Methyl bromide in surface drinking waters: Gas-chromatographic determination by the headspace technique

A sensitive method for the gas-chromatographic determination of methy bromide in surface drinking waters is reported. The analytical principle is based on the conversion of methyl bromide into methyl iodide by reaction with sodium iodide. Reaction parameters (amount of sodium iodide added, temperature, reaction time and salinity) are reported to provide a simple, precise and sensitive analytical method with a CH₃Br detection threshold of approx. 5 × 10⁻³μgl⁻¹.     

Continuous flow method for determination of total trihalomethanes in drinking water with membrane-separation

A double-tube separation system with an inner tube of microporous poly(tetrafluoroethylene) (PTFE) and an outer tube of PTFE, is proposed for the continuous determination of TTHMs (total trihalomethanes) in drinking water. The TTHMs in the sample after mixing sodium sulfite solution, are separated with the double-tube system at 50°C and are mixed with alkaline nicotinamide solution, and then heated to 98°C. After cooling in an ice bath, the reaction product is fed to a fluorometer and the fluorescence intensity excited at 372 nm is measured at 467 nm. There was no interference from unknown species existing in drinking water and river water by using the membrane separation system. A response was obtained within 8 min. The detection limit (S/N = 3) was 0.8 μg/1. The present method was applied to the determination of the TTHMs in drinking water.     

Halonitromethane formation potentials in drinking waters

Halonitromethanes (HNMs) are highly cyto- and genotoxic nitrogenous disinfection by-products (DBPs) that have been detected in some water distribution systems. In this study, a systematic investigation was conducted to examine the formation potential of HNMs in drinking waters under different oxidation conditions. Formation potential tests of samples obtained from various drinking water sources showed that ozonation-chlorination produced the highest HNM yields followed by in the order of chlorination, ozonation-chloramination, and chloramination. Similar or higher HNM yields were observed in the treated waters (i.e., after conventional water treatment) than in the raw waters, indicating that hydrophilic natural organic matter (NOM) components that are not effectively removed by conventional treatment processes are likely the main precursors of HNMs. This was further confirmed by examining HNM formation potentials of NOM fractions obtained with resin fractionation. Hydrophilic NOM fractions (HPI) showed significantly higher HNM yields than hydrophobic (HPO) and transphilic (TPH) fractions. The correlation analysis of HNM formation potentials during ozonation-chlorination with various water quality parameters showed the best correlation between the HNM yields and the ratio of dissolved organic carbon to dissolved organic nitrogen concentrations in the water samples tested.     

Organics isolation from fresh and drinking waters by macroporous anion-exchange resins

A research on the isolation of organic pollutants from water is presented. Five macroporous anionic resins: Varion AT400, Asmit 229N, Zerolite 553N, Wofatite EA60 and Amberlite IR93 were used for humic substances and other anionic organics isolation. Varion AT400 resulted to be the best anionic resin (about 90% recovery of humic substances and a lower recovery for other anionic substances). Nearly complete desorption was achieved by NaCl/NaOH 10%/2% solution, at a volume of about 3.5 times the resin bed volume.     

Modeling of bromate formation by ozonation of surface waters in drinking water treatment

The main objective of this paper is to try to develop statistically and chemically rational models for bromate formation by ozonation of clarified surface waters. The results presented here show that bromate formation by ozonation of natural waters in drinking water treatment is directly proportional to the "Ct" value ("Ctau" in this study). Moreover, this proportionality strongly depends on many parameters: increasing of pH, temperature and bromide level leading to an increase of bromate formation; ammonia and dissolved organic carbon concentrations causing a reverse effect. Taking into account limitation of theoretical modeling, we proposed to predict bromate formation by stochastic simulations (multi-linear regression and artificial neural networks methods) from 40 experiments (BrO(3)(-) vs. "Ctau") carried out with three sand filtered waters sampled on three different waterworks. With seven selected variables we used a simple architecture of neural networks, optimized by "neural connection" of SPSS Inc./Recognition Inc. The bromate modeling by artificial neural networks gives better result than multi-linear regression. The artificial neural networks model allowed us classifying variables by decreasing order of influence (for the studied cases in our variables scale): "Ctau", [N-NH(4)(+)], [Br(-)], pH, temperature, DOC, alkalinity.     

