Total organic halogen (TOX) in human urine: A halogen-specific method for human exposure studies

Disinfection by-products(DBPs) are a complex mixture of compounds unintentionally formed as a result of disinfection processes used to treat drinking water. Effects of long-term exposure to DBPs are mostly unknown and were the subject of recent epidemiological studies. However,most bioanalytical methods focus on a select few DBPs. In this study, a new comprehensive bioanalytical method has been developed that can quantify mixtures of organic halogenated compounds, including DBPs, in human urine as total organic chlorine(TOCl), total organic bromine(TOBr), and total organic iodine(TOI). The optimized method consists of urine dilution, adsorption to activated carbon, pyrolysis of activated carbon, absorption of gases in an aqueous solution, and halide analysis with ion chromatography and inductively coupled plasma-mass spectrometry. Spike recoveries for TOCl, TOBr, and TOI measurements ranged between 78% and 99%. Average TOCl, TOBr, and TOI concentrations in five urine samples from volunteers who consumed tap water were 1850, 82, and 21.0 μg/L as X~-, respectively.Volunteers who consumed spring water(control) had TOCl, TOBr, and TOI average concentrations in urine of 1090, 88, and 10.3 μg/L as X~-, respectively. TOCl and TOI in the urine samples from tap water consumers were higher than the control. However, TOBr was slightly lower in tap water urine samples compared to mineral water urine samples, indicating other sources of environmental exposure other than drinking water. A larger sample population that consumes tap water from different cities and mineral water is needed to determine TOCl, TOBr, and TOI exposure from drinking water.     

黄河原水中消毒副产物前体物的组成特征及其化学预氧化处理效果对比

以取自河南省郑州市石佛原水厂的黄河原水为研究对象,系统研究了原水中消毒副产物(DBPs)前体物的组成规律,对比分析了3种预氧化剂(高锰酸钾、自由氯和二氧化氯)对原水中DBPs生成潜能的消减规律.试验结果表明:原水中DBPs的前体物均以小分子有机物和疏水性组分(52.51%)为主;分子量小于1 k Da有机物组分是生成含氮消毒副产物(N-DBPs)和三卤甲烷(THMs)的主要前体物;疏水性有机物是生成THMs的主要前体物,亲水性有机物是生成N-DBPs的主要前体物.经Cl2预氧化后,直接生成的DBPs随着自由氯投加量的增加而增加,Cl O2和KMn O4预氧化直接增加DBPs产生量.经3种预氧化剂氧化后,原水中三卤甲烷生成潜能(THMFP)均呈现一定的下降,其降低量依次为Cl O2Cl2KMn O4;然而3种预氧化剂都不能有效的减少含氮消毒副产物生成潜能(N-DBPFP),Cl O2预氧化和Cl2预氧化可增加N-DBPs生成潜能,尤其在较高投加量下,Cl2预氧化将大大增加N-DBPs生成潜能.为有效消减总DBPs生成潜能,水厂可优先采用KMn O4或Cl O2作为预氧化剂处理引黄水库或沉砂池水.     

Uncertainty characterization approaches for risk assessment of DBPs in drinking water: A review

The management of risk from disinfection by-products (DBPs) in drinking water has become a critical issue over the last three decades. The areas of concern for risk management studies include (i) human health risk from DBPs, (ii) disinfection performance, (iii) technical feasibility (maintenance, management and operation) of treatment and disinfection approaches, and (iv) cost. Human health risk assessment is typically considered to be the most important phase of the risk-based decision-making or risk management studies. The factors associated with health risk assessment and other attributes are generally prone to considerable uncertainty. Probabilistic and non-probabilistic approaches have both been employed to characterize uncertainties associated with risk assessment. The probabilistic approaches include sampling-based methods (typically Monte Carlo simulation and stratified sampling) and asymptotic (approximate) reliability analysis (first- and second-order reliability methods). Non-probabilistic approaches include interval analysis, fuzzy set theory and possibility theory. However, it is generally accepted that no single method is suitable for the entire spectrum of problems encountered in uncertainty analyses for risk assessment. Each method has its own set of advantages and limitations. In this paper, the feasibility and limitations of different uncertainty analysis approaches are outlined for risk management studies of drinking water supply systems. The findings assist in the selection of suitable approaches for uncertainty analysis in risk management studies associated with DBPs and human health risk.     

