-effective approaches for managing chloramine discharge to storm sewers. Specifically, we will examine the effects of physicochemical properties of the discharged water as well as environmental conditions, including land- and water-use characteristics, weather conditions, and sewer pipe properties, on chloramine decay and incorporate new parameterizations of the dissipation process into a well-known urban drainage model. The research, if funded, will advance our understanding of chloramine decay in storm sewer systems and will aid municipalities in managing chloraminated water discharges. The results and research framework will be generalizable to many Canadian cities, but are particularly pertinent for our industrial partner, the City of Edmonton's Drainage Services Branch, which has recently changed its Drainage Bylaw to reduce the permissible maximum chlorine discharge concentration in stormwater from 0.2 mg/L to 0.02 mg/L.