•PAC addition enhanced the removal of aromatic organic matters by MBR.•PAC addition reduced the membrane organic fouling by adsorption removal of DOM.•PAC addition significantly reduced THMFP of MBR ...effluents during chlorination.•PAC addition increased THM formation reactivity of MBR effluents.•PAC addition enhanced the formation of high toxic bromine-containing THMs.
In this study, the MBR was used to treat municipal wastewater for reuse. Effects of powdered activated carbon (PAC) addition on MBR system in terms of effluent water quality, trihalomethane (THM) formation and membrane organic fouling tendency of MBR sludge supernatant at the initial stage of PAC addition were investigated. Effects of chlorine dose and contact time on THM formation and speciation were also studied. PAC addition enhanced the removal of organic matters, especially aromatic components, which improved the UV254 removal rate from 34% to 83%. PAC addition greatly reduced the membrane organic fouling tendency of MBR sludge supernatant. PAC addition reduced the MBR effluent trihalomethane formation potential (THMFP) from 351.29 to 241.95μg/L, while increased THM formation reactivity by 42%. PAC addition enhanced the formation of higher toxic bromine-containing THMs. High chlorine dose and contact time resulted in higher THM formation but lower proportion of bromine-containing THMs.
The aim of this study is tracing seasonal variability of total organic carbon (TOC), trihalomethanes (THMs) and haloacetic acids (HAA5) as disinfection by-products (DBPs) in drinking water sources ...and the distribution system in the north of Iran. The results showed that the concentrations of TOC were within the range of 0.013-1.42 mg/L. In addition, the results showed that most of the water sources had nearly the same concentration level (i.e. <1 mg/L), with the exception of one peak for groundwater source and middle drinking water distribution system in the city of Sari (1.42 mg/L) and Babol (1.37 mg/L). It was demonstrated that brominated HAA (MBAA) presented the highest concentration in the Sari City (17.3 µg/L) followed by the City of Behshahr (8.9-11.19 µg/L). The Babol City showed the highest concentration of chlorinated HAA (22.403 and 22.503 µg/L for DCAA and TCAA, respectively). Among the different compounds of THMs, the concentration of CHBr
was nearly in the same order of magnitude in the cities of Sari, Babol and Behshahr for both spring and summer seasons. The brominated THM (BDCM) concentrations were also high (14.7 µg/L) in the Behshahr City. The results of independent
-test indicated that the seasonal (spring and summer) difference was statistically significant in the case of temperature and TTHM (
< 0.05). Furthermore, total HAA
≤ 60 µg/L and THM ≤100 µg/L in all the considered cities over the period of the study. The TTHMs concentration was 56 µg/L in treating surface water (TSW) source in the summer season at the Sari city.
•MBR effluents were fractionated by UF according to molecular weight (MW).•Fractions of MW >30kDa were the main source of THMs precursor.•THMs formation was mostly attributed to slow chlorine ...decay.•THMs yield coefficients of the MW >30kDa fractions were low.•THMFP and specific THMFP increased linearly with DOC and SUVA, respectively.
In this study, effects of dissolved organic matter (DOM) size fractions on trihalomethanes (THMs) formation in MBR effluents during chlorination were investigated by fractionating DOM into >100, 30–100, 10–30, 5–10 and <5kDa fractions using ultrafiltration (UF) membranes based on molecular weight (MW). Fractions of MW>30kDa constituted 87% of DOM and were the main THMs precursors, which exhibited higher specific ultraviolet absorbance (SUVA) and THMs formation potential (THMFP) and should be reduced to control THMs formation. For these fractions, THMs formation was mostly attributed to slow chlorine decay, and THMs yield coefficients were low because halogenated intermediates derived from the macromolecular DOM were difficult to decompose to produce THMs. Moreover, there was a strong linear correlation between dissolved organic carbon (DOC) concentration and THMFP (R2=0.981), as well as between the SUVA and specific THMFP (R2=0.993) in all fractions.
Chlorination in a drinking water treatment plant is the critical process for controlling harmful pathogens. However, the reaction of chlorine with organic matter forms undesirable, harmful, and ...halogenated disinfection by-products. Carbonaceous disinfection by-products, such as trihalomethanes (THMs) and haloacetic acids (HAAs), are genotoxic or carcinogenic and are reported at high concentration in drinking water. This study is aimed at developing a mathematical model for predicting concentration levels of THMs and HAAs in drinking water treatment plants in South Korea because no previous attempts to do so have been reported for the country. The THMs concentration levels ranged from 29 to 39 μg/L, and those for the HAAs from 6 to 7 μg/L. Multiple regression models, i.e., both linear and nonlinear, for THMs and HAAs were developed to predict their concentration levels in water treatment plants using datasets (January 2015 to December 2016) from three treatment plants located in Seoul, South Korea. The constructed models incorporated principal factors and interactive and higher-order variables. The principal factor variables used were dissolved organic carbon, ultraviolet absorbance, residual chlorine, bromide, contact time, chlorine dose and temperature for treated water, and pH for both raw and treated water at the plant. The linear models for both THMs and HAAs were found to give acceptable fits with measured values from the water treatment plants and predictability values were found to be 0.915 and 0.772, respectively. The models developed were validated with a later dataset (January 2017 to July 2017) from the same water treatment plants. In addition, the models were applied to two different water treatment plants. Application and validation results of the constructed model showed no significant differences between predicted and observed values.
