Effects of bromide on the formation and transformation of disinfection by-products during chlorination and chloramination

Analyzing disinfection by-products yield and mechanisms in UV/Cl2 using response surface methodology and quantitative structure-activity relationship models

The study aimed to investigate the formation of halogenated disinfection byproducts (DBPs) during applying UV/chlorine (UV/Cl2) and unravel the interactive impacts of critical operational parameters and the mechanisms behind DBPs formation. Response surface methodology and quantitative structure-activity relationship models were developed to evaluate the contribution of electrophilic, nucleophilic, and free radical reactions to the formation of DBPs in UV/Cl2. The study found that Cl2 and its interactions dominated the total DBPs and non-Br-DBPs formation, while Br- and the Cl2-Br- interaction played a decisive role in the Br-DBPs formation. The study also observed significant interactions of Br, Cl2, and pH on chloroform, bromodichloromethane, dichloroacetonitrile, 1,1-dichloro-2-propanone, trichloroactic acid, and chlorodibromoacetic acid formations, while no evident interaction on chloral hydrate, dibromochloromethane, trichloroacetone, dibromoacetic acid, and bromodichloroacetic acid formations. The electrophilic substitution of HOBr mainly controlled the formation of trihalomethanes, and the contribution of nucleophilic, electrophilic, and free radical (•OH, Cl•, Cl2•- and ClO•) reactions depended on the molar ratio of Cl2 to Br, and pH-determined hydrolysis rate constants of DBPs and the types of free radicals. Overall, the response surface methodology and quantitative structure-activity relationship models provided a reference for revealing DBPs formation mechanisms in other disinfection processes.

Water quality of The Gambia River: A prospective drinking water supply

Drinking water in The Gambia is mostly derived from boreholes that could potentially be contaminated. The Gambia River, a major river in West Africa that covers 12 % of the country's area, could be more exploited for drinking water supply. During the dry season, the total dissolved solids (TDS), ranging from 0.02 to 33 g/L in The Gambia River, decreases with the distance to the river mouth with no major inorganic contamination. The freshwater (<0.8 g/L TDS) starts from Jasobo at approximately 120 km from the river mouth and extends by about 350 km to the eastern border of The Gambia. With a dissolved organic carbon (DOC) ranging from 2 to 15 mgC/L, the natural organic matter (NOM) of The Gambia River was characterised by 40-60 % humic substances of paedogenic origin. With such characteristics, unknown disinfection by-products could be formed if chemical disinfection, such as chlorination, was implemented during treatment. Out of 103 types of micropollutants, 21 were detected (4 pesticides, 10 pharmaceuticals, 7 per- and polyfluoroalkyl substances (PFAS)) with concentrations ranging from 0.1 to 1500 ng/L. Pesticides, bisphenol A and PFAS concentrations were below the stricter EU guidelines set for drinking water. These were mainly confined to the urban area of high population density near the river mouth, while the quality of the freshwater region of low population density was surprisingly pristine. These results indicate that The Gambia River, especially in its upper regions, would be well suited as a drinking water supply when using decentralised ultrafiltration treatment for the removal of turbidity, as well as, depending on pore size, to a certain extent microorganisms and DOC.

Treatment of bromate in UV/sulfite autoxidation process enhances formation of dibromoacetonitrile during chlorination

The integration of UV/sulfite autoxidation process (USAP, i.e., UV activation of sulfite in the presence of 5 ∼ 10 mg/L O₂) into conventional water to degrade micropollutants rises extensive attention, but its impact on water quality, and especially the formation of disinfection byproducts is still unclear. Herein, the formation of dibromoacetonitrile (DBAN) from bromate (BrO₃^-) upon treatment with USAP followed by chlorination was evaluated, in the presence of amino acids (AAs) selected as representative organic matter in drinking water. Results revealed that hydrated electrons (e_aq^-) produced during USAP contribute to the reduction of BrO₃^- to Br^-, which is then converted into HBrO/BrO^- during post-chlorination. At the same time, sulfate radicals (SO₄^•-) and hydroxyl radicals (•OH) generated in USAP mediated AAs' conversion via α-hydrogen abstraction and NH₂-hydrogen abstraction reactions to produce HN=C(CH₃)‒COOH, CH₃‒CH=NH, and CH₃‒CN, which are released into the post-chlorination stage and therefore, enhance the bromine utilization factor (BUF) value and DBAN formation. The effects of the USAP treatment time, BrO₃^- concentration, AA concentration, pH, and real waters were also evaluated. Although 63.5% of BrO₃^- was eliminated by USAP followed by chlorination, the toxicity index (TI) was increased by 1.5-fold due to the formation of the all brominated CX₃R-type nitrogenous disinfection byproducts (N-DBPs), demonstrating the potential risk of applying USAP as a treatment process in BrO₃^- containing waters.