Coliform culturability in over- versus undersaturated drinking waters

The culturability of Escherichia coli in undersaturated drinking water with respect to CaCO3 (corrosive water) or in oversaturated water (non-corrosive water) was tested in different reactors: glass flasks (batch, "non-reactive" wall); glass reactors (chemostat, "non-reactive" wall) versus a corroded cast iron Propella reactor (chemostat, "reactive" wall) and a 15-year-old distribution system pilot (chemostat, "reactive" wall with 1% corroded cast iron and 99% cement-lined cast iron). The E. coli in E. coli-spiked drinking water was not able to maintain its culturability and colonize the experimental systems. It appears from our results that the optimal pH for maintaining E. coli culturability was around 8.2 or higher. However, in reactors with a reactive wall (corroded cast iron), the decline in E. coli culturability was slower when the pH was adjusted to 7.9 or 7.7 (i.e. a reactor fed with corrosive water; pHpHs). We tentatively deduce that corrosion products coming from chemical reactions driven by corrosive waters on the pipe wall improve E. coli culturability.     

A survey of organic contaminants in household and bottled drinking waters in Kuwait

Chemical analysis of volatile organic compounds (VOCs) and semivolatiles (SVs), including pesticides, was performed on 623 and 568 samples, respectively, of household drinking water, as well as on 113 samples from 71 brands of bottled water available in Kuwaiti markets. The analysis was performed according to United States Environmental Protection Agency (US-EPA) Methods 524.2 and 525.2. Nine VOCs and eight SVs were found in household water. Furthermore, between one and seven of 12 VOCs were detected in 93% of the bottled water brands. All bottled waters were found to be completely free of SVs. Styrene was the main pollutant found in all brands packaged in polystyrene containers of sizes 200-mL and 250-mL, with levels generally higher than the WHO guideline value of 20 µg/L. The levels of styrene, toluene, ethyl benzene and xylenes were found to increase with storage time, which indicates that these VOCs were migrating from the container material. No effect was detected due to changes in the storage temperature. All detected VOCs and SVs in household and bottled waters, except styrene, were found at concentrations much lower than those established as safe by WHO guidelines and US-EPA maximum contaminant levels (MCLs), respectively.     

Determination of particulate organic carbon in waters by the chemical oxidation method

Particulate organic carbon (POC) in waters was determined by chemical oxidation method which has been widely used for the determination of total organic carbon and/or dissolved organic carbon. In this method, a water sample was filtered through a filter paper and the paper was placed in a glass ampoule, followed by the determination of POC with a total carbon analyzer. This paper discussed the problems of carbon contamination dissolving from filter papers. The selection of filter papers, the carbon blank values resulting from the papers and the pretreatment of the papers were studied. It became clear that the glass-fiber filter paper pretreated at 500°C for 8 h was superior to the filter papers treated under other conditions. The POC's in waters were determined by this method, and the results agreed well with those obtained by an ordinary dry combustion method.     

Stirring bar sorptive extraction in the determination of PAHs in drinking waters

The application of a new extraction technique which is known as stir bar sorptive extraction (SBSE), followed by high-performance liquid chromatography with a fluorescence detector, was assessed for determining eight polycyclic aromatic hydrocarbons (PAHs) in water samples. The extraction conditions such as acetonitrile addition; effects of temperature and salt; and finally, extraction and desorption time profiles were studied. Once SBSE was optimized, analytical method parameters such as linearity (r(2)>0.991), precision (<9%), detection (0.5-7.3 ng/L) and quantitation (1.0-22 ng/L) limits were estimated. To correct for the 43-57% absolute recovery depending on the PAH, calibration was done with a line obtained submitting standard-spiked blank tap waters to the complete sample treatment and analysis. Consequently, relative recovery was about 100% because all water samples (those for calibration purposes and those for recovery estimation) were processed in the same way and the absolute recovery remained constant. SBSE method characteristics were checked with the analysis of real drinking waters in the search for PAHs.     

