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”并对人体健康造成重大风险，加拿大和国外的许多市政当局对饮用水进行氯胺处理。氯胺消毒产生的长效消毒剂是该工艺的一个关键优势；然而，当一氯胺从城市供水引入雨水下水道系统并随后进入下游水源时，其长寿命也对环境构成风险。随着时间的推移，氯胺在管道系统中自然消散；然而，很少有人开展研究来监测和表征氯胺的衰变，以及研究不同的环境和生物参数对其在雨水下水道系统中分解的影响。因此，拟议的研究旨在更深入地了解影响雨水排水系统中氯胺消散的物理、化学、生物和环境因素，并改进决策支持工具，以评估特定氯胺废水排放的风险。为此，这项研究将结合现场样本调查、实验室实验和模拟模型，研究氯胺的衰减机理，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水渠的实用、成本效益的方法。具体地说，我们将研究排放水的物理化学特性以及环境条件，包括土地和水的使用特性、天气条件和污水管特性对氯胺衰减的影响，并将消散过程的新参数纳入一个著名的城市排水模型中。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减的了解，并将帮助市政当局管理氯胺水的排放。研究结果和研究框架将适用于加拿大许多城市，但尤其适用于我们的工业合作伙伴埃德蒙顿市排水服务部，该局最近修改了排水附例，将雨水中允许的最大氯排放浓度从0.2 mg/L降至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.