The impact of iodinated X-ray contrast agents on formation and toxicity of disinfection by-products in drinking water

The presence of iodinated X-ray contrast media (ICM) in source waters is of high concern to public health because of their potential to generate highly toxic disinfection by-products (DBPs). The objective of this study was to determine the impact of ICM in source waters and the type of disinfectant on the overall toxicity of DBP mixtures and to determine which ICM and reaction conditions give rise to toxic by-products. Source waters collected from Akron, OH were treated with five different ICMs, including iopamidol, iopromide, iohexol, diatrizoate and iomeprol, with or without chlorine or chloramine disinfection. The reaction product mixtures were concentrated with XAD resins and the mammalian cell cytotoxicity and genotoxicity of the reaction mixture concentrates was measured. Water containing iopamidol generated an enhanced level of mammalian cell cytotoxicity and genotoxicity after disinfection. While chlorine disinfection with iopamidol resulted in the highest cytotoxicity overall, the relative iopamidol-mediated increase in toxicity was greater when chloramine was used as the disinfectant compared with chlorine. Four other ICMs (iopromide, iohexol, diatrizoate, and iomeprol) expressed some cytotoxicity over the control without any disinfection, and induced higher cytotoxicity when chlorinated. Only iohexol enhanced genotoxicity compared to the chlorinated source water.     

污水氯、二氧化氯消毒处理中水质及毒性变化的比较

分别从水质和毒性2方面比较了氯、二氧化氯消毒对污水的影响.结果表明:在水质特性方面,氯消毒对污水色度影响不大,而二氧化氯消毒明显降低了污水的色度;氯、二氧化氯消毒前后污水的DOC基本没有变化;氯消毒后污水的UV₂₃₀明显增加,二氧化氯消毒后污水的UV₂₃₀略有降低,当二者投加量均为30mg/L时,氯消毒使污水的UV₂₃₀增加约0.7cm^-1,二氧化氯消毒使污水的UV₂₃₀降低约0.05cm^-1.在毒性生成方面,氯、二氧化氯消毒产生的急性毒性均随消毒剂投加量的增加而增大,氯消毒产生的急性毒性明显高于二氧化氯消毒;氯消毒在一定程度上增大了污水的遗传毒性,而二氧化氯消毒在一定程度上降低了污水的遗传毒性.     

TIC-Tox: A preliminary discussion on identifying the forcing agents of DBP-mediated toxicity of disinfected water

The disinfection of drinking water is a major public health achievement; however, an unintended consequence of disinfection is the generation of disinfection by-products (DBPs). Many of the identified DBPs exhibit in vitro and in vivo toxicity, generate a diversity of adverse biological effects, and may be hazards to the public health and the environment. Only a few DBPs are regulated by several national and international agencies and it is not clear if these regulated DBPs are the forcing agents that drive the observed toxicity and their associated health effects. In this study, we combine analytical chemical and biological data to resolve the forcing agents associated with mammalian cell cytotoxicity of drinking water samples from three cities. These data suggest that the trihalomethanes (THMs) and haloacetic acids may be a small component of the overall cytotoxicity of the organic material isolated from disinfected drinking water. Chemical classes of nitrogen-containing DBPs, such as the haloacetonitriles and haloacetamides, appear to be the major forcing agents of toxicity in these samples. These findings may have important implications for the design of epidemiological studies that primarily rely on the levels of THMs to define DBP exposure among populations. The TIC-Tox approach constitutes a beginning step in the process of identifying the forcing agents of toxicity in disinfected water.     

Chloramination of wastewater effluent: Toxicity and formation of disinfection byproducts

