The Biotesting of tap water treated with silicon mineral using plant test organisms

The biotesting of tap water treated in static conditions with gray and black silicon mineral was carried out using plant test organisms. Onion (Allium cepa) and wheat grains (Triticum vulgare) were used as the test organisms. It was shown that the silicon-activated water stimulates metabolic processes during the germination of onion and wheat grains. It was observed that the development of the root system of the plant test organisms was stimulated, which indicates that the toxic resistance of the plants increases at the early stages of the development (start-up effect). The test data obtained confirm the high biological activity of silicon in water environment resulting in the stimulation of the growth and development, as well as in the improvement of the resistance to the toxic effects of plant organisms.     

Lead contamination in tap water of households with children in Lower Saxony, Germany

Lead has numerous acute and chronic adverse effects on human beings. This is especially true for infants and children. The main path of lead ingestion in children can be different according to housing and living situation. The intake of lead through drinking water is commonly due to metal corrosion. The users plumbing can be an important factor. In recent years, many lead pipes in Germany have been replaced by pipes made of an alternative material. The aim of this study is to assess the present state of drinking water contamination and the resulting exposure of infants to lead. For this purpose mothers of new-born babies were offered a free examination of their drinking water. After a written declaration of consent had been obtained and after the infant in question had reached an age of 3 months, a stagnation sample of cold tap-water after overnight stagnation together with a random daytime sample was obtained from the family. The collected samples were analysed by atomic absorption spectrometry for their lead concentration. In total, 1485 samples from households were collected. Of the 1434 stagnation samples, 3.1% had lead concentrations greater than 0.01 mg/l (recommended limit of the WHO) and 0.6% had concentrations above the limit of the German drinking water regulation (0.04 mg/l). The values for the 1474 random daytime samples were 2.1% above 0.01 mg/l and 0.2% greater than 0.04 mg/l, respectively. By region, the areas Bovenden, Friedland, Duderstadt, Northeim and Rosdorf were particularly affected. The highest measured concentrations of lead in the stagnation samples were 0.11 mg/l and 0.15 mg/l in the random daytime samples, respectively.     

Trihalomethanes formation in water treated with chlorine dioxide

Formation of trihalomethanes (THMs) was investigated in water treated with chlorine dioxide (ClO₂) and/or chlorine (Cl₂) where humic acid (HA) was used as THMs precursors. When ClO₂ was used as the only disinfectant, no THMs were detected in bromide-free water; while only CHBr₃ was formed in water containing bromide ion because ClO₂ could oxide bromide to form hydrobromous acid which subsequently reacted with HA, and the yield CHBr₃ increased with bromide concentration and ClO₂ dosing. When water was treated with ClO₂ combined with Cl₂, only CHCl₃ was formed in the absence of bromide, however, all four species of THMs were formed in the presence of bromide; the THMs formation potential decreased gradually with an increase in the ratio of ClO₂ to Cl₂ because ClO₂ reacted with HA to render them unreactive or unavailable for THMs production. When water (with or without bromide ion) was irradiated by light, the yield of THMs was increased as a function of irradiation time to a maximum, and thereafter decreased markedly; the possible mechanism is that irradiation could activate the THMs precursors in HA, and at the same time destroy the reactivity of ClO₂ or Cl₂. The same results could be collected from natural water treated by ClO₂ with or without irradiation.     

Trihalomethanes formation in point of use surface water disinfection with chlorine or chlorine dioxide tablets

In remote or underdeveloped areas, natural disaster emergencies and armed conflict zones, point‐of‐use surface water disinfection with chlorine tablets provides microbiologically safe water, but disinfection by‐products such as trihalomethanes (THMs) are formed. While the health risks from THMs are much less than the risks from consuming microbiologically unsafe water, it is nonetheless desirable to understand and minimise THM formation. We show that THM concentrations in surface water samples from the Northern British Isles disinfected with chlorine tablets increased with contact time, in some cases to significantly exceed EU, US EPA and WHO drinking water guidance values after more than an hour. More stagnant water from ponds and lochs had higher THM formation than river water. Doubling the chlorine tablet dose slightly enhanced THM formation, and passing water through coffee filter paper reduced it. Chlorine dioxide tablets produced minimal amounts of THMs.     

