饮用水消毒副产物DBPs的研究进展

饮用水消毒副产物(DBPs)是消毒剂和一些天然有机物(NOM)反应生成的化合物,主要包括三卤甲烷(THMs)、卤代乙酸(HAAs)、卤代乙腈(HANs)和致诱变化合物(MX)等,文章介绍了饮用水中消毒副产物的研究状况,对DBPs的种类与分布状况、生成影响因素、毒性与健康效应、饮水DBPs控制方法的研究概况及进展进行了综述。     

活性炭深度处理技术的化学安全性及影响因素研究

活性炭技术是净化微污染源水的有效手段,但其化学安全性值得关注。研究发现,活性炭出水中微量有机污染物仍有一定含量,AOC浓度仍达211 μg/L,并可检测到新的有机化合物,去除效果受炭种、源水水质和工艺运行等因素影响;活性炭对消毒副产物的去除效果不稳定,生物活性炭对卤乙酸前质（HAAs）表现出较好去除效果,但对三卤甲烷前质（THMs）的去除效果有限,去除效果与活性炭类型和工艺运行参数等因素有关;活性炭技术可以去除大部分臭氧化副产物的溴酸盐和甲醛,但水厂用纯氧生产臭氧时,活性炭的处理情况有所不同。活性炭易于吸附微囊藻毒素,微生物对藻毒素也有降解作用,仍应注意源水水质情况。另外,活性炭能有效去除致突变活性物质,即使在活性炭吸附TOC饱和后,仍能显著地去除致突变活性物质。     

高锰酸盐复合药剂预氧化去除腐植酸色度研究

选取三种不同类型的辅剂与高锰酸钾复合,研制出高锰酸盐复合药剂PPC—A、PPC-N和PPC-C,并对三种高锰酸盐复合药剂对腐植酸色度的去除效能进行研究。研究结果表明,与单独投加硫酸铝相比,投加少量高锰酸盐复合药剂就可以显著提高对色度、TOC及UV254的去除效果,并且对加氯消毒后氯仿生成量也有较好的控制作用。三种复合药剂中,PPC-C具有最优的除色效能。高锰酸盐复合药剂对腐植酸的去除是高锰酸钾、新生态水合二氧化锰及辅剂共同作用的结果。     

微生物起泡剂影响因素分析

阐述高级醇起泡剂的微生物合成机理,分析多种因素(菌种、接种量、物料碳氮含量、温度、pH值、溶氧量、各种阳离子种类及浓度等)对高级醇生成量及生成种类的影响。不同的因素对高级醇形成的影响不同。     

某市供水管网中氯消毒副产物（DBPs）的致癌风险评价

以美国环保署（USEPA）推荐的致癌风险评价模型为理论基础,针对对江南某市配水管网中的消毒副产物（DBPs）的致癌性进行了风险评估。笔者将存在致癌风险的三卤甲烷和二卤乙酸作为研究重点并进行致癌风险研究。通过监测管网沿线三卤甲烷和二卤乙酸的变化情况,探究不同区域上的致癌风险情况。结果表明：消毒副产物在管网沿线有升高的趋势,且致癌风险值随之升高,经计算得出管网供水区域内的致癌风险最大值为RTmax=4．72e-5,小于USEPA规定的极限值RT=5．10×10-5。说明区域内的消毒副产物未对人体健康造成致癌威胁,不存在健康风险。     