The reclamation and disinfection of waters impacted by human activities (e.g., wastewater effluent discharges) are of growing interest for various applications but has been associated with the formation of toxic nitrogenous disinfection byproducts (N-DBPs). Monochloramine used as an alternative disinfectant to chlorine can be an additional source of nitrogen in the formation of N-DBPs. Individual toxicity assays have been performed on many DBPs, but few studies have been conducted with complex mixtures such as wastewater effluents. In this work, we compared the cytotoxicity and genotoxicity of wastewater effluent organic matter (EfOM) before and after chloramination. The toxicity of chloraminated EfOM was significantly higher than the toxicity of raw EfOM, and the more hydrophobic fraction (HPO) isolated on XAD-8 resin was more toxic than the fraction isolated on XAD-4 resin. More DBPs were also isolated on the XAD-8 resin. N-DBPs (i.e., haloacetonitriles or haloacetamides) were responsible for the majority of the cytotoxicity estimated from DBP concentrations measured in the XAD-8 and XAD-4 fractions (99.4% and 78.5%, respectively). Measured DBPs accounted for minor proportions of total brominated and chlorinated products, which means that many unknown halogenated compounds were formed and can be responsible for a significant part of the toxicity. Other non-halogenated byproducts (e.g., nitrosamines) may contribute to the toxicity of chloraminated effluents as well.     

Zebrafish embryo toxicity of 15 chlorinated, brominated, and iodinated disinfection by-products

Disinfection to protect human health occurs at drinking water and wastewater facilities through application of non-selective oxidants including chlorine. Oxidants also transform organic material and form disinfection by-products (DBPs), many of which are halogenated and cyto- and genotoxic. Only a handful of assays have been used to compare DBP toxicity, and researchers are unsure which DBP(s) drive the increased cancer risk associated with drinking chlorinated water. The most extensive data set employs an in vitro model cell, Chinese hamster ovary cells. Traditionally, most DBP research focuses on the threat to human health, but the effects on aquatic species exposed to DBPs in wastewater effluents remain ill defined. We present the developmental toxicity for 15 DBPs and a chlorinated wastewater to a model aquatic vertebrate, zebrafish. Mono-halogenated DBPs followed the in vivo toxicity rank order: acetamides > acetic acids > acetonitriles ~ nitrosamines, which agrees well with previously published mammalian in vitro data. Di- and tri-halogenated acetonitriles were more toxic than their mono-halogenated analogues, and bromine- and iodine-substituted DBPs tended to be more toxic than chlorinated analogues. No zebrafish development effects were observed after exposure to undiluted or non-concentrated, chlorinated wastewater. We find zebrafish development to be a viable in vivo alternative or confirmatory assay to mammalian in vitro cell assays.     

二氧化氯消毒前后污水毒性的变化及消毒条件的影响

采用发光细菌试验和umu试验,分别考察了二氧化氯投加量和反应时间对污水二氧化氯消毒后急性毒性和遗传毒性变化的影响.结果表明,随着二氧化氯消毒剂投加量的增加,消毒后水样的急性毒性不断增大,但遗传毒性逐渐减小后趋于稳定.随着反应时间的延长,二氧化氯的消耗量不断增大,消毒后水样的急性毒性先增大后减小,遗传毒性逐渐减小后趋于稳定.由于消毒条件对污水急性毒性和遗传毒性有着不同的影响,说明污水中产生急性毒性和产生遗传毒性的物质不同,对于某一种污水,通过控制消毒条件可以使消毒后污水的急性毒性和遗传毒性都较低.     

饮用水源中三卤甲烷含量及与遗传毒性的相关性研究

通过对某市饮用水源中不同点位的三卤甲烷浓度测试,同时采用SOS/ Umu 试验对水体进行生物遗传毒性分析,结果表明:采用液氯消毒工艺的地表水厂在消毒后水样和用户端水样中检出的三卤甲烷含量较高,而采用二氧化氯消毒的地下水厂的出水中挥发性有机物仅略有上升;进行三卤甲烷浓度和生物遗传毒性之间的相关性分析得知,三卤甲烷和间接遗传毒性的相关性较好.     

Sequential use of ultraviolet light and chlorine for reclaimed water disinfection

Several disinfection processes of ultraviolet (UV), chlorine or UV followed by chlorine were investigated in municipal wastewater according to the inactivation of Escherichia coli, Shigella dysenteriae and toxicity formation. The UV inactivation of the tested pathogenic bacteria was not affected by the quality of water. It was found that the inactivated bacteria were obviously reactivated after one day in dark. Fluorescent light irradiation increased the bacteria repair. The increase of UV dosage could cause more damage to bacteria to inhibit bacteria self-repair. No photoreactivation was detected when the UV dose was up to 80 mJ/cm² for E. coli DH5αup, and 23 mJ/cm² for S. dysenteriae. Nevertheless, sequential use of 8 mJ/cm² of UV and low concentration of chlorine (1.5 mg/L) could effectively inhibit the photoreactivation and inactivate E. coli below the detection limits within seven days. Compared to chlorination alone, the sequential disinfection decreased the genotoxicity of treated wastewater, especially for the sample with high NH₃-N concentration.     