Formation of halonitromethanes from methylamine in the presence of bromide during UV/Cl2 disinfection

The UV/Cl₂ process is commonly used to achieve a multiple-barrier disinfection and maintain residuals. The study chose methylamine as a precursor to study the formation of high-toxic halonitromethanes (HNMs) in the presence of bromide ions (Br^-) during UV/Cl₂ disinfection. The maximum yield of HNMs increased first and then decreased with increasing concentration of Br^-. An excessively high concentration of Br^- induced the maximum yield of HNMs in advance. The maximum bromine incorporation factor (BIF) increased, while the maximum bromine utilization factor (BUF) decreased with the increase of Br^- concentration. The maximum yield of HNMs decreased as pH value increased from 6.0 to 8.0 due to the deprotonation process. The BUF value remained relatively higher under an acidic condition, while pH value had no evident influence on the BIF value. The maximum yield of HNMs and value of BUF maximized at a Cl₂:Br^- ratio of 12.5, whereas the BIF value remained relatively higher at low Cl₂:Br^- ratios (2.5 and 5). The amino group in methylamine was first halogenated, and then released into solution as inorganic nitrogen by the rupture of C-N bond or transformed to nitro group by oxidation and elimination pathways. The maximum yield of HNMs in real waters was higher than that in pure water due to the high content of dissolved organic carbon. Two real waters were sampled to verify the law of HNMs formation. This study helps to understand the HNMs formation (especially brominated species) when the UV/Cl₂ process is adopted as a disinfection technique.

Acute toxicity of disinfection by-products from chlorination of algal organic matter to the cladocerans Ceriodaphnia silvestrii and Daphnia similis: influence of bromide and quenching agent

Algal organic matter (AOM) in water reservoirs is a worldwide concern for drinking water treatment; once it is one of the main precursors for disinfection by-products formation (DBPs). In this context, this study investigated the ecotoxicity of DBPs from chlorination of AOM to Ceriodaphnia silvestrii and Daphnia similis (Crustacea, Cladocera). The bioassays evaluated three scenarios, including the AOM extracted from Chlorella sorokiniana, the quenching condition used in the tests, and the DBPs formed after the chlorination of the two test waters with AOM (with and without bromide presence). The results showed that AOM has no toxic effects for the tested species under typical environmental concentration (5 mg∙L^-1). However, since AOM is a potential precursor of DBPs, the toxicity of two test waters (TW-1 and TW-2) after the chlorination process (25 mg Cl₂·L^-1, for 7 days, at 20 °C) was tested. The sample with higher toxicity to the tested species was TW-1, in which chloroform and chloral hydrate were quantified (615 and 267 µg∙L^-1, respectively). However, TW-2 showed lower concentration of chloroform and chloral hydrate (260 and 157 µg∙L^-1, respectively), although bromodichloromethane, dibromochloromethane, and bromoform were also detected (464, 366, and 141 µg∙L^-1, respectively). Although free chlorine is highly toxic to the tested species, the quenching conditions also affected the organisms' survival due to the use of ascorbic acid and the presence of reaction intermediates. Nonetheless, both species were more affected by TW-1 and TW-2 than the quenching condition. These results endorse the importance of removing the AOM before the disinfection process to avoid the formation of DBPs. In addition, ecotoxicological analyses could provide a more comprehensive assessment of water quality, especially considering the challenges of quantifying DBPs and other emerging contaminants.