Low trihalomethane formation in Korean drinking water

Organics in water have the potential to generate harmful disinfection by-products (DBPs) such as trihalomethanes (THMs) during the chlorination process. To clarify the regulatory implications of Korean THMs levels which appear to be significantly lower than those in the US where the Stage 1 and 2 D/DBPs rule has been promulgated, the characteristics of THMs formation were investigated on five major river waters in Korea. Water samples were taken from 12 water treatment plants on five major rivers that serve as drinking water sources for more than 90% of the Korean population. Trihalomethane formation potential (THMFP), total organic halide formation potential (TOXFP) and ultraviolet absorbance at 254 nm (UV(254)) were determined and compared with those from US data. A survey of existing data [J Korean Soc Water Qual; 16(4) 2000b 431-443] provided evidence that THMs levels in treated drinking water in Korea were one-third of those reported in the US. The lower THMs levels were mainly attributable to the differences in the level and THMFP of dissolved organic carbon (DOC). The DOC levels and the THMFP normalized to DOC were approximately 60% of those in the US. Results which combined could quantitatively account for the lower THMs levels (i.e. 0.6 x 0.6 approximately 1/3) in Korea. The observed Korean THMs levels were over-predicted by the THMs model () developed in the US. The level of THMFP was found to be similar if normalized for aromaticity as measured by UV(254). These findings suggest that: (i) the case for more stringent THMs control is not likely to be a high priority among issues of drinking water quality in Korea; and (ii) significant variation of THMFP level may exist over different geographic regions; hence (iii) independent THMs models should be developed to make accurate predictions for different regions.     

A retrospective cohort study of trihalomethane exposure through drinking water and cancer mortality in northern Italy

A few epidemiologic studies have suggested that consumption of drinking water with high trihalomethane content increases the risk of cancer. We investigated the mortality of a cohort of 5144 residents in Guastalla, northern Italy, who were supplied tap water with high chloroform and trihalomethane content between 1965 and 1987. Using death rates of a nearby community as reference rates, the standardized mortality ratio from all cancers between 1987 and 1999 was slightly increased for both males (1.2, 95% confidence interval 1.1-1.4) and females (1.1, 95% confidence interval 1.0-1.3). This was mainly due to a higher mortality from stomach, liver, lung, prostate and bladder cancer in males and from stomach, pancreas, breast and ovarian cancer and lymphocytic leukemia in females. We also noted excess mortality from melanoma in both males and females. Overall, our findings were consistent with an association between trihalomethane exposure and increased cancer risk at some sites. However, the point estimates were statistically imprecise, due to the limited number of deaths for some site-specific cancers. In addition, we were unable to rule out the possibility of confounding due to smoking and other life-style factors with regard to some of the excess rates.     

Superparamagnetic nanoparticles in tap water

Magnetization measurements are a useful tool in the characterization of corrosion products formed in municipal water pipes made of iron or steel. Fine particles formed in corrosion processes exhibit superparamagnetic behavior. The size of such particles, which determines their capacity to adsorb hazardous species, can therefore be found from magnetic measurements. Application of this methodology to samples extracted from flowing and stagnant tap water, respectively, has shown that the flowing water samples contained multidomain (>100nm) ferromagnetic particles as well as aggregates of very fine superparamagnetic subdomain particles. The sizes of the fine particles are of the order of 3.2-5.6nm. In addition to small subdomain superparamagnetic particles stagnant water samples also contained larger subdomain particles with average dimensions of 59-67nm. Both large and small subdomain particles were trapped by the fine charcoal in household filters.     

Model development for predicting changes in DBP exposure concentrations during indoor handling of tap water

Disinfection by-products (DBPs) in municipal drinking water are a matter of concern because of their possible risks to human health. Risk assessment studies often use measurements of DBPs in water distribution systems, whereas populations are typically exposed to the indoor tap water. Further to this, consumers often employ several indoor strategies to handle tap water (e.g., storing in a refrigerator, boiling, filtering, etc.) prior to use. The indoor handling of municipal water may have implications on DBPs' exposure assessment. This study investigates and develops models to predict the effects of various indoor handling strategies on trihalomethanes (THMs) and haloacetic acids (HAAs). Linear and nonlinear models are developed to predict changes in THM and HAA concentrations due to various indoor water manipulation strategies. The models are capable of assessing representative exposure concentrations of THMs and HAAs as a result of indoor handling, which might be useful in gaining a better understanding of exposure and risks from DBPs in municipal drinking water.     

