•Thermally regenerated GAC showed the best recovery in DOC adsorption.•F400, TiO2- and Ag-GAC exhibited preferential adsorption for hydrophobic Br-THMs.•Greater adsorption recovery was observed for ...Br-THMs than Cl-THMs.•Free chlorine were completely decomposed before and after all GAC regeneration.•Ag-GAC showed a strong anti-microbial activity recovery after ozone regeneration.
Spatial and temporal variations of trihalomethanes (THMs) in distribution systems have challenged water treatment facilities to comply with disinfection byproduct rules. In this study, granular activated carbon (GAC) and modified GAC (i.e., Ag-GAC and TiO2-GAC) were used to treat chlorinated tap water containing CHCl3 (15–21μg/L), CHBrCl2 (13–16μg/L), CHBr2Cl (13–14μg/L), and CHBr3 (3μg/L). Following breakthrough of dissolved organic carbon (DOC), GAC were regenerated using conventional and novel methods. GAC regeneration efficiency was assessed by measuring adsorptive (DOC, UV absorbance at 254nm, and THMs) and physical (surface area and pore volume) properties. Thermal regeneration resulted in a brief period of additional DOC adsorption (bed volume, BV, ∼6000), while ozone regeneration was ineffective regardless of the GAC type. THM adsorption was restored by either method (e.g., BV for ≥80% breakthrough, CHBr3 ∼44,000>CHBr2Cl ∼35,000>CHBrCl2 ∼31,000>CHCl3 ∼7000). Cellular and attached adenosine triphosphate measurements illustrated the antimicrobial effects of Ag-GAC, which may have allowed for the extended THM adsorption compared to the other GAC types. The results illustrate that ozone regeneration may be a viable in-situ alternative for the adsorption of THMs during localized treatment in drinking water distribution systems.
The effects of calcium, cupric, ferrous and ferric ions on the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) were investigated using natural organic matter (NOM), small molecular ...weight NOM surrogates and natural water samples. The results showed that the effects were greatly dependent on the disinfection byproduct (DBP) precursor structure and molecular weight, and metal ions species. While using NOM as precursors, addition of 4.00 mM calcium ions increased the formation of THMs, dihaloacetic acids (DHAAs) and trihaloacetic acids (THAAs) by 24–47%, 51–61% and 15–25%, respectively. Addition of cupric ions at 0.02 mM increased the formation of THMs and DHAAs by 74–83% and 90–100%, respectively, but decreased the formation of THAAs by 26–27%. Similar effect was not observed when 0.04 mM ferrous or ferric ions were added. The effects of calcium and cupric ions on DBP formation were generally more evident for the NOM surrogates than that for NOM. The primary catalytic effect of calcium ions was due to complexation and less sensitive to molecular structure or weight, while that of cupric ions was attributed to redox reactions and greatly dependent on molecular structure. Both ferric and ferrous iron had substantial effects on the DBP formation of surrogates (citric acid and catechol in particular), which implied that the catalytic effects of ferric and ferrous iron mainly depended on molecular weight. The catalytic effect of cupric ions was also observed on natural water samples, while the effects of calcium, ferrous and ferric ions on natural water samples were not evident.
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•Primary catalytic mechanism of calcium and cupric were complexation and redox reaction, respectively.•Catalytic effect of calcium was less sensitive to molecular structure or weight.•Catalytic effect of cupric was greatly dependent on molecular structure.•Catalytic effect of ferric and ferrous iron critically depended on molecular weight.
Disinfection is an essential step in drinking water treatment to prevent waterborne illnesses. However, reaction of disinfectants with organic matter in the water can produce carcinogenic ...disinfection byproducts (DBPs), including trihalomethanes (THMs) and haloacetic acids (HAAs). Magnetic ion exchange (MIEX) resin has been used as a pretreatment to remove organics and reduce DBPs. In this study, a pilot-scale water treatment plant in Birmingham, AL (USA) that employed MIEX as a pretreatment to the conventional pilot treatment train was compared against an adjacent full-scale train that did not use MIEX. THM and HAA formation was tested via simulated distribution system (SDS) testing, and changes in organic character were assessed using fluorescence spectroscopy. MIEX treatment provided 20 % and 25 % removal of THMs and HAAs, respectively, compared to the full-scale treatment under typical SDS conditions. With higher residence times and incubation temperatures (15 days at 35 °C), MIEX treatment reduced HAAs by 36 %. Parallel factor (PARAFAC) analysis revealed that MIEX treatment reduced loadings for a terrestrial humic-like component. Additionally, MIEX treatment resulted in secondary benefits, including a reduction in the coagulant feed rate and a more stable pH and chlorine residual in the MIEX-treated water compared to full-scale treatment.