复合盐类侵蚀对硅酸盐水泥固化氯离子影响研究

研究了硫酸盐、碳酸盐和硝酸盐与氯盐复合侵蚀下硅酸盐水泥固化氯离子性能,采用水溶法测定了水泥净浆中自由氯离子含量并计算得出其氯离子固化率,对试样进行了XRD物相分析以及其水溶液的pH值测定。结果表明,水泥浆体的氯离子固化率随水化龄期的增长而增加;随氯离子浓度增大,水泥浆体中F盐的生成量增加,其氯离子固化率先增大后减小。随硫酸盐和碳酸盐浓度增大,水泥浆体的氯离子固化率均降低,硫酸盐的降低程度稍微比碳酸盐大。硫酸盐和碳酸盐通过结合AFm分别生成钙矾石(3CaO·Al_2O_3·3CaSO_4·31H_2O)和单碳硫铝酸钙(3CaO·Al_2O_3·CaCO_3·12H_2O)提高了水泥浆体的pH值,减少了F盐的生成量。硝酸盐对水泥浆体的氯离子固化率和F盐的生成没有影响。     

柠檬酸钠还原法制备金纳米颗粒的影响因素分析

通过化学还原法制备金纳米材料,以柠檬酸钠为还原剂,通过加热还原氯金酸,得到金纳米颗粒水溶液。利用紫外-可见吸收光谱,研究了制备工艺参数对产物尺寸以及产物生成速率的影响。结果表明,反应物浓度比、反应物加入次序、溶液pH在一定程度上影响产物的尺寸,保温温度、保温时间以及搅拌速率对产物生成速率有较大影响。并对金纳米颗粒生成过程相关影响因素进行了分析。     

羟基磷灰石的形态结晶控制

对化学沉淀法制备羟基磷灰石中的制备温度、pH值、分散剂浓度、反应物浓度以及搅拌速度等因素对羟基磷灰石生长形态和结晶的影响进行了系列研究。结果表明：上述因素分别对HA的生长形态和结晶状况有不同程度的影响．通过对工艺参数的合理选择可以得到具有不同结晶状况和形态的羟基磷灰石颗粒。     

并流共沉淀法合成Dy_(2)O_(3)-ZrO_(2)纳米粉体EI北大核心CSCD

采用并流化学共沉淀法合成了Dy_(2)O_(3)掺杂ZrO_(2)(DySZ)纳米粉体材料,系统研究稳定剂掺杂量、阳离子浓度、反应系统pH值和煅烧温度对粉体材料物相组成、晶体结构和微观形貌的影响。结果表明:不同合成工艺条件下,DySZ粉体材料均具有纳米尺度特征,球形颗粒尺寸为10~30 nm,Dy_(2)O_(3)的掺杂可以起到稳定晶型的作用;稳定剂掺杂量对DySZ粉体的物相组成具有明显影响,掺杂量为10%(质量分数)时可合成单一四方相结构的DySZ粉体;DySZ粉体材料的四方度和微观形貌对稳定剂掺杂量、阳离子浓度、反应体系pH值和煅烧温度均不敏感,但其平均晶粒尺寸随稳定剂掺杂量、阳离子浓度和反应体系pH值的升高略有降低,随煅烧温度的提高而显著增加。     

环境因子对磁性瓜环去除腐殖酸的影响及其稳定性研究

采用紫外可见分光技术研究了磁性瓜环(MQ[n])对水体污染物腐殖酸(HA)的去除性能、稳定性及磁性能。考察了MQ[n]的投加量、HA的初始浓度、溶液温度、作用时间及pH值等因素对去除HA的影响。结果表明,MQ[n]对HA具有很好的去除作用,其中,MQ[n]投加量与pH值对HA的去除效果影响较大。其较优条件为MQ[n]投加量20mg、HA初始质量浓度10 mg/L、吸附温度315 K、平衡时间360 min、pH值7.0,在此条件下,MQ[n]对HA的去除率达到98.73%。MQ[n]稳定性好,且易于磁性分离。     

Molecular size distribution of dissolved organic matter in water of the Pearl River and trihalomethane formation characteristics with chlorine and chlorine dioxide treatments

