供水管网生物膜有机物的二氯乙腈与二氯乙酰胺生成特性

在饮用水输配系统中,来源于管壁生物膜的有机物可能耗氯并生成消毒副产物(DBPs),包括二氯乙腈(DCAN)与二氯乙酰胺(DCAcAm)等高毒性含氮DBPs(N-DBPs).研究考察管网常见的细菌与其胞外聚合物(EPS)以及模拟管壁生物膜氯化与氯胺化后DCAN与DCAcAm的生成,并与天然有机物(NOM)和水源水有机物进行比较.结果显示,铜绿假单胞菌、恶臭假单胞菌与藤黄微球菌与氯反应生成的DCAN、DCAcAm浓度分别为1.48～2.02、0.21～0.38μg·mg~(-1)(mg~(-1)以TOC计),高于同反应条件下NOM的生成量;相比于氯化反应,3株细菌细胞氯胺化生成的DCAN与DCAcAm浓度明显更低.3株菌的EPS也是氯与氯胺化反应生成DCAN与DCAcAm的前体物,且其氯胺化反应生成的DCAcAm浓度高于氯化反应生成的.与NOM、水源水相比,模拟管壁生物膜氯化后生成的N-DBPs与三氯甲烷(TCM)浓度比更高,表明生物膜有机物比NOM与水源水有机物更倾向生成DCAN与DCAcAm类N-DBPs,且模拟管壁生物膜氯胺化的DCAcAm生成量高于氯化反应的,说明管壁生物膜有机物是供水管网系统中DCAN与DCAcAm类N-DBPs的重要前体物.     

生物过滤饮用水深度处理:机遇与挑战

源水水质的恶化给传统的饮用水处理工艺带来了挑战.生物过滤是饮用水消毒输配之前管理、维护及增强颗粒滤料表面生物活性以去除有机和无机物的过程.由于具有高效、低成本等优点，生物过滤在饮用水深度处理工艺中逐渐得到广泛的应用.本文综述了生物过滤在饮用水处理过程中对水中溶解性有机质（消毒副产物前体物）的去除、微量污染物的削减、嗅味化合物及氨氮的去除等.此外，针对生物过滤在水深度处理过程中存在的问题，本文详细讨论了含氮消毒副产物前体物的生成、低温下生物过滤效能下降等挑战，并提出了今后需要研究的问题.     

J市饮用水氯消毒副产物分析及其健康风险评价

J市位于太湖下游,其水源水质受上游和自身工农业发展的影响,有机物和氨氮浓度较高,氯消毒副产物及其引发的健康风险广泛受到关注.2012年5、8、10月以及2013年1月采样,使用气相色谱法分析了J市饮用水中4种三卤甲烷和5种卤乙酸的含量,发现自来水中三卤甲烷浓度占三卤甲烷与卤乙酸总和的88.1%以上,5月、8月和次年1月浓度较高(分别为39.34、50.37和28.02μg.L-1),10月浓度(19.19μg.L-1)较低,远高于卤乙酸的浓度(2.58～4.02μg.L-1).自来水煮沸3min后,三卤甲烷可去除92.3%以上,但卤乙酸会大幅度增加.基于EPA推荐的健康风险评价模型对经口摄取途径时氯消毒副产物的致癌和非致癌风险进行计算,发现化学致癌物质的健康风险为3.1×10-6～7.3×10-6,高于可接受风险水平1×10-6;煮沸后致癌物质的健康风险大幅度降低至7.9×10-7,低于可接受风险水平.煮沸后非致癌氯消毒副产物的健康风险由2.1×10-11显著升高至3.4×10-9,未超过10-5的风险管理参考值.     

Chlorination Byproducts in Drinking Water Produced from Thermal Desalination in United Arab Emirates

Oil activities in the Arabian Gulf can potentially affect the quality of the intake water available for coastal desalination plants. This paper addresses such situation by investigating the quality of intake water and desalinated water produced by a desalination plant located near a coastal industrial complex in United Arab Emirates (UAE). Analyses of the organic compounds on the intake seawater reported non-detected levels in most samples for the three tested organic groups; namely Polyaromatic Hydrocarbons (PAHs), Phenols, and Polychlorinated Biphenyls (PCBs). Trihalomethanes (THMs) and Haloacetic Acids (HAAs) were also tracked in the intake sea water, throughout the desalination processes, and in the final produced drinking water, to evaluate the undertaken pre- and post chlorination practices. The levels of considered Chlorination Byproducts (CBPs) were mostly found below the permissible international limits with few exceptions showing tangible levels of bromoform in the intake seawater and in the final produced drinking water as well. Lab-controlled experiments on the final produced distillate showed little contribution of its blending with small percentage of seawater upon the formation of trihalomethane and in particular, bromoform. Such results indicate that the organic precursors originated in the seawater are responsible for bromoform formation in the final distillate.     

Levels and risk assessment of chemical contaminants in byproducts for animal feed in Denmark

With aim to provide information on chemical contaminants in byproducts in animal feed, the data from an official control by the Danish Plant Directorate during 1998–2009, were reviewed and several samples of citrus pulp and dried distillers grains with solubles (DDGS) were additionally collected for analysis and risk assessment. The levels of contaminants in the samples from the official control were below maximum limits from EU regulations with only a few exceptions in the following groups; dioxins and dioxin-like polychlorobiphenyls (PCBs) in fish-containing byproducts and dioxins in vegetable and animal fat, hydrogen cyanide in linseed, and cadmium in sunflowers. The levels of pesticides and mycotoxins in the additionally collected samples were below maximum limits. Enniatin B (ENN B) was present in all DDGS samples. The hypothetical cases of carry-over of contamination from these byproducts were designed assuming total absorption and accumulation of the ingested contaminant in meat and milk and high exposure (a byproduct formed 15–20% of the feed ration depending on the species). The risk assessment was refined based on literature data on metabolism in relevant animal species. Risk assessment of contaminants in byproducts is generally based on a worst-case approach, as data on carry-over of a contaminant are sparse. This may lead to erroneous estimation of health hazards. The presence of ENN B in all samples of DDGS indicates that potential impact of this emerging mycotoxin on feed and food safety deserves attention. A challenge for the future is to fill up gaps in toxicological databases and improve models for carry-over of contaminants.     