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•Pilot study to investigate MIEX performance compared to conventional treatment•MIEX pretreatment lowers coagulant feed rates and yields a higher chlorine residual.•MIEX pretreatment reduced THM and HAA formation alongside lower coagulant dosages.•MIEX preferentially removed humic-like fluorescent organic matter.
The contribution and role of different precursors in the formation of three class of disinfection by-products (DBPs) trihalomethanes (THMs), haloacetic acids (HAAs), and halonitromethanes (HNMs) in ...swimming pool waters were examined using filling waters obtained from five drinking water treatment plant (WTP) effluents and three body fluid analogs (BFAs). BFAs exerted higher chlorine demands as compared to natural organic matter (NOM) in filling waters. BFAs exhibited higher HAA formation potentials than THM formation potentials, while the opposite was observed for the filling water NOM. There was no appreciable difference in the HNM formation potentials of BFAs and filling water NOM. Different components in the BFAs tested exhibited different degree and type of DBP formation. Citric acid had significantly higher THM and HAA yields than other BFA components. The effect of temperature was greater on THM formation, whereas the effect of contact time had more impact on HAA formation. Experiments with filling waters collected from WTP effluents at three different times showed more variability in HAA than THM formation at the WTPs studied.
The reactions between natural organic matter, anthropogenic contaminants, ions, and disinfectants lead to the formation of disinfection by-products (DBPs) such as trihalomethanes (THMs) in drinking ...water. The formation of THMs is strongly related to the chlorination of water. The study’s central objective was to compare the concentration of THMs in twenty developed and developing countries and their disinfection techniques. The THM concentration in 11 developed and 9 developing countries ranged from 0.5 µg/L (Germany) to 215 µg/L (Russia) and 3 µg/L (China) to 439.2 µg/L (Bangladesh), respectively. The developed country has partially succeeded in reducing THM concentration in drinking water, whereas significant steps are needed in developing countries to reduce the existing high THM concentration. The concentration of THMs in water varies among these countries because of the different water sources, water quality, environmental conditions, and efficiency of water treatment technologies. A meaningful relationship has been observed between the properties of water and the THM formation. The use of chemical disinfectants will result in new forms of DBPs that are undesirable due to their carcinogenic and mutagenic effects on human health. The DBP guidelines by various national and international agencies have helped to control and manage the THM concentration in drinking water. However, these regulatory standards are not continuously monitored. Therefore, the formation of these compounds should be prevented either by removing THMs forming precursors or by using an integrated approach for controlling THM formation by implementing advanced water treatment technology. Extensive research is desirable in domains like THM minimization strategies which are easy to deploy, scalable, and cost-effective.
Graphical abstract
This study addresses the limited understanding of factors affecting the efficiency of water treatment plants in reducing trihalomethane (THM) formation through total organic carbon (TOC) removal, ...highlighting significant challenges in improving treatment effectiveness. The aim of this study was to examine the influence of water quality on the efficiency of water treatment plants to remove TOC and reduce THM formation. Linear regression and correlation analyses were conducted to examine the relationship between water quality parameters and THM concentrations. The results showed that there was a negative relationship between turbidity, metals, and TOC concentration with TOC removal efficiency. Positive correlations were found between parameters and the formation of THMs in water. Of these parameters, water temperature was observed to have relatively less influence on THM formation. It was observed that seasonal variations in water quality affect the efficiency of TOC removal and THM content in treated water. THM levels in chlorinated water were found to be within the permissible range of the World Health Organization's drinking water quality guidelines. However, it is still important to maintain continuous monitoring and take measures to reduce THMs. The model demonstrated a strong correlation (R
= 0.906) between predicted and measured THM values.