污水二氧化氯和氯消毒过程中遗传毒性的变化及氨氮的影响

采用umu遗传毒性测试方法考察了二氧化氯和氯消毒对几种城市污水生物处理出水遗传毒性的影响,发现当二氧化氯消毒剂从0　mg/L增加到30　mg/L时,几种污水的遗传毒性均先迅速降低后趋于稳定,而当氯消毒剂从0　mg/L增加到30　mg/L时,几种污水的遗传毒性的变化规律不同.进一步研究氨氮对污水消毒过程中遗传毒性变化的影响,发现氨氮对污水二氧化氯消毒过程中遗传毒性的变化规律没有显著影响,但是对污水氯消毒过程中遗传毒性的变化规律却起着至关重要的作用.当氨氮含量较小（<10～20　mg/L）时,污水氯消毒后的遗传毒性小于消毒前;当氨氮含量较大时（>10～20　mg/L）,污水氯消毒后的遗传毒性大于消毒前.     

氯/氯胺和紫外顺序消毒对管网抗性基因的去除

为探究供水系统中氯/氯胺与低压紫外顺序消毒对抗生素抗性基因(ARGs)分布特征的影响,采用生物膜反应器模拟供水管网,对管网出水和生物膜进行60mJ/cm²低压紫外线(254nm)消毒,并利用高通量定量PCR技术检测模拟管网进、出水及生物膜内的典型ARGs和遗传原件(MGEs).结果表明,管网反应器运行150d,氯和氯胺管网出水ARGs总相对丰度分别为0.13和0.137,生物膜ARGs分别为2.45和0.277,表明供水管网中低剂量的氯或氯胺可有效降低水相和生物膜相中ARGs的相对丰度达90%,且氯胺消毒对生物膜中的ARGs控制作用更显著.氯和氯胺消毒后管网出水再经低压紫外线照射后,ARGs相对丰度分别为0.0682和0.0537,管网生物膜中ARGs的相对丰度分别为2.01和0.194.ARGs与MGEs间的相关性发生显著变化,转座子与strB和mepA的相关性增强,与ermX和tetM相关性减弱,而整合子与acrF、cmlA1-01、oprJ及tolC-01的相关性增强.研究表明,将紫外线消毒工艺设置在用水终端可以显著降低氯和氯胺管网水中ARGs丰度,但对管网生物膜中的ARGs影响较小.     

不同消毒方式对饮用水生物活性炭出水消毒效果的对比研究

针对水厂生物活性炭深度处理工艺可能产生的细菌泄露问题,采用上海徐泾水厂生物活性炭出水,通过对异养菌平板计数和卤代烃气相色谱检测分析,比较了次氯酸钠和氯胺2种消毒方式对出厂水水质安全保障的效果.在水温30℃下,采用NaClO消毒剂进行消毒处理时,初始余氯值达到1.84 mg/L、接触30 min即可保障灭活率lg(N0/...     

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。     

Change in genotoxicity of wastewater during chlorine dioxide and chlorine disinfections and the influence of ammonia nitrogen

The effects of chlorine dioxide and chlorine disinfections on the genotoxicity of different biologically treated sewage wastewater samples were studied by umu-test. The experiment results showed that when chlorine dioxide dosage was increased from 0 to 30 mg/L, the genotoxicity of wastewater first decreased rapidly and then tended to be stable, while when the chlorine dosage was increased from 0 to 30 mg/L, the genotoxicity of wastewater changed diversely for different samples. It was then found that ammonia nitrogen did not affect the change of genotoxicity during chlorine dioxide disinfection of wastewater, while it greatly affected the change of genotoxicity during chlorine disinfection of wastewater. When the concentration of ammonia nitrogen was low (< 10–20 mg/L), the genotoxicity of wastewater decreased after chlorine disinfection, and when the concentration of ammonia nitrogen was high (> 10–20 mg/L), the genotoxicity of wastewater increased after chlorine disinfection.     

