Impact of combining chlorine dioxide and chlorine on DBP formation in simulated indoor swimming pools

The main objective of this study was to assess the combined use of chlorine dioxide (ClO2) and chlorine (Cl2) on the speciation and kinetics of disinfection by-product (DBP) formation in swimming pools using synthetic pool waters prepared with a body fluid analog (BFA) and/or fresh natural water. At 1:25 (mass ratio) of ClO2 to Cl2, there was no significant reduction in the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) for both BFA solution and natural water compared to the application of Cl2 alone. When the mass ratio of ClO2 to Cl2 increased to 1:1, substantial decreases in both THMs and HAAs were observed in the natural water, while there was almost no change of DBP formations in the BFA solution. Haloacetonitriles and halonitromethanes levels in both water matrices remained similar. In the presence of bromide, the overall DBP formation increased in both BFA solution and natural water. For the DBP formation kinetics, after 72 hr of contact time, very low formation of THMs and HAAs was observed for the use of ClO2 only. Compared to Cl2 control, however, applying the 1:1 mixture of ClO2/Cl2 reduced THMs by > 60% and HAAs by > 50%. Chlorite was maintained below 1.0 mg/L, while the formation of chlorate significantly increased over the reaction time. Finally, in a bench-scale indoor pool experiment, applying ClO2 and Cl2 simultaneously produced less THMs compared to Cl2 control and kept chlorite at < 0.4 mg/L, while HAAs and chlorate accumulated over 4-week operation period.     

Review on fate of chlorine during thermal processing of solid wastes

Chlorine(Cl) is extensively present in solid wastes, causing significant problems during the thermal conversion of waste to energy or fuels, by combustion, gasification or pyrolysis.This paper introduces the analytical methods for determining the Cl content in solid materials and presents the concentrations of Cl in various types of wastes, as reported in literature. Then, it provides a comprehensive analysis on the Cl emission behavior and Cl species formed during the thermal processing of the inorganic and organic Cl sources. The challenges resulted from the reactions between the formed Cl species and the ferrous metals, the heavy metals and the organic matters are summarized and discussed, e.g., high temperature corrosion, heavy metal evaporation and dioxin formation. The quality degradation of products(oil, char and syngas) by Cl is analyzed. Finally, the available controlling methods of Cl emission, including pre-treatment(water washing, sorting,microwave irradiation and stepwise pyrolysis) and in-furnace(absorbents, co-treatment and catalysts) methods are assessed.     

Comparisons of the film peeling from the composite oxides of quartz sand filters using ozone, hydrogen peroxide and chlorine dioxide

To solve the problem of shortened backwashing intervals in groundwater plants, several disinfectants including ozone (O₃), hydrogen peroxide (H₂O₂) and chlorine dioxide (ClO₂) were examined to peel off the film from the quartz sand surface in four pilot-scale columns. An optimized oxidant dosage and oxidation time were determined by batch tests. Subsequently, the optimized conditions were tested in the four pilot-scale columns. The results demonstrated that the backwashing intervals increased from 35.17 to 54.33 (H₂O₂) and to 53.67 hr (ClO₂) after the oxidation treatments, and the increase of backwashing interval after treatment by O₃ was much less than for the other two treatments. Interestingly, the treatment efficiency of filters was not affected by O₃ or H₂O₂ oxidation; but after oxidation by ClO₂, the treatment efficiency was deteriorated, especially the ammonia removal (from 96.96% to 24.95%). The filter sands before and after the oxidation were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. Compared with the oxidation by O₃ and H₂O₂, the structures on the surface of filter sands were seriously damaged after oxidation by ClO₂. The chemical states of manganese on the surfaces of those treated sands were only changed by ClO₂. The damage of the structures and the change of the chemical states of manganese might have a negative effect on the ammonia removal. In summary, H₂O₂ is a suitable agent for film peeling.     

