Search

Water disinfection processes may generate several dangerous substances that can affect both human beings and the environment. As a known contaminant in drinking water, the compound 2,6-dichloro-1,4-benzoquinone (DCBQ) and its degradation products in aqueous solution are of continuing concern regarding environmental, biomedical, and technical applications. There is great interest in the development of analytical methods capable of elucidating the mechanisms of the interactions of DCBQ and its degradation products with the nucleic acids of living organisms. Here, a systematic voltammetric study employing a glassy carbon electrode was performed, for the first time, to investigate the redox properties of DCBQ and its interactions with double-stranded DNA (dsDNA). The DCBQ has a reversible process at pH range from 3.70 to 12.60 and pH-dependent until pH 9.20, resulting in the formation of a reversible oxidation product in a pH-dependent system to pH 6.00 at a glassy carbon electrode. By varying incubation time and pH of electrolyte solutions, DCBQ showed spontaneous degradation which was presented by the change of its electrochemical behavior in solution. The spontaneously degraded DCBQ underwent a reversible and pH-dependent process for 3.70 ≤ pH ≤ 6.00. By spectrophotometry experiments, the spontaneous decomposition of DCBQ in aqueous solution was verified. DCBQ interacted indirectly with dsDNA and its degradation product(s) interacted with the deoxyguanosine homopolynucleotide with release of guanine and adenine from the double helix, but no oxidative damage to the dsDNA by DCBQ or its product(s) was detected.

The objective of this study was to investigate the effects of combined low-pressure ultraviolet (UV)irradiation and chlorination on the formation of disinfection by-products (DBPs) from different dissolved organic matter (DOM) as DBP precursors. Commercially available humic acid (HA), extracellular organic matter (EOM) from green algae, cyanobacteria, and diatom, namely Scenedesmus quadricauda (SQ), Merismopedia sp. (Msp), and Phaedactylum tricornutum (PT), were used as the sources of DOM. The DBP formation increased with increasing total residual chlorine; EOM from PT presented the highest formation potential followed by HA, Msp, and SQ. The low dosage of 40 mJ/cm2 UV irradiation is insignificant to change the DBP formation from HA and SQ; however, it decreased the DBP formation from bromide-containing EOM of PT and promoted the DBP formation from EOM of Msp at various total residual chlorines. The DBP formation of each DOM correlated well with total residual chlorine. The maximum DBP formation potential (DBPFP) reduction of 42.25 and 13.75% for haloacetic acid formation potential (HAAFP) and trihalomethane formation potential (THMFP) was obtained at the UV irradiation dosage of 300 mJ/cm2 for EOM of PT. However, for the EOM derived from Msp, a maximum increase of 58.1 and 51.1% for HAAFP and THMFP was observed after UV-chlorination. HIGHLIGHTS Disinfection by-product (DBP) formation increased linearly with total residual chlorine from 0.28 to 1.02 mg/L.; Ultraviolet (UV) irradiation did not significantly alter the DBP formation from humic acid and algal organic matter (AOM) of Scenedesmus quadricauda.; The haloacetic acid formation potential (HAAFP) and trihalomethane formation potential (THMFP) decreased by 42.25 and 13.75%, respectively, under the UV irradiation dosage of 300 mJ/cm2 for AOM of Phaedactylum tricornutum, while the maximum increment of 58.1 and 51.1% for HAAFP and THMFP were observed from the AOM of Merismopedia sp.