Elevated risk of haloacetonitrile formation during post-chlorination when applying sulfite/UV advanced reduction technology to eliminate bromate

The formation of haloacetonitriles (HANs) during chlorination after sulfite/ultraviolet (UV) treatment of bromate (BrO₃^-) in the presence of amino acids (AAs) was investigated. During sulfite/UV treatment, the primary species hydrated electrons (e_aq^-) and hydrogen atom radicals (H) dominated the reduction of BrO₃^- to bromide (Br^-), whereas the sulfite anion radicals (SO₃^-) and H degraded AAs to produce the intermediates HN=C(CH₃)-COOH, CH₃-CH=NH, and CH₃-C≡N via α‑hydrogen abstraction and NH₂-hydrogen abstraction mechanisms. During post-chlorination, Br^- was converted to HBrO/BrO-, and the HN=C(CH₃)-COOH, CH₃-CH=NH, and CH₃-C≡N groups featured higher bromine utilization factor (BUF) and chlorine utilization factor (CUF) values than AAs, enhancing the formation of dibromoacetonitrile (DBAN) and dichloroacetonitrile (DCAN). The energetic feasibility of the transformation pathway, that is, HN=C(CH₃)-COOH, CH₃-CH=NH, and CH₃-C ≡ N formation via hydrogen abstraction by SO₃^- and H and their further conversion to HANs, was proved by density functional theory calculations, which showed stepwise negative Gibbs free energy changes (ΔG < 0). The effects of pH and water matrices (e.g., HCO₃^-, Cl^-, Fe³⁺, and natural organic matter) were comprehensively evaluated. Although 72% of BrO₃^- was removed by sulfite/UV treatment in the presence of AAs, the cytotoxicity index (CTI) and genotoxicity index (GTI) during post-chlorination increased by 213% and 125%, respectively, due to the formation of 24 CX₃R-type disinfection by-products (DBPs), especially brominated DBPs. Accordingly, more attention should be given to the formation of brominated DBPs during post-chlorination when using sulfite/UV processes to remove BrO₃^- in the presence of AAs. As a solution, using monochloramine instead of chlorine as a disinfectant after the sulfite/UV process could significantly lower the CTI and GTI values by alleviating the formation of brominated DBPs.

Disinfection by-product (DBP) research in China: Are we on the track?

Disinfection by-products (DBPs) formed during water disinfection has drawn significant public concern due to its toxicity. Since the first discovery of the trihalomethanes in 1974, continued effort has been devoted on DBPs worldwide to investigate the formation mechanism, levels, toxicity and control measures in drinking water. This review summarizes the main achievements on DBP research in China, which included: (1) the investigation of known DBP occurrence in drinking water of China; (2) the enhanced removal of DBP precursor by water treatment process; (3) the disinfection optimization to minimize DBP formation; and (4) the identification of unknown DBPs in drinking water. Although the research of DBPs in China cover the whole formation process of DBPs, there is still a challenge in effectively controlling the drinking water quality risk induced by DBPs, an integrated research framework including chemistry, toxicology, engineering, and epidemiology is especially crucial.

Derivates variation of phenylalanine as a model disinfection by-product precursor during long term chlorination and chloramination

Dissolved nitrogenous organic matter in water can contain precursors of disinfection by-products (DBPs), especially nitrogenous DBPs (N-DBPs). Amino acids are ubiquitous as dissolved nitrogenous organic matter in source water and can pass through drinking water treatment processes to react with disinfectants in finished water and in the distribution system. Phenylalanine (Phe) was selected as a model amino acid precursor to investigate its derived DBPs and their variations during a chlorination regime that simulated water distribution with residue chlorine. The 7-day DBPs formation potential (DBPsFP) test with chlorine revealed chlorination by-products of phenylalanine including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and halonitromethanes (HNMs), but not trichloronitromethane (TCNM) which was a significant N-DBP detected during the first 48 h of chlorine contact. The formation of most carbonaceous DBPs (C-DBPs) increased with chlorination time; however N-DBPs and non-chlorinated byproducts of phenylacetonitrile and phenylacetaldehyde reached their highest concentration after 2 h of reaction, and then gradually decreased until below detection after 7 days. The chlorination influencing factors indicated that light enhanced the peak yield of DBPs; the pH value showed different influences associated with corresponding DBPs; and the presence of bromide ions (Br^-) generated a variety of bromine-containing DBPs. The DBPsFP test with chloramine reduced C-DBPs generation to about 1/3 of the level observed for chlorine disinfection and caused an increase in dichloroacetonitrile. Surveillance of DBPs during drinking water distribution to consumers should consider the varying contact times with disinfectants to accurately profile the types and concentrations of C-DBPs and N-DBPs present in drinking water.