Empirical rate equation for trihalomethane formation with chlorination of humic substances in water

Trihalomethane (THM) in drinking water is formed by chlorination of humic substances. In this study, the rates of THM formation in aqueous solution of humic acid were examined under various conditions. The following rate equation was obtained empirically. [THM] = k (pH − a)[TOC][Cl₂]₀^mtⁿ.

Here, [THM] is the concentration of total THM after t h, [TOC] and [Cl₂]₀ are the concentrations of total organic carbon and chlorine dose, k is the rate constant and a, m and n are parameters. The values of k, a, m and n for humic acid as reagent were obtained as 8.2 × 10⁻⁴ (l^mmg^−mh⁻ⁿ), 2.8, 0.25 and 0.36, respectively. The activation energy was obtained as 37 kJ mol⁻¹. Further, it was proved that the above equation could be applied to the rates of THM formation from precursors in actual river and lake waters.     

浅谈净水厂用氯安全管理

本文根据净水厂用氯的特点,具体介绍氯的特性,分析氯瓶贮存、使用以及净水厂加氯系统可能存在的安全隐患和危险性,并提出净水厂用氯安全管理方法和控制措施。     

Understanding data requirements for trihalomethane formation modelling in water supply systems

Tighter regulatory standards for trihalomethanes in drinking water have been introduced in many countries in response to improved epidemiological evidence. This has led to the need to model better the THM concentrations in water distribution systems in order to manage efficiently economic, chemical and microbiological factors. THM modelling is a challenging process given the complex chemistry and dependence on river catchment, water treatment works and distribution system characteristics. It is demonstrated that a good understanding of the system from raw water to tap is needed if cost effective models of appropriate fidelity are to be produced. For appropriate systems models can incorporate, through empirical relationships, raw water quality variations based on river flow predictions, aspects of unit process management decision making variables as well as distribution system characteristics. In many systems model fidelity and hence efficient management is constrained by a lack of knowledge of system response.     

Predicting the presence of E. coli in tap water using machine learning in Nepal

Within developing countries, a multitude of problems that affect the water supply process can result in the contamination of water taps. While machine learning applications have become popular for attaining efficient water quality predictions, acquiring the necessary data for modelling for developing countries is challenging. This study constructs water quality prediction models by machine learning with a pseudo-pipeline network to complement the missing data of the water supply process. Using both water source and water tap quality information measured by the Government of Nepal, we apply the three machine learning models: support vector machine (SVM), random forest (RF) and LightGBM. Furthermore, we also apply a traditional statistical method—logistic regression (LR)—to the prediction of the Escherichia coli (E. coli) contamination in water taps. With some input variables (such as the length from the nearest sources) obtained from the pseudo-pipeline network, the results show that SVM has stable and high accuracy for both the 26 cities (70%) and for the 25 cities except for Kathmandu (79%). LR performed a significantly lower accuracy for all cities (61%) than for 25 cities (79%). Additionally, we show that our method can be applied to other regions where a water quality survey has not yet been conducted.     

Combined air conditioning and tap water heating plant using CO2 as refrigerant

A combined air conditioning and tap water heating plant using carbon dioxide (CO₂) as refrigerant has been investigated theoretically and experimentally. The system is suitable for countries with year around cooling demand, such as Indonesia or Singapore, and a need for hot tap water. A unique CO₂ transcritical cycle characteristic for heating process can afford an improvement to a CO₂ air conditioning system when rejected heat from the system is recovered. Some parameters affecting performance of the combined system are discussed.     

Use of regression models to link raw water characteristics to trihalomethane concentrations in drinking water