Characterization of halogenated DBPs and identification of new DBPs trihalomethanols in chlorine dioxide treated drinking water with multiple extractions

Chlorine dioxide(ClO_2) is a widely used alternative disinfectant due to its high biocidal efficiency and low-level formation of trihalomethanes and haloacetic acids. A major portion of total organic halogen(TOX), a collective parameter for all halogenated DBPs, formed in ClO_2-treated drinking water is still unknown. A commonly used pretreatment method for analyzing halogenated DBPs in drinking water is one-time liquid–liquid extraction(LLE), which may lead to a substantial loss of DBPs prior to analysis. In this study, characterization and identification of polar halogenated DBPs in a ClO_2-treated drinking water sample were conducted by pretreating the sample with multiple extractions. Compared to one-time LLE, the combined four-time LLEs improved the recovery of TOX by 2.3 times. The developmental toxicity of the drinking water sample pretreated with the combined four-time LLEs was 1.67 times higher than that pretreated with one-time LLE.With the aid of ultra-performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry, a new group of polar halogenated DBPs, trihalomethanols,were detected in the drinking water sample pretreated with multiple extractions; two of them,trichloromethanol and bromodichloromethanol, were identified with synthesized standard compounds. Moreover, these trihalomethanols were found to be the transformation products of trihalomethanes formed during ClO_2disinfection. The results indicate that multiple LLEs can significantly improve extraction efficiencies of polar halogenated DBPs and is a better pretreatment method for characterizing and identifying new polar halogenated DBPs in drinking water.     

Effects of reductive inorganics and NOM on the formation of chlorite in the chlorine dioxide disinfection of drinking water

Chlorine dioxide (ClO₂) disinfection usually does not produce halogenated disinfection by-products, but the formation of the inorganic by-product chlorite (ClO₂^–) is a serious consideration. In this study, the ClO₂^– formation rule in the ClO₂ disinfection of drinking water was investigated in the presence of three representative reductive inorganics and four natural organic matters (NOMs), respectively. Fe²⁺ and S^2– mainly reduced ClO₂ to ClO₂^– at low concentrations. When ClO₂ was consumed, the ClO₂^– would be further reduced by Fe²⁺ and S^2–, leading to the decrease of ClO₂^–. The reaction efficiency of Mn²⁺ with ClO₂ was lower than that of Fe²⁺ and S^2–. It might be the case that MnO₂ generated by the reaction between Mn²⁺ and ClO₂ had adsorption and catalytic oxidation on Mn²⁺. However, Mn²⁺ would not reduce ClO₂^–. Among the four NOMs, humic acid and fulvic acid reacted with ClO₂ actively, followed by bovine serum albumin, while sodium alginate had almost no reaction with ClO₂. The maximum ClO₂^– yields of reductive inorganics (70%) was higher than that of NOM (around 60%). The lower the concentration of reductive substances, the more ClO₂^– could be produced by per unit concentration of reductive substances. The results of the actual water samples showed that both reductive inorganics and NOM played an important role in the formation of ClO₂^– in disinfection.     

饮水消毒的变革——新型消毒剂二氧化氯取代液氯的前景

本文论述了传统饮水消毒剂液氯消毒引起的问题 ,即可产生致癌致畸变的三卤甲烷类化合物 ;介绍了新型消毒剂二氧化氯消毒的优点及取代氯的前景。     

沿海城市灰霾天气与海盐氯损耗机制的关系

随着经济规模迅速扩大和城市化进程加快,大气气溶胶污染日趋严重,由细粒子气溶胶造成的能见度恶化事件越来越多,这些人类活动排放的污染物,可形成灰霾天气致使能见度下降。尤其值得注意的是沿海城市灰霾天气增长较快,沿海城市灰霾天气增多与海盐气溶胶粒子的氯损耗机制关系密切。我国30年前在粉尘污染时代建立的空气质量评价体系,已经远远不能描述新型复合空气污染类型,尤其是不能描述细粒子污染的情况,能见度的恶化主要与细粒子的浓度关系比较大,而与气溶胶的质量浓度关系不大。能见度与PM2.5尤其是PM1有非常好的关系,因而目前用能见度来描述灰霾天气是最好的指标。     