Interactions of fluoroquinolone antibiotics with sodium hypochlorite in bromide-containing synthetic water: Reaction kinetics and transformation pathways

Seven popular fluoroquinolone antibiotics (FQs) in synthetic marine aquaculture water were subject to sodium hypochlorite (NaClO) disinfection scenario to investigate their reaction kinetics and transformation during chlorination. Reactivity of each FQ to NaClO was following the order of ofloxacin (OFL) > enrofloxacin (ENR) > lomefloxacin (LOM) > ciprofloxacin (CIP) ~ norfloxacin (NOR) >> pipemedic acid (PIP), while flumequine did not exhibit reactivity. The coexisting chlorine ions and sulfate ions in the water slightly facilitated the oxidation of FQs by NaClO, while humic acid was inhibitable to their degradation. The bromide ions promoted degradation of CIP and LOM, but restrained oxidation of OFL and ENR. By analysis of liquid chromatography with tandem mass spectrometry (LC-MS/MS), eight kinds of emerging brominated disinfection byproducts (Br-DBPs) caused by FQ_S were primarily identified in the chlorinated synthetic marine culture water. Through density functional theory calculation, the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO) characteristic as well as the charge distribution of the FQs were obtained to clarify transformation mechanisms. Their formation involved decarboxylation, ring-opening/closure, dealkylation and halogenation. Chlorine substitution occurred on the ortho-position of FQs's N4 and bromine substitution occurred on C8 position. The piperazine ring containing tertiary amine was comparatively stable, while this moiety with a secondary amine structure would break down during chlorination. Additionally, logK_ow and logBAF of transformation products were calculated by EPI-Suite^TM to analyze their bioaccumulation. The values indicated that Br-DBPs are easier to accumulate in the aquatic organism relative to their chloro-analogues and parent compounds.

Reaction of phenazone-type drugs and metabolites with chlorine and monochloramine

This work studies the chlorination and monochloramination reaction kinetics of two phenazone-type drugs (phenazone - Phe and propyphenazone - PrPhe) and three metabolites of phenazone-type drugs (4-formylaminoantipyrine - FAA, 4-aminoantipyrine - AA and 4-acetoamidoantipyrine - AAA). Kinetics were faster with chlorine (apparent second-order constants between 100 and 66,500 times higher) than with monochloramine. For FAA and AAA, no significant reaction was observed during monochloramination. Further, apparent rate constants decreased as the pH increased from pH 5.7 to 8.3, except during chlorination of AA. The transformation products (TPs) formed were also elucidated by liquid chromatography-high resolution mass spectrometry. The main transformation pathway for Phe and PrPhe consisted of halogenations, hydroxylations and dealkylations, while AAA and FAA were firstly transformed to AA, then followed by pyrazole ring opening and hydroxylations. The extend of the reaction was also tested in real water samples, where, in general, slower reaction kinetics were obtained during monochloramination, while the chlorination reaction showed similar half-lives to ultrapure water. Finally, acute and chronic toxicity of the TPs were estimated using two quantitative structure-activity relationship (QSAR) software (ECOSAR and TEST), showing that some TPs could be more toxic than their precursor compounds.

The effect of operational conditions on the disinfection by-products formation potential of exopolymeric substances from biofilms in drinking water