A study was conducted to examine the effect of raw water bromide on the formation and distribution of trihalomethanes (THMs) in finished drinking water. Twenty major water supplies in East Tennessee were selected for their significant levels of bromine-containing THMs, as demonstrated by previous studies. The cities were sampled quarterly for raw water pH, temperature, NVTOC, and bromide content, as well as finished water pH, NVTOC, and applied chlorine dose, coupled with conjunctive measurement for 7-day THMs.Few data for bromide levels in natural waters are currently available since most conventional colorimetric applications lack desired sensitivity, as does direct ion chromatography (IC). Although Fishman's kinetic permanganate method is adequate in the 10–100 μp 1⁻¹ range, it is time-consuming, and prone to certain interferences. An IC method using a sample preconcentration column has been evaluated. The method produced a 1 μg 1⁻¹ minimum detection level using deionized water based standards, with 3% relative precision completed at a standard concentration of 1000μg 1⁻¹. Bromide levels in the raw waters sampled were found to range from 10 to 225 μg 1⁻¹.Concurrent with the field sampling, laboratory chlorination experiments were conducted using Tennessee River water, under controlled laboratory conditions of bromide level, chlorine dose, pH, ionic strength, temperature, and organic precursor concentration. Resultant THM formations were monitored over a 96 h reaction period. The results concurred with observations made in previous work by such researchers as Bird and Rook.Nonlinear regression models for THM formation were generated using the laboratory chlorination data with respect to pH, temperature, chlorine dose, bromide, and NVTOC level. Actual values for these variables were substituted into the regression models, using the seasonal field data. Resultant predictive THM values were then compared with actual THM values for those data sampled. In general, these models were found to give acceptable fits. Overall 74.1% of the predicted values were within ± 15% of the measured values.     

Chemometric modeling and prediction of trihalomethane formation in Barcelona's water works plant

Formation and occurrence of trihalomethanes (CHCl3, CHBr3, CHCl2Br, and CHBr2Cl) are investigated in water chlorination disinfection processes in the Barcelona's water works plant (WWP). Twenty-three WWP variables were measured and investigated for correlation with trihalomethane formation. Multivariate statistical methods including principal component analysis (PCA), multilinear regression (MLR), stepwise MLR (SWR), principal component regression (PCR) and partial least squares regression (PLSR) have been used and compared to model and predict the complex behavior observed for the measured trihalomethane concentrations. The results, obtained by PCA as well as the evaluation of the statistical significance of the coefficients in the linear regression vectors, revealed that the most important WWP variables for trihalomethane formation were: water temperature, total organic carbon, added chlorine concentrations, UV absorbance and turbidity at different sites of the WWP, as well as other variables like wells supply flow levels and carbon filters age. Overall, MLR and PLSR methods performed the best and gave similar good predictive properties. Best results were obtained for the total sum of trihalomethane concentrations, TTHM, with average modeling and prediction relative errors of 12% and 16%, respectively. Among the individual trihalomethanes, the concentrations of CHBr3 were the worst predicted ones with average modeling and prediction relative errors between 21-25% and 29-31%, respectively, followed by CHCl2Br with 23-26% and 25-27%. Better predictions were obtained for the concentrations of CHBr2Cl with relative modeling and prediction errors varying between 14-17% and 21%, and for the concentrations of CHCl3 with 21-24% and 23-25% errors, respectively.     

Exposure levels to brominated compounds in seawater swimming pools treated with chlorine

Despite evidence of formation of brominated compounds in seawater swimming pools treated with chlorine, no data about exposure levels to these compounds have been reported. To address this issue, a survey has been carried out in four establishments (representing 8 pools) fed with seawater and devoted to relaxing and cure treatments (thalassotherapy centres located in Southeast of France). Carcinogenic and mutagenic brominated disinfection byproducts (trihalomethanes -THM- and halogenated acetic acids -HAA-) were quantified at varying levels, statistically related to organic loadings brought by bathers, and not from marine organic matter, and also linked to activities carried out in the pools (watergym vs swimming). Bromoform and dibromoacetic acid, the most abundant THM and HAA detected, were measured at levels up to 18-fold greater than the maximum contaminant levels of 60 and 80 μg/L fixed by US.EPA in drinking waters. The correlations between these disinfection byproducts and other environmental factors such as nitrogen, pH, temperature, free residual chlorine, UV₂₅₄, chloride and bromide concentrations, and daily frequentation were examined. Because thalassotherapy and seawater swimming pools (hotels, cruise ships,…) are increasing in use around the world and because carcinogenic and mutagenic brominated byproducts may be produced in chlorinated seawater swimming pools, specific care should be taken to assure cleanliness of users (swimmers and patients taking the waters) and to increase water circulation through media filters to reduce levels of brominated byproducts.     