River water sample was collected from Guangzhou section of the Pearl River to investigate soluble organic fractions and formation of trihalomethane (THMs) after chlorine and chlorine dioxide treatments. The water sample was passed through Amicon YC-05, YM-1, YM-3, YM-10, YM-30, YM-100 and ZM-500 series membranes after a pre-treatment. The molecular weight distribution and the specific ultra-violet absorbance (SUVA(254)) of each fraction obtained from membrane were analyzed, and these fractions were further disinfected with chlorine and chlorine dioxide. The results showed that reverse osmosis (RO) fraction contained mainly dissolved organic matter (DOM) from the water sample, suggesting that the water has been highly contaminated by anthropogenic activities. Meanwhile, the THMs concentration and SUVA(254) increased gradually as the molecular weight of the obtained fractions reduced, indicating that the low molecular weight DOM was the major THMs precursor in the disinfection process with chlorine and chlorine dioxide. The results suggest that THMs in source water of Pearl River could be effectively reduced when pollution of human activity is greatly controlled. Between the two disinfection processes tested, chlorine dioxide produced less THMs than chlorine in this study.     

Investigation of bromide ion effects on disinfection by-products formation and speciation in an Istanbul water supply

Recent epidemiological studies reported that brominated DBPs may be more carcinogenic than their chlorinated analogs. Thus, this research was designed to investigate the role of bromide ion in the formation and speciation of disinfection by-products (DBPs) during chlorination of Buyukcekmece Lake Water (BLW) in Istanbul. Chlorination of BLW samples was carried out at pH 7.0 with 5 and 12 mg/l chlorine dosages. For each chlorine dosage, six bromide concentrations ranging from 0.05 to 4.0mg/l were added to form a 2 x 6 experimental matrix. In general, increasing bromide concentration gradually shifted trihalomethanes (THMs) and haloacetic acids (HAAs) speciation from chlorinated species to the mixed bromochloro species during chlorination. The halogen substitution ability of HOBr and HOCl during the formation of THMs and HAAs can be estimated through the use of probability theory. It was concluded that, in both halogen substitution for THM and dihalogenated HAA formation, HOBr was found to be 20 times more reactive than HOCl.     

The formation of disinfection by-products in water treated with chlorine dioxide

In this study, chlorine dioxide (ClO(2)) was used as an alternative disinfection agent with humic acid as the organic precursor in a natural aquatic environment. The major topics in this investigation consisted of the disinfection efficiency of ClO(2), the formation of disinfection by-products (DBPs), and the operating conditions. The results indicated that the pH value (pH 5-9) did not affect the efficiency of disinfection while the concentration of organic precursors did. The primary DBPs formed were trihalomethanes (THMs) and haloacetic acids (HAAs). The distribution of the individual species was a function of the bromide content. The higher the ClO(2) dosage, the lower the amount of DBPs produced. The amount of DBPs increased with reaction time, with chlorite ions as the primary inorganic by-product.     

A study for producing drinking water with safe trihalomethane concentrations

This article investigates trihalomethanes (THMs) production and simulates water age in Assiut drinking water system using WaterCAD software. Pre-chlorinated water samples were collected from Nazlet Abdellah water treatment plant and post-disinfected with chlorine/chloramines with different chlorine-to-nitrogen ratios (Cl₂/N). Experiments have examined varying residence times, ratios of Cl₂/N, pH conditions, and storage containers’ type on THMs formation. The results showed that as the residence time increased, THMs concentrations increased. Water age in Assiut drinking water distribution network reaches more than 10 h. Using chloramines instead of free chlorine for post-disinfection resulted in lowering THMs concentrations to 58.9 % after 48 h of disinfection. Ratios of Cl₂/N (2:1–6:1) were comparable and effective on lowering THMs concentrations, and the most effective ratio was 4:1. Also, as the pH increased, the THMs increased. The measured THMs concentrations in chloraminated water stored in glass and plastic bottles were approximately the same.     