Whole effluent toxicity assessment at a wastewater treatment plant upgraded with a full-scale post-ozonation using aquatic key species

Ozonation as final wastewater (WW) polishing step, following conventional activated sludge treatment is increasingly implemented in sewage treatment for contaminant degradation to prevent surface water pollution. While the oxidative degradation of chemicals has been extensively investigated, the in vivo toxicological characteristics of ozonated whole effluents are rarely a matter of research.In the present study, whole effluents were toxicologically evaluated with an in vivo test battery before and after full-scale ozonation and subsequent sand filtration on site at a treatment plant. One aquatic plant (duckweed, Lemna minor) and five invertebrate species of different systematic groups (Lumbriculus variegatus, Chironomus riparius, Potamopyrgus antipodarum, Daphnia magna) were exposed to the effluents in a flow-through-designed test system with a test duration of 7-28 d.None of the considered toxicity endpoints correlated with the pollutant elimination. A tendency towards an increased toxicity after ozonation was apparent in three of the test systems showing [statistically] significant adverse effects in the L. variegatus toxicity test (decrease in reproduction and biomass). After sand filtration, adverse effects were reduced to a similar level like after conventional treatment. Solely the Daphnia reproduction test revealed beneficial effects after ozonation in combination with sand filtration.Results of the test battery indicate the formation of adverse oxidation products during WW ozonation. L. variegatus appeared to be the most sensitive of the five test species. Sand filtration effectively removes or detoxifies toxic oxidation products, as toxic effects were subsequently reduced to the level after conventional treatment.     

Minimization of the formation of disinfection by-products

The drinking water industry is required to minimize DBPs levels while ensuring adequate disinfection. In this study, efficient and appropriate treatment scheme for the reduction of disinfection by-product (DBPs) formation in drinking water containing natural organic matter has been established. This was carried out by the investigation of different treatment schemes consisting of enhanced coagulation, sedimentation, disinfection by using chlorine dioxide/ozone, filtration by sand filter, or granular activated carbon (GAC). Bench scale treatment schemes were applied on actual samples from different selected sites to identify the best conditions for the treatment of water. Samples were collected from effluent of each step in the treatment train in order to analyze pH, UV absorbance at 254 nm (UVA₂₅₄), specific UV absorbance at 254 nm (SUVA₂₅₄), dissolved organic carbon (DOC), haloacetic acids (HAAs) and trihalomethanes (THMs). The obtained results indicated that using pre-ozonation/enhanced coagulation/activated carbon filtration treatment train appears to be the most effective method for reducing DBPs precursors in drinking water treatment.     

Do DBPs swim in salt water pools? Comparison of 60 DBPs formed by electrochemically generated chlorine vs. conventional chlorine

Disinfectants are added to swimming pools to kill harmful pathogens. Although liquid chlorine(sodium hypochlorite) is the most commonly used disinfectant, alternative disinfection techniques like electrochemically generated mixed oxidants or electrochemically generated chlorine, often referred to as salt water pools, are growing in popularity. However, these disinfectants react with natural organic matter and anthropogenic contaminants introduced to the pool water by swimmers to form disinfectio...     

Neurotoxicity and transcriptome changes in embryonic zebrafish induced by halobenzoquinone exposure

Halobenzoquinones(HBQs) are emerging disinfection byproducts(DBPs) with a widespread presence in drinking water that exhibit much higher cytotoxicity than regulated DBPs. However, the developmental neurotoxicity of HBQs has not been studied in vivo. In this work, we studied the neurotoxicity of HBQs on zebrafish embryos, after exposure to varying concentrations(0-8 μmol/L) of three HBQs, 2,5-dichloro-1,4-benzoquinone(2,5-DCBQ), 2,6-dichloro-1,4-benzoquinone(2,6-DCBQ), and 2,5-dibromo-1,4-benzoqu...     

Formation and speciation of disinfection byproducts during chlor(am)ination of aquarium seawater

The chemistry associated with the disinfection of aquarium seawater is more complicated than that of freshwater, therefore limited information is available on the formation and speciation of disinfection byproducts(DBPs) in marine aquaria. In this study, the effects of organic precursors, bromide(Br-) and pre-ozonation on the formation and speciation of several typical classes of DBPs, including trihalomethanes(THM4), haloacetic acids(HAAs),iodinated trihalomethanes(I-THMs), and haloacetamides(HAc Ams), were investigated during the chlorination/chloramination of aquarium seawater. Results indicate that with an increase in dissolved organic carbon concentration from 4.5 to 9.4 mg/L, the concentrations of THM4 and HAAs increased by 3.2–7.8 times under chlorination and by 1.1–2.3 times under chloramination. An increase in Br-concentration from 3 to 68 mg/L generally enhanced the formation of THM4, I-THMs and HAc Ams and increased the bromine substitution factors of all studied DBPs as well, whereas it impacted insignificantly on the yield of HAAs. Pre-ozonation with 1 mg/L O3 dose substantially reduced the formation of all studied DBPs in the subsequent chlorination and I-THMs in the subsequent chloramination. Because chloramination produces much lower amounts of DBPs than chlorination, it tends to be more suitable for disinfection of aquarium seawater.