Biofilms are ubiquitous in drinking water systems due to their external matrix of exopolymeric substances (EPS) that provide them protection and adaptability. They are even more common in low flow conditions where hydraulics favor their growth. EPS are organic substances (i.e., proteins, carbohydrates and humic substances) that can react with disinfectant, forming disinfection byproducts (DBP), some of which are controlled by water regulation. However, there is little information available on biofilm-disinfectant interaction and the effect of operational conditions such as biofilm age, water velocity, chlorine and pipeline length on the DBP formation potential of EPS (DBP_fpEPS). Using experimental setup and studies of two different biofilms: Biofilm 1 (2.6 ± 0.8 mg Cl/L) and Biofilm 2 (0.7 ± 0.2 mg Cl/L), the DBP_fpEPS was studied and compared to the DBP_fp of filtered water (FW). The DBP studied were trihalomethanes (THM), haloacetic acids (HAA), haloacetonitriles (HAN), chloropropanones (CP) and chloropicrin (CPK). The DBP concentration trend in both EPS and FW was HAA > THM > CP > HAN > CPK. Biofilm age only increased chloroform (CF)_fpEPS in Biofilm 1, while other DBP_fpEPS decreased. A direct relationship between water velocity and CF_fp in Biofilm 1 was found, probably related to higher chlorine diffusion and the production of a more reactive matrix. Chlorine positively affected DBP_fpEPS, increasing Cl-HAA, Cl-THM, CPK and Br-HAN. Biofilm 2 produced higher quantities of EPS per meter of pipeline, this constituting a precursor of intermediary DBP 1,1 dichloropropanone (1,1, DCP). The study compared DBP in chlorinated water in contact with biofilm (BCW) and without (CW). Biofilm 1 increased levels of Cl-HAA, Cl-CP and dichloro-acetonitrile, while Biofilm 2 diminished Cl-HAA and Cl-HAN. Biofilm 1 reduced some Br-HAA in BCW, whereas Biofilm 2 promoted Br-HAA and 1,1, DCP in BCW. EPS and biofilms were significant in terms of their effect on DBP formation.

Covalent organic frameworks as an efficient adsorbent for controlling the formation of disinfection by-products (DBPs) in chlorinated drinking water

2,5-Dimethyl-p-phenylenediamine-1,3,5-triformylphloroglucinol covalent organic frameworks (PATP COF) were prepared and used as novel adsorbent for controlling the formation potential (FP) and reducing the toxic potential of both carbonaceous disinfection by-products (C-DBPs) and nitrogenous DBPs (N-DBPs) during their subsequent chlorination. During the PATP COF adsorption pretreatment process, the FP of C-DBPs, N-DBPs and total organic halogen (TOX) were reduced by 86.5, 75.4 and 81.1%, respectively. These removal efficiencies were significantly higher when compared with those obtained using a traditional activated carbon (AC) adsorption pretreatment process (42.7, 19.4 and 28.7%, respectively). By comprehensive toxicity calculations, a significant reduction in both the acute and chronic toxic potential of C-DBPs and N-DBPs were observed during the PATP COF adsorption process (with reduction rates of ~85 and ~ 75% observed for the C-DBPs and N-DBPs, respectively), which were comparable to the removal efficiencies observed for C-DBPs FP and N-DBPs FP by weight, suggesting the simultaneous and effective control of DBPs FP and their toxic potential. Cycling tests and stability trial also showed the excellent reusability, wide pH adaptability, and high stability of PATP COF, demonstrating its great potential application to the treatment of drinking water.

Chlorination of soil-derived dissolved organic matter: Long term nitrogen deposition does not increase terrestrial precursors of toxic disinfection byproducts

Terrestrial dissolved organic matter (DOM) in forested watersheds is a known precursor of disinfection byproducts (DBPs) in drinking water. Although the characteristics of terrestrial DOM may change with increasing nitrogen (N) deposition in forests, how these changes alter formation potential and toxicity of DBPs remains unexplored. We analyzed the speciation and toxicity of DBPs from chlorination of DOM derived from soils (O, A, and B horizons) in an experimental temperate forest with 22 years of N addition. With long-term N addition, the DOM reactivity toward the formation of trihalomethanes (from 27.7-51.8 to 22.8-31.1 µg/mg-dissolved organic carbon (DOC)) and chloral hydrate (from 1.25-1.63 to 1.14-1.36 µg/mg-DOC) decreased, but that toward the formation of haloketones increased (from 0.23-0.26 to 0.26-0.33 µg/mg-DOC). The DOM reactivity toward the formation of haloacetonitriles was increased in the deeper soil but reduced in the surface soil. The DBP formation potential of DOM draining from a certain area of forest soils (in µg-DBP/m²-soil) was estimated to be reduced by 20.3% for trihalomethanes and increased by 37.5% for haloketones and have minor changes for haloacetonitriles and chloral hydrate (both <7%). Furthermore, the DBPs from chlorination of the soil-derived DOM showed lowered microtoxicity with N addition possibly due to reduced brominated DBP formation. Overall, this study highlights that N deposition may not increase drinking water toxicity through altering terrestrial DOM characteristics.

