UNSW Water Research Centre, School of Civil & Environmental Engineering, University of New South Wales, NSW 2052, Australia.
School of Computing Engineering and Mathematics, University of Western Sydney, Kingswood, NSW 2747, Australia.
Sci Total Environ. 2022 Jul 15;830:154324. doi: 10.1016/j.scitotenv.2022.154324. Epub 2022 Mar 11.
The stability of drinking water disinfectant residuals is known to be influenced by multiple variables. To evaluate the effects of various influencing variables on disinfectant stability, a multivariate analysis of chloramine decay and associated disinfection by-products (DBPs) formation was investigated in a series of bench-scale experiments. Of nine water quality variables previously identified, monochloramine dose, pH, and bromide concentration were selected as key water quality variables based on previous investigations and modelling. Co-effects of these key variables on monochloramine decay and formation of 33 halogenated and nitrogen-containing DBPs were investigated using response surface experimental design. Rechloramination conditions, including monochloramine dose, pH and bromide concentration, were optimised via a 3-factorial multivariate analysis of monochloramine stability in post-treatment drinking water. Effects of influencing variables on disinfectant decay and DBP formation were assessed and graphically presented as response surfaces with minimal experiments using Doehlert matrix experimental design compared to other multivariate experimental designs. Concentrations of trihalomethanes (THMs), haloacetic acids (HAAs), and N-nitrosamines were found to increase with water age, whereas opposite phenomenon was observed in the net production of haloacetonitriles (HANs). Increasing pH was found to stabilise monochloramine but it could cause DBP speciation to shift. Furthermore, increasing bromide concentration elevated Br-DBP formation. In bromide-containing water, pH = 7.8-8.0 should be considered as higher pH increases Br-THMs formations and lower pH increases formations of Br-HAAs and Br-HANs. However, water age or pH has insignificant impacts on DBP formation after significant monochloramine decay or at low initial monochloramine dose. These findings indicate that effective combined control measures to maintain monochloramine stability should include the application of high monochloramine dose (>1.5 mg-Cl.L) under conditions of moderate to high pH (pH = 7.8-8.0) and minimal bromide concentration. This study provides relevant insights to water utilities aiming to design effective disinfectant residual management strategies for controlling monochloramine decay and DBP formation.
饮用水消毒剂残余物的稳定性已知会受到多个变量的影响。为了评估各种影响变量对消毒剂稳定性的影响，在一系列台式实验中对氯胺衰减和相关消毒副产物（DBP）形成进行了多变量分析。在之前确定的九个水质变量中，根据先前的研究和建模，选择一氯胺剂量、pH 值和溴化物浓度作为关键水质变量。使用响应面实验设计研究了这些关键变量对一氯胺衰减和 33 种卤化和含氮 DBP 形成的协同作用。通过对后处理饮用水中单氯胺稳定性的 3 因素多变量分析，优化了再氯化条件，包括单氯胺剂量、pH 值和溴化物浓度。使用 Doehlert 矩阵实验设计，与其他多变量实验设计相比，使用最少的实验评估了影响变量对消毒剂衰减和 DBP 形成的影响，并以响应面的形式进行了图形化呈现。三卤甲烷（THMs）、卤乙酸（HAAs）和 N-亚硝胺的浓度随着水龄的增加而增加，而卤乙腈（HANs）的净生成则出现相反的现象。发现增加 pH 值可以稳定一氯胺，但会导致 DBP 形态发生变化。此外，增加溴化物浓度会增加 Br-DBP 的形成。在含溴化物的水中，pH = 7.8-8.0 应被视为较高的 pH 值会增加 Br-THMs 的形成，而较低的 pH 值会增加 Br-HAAs 和 Br-HANs 的形成。然而，在一氯胺大量衰减或初始一氯胺剂量较低的情况下，水龄或 pH 值对 DBP 的形成没有显著影响。这些发现表明，为了保持一氯胺的稳定性，有效的综合控制措施应包括在中等至高 pH 值（pH = 7.8-8.0）和最小溴化物浓度条件下应用高一氯胺剂量（>1.5mg-Cl.L）。本研究为旨在设计有效消毒剂残留管理策略以控制一氯胺衰减和 DBP 形成的水务公司提供了相关见解。