Comparison of NOM character in selected Australian and Norwegian drinking waters

Observations from many countries around the world during the past 10-20 years indicate increasing natural organic matter (NOM) concentration levels in water sources, due to issues such as global warming, changes in soil acidification, increased drought severity and more intensive rain events. In addition to the trend towards increasing NOM concentration, the character of NOM can vary with source and time (season). The great seasonal variability and the trend towards elevated NOM concentration levels impose challenges to the water industry and the water treatment facilities in terms of operational optimisation and proper process control. The aim of this investigation was to compare selected raw and conventionally treated drinking water sources from different hemispheres with regard to NOM character which may lead to better understanding of the impact of source water on water treatment. Results from the analyses of selected Norwegian and Australian water samples showed that Norwegian NOM exhibited greater humic nature, indicating a stronger bias of allochthonous versus autochthonous organic origin. Similarly, Norwegian source waters had higher average molecular weights than Australian waters. Following coagulation treatment, the organic character of the recalcitrant NOM in both countries was similar. Differences in organic character of these source waters after treatment were found to be related to treatment practice rather than origin of the source water. The characterisation techniques employed also enabled identification of the coagulation processes which were not necessarily optimised for dissolved organic carbon (DOC) removal. The reactivity with chlorine as well as trihalomethane formation potential (THMFP) of the treated waters showed differences in behaviour between Norwegian and Australian sources that appeared to be related to residual higher molecular weight organic material. By evaluation of changes in specific molecular weight regions and disinfection parameters before and after treatment, correlations were found that relate treatment strategy to chlorine demand and DBP formation.     

Survey of volatile halogenated organics (VHO) in Italy: Levels of VHO in drinking waters, surface waters and swimming pools

A survey undertaken in Italy (Emilia-Romagna region) has shown that Volatile Halogenated Organics (VHO) are present in many water samples; analysis has been performed by static head-space gas chromatographic technique.In drinking water samples low levels of pollution have become evident before any treatment, while after chlorination with sodium hypochlorite, or chlorine as a gas, VHO have appeared, almost exclusively as trihalomethanes (THM), sometimes at fairly high levels (max = 41.8 μg l⁻¹).Surface water samples have been collected every other month in one year, and have shown different levels of contamination; in most cases VHO (mainly chlorinated solvents) appeared just as traces, seldom at high concentration (max = 263 μg l⁻¹).Swimming pool samples have shown the high levels of contamination (max = 177.4 μg l⁻¹), mainly due to THM, as a consequence of chlorination with sodium hypochlorite.As a matter of fact, it has become evident that VHO pollution is wide-spread in every kind of water; while contamination of surface waters can only involve environmental and aquatic life, contamination especially of drinking waters, and also of swimming pool waters must be controlled as it can directly act on human health.     

Detection,occurrence, and removal of selected pharmaceuticals in Missouri source and finished drinking waters

A simple, sensitive, and selective solid phase extraction – ultra-fast liquid chromatography – tandem mass spectrometry (SPE-UFLC-MS/MS) method was developed and applied for the analysis of selected important pharmaceutical compounds in source and finished drinking waters. The method detected the following six pharmaceuticals, cotinine, cephapirin, ciprofloxacin, enrofloxacein, azithromycin, and diphenhydramine, at sub-μg/L level in multiple water matrices after pre-concentration by SPE. Cotinine-d₃ and ¹³C₃¹⁵ N-Ciprofloxacin were used as internal standards for accurate quantitation. This method was validated through spike recoveries (67–129%), reproducibility (RSD: 2.3–15.7%), and method detection limits (MDLs: 2–5 ng/L). The method was used to test for occurrence of these pharmaceuticals in source and drinking waters from 13 Missouri water treatment facilities in four different seasons. In general, higher detection frequency and concentrations of pharmaceuticals were observed in colder months due presumably to less dilution (at lower flows) and slower degradation. The PPCP removals by different activated carbons were also evaluated. The occurrence and removal results in this study provide valuable information to help water treatment facilities taking appropriate strategies for better control of trace pharmaceuticals in drinking water.     

Haloacetic acids and trihalomethanes in finished drinking waters from heterogeneous sources

Trihalomethanes (THM) and haloacetic acids (HAA) are the most frequent chlorination by-products (CBP) in finished drinking waters. Traditionally, THM have been used as surrogates for CBP although the quantitative association between THM and other CBP is not well established. This problem is addressed in the present study from the analysis of THM and HAA in drinking water samples from four Spanish regions, representing areas with very different CBP composition, e.g. between 86 and 8.0 microg/l of THM and 50-3.0 microg/l of HAA.The resulting dataset exhibit a statistically significant correlation between total THM and HAA (Pearson's correlation coefficient, r(p)=0.815,p<0.0005). Furthermore, specific HAA are highly correlated with specific THM or their combinations. Accordingly, multivariate linear regression analysis of the concentrations observed show that the levels in total and specific HAA can be predicted from the THM content. These results are relevant for epidemiological studies on health effects from CBP exposure since they usually involve comparison of populations consuming waters of very distinct quality.     