Formation and control of disinfection byproducts and toxicity during reclaimed water chlorination: A review

Chlorination is essential to the safety of reclaimed water; however, this process leads to concern regarding the formation of disinfection byproducts (DBPs) and toxicity. This study reviewed the formation and control strategies for DBPs and toxicity in reclaimed water during chlorination. Both regulated and emerging DBPs have been frequently detected in reclaimed water during chlorination at a higher level than those in drinking water, indicating they pose a greater risk to humans. Luminescent bacteria and Daphnia magna acute toxicity, anti-estrogenic activity and cytotoxicity generally increased after chlorination because of the formation of DBPs. Genotoxicity by umu-test and estrogenic activity were decreased after chlorination because of destruction of toxic chemicals. During chlorination, water quality significantly impacted changes in toxicity. Ammonium tended to attenuate toxicity changes by reacting with chlorine to form chloramine, while bromide tended to aggravate toxicity changes by forming hypobromous acid. During pretreatment by ozonation and coagulation, disinfection byproduct formation potential (DBPFP) and toxicity formation potential (TFP) occasionally increase, which is accompanied by DOC removal; thus, the decrease of DOC was limited to indicate the decrease of DBPFP and TFP. It is more important to eliminate the key fraction of precursors such as hydrophobic acid and hydrophilic neutrals. During chlorination, toxicities can increase with the increasing chlorine dose and contact time. To control the excessive toxicity formation, a relatively low chlorine dose and short contact time were required. Quenching chlorine residual with reductive reagents also effectively abated the formation of toxic compounds.     

CHO cell cytotoxicity and genotoxicity analyses of disinfection by-products: An updated review

The disinfection of drinking water is an important public health service that generates high quality, safe and palatable tap water. The disinfection of drinking water to reduce waterborne disease was an outstanding public health achievement of the 20th century. An unintended consequence is the reaction of disinfectants with natural organic matter, anthropogenic contaminants and bromide/iodide to form disinfection by-products (DBPs). A large number of DBPs are cytotoxic, neurotoxic, mutagenic, genotoxic, carcinogenic and teratogenic. Epidemiological studies demonstrated low but significant associations between disinfected drinking water and adverse health effects. The distribution of DBPs in disinfected waters has been well defined by advances in high precision analytical chemistry. Progress in the analytical biology and toxicology of DBPs has been forthcoming. The objective of this review was to provide a detailed presentation of the methodology for the quantitative, comparative analyses on the induction of cytotoxicity and genotoxicity of 103 DBPs using an identical analytical biological platform and endpoints. A single Chinese hamster ovary cell line was employed in the assays. The data presented are derived from papers published in the literature as well as additional new data and represent the largest direct quantitative comparison on the toxic potency of both regulated and emerging DBPs. These data may form the foundation of novel research to define the major forcing agents of DBP-mediated toxicity in disinfected water and may play an important role in achieving the goal of making safe drinking water better.     

基于A2/O处理工艺的生活污水的成组生物毒性评价

为了更加准确评估城市生活污水的综合生物毒性以及处理工艺对污水毒性的削减状况,本研究通过发光菌急性毒性、遗传毒性、雌激素活性检测方法对A~2/O工艺处理前后污水的毒性进行评价,同时通过斑马鱼暴露实验分析污水和回用水对水生生物内分泌干扰效应的作用模式.结果表明,污水厂进水具有较强的急性毒性、遗传毒性以及雌激素活性,水质较差.经二级生物处理后,上述毒性显著性降低,污水厂出水水质提高.但污水出水雌二醇当量为1.89 ng·L-1,仍可能会对受纳水体的水生生物产生潜在危害.浓缩2.5倍的水样导致雄性斑马鱼肝脏的卵黄原蛋白基因(vtg1)和雌激素受体基因(esr1)的表达水平显著上升,由此可以得出污水可通过干扰目的基因的表达来调控水生生物的内分泌活动.而esr1基因在肝脏的表达被抑制说明污水可能具有抗雌激素作用,同时反映进行生物毒性效应分析时应从多个组织或器官考虑,以获得比较全面的信息.     

