Modeling and verifying chlorine decay and chloroacetic acid formation in drinking water chlorination

This study presents a phenomenological model that can be used by the water professionals to quantify chlorine decay and disinfection byproduct (DBP) formation in water. The kinetic model was developed by introducing the concept of limiting chlorine demand and extending an established reactive species approach. The limiting chlorine demand, which quantifies chlorine reactive natural organic matter (NOM) on an equivalent basis, was mathematically defined by the relation between ultimate chlorine residue and initial chlorine dose. It was found experimentally that NOM in water has limiting chlorine demand that increases with chlorine dose once the ultimate residue is established. These results indicated that the complex NOM has a unique ability to adjust chemically to the change in redox condition caused by the free chlorine. It is attributed mainly to the redundant functional groups that persist in heterogeneous NOM molecules. The results also demonstrated that the effect of chlorine dose on the rate of chlorine decay can be quantitatively interpreted with the limiting chlorine demand. The kinetic model developed was validated for chlorine decay and chloroacetic acid formation in finished drinking water.     

Evaluating the effects of granular and membrane filtrations on chlorine demand in drinking water

In this study, chlorine decay experiments were conducted for the raw water from Nakdong river that is treated by Chilseo Water Treatment Plant (CWTP) situated in Haman, Korea as well as the effluents from sand and granular activated carbon (GAC) filters of CWTP and fitted using a chlorine decay model. The model estimated the fast and slow reacting nitrogenous as well as organic/inorganic compounds that were present in the water. It was found that the chlorine demand due to fast and slow reacting (FRA and SRA) organic/inorganic substances was not reduced significantly by sand as well as GAC filters. However, the treated effluents from those filters contained FRA and SRA that are less reactive and had small reaction rate constants. For the effluents from microfiltration, ultrafiltration, and nanofiltration the chlorine demand due to FRA and SRA were further reduced but the reaction rate constants were larger compared to those of sand and GAC filter effluents. This has implications in the formation of disinfection by products (DBPs). If DBPs are assumed to form due to the interactions between chlorine and SRA, then it is possible that the DBP formation potential in the effluents from membrane filtrations could be higher than that in the effluents from granular media filters.     

Evaluating the e ects of granular and membrane filtrations on chlorine demand in drinking water

In this study, chlorine decay experiments were conducted for the raw water from Nakdong River that is treated by Chilseo Water Treatment Plant (CWTP) situated in Haman, Korea as well as the e uents from sand and granular activated carbon (GAC) filters of CWTP and fitted using a chlorine decay model. The model estimated the fast and slow reacting nitrogenous as well as organic/inorganic compounds that were present in the water. It was found that the chlorine demand due to fast and slow reacting (FRA and SRA) organic/inorganic substances was not reduced significantly by sand as well as GAC filters. However, the treated e uents from those filters contained FRA and SRA that are less reactive and had small reaction rate constants. For the e uents from microfiltration, ultrafiltration, and nanofiltration the chlorine demand because FRA and SRA were further reduced but the reaction rate constants were larger compared to those of sand and GAC filter e uents. This has implications in the formation of disinfection by products (DBPs). If DBPs are assumed to form due to the interactions between chlorine and SRA, then it is possible that the DBP formation potential in the e uents from membrane filtrations could be higher than that in the e uents from granular media filters.     

铜管模拟输配系统中氯胺衰减过程与模拟

研究了氯胺在铜管模拟输配系统中的衰减过程,并利用一级反应动力学模型对氯胺衰减规律进行了模拟;考察了pH、初始氯胺浓度等水质条件与流速等水力条件对氯胺衰减速率的影响.结果表明,pH值是影响氯胺衰减速率与金属铜溶出的重要因素,pH越低氯胺衰减越快;提高氯胺初始浓度可加快氯胺衰减速度,也可增加金属铜的溶出量;流速对氯胺衰减速率的影响不大.此外,衰减动力学过程模拟结果表明,采用一级反应动力学模型可以较好地拟合不同条件下的氯胺衰减规律.从而对于工程中不同条件下消毒剂浓度预测具有重要意义.     

Biological stability in drinking water: a regression analysis of influencing factors

Some parameters, such as assimilable organic carbon(AOC), chloramine residual, water temperature, and water residence time, were measured in drinking water from distribution systems in a northern city of China. The measurement results illustrate that when chloramine residual is more than 0.3 mg/L or AOC content is below 50μg/L, the biological stability of drinking water can be controlled.Both chloramine residual and AOC have a good relationship with Heterotrophic Plate Counts( HPC)(Iog value), the correlation coefficient was-0.64 and 0.33, respectively. By regression analysis of the survey data, a statistical equation is presented and it is concluded that disinfectant residual exerts the strongest influence on bacterial growth and AOC is a suitable index to assess the biological stability in the drinking water.     