The availability of freshwater sources is declining as a result of increasing populations, economic activities, and climate change. These increasing trends will also drive up the demand for potable water that will require the use of alternative sources including wastewater-impacted and saline waters. Therefore, it is crucial to understand the formation of emerging toxic DBPs from advanced treatment of treated secondary wastewater effluents for potable reuse. In this study, a highly sensitive analytical method was developed to characterize 25 DBPs from 5 chemical classes (haloacetonitriles, halonitromethanes, haloacetaldehydes, haloketones, and iodinated trihalomethanes) in recycled wastewaters using a gas chromatography tandem mass spectrometer (MS/MS). The high sensitivity of MS/MS technology permitted a reduced sample concentration factor (50×) that required only 30 min of extraction time and 10 mL of sample volume. Method detection limits are the lowest reported between 2.0–68.9 ng L−1. Matrix effects in secondary wastewater effluents were low (0–30%) compared to ultra pure water. A full-scale facility for wastewater reuse that treated secondary wastewater effluents through microfiltration (UF), followed by ozone (UF/O3) or reverse osmosis (UF/RO) was evaluated. Water samples from each process were chlorinated (HOCl) and chloraminated (NH2Cl) to evaluate DBP precursor removal and DBP formation potential, the first study of its kind. Overall, HOCl formed higher summed DBP levels (0.5–18.5 μg L−1) compared to NH2Cl (0.2–8.5 μg L−1). HAN was significantly lower in UF/O3/HOCl (59%) and UF/RO/HOCl (99%) compared to UF/HOCl. However, HNM was enhanced after UF/O3/HOCl. In chloraminated samples, UF/O3/NH2Cl produced a higher amount of DBPs compared to UF/NH2Cl including haloacetonitriles, halonitromethanes, haloketones, and iodinated trihalomethanes.

Serving as the last barrier to secure drinking water safety, household water treatment and safe storage (HWTS) is perceived as an interim measure for removing pathogens from drinking water and reducing disease risk. In recent years, the application of HWTS has shown a growing trend, and its performance in controlling chemicals has also received much attention. Disinfection by-products (DBPs) are formed by the reaction of chemical disinfectants and precursors, and are present at sub-μg·L−1 or low-to-mid-μg·L−1 levels in drinking water. Although precursor control and disinfection operation modification could contribute to DBP mitigation to some degree, DBP removal after their formation emerges as an important strategy due to the ubiquitous existence of DBPs in distribution systems and tap water. In order to figure out how DBP concentrations vary during the residence time of drinking water in households, this review summarizes the effectiveness and mechanism of HWTS and combination technologies for DBP control in municipal tap water, and makes a comparison with regard to technologies implementing different removal mechanisms as well as DBPs possessing different natures. Based on these results, this article provides an insight into DBP risk assessment and human health protection.

In this study, water quality parameters and disinfection by products (DBPs) were monitored and correlations between them were statistically investigated in a swimming pool in the province of Bitlis...

Trace disinfection by-products (DBPs) produced during the disinfection of drinking water are potentially carcinogenic, teratogenic and mutagenic, which has aroused much attention recently. In this study, a molecularly imprinted (MIP) solid -phase microextraction (SPME) fiber coating was prepared by an in-situ polymerization method using a dummy template molecule for the analysis of trace 2,6-dichloroindole-1,4-benzoquinone (2,6-DCBQ), a typical DBP. The characterization results suggested that this monolithic SPME fiber under the optimized conditions had the porous structure, large surface area and good thermal stability. Due to the strong structural recognition and molecular interaction between MIP SPME coating and target molecule, it showed good extraction selectivity and capacity to trace 2,6-DCBQ with an imprinting factor of 4.7. Then, coupling with high-performance liquid chromatography (HPLC)-ultraviolet (UV) detection, a sensitive analytical method for trace 2,6-DCBQ in water samples was successfully established with a detection limit down to 2.3 ng/mL. The recoveries of the proposed method were in range of 84.4–122% with the relative standard deviations of 1.0–13% (n = 3). The results showed that this MIP SPME-HPLC-UV method possessed high analytical selectivity and sensitivity for trace 2,6-DCBQ in water, which would benefit the improvement of the practicability of DBPs monitoring and detection methodology.

Disinfection is an essential step to keep humans healthy from microorganisms present in drinking water. However, the formation of disinfection by-products (DBPs) is associated with adverse health effects, and the presence of organic pollutants in groundwater results in even more detrimental effects. Therefore, a better treatment technique is required to disinfect and remove organic pollutants simultaneously to control the formation of DBPs. Electro-chlorination (EC) was carried out using graphite electrode at the current density of 0.54–1.09 mA/cm2 and sodium chloride for in-situ hypochlorite generation to treat groundwater contaminated with phenol and aniline. The comparative study between chlorination and EC showed a significant level of oxidation of phenol and aniline, resulting in their reduction up to 98.48% and 99.47%, respectively, in the EC process. Due to the higher mineralization rate of aniline, both chlorination and EC method are found to be effective. However, only the EC method is found to be appropriate and effective for treating phenol-contaminated water as the chlorination method resulted in the formation of complicated phenolic by-products. Gas-Chromatography/Mass-Spectrometry (GCMS) was used to assess the by-product formation of chlorination and EC in contaminated groundwater through the full-scan.