Low water treatability efficiency of wildfire-induced dissolved organic matter and disinfection by-product precursors

Wildfire could alter both the quantity and composition of terrestrial organic matter exported into source water, and water treatability of fire-impacted dissolved organic matter (DOM) could be different from its unburned counterpart. Currently, there is no standard protocol to treat wildfire-impacted source water. To identify the best treatment practices in handling post-fire runoffs, we conducted a systematic controlled study using leachates of unburned white fir (Abies concolor) and Ponderosa pine (Pinus ponderosa) and black and white ashes (collected immediately and one year after the 2013 Rim Fire, California) to evaluate coagulation and oxidation strategies for controlling disinfection byproducts (DBPs) formation. Results showed that the efficiency (%) of alum coagulation in removing dissolved organic carbon and nitrogen followed the order of litter > ash immediately after the fire > ash one year after the fire. Alum coagulation was less effectiveness in removing DOM and DBP precursors in ash leachates, compared to litter leachates. This may be attributed to the loss of side chains and the decrease of DOM molecular weight during the wildfire, thus inducing lower removal efficiency of the DOM and DBP precursors during the alum coagulation. Considering use of brominated flame retardants by firefighters, the addition of bromide (Br^-) (100 μg/L) greatly increased the formation of haloacetonitriles by chlorine, and this increase was relatively lower in ash leachates. The influence of reaction time and pH on DOM reactivity was similar among the leachates of litter and ash samples. Our results show that alum coagulation followed by chloramination at alkaline pH is an effective strategy for reducing post-fire DBP formation in drinking water.

Formation of haloacetic acids from different organic precursors in swimming pool water during chlorination

Haloacetic acids (HAAs) were reported to be the most abundant category of DBPs in swimming pool water. In this study, the formation of HAAs from different organic precursors in swimming pool water, including UV filters, human body fluids, and natural organic matter (NOM), during chlorination was examined, and the effects of chlorine dose and halide concentrations on the formation of HAAs were evaluated. The results show that the total HAA yields from benzophenone-3 (BP-3) and Suwannee River humic acid (SRHA) were the highest among the nine organic precursors, and the yields of dichloroacetic acid and bromochloroacetic acid were higher than that of the other HAA species. In all the chlorinated samples of different organic precursors, longer chlorination time enhanced HAA formation. Both chlorine dose and bromide concentration significantly affected the formation of HAAs from BP-3 and SRHA during chlorination. With the increasing chlorine dose, the total HAA yields from SRHA and BP-3 significantly increased. Besides, the proportion of trihaloacetic acids (THAAs) rose while that of dihaloacetic acids (DHAAs) and monohaloacetic acids (MHAAs) declined with the increasing chlorine dose. With the increasing bromide concentration, HAA formation from SRHA increased while that of BP-3 decreased. The bromine incorporation factor (BIF) of the formed MHAAs, DHAAs and THAAs from SRHA and BP-3 both increased with the increasing bromide concentration in the following order: BIF_DHAAs > BIF_THAAs > BIF_MHAAs, indicating that bromine was easier to be incorporated into DHAAs rather than MHAAs or THAAs. Moreover, bromide promoted the formation of Br-HAAs.

Formation potential of emerging disinfection by-products during ozonation and chlorination of sewage effluents

This study investigates the formation potential of emerging DBPs (haloacetonitriles, halonitromethanes and halopropanones) during ozonation and ozonation/hydrogen peroxide treatment and subsequent chlorination of sewage effluent under various experimental conditions. Estimation of possible risk due to DBPs by calculation of cytotoxicity and genotoxicity was attempted. The studied DBPs showed different formation behavior during chlorination, with maximum yields within 0.5-48 h. Maximum cytotoxicity and genotoxicity was observed after 4 h of chlorination with dibromoacetonitrile being the major contributor. Ozonation and O₃/H₂O₂ treatment resulted in increase of trichloronitromethane followed by a decline at higher doses, and reduction of haloacetonitriles. High ozone doses reduced cytotoxicity and genotoxicity of treated effluents. The presence of bromide shifted to bromo-DBPs formation and enhanced both cytotoxicity and genotoxicity. Particulate fraction in effluents significantly contributed to the formation of DBPs and consequently to the their toxicity.

