Formation potentials of typical disinfection byproducts and changes of genotoxicity for chlorinated tertiary e uent pretreated by ozone

The effects of ozonation on the formation potential of typical disinfection byproducts (DBPs) and the changes of genotoxicity during post chlorination of tertiary effluent from a sewage treatment plant were investigated. Ozonation enhanced the yields of all detected chlorine DBPs except CHCl3. At a chlorine dose of 5 mg/L, the three brominated THMs and five HAAs increased, while chloroform decreased with the increase of ozone dose from 0 to 10 mg/L (ozone dose in consumption base). At a chlorine dose of 10 mg/L, the two mixed bromochloro species THMs and two dominant HAAs (DCAA and TCAA) firstly increased and then decreased with the increase of ozone dose, with the turning point approximately occurring at an ozone dose of 5 mg/L. The genotoxicity detected using umu test, on the other hand, was removed from 7 μg 4-NQO/L to a negligible level by ozonation under an ozone dose of 5 mg/L. Chlorination could further remove the genotoxicity to some extent. It was found that SUVA (UV absorbance divided by DOC concentration) might be used as an indicative parameter for monitoring the removal of genotoxicity during the oxidation.     

Characterization of dissolved organic matter fractions and its relationship with the disinfection by-product formation

Dissolved organic matter(DOM) has been identified as precursor for disinfection by-products(DBPs) formation during chlorination. Recently,it has been demonstrated that the characteristics of DOM influence the DBPs formation mechanism. A study was,therefore,initiated to investigate the effects of DOM fractions on DBPs formation mechanism. In the chlorination process,organic acids are dominant precursors of total thihalomethanes(TTHM) because of the νC-O and unsaturated structures. Furthermore,the TTHM format...     

UV/氯联合处理含溴溶液中溴酸根的生成

研究了UV和氯联合作用下溴酸根离子(BrO^-₃)在低浓度含溴溶液中的生成,旨在探讨pH、次氯酸钠(NaOCl)浓度、溶解氧(DO)、光强和温度等因素对其生成的影响.研究表明,暗反应条件下H₂O-NaOCl-Br^-体系较稳定,而UV照射可使游离氯浓度持续降低,同时伴有部分Br^-（6 .6%～32%）被氧化成BrO^-₃离子;pH、温度和光强恒定时余氯的分解可用拟一级反应速率方程拟合;实验条件下（I为610～1 896 μW/cm²,T为12 .2～36 .1℃）,拟一级反应速率常数分别与体系温度和光强值有线性关系;BrO^-₃的生成大致可以分为快速、慢速和平缓3个阶段;在慢速生成阶段,BrO^-₃的生成量与余氯的分解量有良好的线性关系（绝大部分相关系数在0 .96以上）;实验范围内（pH为4 .41～11 .07,DO为1 .5～9 　mg/L,Cl₂为1 .23～4 .50 　mg/L）,低pH、低DO和高初始NaOCl（以氯计）浓度有利于溴酸根的生成,提高温度与光强均不同程度提高溴酸根生成速度,但同时因加速余氯的分解而减少了溴酸根的总生成时间.     

MBR处理医院污水后续氯消毒及其消毒副产物研究

针对医院污水中致病微生物的特殊排放要求,研究了膜生物反应器（MBR）应用于医院污水处理中的预消毒及其后续氯消毒特性.结果表明,在工程应用中MBR具有显著的预消毒作用,对医院污水中的细菌总数和粪大肠杆菌的去除率分别达到2.0～3.1 lg和2.8～4.0 lg;对于MBR出水中残留的微生物,采用次氯酸钠进行后续消毒,当接触时间为1 h,在有效氯浓度为0.8 　mg/L时,可检测不出粪大肠杆菌,且放置6 h未见再生长,相应的THMs和HAAs分别为16.94 μg/L和32.10 μg/L;固定接触时间,随着Cl₂/DOC值的增加,MBR出水中THMs和HAAs均近似呈线性增长趋势（r²分别为0.941?5和 0.965?2）,且HAAs的增长速率高于THMs.     

传统给水处理厂氯消毒模型的开发与应用

以建立给水处理过程的风险分析方法为目标,提出了适用于传统给水处理工艺的氯消毒概率机理模型.模型既考虑氯消毒过程中有机物、余氯、氨氮、溴离子之间化学反应,又考虑水厂混凝、沉淀和过滤工艺过程中的物理和生物作用.典型水厂的现场监测数据表明,该模型能够较好地模拟水厂中高锰酸盐指数、氨氮以及4种三卤甲烷的浓度概率分布.Monte Carlo模拟的结果表明,与我国城市供水水质标准相比,该水厂高锰酸盐指数和单种三卤甲烷的超标概率极低,但总三卤甲烷的超标概率略高,约为2.3%.     

Experimental and modeling study of de novo formation of PCDD/PCDF on MSW fly ash

The effect of sulfur dioxide （SO2） on the formation of polychlorinated dibenzo-p-dioxins （PCDDs） and polychlorinated dibenzofurans （PCDFs） has been studied in an entrained-flow reactor （EFR） under simulated waste combustion conditions. A chlorination model based on conditional probability was employed to evaluate the homologue patterns of PCDDs and PCDFs. Results revealed that the presence of SO2 did not alter the formation pathway although SO2 suppressed PCDD/F formation. The prediction model of PCDF showed good agreement with the experimental data （R--0.95）, whereas the prediction for PCDDs did not correlate well with the experimental data. This may be explained because potential chlorination pathways play a significant role in PCDF formation, whereas PCDDs are mainly formed through condensation reactions. Furthermore, the result indicated that the steric hindrance during formation has more effects on PCDD than on PCDF due to the symmetric molecular structures of PCDDs.     

水中典型含氮有机物氯化生成消毒副产物的潜能研究

选取了受污染原水中广泛存在的12种含氮有机物（除草剂、杀虫剂、氨基酸、工业品等）,开展了氯化和氯胺化培养生成典型消毒副产物的实验,目的是通过对水中脲类除草剂、嗪类除草剂和其他含氮化合物培养生成不同消毒副产物的生成量,讨论不同种类含氮化合物生成含碳和含氮消毒副产物规律以及考察不同消毒副产物的可能前体物.研究发现,脲类除草...     

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.     

氯消毒中有机防晒剂BP9的去除转化与风险评价

对典型有机防晒剂二苯甲酮-9（BP9）在氯消毒过程中的氧化反应进行研究,考察BP9初始浓度、余氯初始浓度、溶液pH值和氨氮浓度对反应的影响,探究BP9氯氧化降解机理,评估其生态风险.结果表明,在BP9初始浓度5mg/L、余氯初始浓度5mg/L的条件下,90s内BP9去除率达到91.3%,符合准一级反应动力学.降解速率常数随着BP9初始浓度及氨氮浓度增加而减小,随余氯初始浓度增大而增大,中性条件下有利于BP9氯氧化反应.基于HPLC-MS/MS和GC-MS解析出7种中间产物,提出可能降解路径.发光细菌毒性分析和ECOSAR预测均表明,BP9氯氧化反应生成了比母物质毒性更高的中间产物,对饮用水水质安全造成潜在风险.     

4-壬基酚在氯消毒过程中的氧化途径

利用固相萃取－GC－MS测定壬基酚（NP）及其在氯气消毒过程中产生的副产物。结果表明，NP容易和次氯酸发生反应，并检出了包括一氯壬基酚，二氯壬基酚，三氯苯酚在内的7种副产物。用量子化学模型探讨了NP和次氯酚的反应机理，NP和次氯酸的反应包括了苯环上的氯取代反应及壬基侧链的断裂反应。