The current study summarizes the current status of wastewater stabilization ponds (WSPs) treatment plants that have already been built in 11 governorates throughout Egypt. Moreover, this study aims ...to determine the most appropriate chlorine dose for waste stabilization ponds (WSPs) effluents to ensure the treated effluents are suitable for reuse in unrestricted irrigation and to comply with the current legislation on direct discharge onto water bodies. According to the findings, the chlorine doses used as a disinfectant in the treated effluents of the majority of WSP treatment plants ranged from 3 to 13 mg/L. Meanwhile, two of the WSPs treatment plants effluents, the Qus WSPs treatment plant in Qena governorate and the Al Zarabii WSPs treatment plant in Asyut governorate used high chlorine doses reached to 17 and 19 mg/L, respectively. This is due to the fact that both the Qus and Al Zarabii WSPs treatment plants have a high organic load, which necessitated the use of more chlorine to achieve the optimum chlorine dose at 13 mg/L for Qus and 11mg/L for Al Zarabii. The findings demonstrated that chlorine has a powerful effect in completely removing bacteria. Furthermore, in most chlorine-treated wastewater final effluents, as the chlorine doses increased, the chlorophyll-a reading decreased. The amount of trihalomethanes (THMs) produced as disinfectant byproduct was measured. The results proved that the water can be used in unrestricted irrigation, and after adding chlorine, it can be dumped on water bodies without health risks.
Trihalomethanes (THMs) are a class of disinfection by-products that were proved to have adverse effects to human health. Investigation into its content change and molecular composition variation of ...its main precursor, which is believed to be dissolved organic matter (DOM) during water purification process, can help understand the formation mechanism of THMs and optimize the processes in drinking water treatment plant (DWTP). This is of great significance to ensure the safety of urban water supply. In this study, detailed changes of THMs’ content and formation potential were determined during the water purification process in summer and winter at a typical DWTP in south China. Specific molecular composition changes of DOM were also characterized by ultrahigh-resolution mass spectrometry, to comprehensively study its correlation with the formation of THMs in different water processing units and seasons. The result showed that chlorination will cause drastic changes of water quality and a sharp increase in the concentration of THMs (18.7 times in summer and 13.9 times in winter). Molecular-level characterization of DOM indicates that a range of lignin-like substance with lower O/C (< 0.5) and H/C (< 1.25) vanished and considerable amount of protein-like and tannins-like substance with higher H/C (> 1.25) and O/C (> 0.5) was formed after chlorination. Analysis of Cl-containing products demonstrated that a bulk of CHOCl
1
and CHOCl
2
compounds with moderate molecular weights were formed in both winter and summer. However, the newly formed CHOCl
1
molecules showed a relatively higher mass weight in summer (> 500 Da) compared to winter (300–500 Da). Seasonal differences also emerged in the result of correlation between the trihalomethanes formation potential and total organic carbon. The correlation coefficient in summer (0.500) was lower than that in winter (0.843). The results suggested that the exhaustive reaction and contribution of DOM to THMs may vary in different seasons.
Abstract
In this study, nanofiltration (NF) was used to further treat the water from the disinfection process of a drinking water treatment plant (DWTP). The results indicate that the NF process ...reduced the dissolved organic carbon (DOC) by 92.87%, UV absorbance at 254 nm (UVA254) by 88.68%, conductivity by 94% and total dissolved solids by 94.49%. The removal efficiencies of trihalomethanes (THMs), 2-methylisoborneol (2-MIB) and trans-1,10-dimethyl-trans-9-decalol (geosmin) were also evaluated for both the DWTP and NF treatment processes. High-performance size-exclusion chromatography (HPSEC) analysis, three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectroscopy and parallel factor (PARAFAC) analysis were applied to characterize the changes in different organic compounds in each process. A correlation analysis was carried out for samples of the raw water, feed water and permeate water to determine the correlations between the maximum fluorescence intensities (Fmax) of the PARAFAC components and the DOC, UVA254 and high specific UV absorbance (SUVA) of the samples. The results showed that a significant correlation (p < 0.01) existed between UVA254 and the Fmax of the three PARAFAC components as well as between DOC and Fmax.
The potential for generation of disinfection byproducts (DBPs) in swimming pools is high due to the concentrations of chlorine required to maintain adequate disinfection, and the presence of organics ...introduced by the swimmers. Health Canada set guidelines for trihalomethanes (THMs) in drinking water; however, no such guideline exists for swimming pool waters. Exposure occurs through ingestion, inhalation and dermal contact in swimming pools. In this research, a multimedia model is developed to evaluate exposure concentrations of THMs in the air and water of an indoor swimming pool. THM water concentration data were obtained from 15 indoor swimming pool facilities in Quebec (Canada). A level III fugacity model is used to estimate inhalation, dermal contact and ingestion exposure doses. The results of the proposed model will be useful to perform a human health risk assessment and develop risk management strategies including developing health-based guidelines for disinfection practices and the design of ventilation system for indoor swimming pools.
► We developed a Level III fugacity model for THMs in indoor swimming pools. ► Exposure doses were estimated for chloroform, BDCM, DBCM and bromoform. ► Five age groups of recreational swimmers were considered. ► Exposure routes included ingestion, inhalation and dermal contact. ► Modeled air concentrations correlated well with air concentrations measured in other studies.
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