Chloramine transport and dissipation in Edmonton storm sewers

为了避免产生传统氯化工艺产生的“消毒副产品”，从而对人类健康造成重大风险，加拿大和国外的许多市政当局对饮用水进行氯胺化处理。氯胺化产生的长效消毒剂是该工艺的关键优势；然而，当一氯胺从市政用水进入雨水下水道系统并因此进入下游水源时，它的长寿命也会对环境构成威胁。氯胺在管道系统中随时间自然消散；然而，很少有研究监测和描述氯胺的衰变，并研究不同的环境和生物参数对其在暴雨下水道系统中的分解的影响。因此，本研究旨在更深入地了解影响氯胺在雨下水道系统中消散的物理、化学、生物和环境因素，并完善评估特定氯胺化水排放风险的决策支持工具。为此，研究将结合实地抽样调查、实验室实验和模拟模型，研究氯胺的衰变机制，并建立一个普遍适用的分析框架，以确定管理氯胺排放到雨下水道的实际、经济有效的方法。具体来说，我们将研究排放水的物理化学性质以及环境条件（包括土地和水的使用特征、天气条件和下水道管道性质）对氯胺衰变的影响，并将新的消散过程参数化纳入一个众所周知的城市排水模型。这项研究如果得到资助，将促进我们对雨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。研究结果和研究框架将推广到加拿大的许多城市，但对我们的工业合作伙伴埃德蒙顿市排水服务部门尤其重要，该部门最近修改了其排水章程，将雨水中允许的最大氯排放浓度从0.2 mg/L降低到0.02 mg/L。

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.