紫外氯胺组合消毒供水系统中病毒微生物的分布特征

为研究紫外氯胺组合消毒对供水系统中病毒微生物的影响特性,以生产规模紫外氯胺组合消毒供水系统为研究对象,应用宏基因组技术对供水系统中病毒微生物的迁移变化、群落结构和病毒宿主进行了分析.结果表明,紫外氯胺组合消毒工艺能降低病毒物种数（6.13%）和基因丰度（51.97%）,但不能完全去除水中病毒微生物.对比美国环保署（USEPA）以培养法检测的水处理病毒去除率可达99%~99.99%,本研究利用宏基因组技术测得的总病毒去除率只有93.46%,以培养法检测水中病毒存在局限性.Caudovirales（有尾噬菌体目）是整个供水系统中最丰富病毒,对氯胺消毒都具有一定敏感性.Lentivirus（慢病毒属）作为能够感染人和脊椎动物的病毒,对紫外照射和氯胺消毒都具有强抵抗力.该供水系统中最大的病毒宿主是细菌（61.50%）.原水中病毒主要寄生在Synechococcus（聚球藻属）中;出厂水以及管网水中,优势病毒宿主均为Pseudomonas（假单胞菌属）;进入管网后,Pseudomonas aeruginosa（铜绿假单胞菌）宿主病毒基因丰度升高342.62%,应加强关注管网系统病毒微生物风险.紫外氯胺组合消毒工艺比单紫外消毒更有利于病毒宿主的去除（51.97%与0.79%）.     

大环内酯类抗生素在饮用水处理过程中的污染特征及其氯化反应机制

饮用水处理过程中抗生素的污染问题引起了人们的广泛关注.监测了6种大环内酯类抗生素（脱水红霉素、克拉霉素、竹桃霉素、罗红霉素、柱晶白霉素和泰乐菌素）在2座饮用水处理厂中的污染情况,并考察了典型大环内酯类抗生素泰乐菌素在氯化消毒处理过程中的反应特性.结果表明,6种大环内酯类抗生素均能在饮用水处理过程中检出,但是其浓度普遍较低,进出水中的浓度范围分别为0.18~3.97 ng ·L^-1和0.02~1.91 ng ·L^-1.6种大环内酯类抗生素在饮用水处理过程中的去除率相差较大,在18%（竹桃霉素）~100%（脱水红霉素）范围内.6种大环内酯类抗生素在氯化处理过程中降解缓慢,且受水质影响较大.其中,泰乐菌素的氯化降解遵循二级反应动力学模式,测得pH 7.0条件下二级反应动力学速率常数为0.77 L ·（mol ·s）^-1.监测到的9种泰乐菌素氯化降解产物,反应途径主要包括叔胺羟基化、芳族氧化和内酯环环氧化加成等.     

Biostability in distribution systems in one city in southern China：Characteristics, modeling and control strategy

This study investigated the bacterial regrowth in drinking water distribution systems receiving finished water from an advanced drinking water treatment plant in one city in southem China. Thirteen nodes in two water supply zones with different aged pipelines were selected to monitor water temperature, dissolved oxygen （DO）, chloramine residual, assimilable organic carbon （AOC）, and heterotrophic plate counts （HPC）. Regression and principal component analyses indicated that HPC had a strong correlation with chloramine residual. Based on Chick-Watson＇s Law and the Monod equation, biostability curves under different conditions were developed to achieve the goal of HPC 100 CFU/mL. The biostability curves could interpret the scenario under various AOC concentrations and predict the required chloramine residual concentration under the condition of high AOC level. The simulation was also carded out to predict the scenario with a stricter HPC goal （≤50 CFU/mL） and determine the required chloramine residual. The biological regrowth control strategy was assessed using biostability curve analysis. The results indicated that maintaining high chloramine residual concentration was the most practical way to achieve the goal of HPC ≤ 100 CFU/mL. Biostability curves could be a very useful tool for biostability control in distribution systems. This work could provide some new insights towards biostability control in real distribution systems.     

饮用水氯化消毒过程的动力学模型研究进展

饮用水氯化消毒的安全性问题一直是水处理领域的研究重点,其氯化消毒过程动力学过程模型的建立,对于饮用水含氯量监测、评价及生成消毒副产物的控制具有重要意义。本文概述了饮用水氯化消毒过程的有关动力学模型研究现状及进展,从模型依据的机理和表达形式等方面分析了饮用水氯化消毒过程的动力学模型研究进展,介绍了广泛应用的几种模型,如Clark自由氯衰减模型、Valentine氯胺衰减模型等,通过对相关模型的原理、异同点、优缺点、适用性的对比及对影响模型的因素分析,对氯化消毒过程中动力学模型的今后发展趋势作了展望。     

基于呼吸计量法的异养菌动力学参数优化估计

利用双水解模型对活性污泥数学模型(ASM)进行改进,并通过呼吸计量试验和非线性最优化算法建立了异养菌动力学参数的优化估计方案.该方案在上海2个污水处理厂的测定结果表明,经优化求解后,ASM改进模型能够准确模拟批式试验的耗氧速率曲线.26℃下,曲阳厂和白龙港厂活性污泥的异养菌衰减系数分别为0.58,0.55d-1,异养菌最大比增长速率常数(均约为4d-1)和半饱和常数(2.00,2.36mg/L)较为接近.白龙港厂进水中慢速可生物降解有机物的水解速率明显高于曲阳厂,这是由于长距离管道输送显著降低水解组分的粒径所致.