Removal of haloacetic acids by nanofiltration

Haloacetic acids, disinfection byproducts (DBPs) formed during drinking water chlorination process are carcinogens. The e cacy of nanofiltration (NF) was examined for the removal of five regulated haloacetic acids (HAA5): chloro-, dichloro-, and trichloro-acetic acid (CAA, DCAA, and TCAA); bromo-, and dibromo-acetic acid (BAA, and DBAA) in synthetic water. NF with the dense negatively charged membrane (ES 10), is the most e cient in removing HAA5 than the loose negatively charged membrane (NTR 7410) and neutral surface membrane (NTR 729HF), due to the greater electrostatic repulsion (Donan exclusion) and sieve e ect. Excellent HAA5 removal e ciency of 90%–100% could be obtained even at a low pressure of 1 105 Pa with ES 10. Changes in cross-flow velocity did not e ect the performance of membranes with a small pore size such as ES 10 and NTR 729HF. The increase in HAA5 concentration exhibited the adverse e ect on the performance of three membranes by strengthening the concentration polarization, which was the driving force for the di usion of HAA anions across the membrane.     

Seasonal variation effects on the formation of trihalomethane during chlorination of water from Yangtze River and associated cancer risk assessment

For the system of water samples collected from Yangtze River,the effects of seasonal variation and Fe(III) concentrations on the formation and distribution of trihalomethanes (THMs) during chlorination have been investigated.The corresponding lifetime cancer risk of the formed THMs to human beings was estimated using the parameters and procedure issued by the US EPA.The results indicated that the average concentration of THMs (100.81 μg/L) in spring was significantly higher than that in other seasons,which ...     

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.     

Characterization of disinfection byproduct formation potential in 13 source waters in China

The formation potential of four trihalomethanes (THMFP) and seven haloacetic acids (HAA7FP) in 13 source waters taken from four major water basin areas in China was evaluated using the simulated distribution system (SDS) chlorination method. The specific ultraviolet absorbance (SUVA254: the ratio of UV254 to dissolved organic carbon (DOC)), which ranged between 0.9 and 5.0 L/(mg m), showed that the organic compounds in di erent source waters exhibited di erent reactivities with chlorine. The HAA7FP of source waters ranged from 20 to 448 g/L and the THMFP ranged from 29 to 259 g/L. The HAA7FP concentrations were higher than the THMFP concentrations in all but one of the samples. Therefore, the risks of haloacetic acids (HAAs) should be of concern in some source waters. TCM (chloroform) and BDCM (bromodichloromethane) were the major THM constituents, while TCAA (trichloroacetic acid) and DCAA (dichloroacetic acid) were the major HAA species. Br-THM (brominated THM species) were much higher than Br- HAA (brominated HAA species), and the formation of Br-DBP (Br-THM and Br-HAA) should be of concern when the bromide concentration is over 100 g/L.     

Formation and cytotoxicity of a new disinfection by-product (DBP) phenazine by chloramination of water containing diphenylamine

Disinfection by-products (DBPs) in drinking water have caused worldwide concern due to their potential carcinogenic effects. The formation of phenazine from diphenylamine (DPhA) chloramination was studied and its cytotoxicities for two human cancer cells were also investigated. Phenazine was detected synchronously with the consumption of DPhA by chloramination, which further confirmed that the new DBP phenazine can be produced along with N-nitrosodiphenylamine (NDPhA) from DPhA chloramination. The formation of phenazine had a maximum molar yield with solution pH increasing from 5.0 to 9.0, with phenazine as the main product for DPhA chloramination at lower pH, but higher pH favored the formation of NDPhA. Thus, solution pH is the key factor in controlling the formation of phenazine and NDPhA. Both the initial DPhA and chloramine concentrations did not show a significant effect on the molar yields of phenazine, although increasing the chloramine concentration could speed up the reaction rate of DPhA with chloramines. The cytotoxicity assays showed that phenazine had significant cell-specific toxicity towards T24 (bladder cancer cell lines) and HepG2 (hepatic tumor cell lines) cells with IC50 values of 0.50 and 2.04 mmol/L, respectively, and T24 cells being more sensitive to phenazine than HepG2 cells. The IC50 values of phenazine, DPhA, and NDPhA for T24 cells were of the same order of magnitude and the cytotoxicity of phenazine for T24 cells was slightly lower than that of NDPhA (IC50, 0.16 mmol/L), suggesting that phenazine in drinking water may have an adverse effect on human health.     