Risk associated with increasing bromide in drinking water sources in Yancheng City, China

The bromide concentration in water source (WS) of Yancheng City in China increased unexpectedly due to industrial discharge and saltwater intrusion, which leads to the formation of trihalomethane (THMs) in finished water of water treatment plants (WTP), especially brominated THMs. In Yancheng City, drinking water is supplied by WTP1 and WTP2, primarily sourced by WS1 and WS2, respectively. In this paper, the seasonal variations of bromide in WS1 and WS2 and THMs species in WTP1 and WTP2 were analyzed and compared. The effects of bromide in WS on THMs formation in finished water of WTP in terms of bromine substitution factor (BSF) were simulated by statistical linear model. Although the THMs concentrations in WTP1 were approximate to that in WTP2, the brominated THMs concentrations in WTP1 were higher than that in WTP2 due to higher bromide concentration in WS1 than WS2. The cancer risk analysis indicated that THMs' species of DBCM is the dominant THMs for WTP1 as well as WTP2, which can provide more information for WTPs with higher bromide concentration in water source.

Monitoring chlorine residual and trihalomethanes in the chlorinated seawater effluent of a nuclear power plant

Periodic sampling of the discharged seawater effluent from Madras Atomic Power Station (Kalpakkam, Tamil Nadu, India) was carried out during 2013-2017 to assess the residual chlorine and trihalomethanes content in the outfall discharge water. The variations in dissolved oxygen, temperature, and pH were correlated with the residual chlorine and trihalomethanes content in the discharged effluent. The difference in temperature (ΔT) between influent and effluent seawater samples ranged from 1.95 to 11.0 °C (6.47 ± 1.87). More than 95% of the ΔT values were within the guideline value of 7 °C. The discharge water was associated with a marginal reduction in dissolved oxygen and a marginal increase in conductivity values. The total residual chlorine content in the discharged seawater at outfall ranged from 0.06 to 0.42 (0.16 ± 0.08) mg/L, which was within the stipulated values of 0.5 mg/L. Trihalomethanes values ranged from 0.04 to 65.03 (13.06 ± 14.38) μg/L. In addition to bromoform as the major constituent, occurrence of significant amount chloroform of was occasionally observed in the discharge water.

Recent electrochemical methods in electrochemical degradation of halogenated organics: a review

Halogenated organics are widely used in modern industry, agriculture, and medicine, and their large-scale emissions have led to soil and water pollution. Electrochemical methods are attractive and promising techniques for wastewater treatment and have been developed for degradation of halogenated organic pollutants under mild conditions. Electrochemical techniques are classified according to main reaction pathways: (i) electrochemical reduction, in which cleavage of C-X (X = F, Cl, Br, I) bonds to release halide ions and produce non-halogenated and non-toxic organics and (ii) electrochemical oxidation, in which halogenated organics are degraded by electrogenerated oxidants. The electrode material is crucial to the degradation efficiency of an electrochemical process. Much research has therefore been devoted to developing appropriate electrode materials for practical applications. This paper reviews recent developments in electrode materials for electrochemical degradation of halogenated organics. And at the end of this paper, the characteristics of new combination methods, such as photocatalysis, nanofiltration, and the use of biochemical method, are discussed.

Recreational Use of Spa Thermal Waters: Criticisms and Perspectives for Innovative Treatments

Natural spa springs are diffused all over the world and their use in pools is known since ancient times. This review underlines the cultural and social spa context focusing on hygiene issues, public health guidelines and emerging concerns regarding water management in wellness or recreational settings. The question of the "untouchability" of therapeutic natural waters and their incompatibility with traditional disinfection processes is addressed considering the demand for effective treatments that would respect the natural properties. Available strategies and innovative treatments are reviewed, highlighting potentials and limits for a sustainable management. Alternative approaches comprise nanotechnologies, photocatalysis systems, advanced filtration. State of the art and promising perspectives are reported considering the chemical-physical component and the biological natural complexity of the spa water microbiota.