二氧化氯的稳定性研究

分别讨论了在一定条件下，通常意义的二氧化氯水溶液与稳定的二氧化氯水溶液的降解速率，同时，研究了ｐＨ值对二氧化氯水溶液稳定性的影响．     

微污染水源水ClO2消毒中ClO-2的来源与控制技术

综述了ClO2消毒微污染水源水的主要无机副产物ClO2-的来源,ClO2-的产生前控制和生成后去除等方法,以减少ClO2-在饮用水中的含量。并提出了氯气氧化控制饮用水中ClO2-含量的新方法。     

二氧化氯的稳定和活化方法研究

采用 Na2 CO3和 H2 O2 作为 Cl O2 的稳定剂并得出最佳配比为 2∶ 3 (摩尔比 ) ,以醋酸、盐酸和柠檬酸作为活化剂进行活化试验 ,得到活化剂用量和活化时间对活化浓度的关系。     

自来水厂液氯贮罐氯气泄漏事故风险评价初探

针对自来水厂液氯贮罐发生泄露的事故风险,应用烟团模式进行了液氯泄露后污染物浓度预测,并根据预测浓度从环境标准和化学物质危险度两方面进行了事故风险评价探讨,得出致死风险.     

高氯离子废水COD的吸收测定方法探讨

本法基于可定量测定K2Cr2O7和Cl-的反应产物Cl2这一原理,在用吸收装置吸收Cl2后,用碘量法测定余氯,从而消除氯离子的干扰.本法具有较高的准确度和精密度.     

二氧化氯制备方法研究进展

二氧化氯是一种具有高氧化性和强消毒性的化合物,介绍了二氧化氯制备的化学法、电解法以及电化学法,并对几种工艺方法的优缺点进行了分析和比较,适合工业化生产的工艺主要是化学法中的氯酸钠法和亚氯酸钠法。     

二氧化氯处理印染废水的研究

二氧化氯是一种性能很好的氧化剂和杀菌消毒剂,本文介绍了二氧化氯的化学性质及在印染废水中的应用,表明二氧化氯与有机物反应具有选择性.     

工业尾气中氯含量测定方法的探讨

选用甲基登分光光度法测定工业尾中氯含量，其优点是试药得，显色稳定，定量范围广，操作简便，分析快速，成本低，同时用相比例法计算氯的含量，结果令人满意。     

我国工业区布局与城市规划建设间存在矛盾的分析

针对我国东部某沿海城市化工园区的建设和规划情况,分析目前的环境风险水平与周边地区建设发展规划存在的矛盾,并提出应尽快开展区域规划环评的建议。     

苯磺酸法制备二氧化氯的研究

亚氯酸钠-苯磺酸制备二氧化氯的方法进行了系统研究,通过正交试验确定了最佳反应条件,并考察了反应时间和反应温度对二氧化氯浓度和纯度的影响。该法反应迅速,可以制备出高纯二氧化氯,反应易于控制,苯磺酸可作为快速释放型二氧化氯固体制剂的活化剂。     

新型消毒剂二氧化氯的开发与应用

从保护饮用水的安全与卫生出发，介绍了替代液氯和其它氯制品的新型消毒剂——二氧化氯所具有的优点，特别是可有效抑制三卤代烷（ＴＨＭＳ）的产生；讨论了二氧化氯的最佳投放方式及ＣｌＯ－２和ＣｌＯ－３等有害副产物生成的机理和控制方法     

化学法ClO2发生器在沈阳市医院污水处理中的应用

介绍了二氧化氯杀菌的性能特点,分析讨论二氧化氯杀菌的机理,化学法二氧化氯发生器在沈阳市医院污水中的推广应用,并进行了技术指标、经济效益评价。