The effects of pH, bromide and nitrite on halonitromethane and trihalomethane formation from amino acids and amino sugars

In this study, the effects of pH, bromide and nitrite on the formation of halonitromethanes (HNMs) and trihalomethanes (THMs) from eight amino acids (glycine, alanine, serine, cysteine, aspartic acid, glutamic acid, lysine and histidine) and four amino sugars (glucosamine, galactosamine, N-acetylglucosamine and N-acetylneuraminic acid) were examined for chlorination and ozonation followed by chlorination. During ozonation-chlorination, two amino acids, glycine and lysine, exhibited distinctly higher HNM formation than the other compounds. The formation of HNMs was higher at pH 8 than 6. Glycine and lysine also produced higher levels of THMs than the other compounds at pH 8. The presence of nitrite resulted in an increase in HNM formation. The presence of bromide increased the HNM formation, especially brominated HNM species. Bromine incorporation factors of trihalogenated HNMs were higher than those of THMs. For chlorination alone, HNM levels were about the detection limit (4 nM or 0.7 μg L⁻¹) at pH 6 and 8, and in the presence of bromide or nitrite. Amino acids and amino sugars tested, except glycine and lysine, showed relatively low levels of THM (∼15 μg L⁻¹) formation.     

再生水中消毒副产物——卤乙酸的测定方法研究

参照美国国家环保局(USEPA)推荐的饮用水卤乙酸类消毒副产物测定方法(Method 552.3),通过优化该方法的预处理条件和改变检测方法,提出了酸化萃取-衍生化-中和萃取-GC-MS测定再生水中卤乙酸含量的分析方法,并分析了北方某市再生水中4种卤乙酸类消毒副产物含量。结果表明,该方法适用于我国再生水水质,能够有效地消除再生水中共存污染物的干扰;其相对标准偏差(n=7)小于10%,方法的精密度较好;检出限与USEPA方法基本一致;样品加标回收率满足USEPA 6251B标准方法中(100±30)%要求;再生水中的卤乙酸比自来水高出几十倍,对环境和人类存在一定的潜在危害。     

Disinfection byproducts and halogen-specific total organic halogen speciation in chlorinated source waters – The impact of iopamidol and bromide

This study investigated the speciation of halogen-specific total organic halogen and disinfection byproducts(DBPs) upon chlorination of natural organic matter(NOM) in the presence of iopamidol and bromide(Br~-).Experiments were conducted with low bromide source waters with different NOM characteristics from Northeast Ohio,USA and varied spiked levels of bromide(2-30 μmol/L) and iopamidol(1-5 μmol/L).Iopamidol was found to be a direct precursor to trihalomethane(THM) and haloacetic acid formation,and in the presence of Br~-favored brominated analogs.The concentration and speciation of DBPs formed were impacted by iopamidol and bromide concentrations,as well as the presence of NOM.As iopamidol increased the concentration of iodinated DBPs(iodo-DBPs) and THMs increased.However,as Br~-concentrations increased,the concentrations of nonbrominated iodo-and chloro-DBPs decreased while brominated-DBPs increased.Regardless of the concentration of either iopamidol or bromide,bromochloroiodomethane(CHBrClI) was the most predominant iodo-DBP formed except at the lowest bromide concentration studied.At relevant concentrations of iopamidol(1 μmol/L) and bromide(2 μmol/L),significant quantities of highly toxic iodinated and brominated DBPs were formed.However,the rapid oxidation and incorporation of bromide appear to inhibit iodoDBP formation under conditions relevant to drinking water treatment.     