Ecotoxicological screening of reclaimed disinfected wastewater by Vibrio fischeri bioassay after a chlorination–dechlorination process

It is well known that different substances can react with chlorine in a water disinfection process to produce disinfection by-products (DBPs). Some of these substances have proven to be carcinogenic in humans and animals. Because it is not possible to detect all DBPs produced in chlorinated wastewater, toxicity tests have been proposed as a useful tool for screening toxic chemicals in treated wastewater. In this study, the Microtox^® bioassay with Vibrio fischeri was used to evaluate the formation of toxic by-products in wastewater, after a chlorination–dechlorination disinfection treatment. All the variables were found to be normally distributed, so analysis of variance could be directly applied without transformation of variables. Significant correlations were obtained between toxicity values and total carbon, total inorganic carbon, total nitrogen, chlorine, and pH. In contrast, total organic carbon, chemical oxygen demand, electrical conductivity and turbidity had no effect on toxicity formation. Toxicity increased with the Cl₂:NH₄⁺ ratio at a higher chlorine concentration released from combined chlorine. Regression models provided a good fit for effective concentration (EC50) as a function of total carbon and total nitrogen, after 5, 10, and 15 min of exposure. These models had greater multiple determination coefficients than previously reported for similar studies, without autocorrelation in the residuals as indicated by the Durbin–Watson statistic test. The measured and predicted ecotoxicity values were strongly correlated.     

Cu(II)-catalyzed THM formation during water chlorination and monochloramination: A comparison study

The catalytic effect of Cu(II) on trihalomethane (THM) formation during chlorination and monochloramination of humic acid (HA) containing water was comparatively investigated under various pH conditions. Results indicate that in the presence of Cu(II), the formation of THMs was significantly promoted as pH decreased in both chlorination and monochloramination. More THMs were formed during Cu(II)-catalyzed monochloramination which was partially due to enhanced hydroxyl radical (OH) generation as demonstrated by electron spin resonance (ESR) analysis. To discriminate the reactive moieties of HA, nine model compounds, which approximately represented the chemical structure of HA, were individually oxidized by chlorine or monochloramine. Results show that Cu(II) could promote THM formation through reacting with citric acid and similar structures in HA. During chlorination and monochloramination of citric acid in the absence of Cu(II), major intermediates including chlorocarboxylic acid, chloroacetone and chloroacetic anhydride were identified. However, the catalysis of Cu(II) did not produce any new intermediate. The complexation of Cu(II) with model compounds was characterized via FTIR analysis. The reaction mechanism for Cu(II)-catalyzed THM formation was proposed to comprise two pathways: (1) indirect catalysis in which OH oxidizes the large molecules of HA into small ones to enhance THM formation; and (2) direct catalysis in which Cu(II) complexes with HA to accelerate the decarboxylation steps for THM formation.     

Formation of disinfection by-products in the chlorination of ammonia-containing effluents: significance of Cl2/N ratios and the DOM fractions

The presence of ammonia nitrogen (NH(3)-N) in the effluent strongly affected the formation of disinfection by-products (DBPs) during its chlorination. The effect of chlorine (as mg/L Cl(2)) to NH(3)-N (as mg/L N) mass ratios (Cl(2)/N) and the chemical fractions of dissolved organic matter (DOM) in the effluent on the DBPs formation was investigated. Results indicated that the formation of DBPs increased with increasing Cl(2)/N. The concentration and speciation of DBPs varied among different DOM fractions at different zones of chlorination breakpoint curves. The formation rate of total haloacetic acids (THAA) and total trihalomethanes (TTHM) was promoted after the chlorination breakpoint, whereas the reaction of monochloramine with HOCl to dichloramine may cause a decrease in the DBPs formation potential thereafter. Organic acids were found to be the dominant precursors of DBPs with or without the presence of NH(3)-N, which indicated that the CC, CO and C-O structures contributed to the formation of DBPs significantly. In addition, the incorporation of bromine in THMs of the HiA fraction increased with the increasing of Cl(2)/N mass ratios before the chlorination breakpoint, but decreased sharply after the breakpoint. ΔA(280) (absorbance at 280 nm), defined as A(280,initial)-A(280,final), was proved to be linearly related to the TTHM and THAA of wastewater without containing Br(-) during chlorination or chloramination.     