Due to the wide-presence of organic amines in natural waters, organic chloramines are commonly formed during (pre-)chlorination. With the increasing application of UV disinfection in water treatment, both the activation mechanism of organic chloramine by UV photolysis and its subsequent impact on water quality are not clear. Using sarcosine (Sar) as an amine group-containing compound, it was found that organic chloramines (i.e., Cl-Sar) would be firstly formed during chlorination even in the presence of natural organic matter. Compared with self-decay of Cl-Sar, UV photolysis accelerated Cl-Sar decomposition and induced N Cl bond cleavage. Using metoprolol (MTP) as a model micro-pollutant, UV-activated Cl-Sar (UV/Cl-Sar) can accelerate micro-pollutant degradation, attributed to reactive radicals formation. HO• and Cl• were important contributors, with a total contribution of 45%‒64%. Moreover, the degradation rate of MTP by UV/Cl-Sar was pH-dependent, which monotonically increased from 0.044 to 0.065 min‒1 under pHs 5.5‒8.5. Although the activation of organic chloramine by UV could accelerate micro-pollutant degradation, UV/Cl-Sar treatment could also enhance disinfection by-products formation. Trichloromethane (TCM) formation was observed during MTP degradation by UV/Cl-Sar. After post-chlorination, TCM, 1,1-dichloropropanone, 1,1,1-trichloropropanone, and dichloroacetonitrile were detected. Their individual and total concentrations were all positively proportional to UV/Cl-Sar treatment time. The total concentration with 30 min treatment (66.93 μg L‒1) was about 2.3 times that with 1 min treatment (28.76 μg L‒1). Finally, the accelerated effect was verified with Cl-glycine and Cl-alanine. It is expected to unravel the non-negligible role of organic chloramine on water quality during UV disinfection.

Chlorination is the most common disinfection method used in the drinking water production. Reactivity of chlorine with organic molecules could generate disinfection by-product (DBPs), which are harmful to the human health. Natural organic matter (NOM) is a complex mixture of chemicals existing in source water. Because of its complexity, it is conjectured that formation of many different DBPs can arise from the reaction of organic matter and a chemical disinfectant. This study used model compounds as NOM surrogates in order to reveal the specific organic fraction and DBPs formation potential removed by different coagulants. Model compounds, as an artificial sample, were made from a mixture of Suwannee River Humic Acid (SRHA), Suwannee River Fulvic Acid (SRFA), Bovine Serum Albumin (BSA), Alginic Acid (AA). Alum and FeCl3 were used as coagulants. The samples were analyzed for organic parameters, such as total organic carbon (TOC), ultraviolet at 254 nm wavelength (UV254), specific UV absorbance (SUVA), and organic fractionated by high performance size exclusion chromatograph with organic carbon detector (HPSEC-OCD). The concentration of trihalomethanes (THMs) and haloacetic acids (HAAs) was measured to present the DBPs formation. The results show alum and FeCl3 removed biopolymer (Peak A), humic substances-like (Peak B, Peak C) at the same percentage, while low molecular weight acid and neutral (Peak D) showed a higher removal with alum than FeCl3. HAAs removal led to a greater reduction than THMs removal, and FeCl3 showed a higher removal than the alum coagulant. It indicated that alum and FeCl3 coagulant have different ability in removing specific organic fractions, which are precursors of THMs and HAAs formation.

A detailed comparison of sand filtration (SF) and ultrafiltration (UF) was conducted in this study with the aim to provide systematic support for alternative UF and SF technologies. The results of natural organic matter (NOM) removal indicated that SF conferred a slightly higher removal rate for UV-absorbing compounds, humic-like substances and protein-like substances than UF, with removal efficiencies of 21.9%, 19.8% and 26.1%, respectively. In addition, SF and UF exhibited different removal performances for organic fractions: UF better removed high molecular-weight (MW) organics, while SF exhibited higher removal of medium-MW organics. Furthermore, chlorine and chlorine dioxide were used as disinfectants to compare the different influences of SF and UF on disinfection by-product (DBP) formation. Unexpectedly, SF exhibited a better capacity for reducing the formation of chlorite than the UF process, with concentrations of 0.57 mg/L and 0.69 mg/L, respectively. Importantly, for the emergency scenario, e.g. seasonal algae pollution, the UF process achieved significantly higher removal of algae cells (98.7%) than SF due to size exclusion, indicating substantial resistance to algae load shocks. Therefore, these findings are beneficial for making practical decisions to adopt SF or UF technology in drinking water treatment plants.