我国污水排放余氯限值规定及监测、控制方法研究进展

含氯消毒剂在我国污水处理过程中普遍使用,其在灭活病原微生物的同时会增加出水余氯浓度,对生态环境造成影响. 新冠肺炎疫情防控期间,含氯消毒剂的使用量大幅增加,余氯问题更加凸显. 为对我国水污染物排放标准中余氯限值的制定和修订提出可参考的建议,比较了国内外现有各类水污染物排放标准中的余氯限值,并总结分析余氯监测及控制方法的研究进展. 结果表明:①我国多项水污染物排放标准包含出水中余氯限值规定,如《医疗机构水污染物排放标准》规定采用氯化消毒的医院污水直接排放总余氯浓度应低于0.5 mg/L,北京、上海等地的地方污水综合排放标准规定直接排放的污水总余氯浓度应低于0.5 mg/L,但我国城镇污水处理厂消毒尾水中的余氯至今仍缺乏标准管控. ②我国余氯测定标准中规定的余氯监测方法为N,N-二乙基-1,4-苯二胺(DPD)滴定法和分光光度法,近年来余氯的仪器分析法和传感器法也得到迅速发展. ③余氯控制方法包括以二氧化硫和亚硫酸盐为脱氯剂的化学脱氯法、活性炭脱氯法和还原性金属材料脱氯法等. 因此,建议我国在未来城镇污水处理厂排放标准中考虑纳入余氯限值规定,并关注余氯监测及控制方法的发展与规范制定.      

医疗污水处理系统中污泥处理工程实践

分析了国内医疗污水处理系统中污泥消毒处理的现状和必要性,并对常用的几种污泥消毒处理的方法进行了比较,提出在不同的环境条件下,使用C IO2和石灰作消毒剂对医疗污水处理系统中污泥进行消毒的工艺路线。工程实践表明,此工艺稳定可靠,运行成本低廉,较好地做到经济和环境效益的统一。     

Evaluation of the infectivity, gene and antigenicity persistence of rotaviruses by free chlorine disinfection

The effects of free chlorine disinfection of tap water and wastewater effluents on the infectivity, gene integrity and surface antigens of rotaviruses were evaluated by a bench-scale chlorine disinfection experiments. Plaque assays, integrated cell culture-quantitative RT-PCR (ICC-RT-qPCR), RT-qPCR, and enzyme-linked immunosorbent assays (ELISA), respectively, were used to assess the influence of the disinfectant on virus infectivity as well as genetic and antigenic integrity of simian rotavirus SA11 as a surrogate for human rotaviruses. The ICC-RT-qPCR was able to detect rotaviruses survival from chlorine disinfection at chlorine dose up to 20 mg/L (60 min contact), which suggested a required chlorine dose of 5 folds (from 1 to 5 mg/L) higher than that indicated by the plaque assay to achieve 1.8 log₁₀ reductions in tap water with 60 min exposing. The VP7 gene was more resistant than the infectivity and existed at chlorine dose up to 20 mg/L (60 min contact), while the antigencity was undetectable with chlorine dose more than 5 mg/L (60 min contact). The water quality also impacted the inactivation efficiencies, and rotaviruses have a relatively higher resistant in secondary effluents than in the tap water under the same chlorine disinfection treatments. This study indicated that rotaviruses have a higher infectivity, gene and antigencity resistance to chlorine than that previously indicated by plaque assay only, which seemed to underestimate the resistance of rotaviruses to chlorine and the risk of rotaviruses in environments. Present results also suggested that re-evaluation of resistance of other waterborne viruses after disinfections by more sensitive infectivity detection method (such as ICC-RT-qPCR) may be necessary, to determine the adequate disinfectant doses required for the inactivation of waterborne viruses.     

曝气生物滤池处理医院污水的实验应用研究

采用曝气生物滤池与二氧化氯相结合的工艺处理医院污水。主要对曝气生物滤池去除COD、氨氮的效果进行了研究,并且在实际应用中证明了用这种相结合的处理方法具有一次投资小、运行费用低、年经济效益高等优点,有良好的技术经济性。