Occurrence of disinfection by-products in low DOC surface waters in Turkey

A total of 29 surface waters from different regions of Turkey were sampled once a month during 2004. Filtered raw water samples were characterized, chlorinated and the concentrations of disinfection by-products (DBPs) were measured. All waters were low in DOC ranging from 0.91 to 4.42 mg/L. The range of annual average trihalomethanes (THMs) and haloacetic acids (HAAs) concentrations in all waters was 21-189 and 18-149mug/L, respectively. Total mass contributions of halides in THMs and HAAs to absorbable organic halides (AOX) ranged between 10 and 56% in all waters on annual average basis, indicating that significant amounts of other DBPs are being formed in the majority of the tested waters. A strong linear correlation was obtained between the concentrations of THMs and HAAs. Rather poor correlations were found for THMs-AOX and HAAs-AOX levels. For both THMs and HAAs, chlorinated species dominated over brominated ones since the majority of water sources had very low bromide levels. While chloroform and trichloroacetic acid were the major THM and HAA compounds, respectively; the extent of formation and speciation of DBPs varied greatly by season and water source. No consistent general trends were observed in terms of seasonal variations in DBP levels, suggesting that the characteristics of NOM moieties and their chlorine reactivity vary by season in almost all waters tested.     

Relationship of chlorine decay and THMs formation to NOM size

Because of increasing concern about balancing health risks for pathogen control and disinfection by-product (DBP) formation in water supplies, utilities are forced to closely examine and optimize their disinfection practices. A better understanding of the relationship between the molecular weights of the natural organic matter (NOM), chlorine decay kinetics and THMs formation can help the utilities to minimize the DBP concentrations, providing healthier and microbially safer water. The authors present data on chlorine decay kinetics and total trihalomethanes (TTHM) formation kinetics and modeling with different molecular weights NOM fractions of Mississippi River water. TTHM modeling results indicated that the TTHM formation in fractionated NOM was a function of chlorine consumption. TTHM yield coefficients ranged from 31 to 42 microg-TTHM/mg-Cl2. As the molecular weight of the fractions decreased, TTHM yield coefficients increased.     

Modeling daily variation of trihalomethane compounds in drinking water system, Houston, Texas

Total trihalomethanes (TTHM) concentrations vary widely and periodically between 70 and 130 ppb. Data from the National Environmental Services Laboratory, Houston, Texas indicate that pH and free residual chlorine contribute minimally to the wide variability of TTHM levels. Temperature variation in drinking fluctuates from 11 to 27 degrees C. The objective of this research is to formulate a model that delineates more clearly the daily variations of the most prevalent volatile trihalomethane by-products: chloroform (CHCl3), bromodichloromethane (CHBr2Cl), and bromoform (CHBr3) levels from drinking water. This model simulates the daily fluctuation of THM at a single location and at any time during the day as a function of the water temperature and the average concentration of TTHM, which can be estimated. The hypothesis of this study is that observed daily fluctuations of TTHM, CHCl3, CHCl2Br, CHClBr2, and CHBr3 are periodic. This hypothesis is tested using autocorrelation functions and it is shown that for the series of pH the correlation coefficient is maximal at zero lags, rapidly decreases to zero, and increases again between 4- and 6-h period. Such pattern suggests random fluctuation unrelated to time. However, the series of free residual chlorine, temperature, TTHM, CHCl3, CHCl2Br, CHClBr2, and CHBr3 suggest a different pattern. The correlation coefficient increases when the time-shift approaches 24 h. These repetitions in fluctuation of content over a 24-h period are statistically significant. The model formulated in this study provides insights in TTHM variation and is a necessary tool to reduce the error when estimating potential risk from exposure to trihalomethane compounds in drinking water system. In general, calculation of potential risk by using a value measured early morning or late afternoon concentrations were found minimal lead to an underestimation of the population risk.