操作条件及水质对海水氯消毒过程中消毒副产物生成的影响

氯消毒广泛应用于海水利用的预处理过程中,以减少生物膜淤积,而消毒过程会导致各类消毒副产物(DBPs)的生成,可能会对海洋生态环境具有潜在危害。系统研究了操作条件和水质对海水氯化消毒过程中生成三卤甲烷(THMs)、卤乙腈(HANs)和卤乙酸(HAAs)的影响。结果表明,氯投加量对DBPs生成的影响最大,随着投氯量的增加,THMs、HANs和HAAs的生成量显著增加,在反应初期随反应时间的延长而增加,随后HANs和HAAs的生成量开始缓慢降低而THMs基本保持不变。随着温度升高,THMs的生成量稳步增加,而HAAs和HANs在分别达到30,25℃后生成量达到最大值,之后随温度的升高而降低。p H对THMs、HANs和HAAs生成的影响相反,在酸性条件下HANs和HAAs的生成量最多,而在碱性条件下THMs的生成量最多。THMs、HANs和HAAs的生成量随溴离子浓度的改变无明显变化,但是随着氨氮浓度的升高,THMs、HANs和HAAs的生成种类和生成量均有明显降低。     

溶解性有机氮乙酰胺氯化生成饮用水THMs的影响因素研究

氯化消毒可以有效杀灭细菌,但同时会产生危害人体健康的消毒副产物(DBPs).溶解性有机氮(DON)是DBPs的重要前体物,为考察DON对THMs的影响,首次选取乙酰胺(AcAm)作为前体物DON的代表物质,采用Plackett-Burman和Box-Behnken方法设计试验,考察了AcAm初始浓度、加氯量、pH、温度、溴离子浓度和反应时间等因素对三卤甲烷(THMs)生成的影响.结果表明,在AcAm生成THMs的过程中,AcAm初始浓度、pH和反应温度3个因素的影响程度较小,溴离子、有效氯和反应时间3因素的影响较大,其中溴离子的影响最为显著.溴离子浓度一定时,改变有效氯的含量,生成的THMs总量变化不大,溴离子对THMs的生成有一定的催化作用,控制溴离子的浓度是减少AcAm生成THMs的有效措施.在有效氯为8.77 mg/Ｌ、溴离子为0.77 mg/Ｌ及接触时间为6.20 h的条件下,THMs存在最大生成量为45.82 μg/L.随着反应时间的推移,溴分配系数n呈上升趋势,控制消毒反应时间,是减少THMs致癌风险的有效方法.同时探讨了AcAm生成THMs的反应路径,表述了溴离子的催化作用机制.     

城乡供水管网中消毒副产物的浓度水平与分布规律

通过12个月采集的153个水样,调查了中国南方城市佛山某水厂城乡集中供水管网中消毒副产物（DBPs）的浓度水平与时空分布情况.在供水管网中,三卤甲烷（THMs）、卤乙醛（HALs）、卤乙腈（HANs）和卤乙酰胺（HAcAms）这4类DBPs均被检出,其中位浓度分别为19.81、2.91、1.70和1.14μg·L-1.4类DBPs浓度在输送至农村方向管网水中的沿程变化规律与在输送至城市方向的相似.供水干管中的THMs、HALs和HANs浓度均随输配距离的增加而增大,且支管中DBPs浓度普遍更高.管网水中的4类DBPs浓度在冬季均相对较低,而THMs、HALs、HANs浓度在春季相对较高.该调查结果补充了对中国南方城乡集中供水的长距离管网输送中DBPs浓度水平与变化规律的认识,为城乡集中供水地区水质安全评价与风险控制提供依据.     

BrO3-等溴类物质在长江水氯化过程中的形成

研究长江上海段原水中Br-在氯化过程中的产物,以BrO3-、Br-和三卤甲烷(THMs)为主要测定物,考察pH值、氯投加量和Br-浓度对三者生成量的影响.研究表明,BrO3-在氯化过程中的形成缓慢,其生成量与氯投加量正相关,常规消毒条件下不会超过10μg/L的国家标准.在余氯充足的情况下,增加Br-浓度主要增加了总有机溴(TOBr),而BrO3-生成量基本不变,弱碱性条件有利于TOBr的生成;THMs和TOBr有一定相关性,Br-浓度升高将导致THMs生成量增加,其中三氯甲烷浓度下降,混合取代的THMs浓度先增加后减少,三溴甲烷浓度显著上升.     