A comparison of disinfection by-products found in chlorinated and chloraminated drinking waters in Scotland

Seven water treatment works were selected to compare disinfection by-products (DBPs) formed when using chlorination and chloramination. DBPs measured included trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), trihalonitromethane, iodinated THMs and nitrosamines. Generally treatment works that used chloramination were able to meet the European THM regulatory limit of 100 μg L⁻¹ whereas the chlorinated works found it significantly more difficult. There were no significant differences in the levels of nitrogenous DBPs between the treatment works using chlorination or chloramination with the exception of the nitrosamine N-nitrosodimethylamine (NDMA) which was present at one treatment works in one season.     

铬天青法和AAS法测定水中铝的方法比对

根据第十次全国城市供水水质检测机构质量控制考核结果,比较分析了铬天青法和原子吸收法对AL的质控盲样的测定,结果表明：两种方法均符合标准要求,铬天青s法应用较广,而石墨炉原子吸收法的使用有局限。     

硬化混凝土中水泥和粗细集料用量的测定方法

混凝土原材料组分决定了混凝土材料的性能,其原材料主要为水泥、水和粗细集料等。目前关于硬化混凝土中水泥含量和粗细集料的测定方法国内外没有统一标准,造成科研和工程应用领域的困难。研究的硬化混凝土原始水泥含量测定的方法是通过化学分析和XRD手段测定出混凝土中的Ca O(Si O2)或Ca元素含量,结合混凝土原材料水泥中的Ca O(Si O2)或Ca元素含量和硬化混凝土的干密度可计算出硬化混凝土中的原始水泥含量,结果表明化学分析法(Ca O)效果最好;硬化混凝土中粗细集料含量的测定方法主要是通过破碎、加热和筛分并进行酸溶解的手段,结果表明不同龄期的样品均取得了较好的试验精度。这些方法的提出和研究为今后该方向的深入研究提供了帮助。     

Screening high-fluoride and high-arsenic drinking waters and surveying endemic fluorosis and arsenism in Shaanxi province in western China

The objectives of this study were to screen high-fluoride and high-arsenic drinking waters, to evaluate the effectiveness of fluoride-reducing projects and to assess the present condition of endemic fluorosis and arsenism in Shaanxi province in western China. For screening high-fluoride drinking waters, five water samples were collected from each selected village where dental fluorosis patients were detected in 8-12 year-old children. For evaluating the effectiveness of fluoride-reducing projects, four water samples were collected from each project at end-user level. Fluoride concentrations in water samples were measured by fluoride-selective electrode method or spectrophotometry. Dental fluorosis in children aging 8-12 years was examined according to Horowitz's Tooth Surface Index of Fluorosis. Skeletal fluorosis in adults was detected clinically and radiologically according to Chinese Criteria of Clinical Diagnosis of Skeletal Fluorosis. For screening high-arsenic waters, 20 water samples were collected from each village which was selected from areas characterized by the geographic features to induce high-arsenic underground water, i.e., alluvial plains, ore mining or smelting areas, geothermal artesians, and thermal springs. Arsenic concentrations in water samples were determined by spectrophotometry or arsine generation atomic fluorospectrophotometry. Arsenism in adults aging 40-89 years was examined in villages with arsenic concentrations in drinking water above 0.05 mg/l according to Chinese Criteria for Classification of Endemic Arsenism Areas and Clinical Diagnoses of Endemic Arsenism. The results showed that the fluoride level of 7144 water samples was 1.17 +/- 0.93 mg/l. There were 3396 (47.6%) high-fluoride waters (fluoride level was above 1.0 mg/l) distributing in 786 (45.1%) villages, where about 0.8 million (50.0%) people inhabited. Additionally, the 1315 fluoride-reducing projects were studied. The fluoride level of the projects was 2.79 +/- 1.09 and 0.98 +/- 0.47 mg/l before and after building the projects, which remained at relatively lower level (1.03 +/- 0.47 mg/l). But there were still 58.0% of the projects providing drinking waters with fluoride concentrations beyond 1.0mg/l. The rates of dental fluorosis and skeletal fluorosis were 38.2% and 11.8%, respectively. The arsenic level of 1732 water samples was 0.010 +/- 0.082 mg/l. There were 174 (14.9%) high-arsenic waters (arsenic level was above 0.010 mg/l) being detected, distributing in 41 (38.7%) villages. The arsenic level in 53 (4.5%) water samples was beyond 0.025 mg/l. There were 3 villages with arsenic level in drinking water beyond Chinese National Permissible Limits (0.050 mg/l), and the prevalence rate of arsenism reached 37.0% in these three villages, 3.7%, 22.2%, and 11.1% of subjects suffering from mild, moderate, and severe arsenism, respectively. Conclusively, the wide distribution of high-fluoride drinking waters contributes to the prevalence of dental and skeletal fluorosis in Shaanxi province and the quality of fluoride-reducing projects should be further improved. Ore mining and smelting induces high-arsenic drinking waters, resulting in arsenism prevalence in Shang-luo city. Proper measures should be taken to deal with water pollution in the ore mining and smelting areas in order to solve the high-arsenic water problem in Shaanxi province.     