饮用水中卤氧化物离子色谱分析方法研究

直接大体积进样,建立生活饮用水中卤氧化物溴酸盐(BrO3-)、亚氯酸盐(ClO2-)、氯酸盐(ClO3-)含量的离子色谱(IC)法。优化的色谱条件为:Metrosep A Supp 7(250 mm)色谱柱配以Metrosep A Supp1保护柱,淋洗液为3.6 mmol/L Na2CO3与1.0 mmol/L NaHCO3;流速为0.6mL/min;进样量为100μL,抑制型电导检测器。方法结果显示:卤氧化物与常见共存阴离子完全分离,标准曲线在(5.0～400)μg/L范围内具有良好的线性关系(r>0.999),精密度高(相对标准偏差RSD<5.0%),样品加标平均回收率在90.8%~105%之间。按S/N=3,BrO3-、ClO2-、ClO3-的检出限分别为(0.9、0.7、1.0)μg/L。该方法操作简单、分离效果好,可与常见阴离子实现同时分析,灵敏度高,重现性好,适合于饮用水中消毒副产物中溴酸盐、亚氯酸盐、氯酸盐的同时测定。     

在线液液萃取-气相色谱-质谱法测定生活饮用水中卤代乙腈

优化建立了在线液液萃取-气相色谱-质谱法测定饮用水中7种卤代乙腈的方法。通过多功能在线进样装置,研究设计了在线液液萃取的技术流程,优化了液液萃取关键参数,并建立了气相色谱-质谱检测方法。该方法对氯乙腈、二氯乙腈、三氯乙腈、溴乙腈、二溴乙腈、溴氯乙腈和碘乙腈等7种卤代乙腈都有较好的检测灵敏度,方法检测限为0.1~0.8 μg/L,纯水中高浓度加标回收率为72.0%~91.4%,精密度为1.8%~3.9%。经技术对比和应用验证,该方法具有高效灵敏、简便快速等特点,样品检测无干扰,自动化程度高,适用于饮用水中卤代乙腈类消毒副产物的检测。     

全国自来水厂卤乙酸浓度调查、风险评估与标准建议

采用高特异性和高灵敏度的UPLC-MS/MS方法对中国34个城市的117个自来水厂出水中9种卤乙酸进行检测,其中二氯乙酸和三氯乙酸的检出率和检出浓度最高,检出率分别为78.6%和81.2%,平均浓度分别为3.47μg/L和3.31μg/L.风险评价结果表明,二氯乙酸导致我国饮用水致癌风险的期望值为5.72′10-6,处于较低风险水平;全国只有1.7%水厂出水TCAA浓度超过20μg/L的健康指导值.在风险评价的基础上结合我国水厂的卤乙酸浓度数据,建议我国饮用水的二氯乙酸和三氯乙酸标准分别修改为16μg/L和20μg/L.     

圆孔多孔板水力空化杀灭大肠杆菌的实验研究

在以圆形孔口多孔板为空化空蚀发生器的水力空化装置中,对含有大肠杆菌的水样进行灭菌处理.通过检测大肠杆菌的灭菌率,研究了水力空化对水中大肠杆菌的灭活效果.分析了大肠杆菌初始浓度,水流空化数,孔口流速,孔口排布,孔口数量,孔口大小,空化空蚀作用时间等参数对灭菌效果的影响.试验结果表明：提高流速,降低空化数,选取适当的初始浓度,延长空化空蚀作用时间,增加孔口数量,减小孔口大小以及改进孔口排布可以进一步提高大肠杆菌的杀灭率.水力空化的空化空蚀作用能够杀灭水中的大肠杆菌,是一种饮用水消毒的新技术.     

微波无极紫外方法对二沉池出水的消毒研究

采用自制微波无极紫外连续式消毒反应器,对二沉池出水进行消毒.紫外光源为自制圆柱形无极灯,灯内充汞10mg、氩气压强666.61Pa紫外光强5.07mW/cm²,进水流量0.072L/s,出水细菌总数2CFU/mL,大肠菌群数0.微波无极紫外作用过程中,微波破坏细胞壁细胞膜结构使蛋白质、K⁺等胞内物质产生渗漏,这种不可逆的破坏过程有效抑制紫外光复活现象.