太湖、钱塘江取水口底泥及周边土壤有机物形成消毒副产物的特征研究

底泥、土壤均是水体有机物的重要来源,但目前相关消毒副产物(DBPs)形成方面的研究偏少.本研究以长三角重要水源地太湖、钱塘江取水口的底泥和周边土壤的浸出液为研究对象,探索氯、臭氧+氯、氯胺、臭氧+氯胺4种消毒方式下,三卤甲烷(THMs)、卤代酮(HKs)、卤乙腈(HANs)、卤代硝基甲烷(HNMs)的形成情况.结果表明,太湖、钱塘江取水口的底泥、周边土壤有机物的芳香度均很低(SUVA254(即比紫外吸光值)2),与腐殖质(Sigma)相比,底泥、土壤有机物不是氯消毒中THMs的重要前驱物,但却是HANs特别是HNMs的重要前驱物.相比氯消毒,氯胺消毒能大幅降低土壤、底泥有机物THMs、HKs、HANs、HNMs的生成量,而且也可抑制含溴DBPs的形成.臭氧预处理大幅提高了氯、氯胺消毒中HKs、HNMs的产量,但对THMs、HANs则不一定.太湖、钱塘江的土壤、底泥存在一定的溴污染,但不管是哪种消毒方式,均是HNMs的溴嵌入因子最大.     

饮用水中典型微生物消毒过程中消毒副产物的生成规律

以饮用水中典型微生物--大肠杆菌（Escherichia coli）为试验对象,研究pH值、氯化时间、氯投量及细菌浓度对大肠杆菌在氯化消毒过程中生成消毒副产物（DBPs）的影响,并分析何种氯化条件下,DBPs控制效果最佳.研究表明：随氯投量增加,二氯乙腈（DCAN）呈先上升后下降趋势;随氯化时间延长,三氯丙酮（1,1,1-TCP）和DCAN先增加后减少;在pH值从5升高到9时,1,1,1-DCP、三氯硝基甲烷（TCNM）、二氯乙酸（DCAA）和三氯乙酸（TCAA）持续降低;细菌污染水源事件在近年常有报道,当水源水中细菌浓度增加时,饮用水中三氯甲烷（TCM）、TCNM、DCAA和TCAA浓度增加,但DCAN、三氯乙腈（TCAN）、二氯丙酮（1,1-DCP）和1,1,1-TCP不一定增加.为了达到低毒性的目的,氯投量浓度不宜太高,同时控制氯化时间为6h和pH>8.     

海水淡化超滤-反渗透工艺沿程溴代消毒副产物变化规律

研究了海水淡化超滤-反渗透(UF-RO)工艺沿程有机物和溴代消毒副产物(Br-DBPs)变化特征.该海水中含有较高浓度的Br-(45.6~50.9 mg·L-1)和较多的芳香类化合物[比紫外吸收值SUVA为3.6~6.0 L·(mg·m)-1];色氨酸类芳香族蛋白质、富里酸类有机物和溶解性微生物代谢产物是海水中主要的荧光特征有机物.UF-RO工艺进水海水经Na Cl O消毒后,DBPs的种类和浓度显著增加,且增加的主要为Br-DBPs,其中三溴甲烷(CHBr3)占总三卤甲烷(THMs)的70.48%~91.50%,二溴乙酸(Br2CHCO2H)占总卤乙酸(HAAs)的81.14%~100%,二溴乙腈(C2HBr2N)占总卤乙腈(HANs)的83.77%~87.45%.UF膜对THMs、HAAs和HANs的去除率分别为36.63%~40.39%、73.83%~95.38%和100%.RO膜可以完全去除HAAs,但是对THMs不能完全去除.进水海水的抗雌激素活性为0.35~0.44 mg·L-1,氯消毒后增加了32%~69%.海水淡化UF-RO系统生成的DBPs和其他生物毒性物质最终被截留到了UF浓水和RO浓水中.     