Simultaneous determination of dissolved organic carbon and phosphorus in waters using flame ionization and photometric detectors

An apparatus with flame ionization and photometric detectors was assembled for the simultaneous determination of dissolved organic carbon (DOC) and phosphorus (DP) in waters. The optimum operating conditions were described. The long-term precision (relative standard deviation) is 5.8% for DOC and 5.2% for DP. The detection limits are 0.09 μg ml⁻¹ for DOC and 0.03 μg ml⁻¹ for DP. The responses for various DOC and DP compounds agreed almost with those obtained by combustion-infrared and persulfate digestion-colorimetric methods, respectively. DOC and DP in several water samples were determined by this method and other methods, and the results obtained by those methods were discussed.     

质子低场核磁共振技术表征建筑石膏水化进程

基于溶解-析晶理论,根据X射线衍射和热重分析结果,将建筑石膏的水化进程划为4个水化阶段,并利用质子低场核磁共振技术研究了不同水膏比m_W/m_G和聚羧酸系减水剂(PCE)掺量下,新拌浆体横向弛豫时间T₂分布、T₂加权平均值■与主峰峰面积S_main随水化时间的变化规律.结果表明：■和S_main的变化趋势与水化阶段均具有良好的相关性;增大m_W/m_G可以使建筑石膏水化阶段出现的时间提前,而掺加PCE则对建筑石膏有明显的缓凝作用.     

Occurrence of bromate, chlorite and chlorate in drinking waters disinfected with hypochlorite reagents. Tracing their origins

Bromate was first reported as a disinfection by-product from ozonated waters, but more recently it has been reported also as a result of treatment using hypochlorite solutions worldwide. The aim of this study was to study the scope of this phenomenon in the drinking waters (n = 509) of Castilla y León, Spain, and in the hypochlorite disinfectant reagents. Two thirds of the treated waters monitored were found to have bromate concentrations higher than 1 µg/l, and of them a median value of 8 µg/l and a maximum of 49 µg/l. These concentrations are higher than those reported so far, however, a great variability can be found. Median values for chlorite were of 5 µg/l, and of 119 µg/l for chlorate. Only 7 out of 40 hypochlorite feedstock solutions were negative for bromate, the rest showing a median of 1022 mg/l; and 4 out of 14 calcium hypochlorite pellets were also negative, the rest with a median of 240 mg/kg. Although bromate is cited as potentially added to water from calcium hypochlorite pellets, no reference is found in scientific literature regarding its real content. Chlorite (median 2646 mg/l) and chlorate (median 20,462 mg/l) and chlorite (median 695 mg/kg) and chlorate (median 9516 mg/kg) were also monitored, respectively, in sodium hypochlorite solutions and calcium hypochlorite pellets. The levels of chlorite and chlorate in water are considered satisfactory, but not those of bromate, undoubtedly owing to the high content of bromide in the raw brines employed by the chlor-alkali manufacturers. Depending on the manufacturer, the bromate concentrations in the treated waters may be very heterogeneous owing to the lack of specification for this contaminant in the disinfectant reagents —the European Norms EN 900 and 901 do not mention it.