Chloramine transport and dissipation in Edmonton storm sewers

为了避免传统氯化工艺产生的“消毒副产品”对人类健康造成重大风险，加拿大和国外的许多城市都对饮用水进行了氯胺化处理。氯胺化产生的长效消毒剂是该工艺的一个关键优势;然而，当一氯胺从市政用水引入雨水下水道系统并因此进入下游水源时，其长寿命也对环境构成风险。随着时间的推移，氯胺自然消散在管道系统中，然而，很少有研究已经进行监测和表征氯胺衰减，并研究不同的环境和生物参数对其分解的影响，在暴雨下水道系统。因此，拟议的研究旨在更深入地了解影响雨水管道系统中氯胺消散的物理，化学，生物和环境因素，并改进用于评估特定氯胺水排放风险的决策支持工具。为此，该研究将整合现场样品调查，实验室实验和模拟建模，以研究氯胺衰减机制，并创建一个普遍适用的分析框架，以确定管理氯胺排放到雨水管道的实用，具有成本效益的方法。具体来说，我们将研究的排放水的物理化学性质以及环境条件，包括土地和水的利用特点，天气条件和下水道管道的性能，氯胺衰减的影响，并将新的参数化的耗散过程到一个著名的城市排水模型。这项研究如果得到资助，将促进我们对雨水下水道系统中氯胺衰变的理解，并将帮助市政当局管理氯胺化水的排放。结果和研究框架将推广到许多加拿大城市，但特别是我们的工业合作伙伴，埃德蒙顿市的排水服务分支，最近改变了其排水附例，以减少雨水中允许的最大氯排放浓度从0.2毫克/升到0.02毫克/升。

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.