臭氧与氯联合消毒对钱塘江水源水DBPs形成及溴取代的影响

本文研究了在pH 6～8、反应时间2～72 h、反应温度10～30℃条件下,钱塘江水源水在臭氧-氯消毒联合作用下,三卤甲烷(THMs)、二卤乙酸(DHAAs)、三卤乙酸(THAAs)、二卤乙腈(HANs)、三卤硝基甲烷(THNMs)等5类消毒副产物(DBPs)的形成和溴取代特征.结果显示,臭氧-氯消毒下DBPs的形成与氯消毒有较多相似之处:①大部分DBPs形成量均随着温度的升高、时间的延长而增加,相应的溴取代因子(BSFs)则随着时间的延长、温度的上升而呈下降趋势;②氯代DHANs倾向于在酸性条件下形成多,而溴代DHANs则倾向于在碱性条件下形成多;③不管是氯消毒还是臭氧-氯消毒,也不管是哪种消毒条件,5类DBPs的BSF值顺序均为BSF_(HNMs)BSF_(DHANs) BSF_(THAAs)BSF_(THMs)≈BSF_(DHAAs).但与氯消毒不同的是,臭氧-氯消毒下THMs、DHAAs、THAAs、HANs的形成产量更低,而THNMs的产量则更高;而且与氯消毒相比,臭氧-氯消毒普遍增加了DBPs的溴取代程度,也改变了溴离子在不同DBPs之间的分配,即减少了THMs、DHAAs、THAAs、DHANs对溴的利用率,但大幅增加了HNMs的溴利用率.鉴于溴代HNMs的极高毒性,因此对于钱塘江水源水,臭氧-氯消毒要注意HNMs带来的健康风险.     

长距离供水系统中消毒副产物分布特征及二次加氯的影响

供水管网覆盖区域大,导致出厂消毒剂量不足以维持管网末梢余氯量,需进行途中二次投氯.以H市供水管网为目标,通过均匀布点采样分析,考察二次加氯消毒型管网中消毒副产物(disinfection by-products,DBPs)的分布特征.结果表明,管网中检出DBPs包括三氯甲烷(TCM)、一溴二氯甲烷(BDCM)、二溴一氯甲烷(DBCM)、三溴甲烷(TBM)、二氯乙酸(DCAA)、三氯乙酸(TCAA)、二氯乙腈(DCAN)、溴氯乙腈(BCAN)和三氯硝基甲烷(TCNM)等,所检水样中DBPs浓度均低于《生活饮用水卫生标准》(GB 5749-2006)规定的标准限值.二次加氯前检出质量浓度(以平均值±偏差表示)分别为:(8.08±3.34)、(9.77±2.91)、(7.38±4.82)、(2.65±2.02)、(2.95±3.26)、(6.02±6.06)、(3.13±2.48)、(1.61±2.05)和(0.15±0.10)μg·L~(-1).二次加氯后检出质量浓度分别为:(10.30±4.55)、(11.73±3.60)、(8.23±5.22)、(2.95±2.45)、(3.29±3.60)、(8.15±7.58)、(3.31±2.61)、(1.33±2.04)和(0.12±0.06)μg·L~(-1).二次加氯后DBPs含量相较于出厂水至二次加氯点呈明显上升趋势,三卤甲烷(THMs)和卤乙酸(HAAs)分别比前段管网含量升高6.32%～26.60%和5.32%～42.71%.此外,原水水质和季节变化对DBPs的形成有一定影响,夏季DBPs的水平普遍高于春季或秋季.出厂水及管网水DBPs生成势分析表明,H市供水系统中DBPs可能存在超标风险,后续需考虑进一步优化处理工艺以保障供水水质.     

氯、氯胺消毒下钱江源水源水消毒副产物形成特征研究

以钱江源水源水为研究对象,以氯、氯胺为消毒方式,研究了不同消毒条件下,三卤甲烷(THMs)、卤乙腈(HANs)、氯代酮(CKs)、二卤乙酸(DHAAs)、三卤乙酸(THAAs)等消毒副产物(DBPs)的形成情况,以便为水务工作者监测钱江源建库前后水质、DBPs形成的变化提供基础数据.结果显示,氯消毒下DBPs的产量比氯胺消毒高出3~7倍甚至1个数量级,但不管是氯消毒还是氯胺消毒,THMs、HAAs形成量均在我国饮用水标准范围内.氯消毒下,大部分DBPs产量为中、碱性条件酸性条件(除了CKs),氯胺消毒则呈现不同的情况(所有DBPs的产量均为p H=6、p H=7p H=8).消毒剂量对所有DBPs形成具有明显的促进作用;溴离子对THMs、DHANs、DHAAs的形成有明显的促进作用.进一步研究表明,钱江源水源水的水质比钱塘江下游九溪水源水好,DBPs形成也较低,某些指标(如有机碳、有机氮、HANs形成量等)甚至比同省水质较好的金兰水库还要好;而且由于其较高的比紫外吸收值(SUVA),DBPs的溴嵌入能力均比九溪水源水、金兰水库低.此外,就目前的钱江源水源水来说,控制消毒剂量(氯、或氯胺)是控制DBPs形成的有效策略.     