Source and occurrence of particulate lead in tap water

Lead samples were collected at the tap from homes with lead service lines (LSLs) in a full-scale utility using both random daytime (RDT) and particulate stimulation sampling (PSS) protocols. Analysis of the results revealed two sources and occurrences of particulate lead. A first source is due to corrosion of lead-bearing elements in the premise plumbing (PP) and occurs mostly at low to moderate concentrations <3 μg/L, with some sporadic higher concentrations (4-12 μg/L). These spikes were consistently observed and considerably increased using PSS, showing that current sampling protocols may miss a significant portion of particulate lead. The second source results from the adsorption of dissolved lead onto iron deposits in LSL/PP, and is continuously present at low to moderate concentrations. Statistical analyses were validated by physical analyses of: (i) lead scales from LSLs; and (ii) lead particles from tap aerators.     

A survey of tap water quality in Kuala Lumpur

A safe drinking water programme known as The National Drinking Water Quality Surveillance Programme (NDWQSP) was launched by the Ministry of Health, Government of Malaysia in 1983 to ensure safe practices in water treatment and distribution. The aim of this work was to assess the effectiveness of this programme in the improvement of tap water quality in and around Kuala Lumpur. The results indicate that there was no microbial contamination in 100 random samples collected from 20 selected areas. Other quality parameters such as colour, pH, turbidity, hardness, magnesium, sulphate and chloride were within acceptable limits. Heavy metals such as Cu²⁺, Pb²⁺, Cr (total), Ni²⁺, Cd²⁺, Fe (total) and Mn (total) were also under control. The only exception was Ba²⁺, which did not comply with the standard and was up to ten times higher than the guideline value. Moreover, there was significant variation in water quality as indicated by the test results.     

Oxidation of pharmaceuticals during water treatment with chlorine dioxide

The potential of chlorine dioxide (ClO2) for the oxidation of pharmaceuticals during water treatment was assessed by determining second-order rate constants for the reaction with selected environmentally relevant pharmaceuticals. Out of 9 pharmaceuticals only the 4 following compounds showed an appreciable reactivity with ClO2 (in brackets apparent second-order rate constants at pH 7 and T = 20 degrees C): the sulfonamide antibiotic sulfamethoxazole (6.7 x 10(3) M(-1) s(-1)), the macrolide antibiotic roxithromycin (2.2 x 10(2) M(-1) s(-1)), the estrogen 17alpha-ethinylestradiol (approximately 2 x 10(5) M(-1) s(-1)), and the antiphlogistic diclofenac (1.05 x 10(4) M(-1) s(-1)). Experiments performed using natural water showed that ClO2 also reacted fast with other sulfonamides and macrolides, the natural hormones estrone and 17beta-estradiol as well as 3 pyrazolone derivatives (phenazone, propylphenazone, and dimethylaminophenazone). However, many compounds in the study were ClO2 refractive. Experiments with lake water and groundwater that were partly performed at microgram/L to nanogram/L levels proved that the rate constants determined in pure water could be applied to predict the oxidation of pharmaceuticals in natural waters. Compared to ozone, ClO2 reacted more slowly and with fewer compounds. However, it reacted faster with the investigated compounds than chlorine. Overall, the results indicate that ClO2 will only be effective to oxidize certain compound classes such as the investigated classes of sulfonamide and macrolide antibiotics, and estrogens.     

Synergistic inactivation of Cryptosporidium parvum using ozone followed by free chlorine in natural water

The synergistic effect of sequential exposure to ozone followed by free chlorine on inactivation of Cryptosporidium parvum oocysts suspended in natural waters was studied in bench-scale batch reactors. Animal infectivity using neonatal CD-1 mice was used to measure oocyst inactivation. The synergistic effect measured in two alkaline (pH 8.1) natural waters was statistically significant but was considerably smaller than previously reported in buffered de-ionized water at pH 6.0. Temperature, ozone primary treatment level, and water type did not have measurable impacts on the synergistic effect. Efforts to increase the synergistic effect by reducing the pH from 8 to 6 by acid addition were unsuccessful. In the two low alkalinity (pH 6.0) natural waters tested, the measured synergistic effect was greater than in the alkaline waters, but was still less than that measured previously in buffered de-ionized water. It was concluded that the synergistic effect reduction in the natural waters tested was due in part to alkalinity and in part to other unidentified water quality characteristics. Sequential treatment with ozone followed by free chlorine may only be a feasible strategy for achieving synergistic C. parvum inactivation credit for water treatment facilities with natural waters having a low pH (near 6.0).