Hydrolysis could contribute to the loss of trihalomethanes (THMs) in the drinking water at elevated temperatures. This study was aimed at investigating THM hydrolysis pertaining to the storage of hot ...boiled water in enclosed containers. The water pH value was in the range of 6.1–8.2 and the water temperature was varied from 65 to 95 °C. The effects of halide ions, natural organic matter, and drinking water matrix were investigated. Results showed that the hydrolysis rates declined in the order following CHBrCl2 > CHBr2Cl > CHBr3 > CHCl3. THM hydrolysis was primarily through the alkaline pathway, except for CHCl3 in water at relatively low pH value. The activation energies for the alkaline hydrolysis of CHCl3, CHBrCl2, CHBr2Cl and CHBr3 were 109, 113, 115 and 116 kJ/mol, respectively. No hydrolysis intermediates could accumulate in the water. The natural organic matter, and probably other constituents, in drinking water could substantially decrease THM hydrolysis rates by more than 50%. When a drinking water was at 90 °C or above, the first order rate constants for THM hydrolysis were in the magnitude of 10−2‒10−1 1/h. When the boiled real tap water was stored in an enclosed container, THMs continued increasing during the first few hours and then kept decreasing later on due to the competition between hydrolysis and further formation. The removal of THMs, especially brominated THMs, by hydrolysis would greatly reduce one's exposure to disinfection by-products by consuming the boiled water stored in enclosed containers.
•Trihalomethanes (THMs) hydrolysis in hot drinking water has long been overlooked.•THM hydrolysis rate constants could reach to 10−2‒10−1 1/h.•Natural organic matter in drinking water substantially reduced hydrolysis rates.•No intermediates accumulated during THM hydrolysis.
Trihalomethanes (THMs) are the first disinfectant by-products in the drinking water distribution network and are classified as potential carcinogens. The presence of THMs in chlorinated water depends ...on the pH, water temperature, contact time between water and chlorine, type and dose of disinfection, bromide ion concentration, and type and concentration of natural organic materials (NOMs). In the present study, the formation of THMs was evaluated by six simple and easy water quality parameters and modeled by an artificial neural network (ANN) approach through five water distribution networks (WDNs) and the Karoun River in Khuzestan province. The results of this study that was conducted from October 2014 to September 2015 showed that THM concentration ranged in five WDNs, including Shoushtar, Ahvaz (2), Ahvaz (3), Mahshahr, Khorramshahr, and total WDNs through N.D.–9.39 µg/L, 7.12–28.60, 38.16–67.00, 17.15–90.46, 15.14–29.99, and N.D.–156, respectively. The concentration of THMs exceeded Iran and EPA standards in many cases in Mahshahr and Khorramshahr WDNs. Evaluation of
R
2
, MSE, and RMSE showed the appropriate correlation between measured and modeled THMs, indicating a reasonable ANN potential for estimating THM formation in water sources.
Trihalomethanes (THMs) are the most common species of disinfection by-products (DBPs) in swimming pools and have received widespread attention due to their risk to public health. However, studies ...examining within-day variation and the carcinogenic health risks from exposure to THMs in indoor swimming pools are limited. Our study aimed to detect the within-day variation of four THMs categories and carcinogenic health risk in indoor swimming pool water in Taiyuan, China, and to examine the correlations between THMs and environmental parameters. Our results showed chloroform (TCM) was the most abundant component in THMs with median concentrations from 0.038–0.118 μg/m
3
. TCM and THMs were significantly positively correlated with FCl and significantly negatively correlated with the cumulative number of swimmers (CNS) in the swimming pool. The concentration of total THMs and TCM, lifetime average daily doses (LADD) of TCM, and the total lifetime cancer risks (ELCR) values of THMs declined with time with the highest level occurring at 8:00 am. ELCR values of THMs were in the range of 1.368 × 10
−5
–1.968 × 10
−5
, which exceeded the negligible risk level (10
−6
) defined by US EPA. Our results suggest that THM occurrence and the carcinogenic health risks in pool water varied temporally. Exposure to pool water THMs may pose a carcinogenic risk to human health, especially at the pool’s opening time.
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