Formation of regulated and unregulated disinfection byproducts during chlorination and chloramination: Roles of dissolved organic matter type, bromide, and iodide

Algal blooms and wastewater effluents can introduce algal organic matter (AOM) and effluent organic matter (EfOM) into surface waters, respectively. In this study, the impact of bromide and iodide on the formation of halogenated disinfection byproducts (DBPs) during chlorination and chloramination from various types of dissolved organic matter (DOM, e.g., natural organic matter (NOM), AOM, and EfOM) were investigated based on the data collected from literature. In general, higher formation of trihalomethanes (THMs) and haloacetic acids (HAAs) was observed in NOM than AOM and EfOM, indicating high reactivities of phenolic moieties with both chlorine and monochloramine. The formation of haloacetaldehydes (HALs), haloacetonitriles (HANs) and haloacetamides (HAMs) was much lower than THMs and HAAs. Increasing initial bromide concentrations increased the formation of THMs, HAAs, HANs, and HAMs, but not HALs. Bromine substitution factor (BSF) values of DBPs formed in chlorination decreased as specific ultraviolet absorbance (SUVA) increased. AOM favored the formation of iodinated THMs (I-THMs) during chloramination using preformed chloramines and chlorination-chloramination processes. Increasing prechlorination time can reduce the I-THM concentrations because of the conversion of iodide to iodate, but this increased the formation of chlorinated and brominated DBPs. In an analogous way, iodine substitution factor (ISF) values of I-THMs formed in chloramination decreased as SUVA values of DOM increased. Compared to chlorination, the formation of noniodinated DBPs is low in chloramination.     

Disinfection byproduct regulatory compliance surrogates and bromide-associated risk

Natural and anthropogenic factors can alter bromide concentrations in drinking water sources. Increasing source water bromide concentrations increases the formation and alters the speciation of disinfection byproducts (DBPs) formed during drinking water treatment. Brominated DBPs are more toxic than their chlorinated analogs, and thus have a greater impact on human health. However, DBPs are regulated based on the mass sum of DBPs within a given class (e.g., trihalomethanes and haloacetic acids), not based on species-specific risk or extent of bromine incorporation. The regulated surrogate measures are intended to protect against not only the species they directly represent, but also against unregulated DBPs that are not routinely measured. Surrogates that do not incorporate effects of increasing bromide may not adequately capture human health risk associated with drinking water when source water bromide is elevated. The present study analyzes trihalomethanes (THMs), measured as TTHM, with varying source water bromide concentrations, and assesses its correlation with brominated THM, TTHM risk and species-specific THM concentrations and associated risk. Alternative potential surrogates are evaluated to assess their ability to capture THM risk under different source water bromide concentration conditions. The results of the present study indicate that TTHM does not adequately capture risk of the regulated species when source water bromide concentrations are elevated, and thus would also likely be an inadequate surrogate for many unregulated brominated species. Alternative surrogate measures, including THM3 and the bromodichloromethane concentration, are more robust surrogates for species-specific THM risk at varying source water bromide concentrations.     

模拟泳池水中氯化消毒副产物的生成规律

以模拟泳池水为研究对象,研究不同的氯化时间、氯投加量、pH值、反应温度条件对泳池水在氯化消毒过程中生成消毒副产物（DBPs）的影响.研究结果表明：延长氯化反应时间,二氯乙酸（DCAA）、三氯乙酸（TCAA）和三氯甲烷（TCM）的浓度不断升高,二氯乙腈（DCAN）、三氯硝基甲烷（TCNM）和1,1,1-三氯丙酮（1,1,1-TCP）的浓度则先升高再降低.DBPs浓度在氯化反应的前24h增幅较大,48h后趋于平缓;随着氯投加量的增加,DCAA、TCAA、TCM、TCNM和1,1,1-TCP浓度一直呈上升趋势,而DCAN浓度则先升高再降低.在氯投加量为2mg/L时,DBPs的浓度较低;在pH值从6升高到8的过程中,DCAA、TCAA、DCAN和1,1,1-TCP浓度先升高再降低,TCM和TCNM浓度则一直升高.pH值在6~7范围内可有效控制DBPs的形成;随着反应温度的升高,DCAA、TCAA、TCM和TCNM浓度持续升高,DCAN和1,1,1-TCP则逐渐降低.综上所述,应合理调节泳池水的氯化消毒条件,在保证舒适度的同时有效控制DBPs的生成.     