Concentration levels of disinfection by-products in 14 swimming pools of China

Swimming has become a popular exercising and recreational activity in China but little is known about the disinfection by-products (DBPs) concentration levels in the pools. This study was conducted as a survey of the DBPs in China swimming pools, and to establish the correlations between the DBP concentrations and the pool water quality parameters. A total of 14 public indoor and outdoor pools in Beijing were included in the survey. Results showed that the median concentrations for total trihalomethanes (TTHM), nine haloacetic acids (HAA9), chloral hydrate (CH), four haloacetonitriles (HAN4), 1,1-dichloropropanone, 1,1,1-trichloropropanone and trichloronitromethane were 33.8, 109.1, 30.1, 3.2, 0.3, 0.6 µg∙L⁻¹ and below detection limit, respectively. The TTHM and HAA9 levels were in the same magnitude of that in many regions of the world. The levels of CH and nitrogenous DBPs were greatly higher than and were comparable to that in typical drinking water, respectively. Disinfection by chlorine dioxide or trichloroisocyanuric acid could substantially lower the DBP levels. The outdoor pools had higher TTHM and HAA9 levels, but lower trihaloacetic acids (THAA) levels than the indoor pools. The TTHM and HAA9 concentrations could be moderately correlated with the free chlorine and total chlorine residuals but not with the total organic carbon (TOC) contents. When the DBP concentration levels from other survey studies were also included for statistical analysis, a good correlation could be established between the TTHM levels and the TOC concentration. The influence of chlorine residual on DBP levels could also be significant.     

Formation of disinfection by-products during sodium hypochlorite cleaning of fouled membranes from membrane bioreactors

•HAAs was dominant among the DBPs of interest. •Rising time, dose, temperature and pH raised TCM and HAAs but reduced HANs and HKs. •Low time, dose and temperature and non-neutrality pH reduced toxic risks of DBPs. •The presence of EPS decelerated the production of DBPs. •EPS, particularly polysaccharides were highly resistant to chlorine. Periodic chemical cleaning with sodium hypochlorite (NaClO) is essential to restore the membrane permeability in a membrane bioreactor (MBR). However, the chlorination of membrane foulants results in the formation of disinfection by-products (DBPs), which will cause the deterioration of the MBR effluent and increase the antibiotic resistance in bacteria in the MBR tank. In this study, the formation of 14 DBPs during chemical cleaning of fouled MBR membrane modules was investigated. Together with the effects of biofilm extracellular polymeric substances (EPS), influences of reaction time, NaClO dosage, initial pH, and cleaning temperature on the DBP formation were investigated. Haloacetic acids (HAAs) and trichloromethane (TCM), composed over 90% of the DBPs, were increasingly accumulated as the NaClO cleaning time extended. By increasing the chlorine dosage, temperature, and pH, the yield of TCM and dichloroacetic acid (DCAA) was increased by up to a factor of 1‒14, whereas the yields of haloacetonitriles (HANs) and haloketones (HKs) were decreased. Either decreasing in the chlorine dosage and cleaning temperature or adjusting the pH of cleaning reagents toward acidic or alkaline could effectively reduce the toxic risks caused by DBPs. After the EPS extraction pretreatment, the formation of DBPs was accelerated in the first 12 h due to the damage of biofilm structure. Confocal laser scanning microscopy (CLSM) images showed that EPS, particularly polysaccharides, were highly resistant to chlorine and might be able to protect the cells exposed to chlorination.     

Assesment of disinfection by‐products removal by ozonation coupled with adsorption

This research work was performed to evaluate ozonation and granular activated carbon adsorption processes from the view‐point of controlling the formation of disinfection by products (DBPs). Both the humic acid and raw water were first preozonated and then adsorbed on the activated carbon to assess the potency for removal of total organic carbon (TOC) and DBPs. The disinfection by‐product including THMs and HAAs, in principle, can be successfully removed through a use of the ozonation and granular activated carbon (GAC) adsorption processes. However, in practice dealing with the raw water, it is necessary to introduce the pilot‐plant to obtain the design and operation guidelines for the water treatment plant through the ICA (Instrumentation Control and Automation) program in our future research work.     

饮用水有机类消毒副产物毒理学研究方法进展

伴随着饮用水消毒技术的改进,有机类消毒副产物(DBPs)的种类日趋多样化,其生物毒性和健康风险受到广泛关注。基于国内外对DBPs毒理学效应的研究成果,结合消毒技术的发展历程,对有机类DBPs进行了系统的分类,针对含碳消毒副产物(C-DBPs)和含氮消毒副产物(N-DBPs)中典型的DBPs的毒理学研究方法进行了详细的介绍,在此基础上分析了相关研究的不足之处和发展趋势,对今后的研究方向提出了建议。