Fe3+和Br-对饮用水氯消毒过程中挥发性卤代烃生成的影响

以腐殖酸模拟天然水体中的活性消毒副产物的前体物,研究了含腐殖酸水样中溴离子和三价铁离子对氯消毒反应过程中挥发性卤代烃三卤甲烷(THMs)的生成量和相对分布的影响.结果表明,水样中的溴离子浓度增加将增加溴代三卤甲烷和总三卤甲烷的生成量, 在Br^-离子浓度1.0 mg/L时,THMs的总量为不含Br^-时的2.7倍;当水样中含有溴离子时,在偏酸性条件下三价铁对三卤甲烷的生成有一定的抑制作用,在偏碱性条件下三价铁离子提高了溴离子与腐殖酸的反应活性,从而提高了三卤甲烷的生成总量.Fe³⁺浓度为5 mg/L时,三溴甲烷的生成量与无Fe³⁺存在时相比,由51.7 μg/L增加到79.4 μg/L, 增加幅度达54%,THMs的总量从113.49 μg/L增加到162.09 μg/L.溴离子对饮用水的安全性具有较大的负面影响,溴离子和三价铁离子共存于偏碱性环境中时对加氯消毒后饮用水的致癌风险的影响显著增大,当Br^-含量为0.2 mg/L、Fe³⁺含量为5 mg/L时,在pH为6和8的条件下,致癌风险比饮用水中不含Br^-和Fe³⁺时分别增加2.5和5.1倍.     

Characteristics of molecular weight distribution of dissolved organic matter in bromide-containing water and disinfection by-product formation properties during treatment processes

The characteristics of dissolved organic matter (DOM) and bromide ion concentration have a significant influence on the formation of disinfection by-products (DBPs). In order to identify the main DBP precursors, DOM was divided into five fractions based on molecular weight (MW), trihalomethane formation potential and haloacetic acid formation potential were determined for fractions, and the change in contents of different fractions and total DBPs during treatment processes (pre-chlorination, coagulation, sand filtration, disinfection) were studied. Moreover, the relationship between bromide concentration and DBP generation characteristics in processes was also analyzed. The results showed that the main DBP precursors were the fraction with MW < 1 kDa and fraction with MW 3−10 kDa, and the DBP''s generation ability of lower molecular weight DOM (< 10 kDa) was higher than that of higher molecular weight DOM. During different processes, pre-chlorination and disinfection had limited effect on removing organics but could alter the MW distribution, and coagulation and filtration could effectively remove organics with higher MW. For DBPs, trihalomethanes (THMs) were mainly generated in pre-chlorination and disinfection, while haloacetic acids (HAAs) were mostly generated during pre-chlorination; coagulation and sand filtration had little effect on THMs but resulted in a slight removal of HAAs. In addition, the results of ANOVA tests suggested that molecular sizes and treatment processes have significant influence on DBP formation. With increasing bromide concentration, the brominated DBPs significantly increased, but the bromine incorporation factor in the processes was basically consistent at each concentration.     

Effect of ferric and bromide ions on the formation and speciation of disinfection byproducts during chlorination

The e ects of ferric ion, pH, and bromide on the formation and distribution of disinfection byproducts (DBPs) during chlorination were studied. Two raw water samples from Huangpu River and Yangtze River, two typical drinking water sources of Shanghai, were used for the investigation. Compared with the samples from Huangpu River, the raw water samples from Yangtze River had lower content of total organic carbon (TOC) and ferric ions, but higher bromide concentrations. Under controlled chlorination conditions, four trihalomethanes (THMs), nine haloacetic acids (HAAs), total organic halogen (TOX) and its halogen species fractions, including total organic chlorine (TOCl) and total organic bromide (TOBr), were determined. The results showed that co-existent ferric and bromide ions significantly promoted the formation of total THMs and HAAs for both raw water samples. Higher concentration of bromide ions significantly changed the speciation of the formed THMs and HAAs. There was an obvious shift to brominated species, which might result in a more adverse influence on the safety of drinking water. The results also indicated that high levels of bromide ions in raw water samples produced higher percentages of unknown TOBr.