Severe wildfires often have dramatic short-term effects on water quality, although there is increasing evidence that in some catchments their effects can persist for many years. Forest recovery after the 2002 Hayman Fire burned catchments that supply drinking water to over a half million users in Denver, CO, has been extremely slow and has caused persistent water quality concerns. To evaluate whether postfire water quality changes increase the potential to form undesirable by-products of water disinfection, we compared stream water from eight burned catchments within the Hayman Fire and five adjacent unburned catchments. We tested dissolved organic carbon (DOC) concentrations and the formation of disinfection byproducts (trihalomethanes [THMs], haloacetonitriles [HANs], chloral hydrate [CHD, and haloketones [HKTs]) in stream water monthly during 2014 and 2015. Stream DOC, THMs, and CHD and specific ultraviolet absorbance at 254 nm (SUVA254) were elevated in catchments with a moderate extent of high-severity wildfire (8-46% of catchment area) relative to catchments that were unburned and those that burned more extensively (>74% of catchment area) 14 yr after the fire. In contrast, formation of highly toxic but unregulated nitrogenous HANs increased linearly with wildfire extent. Although these findings should not raise concern regarding drinking water safety, they highlight the long-term influences of high severity wildfire on source water C content, composition, and treatability.

Water treatments that provide efficient removal of organic and inorganic disinfection by-product (DBP) precursors across variable natural organic matter (NOM) sources are desirable. Treatments that effectively remove inorganic DBP precursors such as bromide, which significantly shift the speciation of DBP formation towards more toxic DBPs, are of particular interest and have been less investigated. This study characterised NOM isolated from three major drinking water sources in Southeast Queensland (SEQ), Australia, and compared it to the International Humic Substances Society (IHSS) Suwannee River NOM isolate (SR) in terms of DBP precursor removal treatments and DBP formation. Each NOM isolate was used to make synthetic water samples with otherwise identical water quality parameters, that were treated with enhanced coagulation (EC) or EC followed by; anion exchange (MIEX® resin), powdered activated carbon (PAC), granular activated carbon (GAC) or silver impregnated activated carbon (SIAC), to investigate the removal of DBP precursors (bromide and DOC), minimisation of DBPs, as well as the change in specific chlorine demand. EC/SIAC treatment was the most effective method of DBP control studied, due to the efficient simultaneous NOM and bromide adsorption of the SIAC (99 ± 1% bromide removal regardless of NOM source). This treatment also resulted in >92% removal of each of the measured DBPs across all NOM sources, with the exception of DBAN and 1,1-DCP, which achieved >80% removal across all NOM sources. Increases in tribromomethane (TBM) and dibromoacetonitrile (DBAN) formation were observed after all other treatment/NOM-isolate combinations, due to increased Br:DOC ratio after treatment, whereas chlorinated DBPs were generally well-controlled by all treatment/NOM-isolate combinations. Differences in reactivity of the individual NOM isolates were found to be related to both the origin of the isolate and the treatment employed, however, bromide removal capacity for each treatment was independent of NOM source.

Soluble microbial products (SMPs) discharged into rivers from sewage treatment plants may increase the health risk for downstream drinking water by acting as a precursor of DBPs. Biotransformation or biodegradation could alter the characteristics of SMPs and affect the subsequent formation of DBPs. This study observed the relative contribution of chemical fractions in SMPs and explored the biodegradation of each fraction and their effect on disinfection by-products (DBPs) formation in surface water. The hydrophilic acid (HPIA) and hydrophobic acid (HPOA) constituted the major portion of the SMPs, which were dominated by fulvic acid and humic acids. The transphilic acid (TPIA) and hydrophobic bases (HPOB) were relatively minor but it contained a relative substantial portion of protein-like materials in SMPs. TPIA and HPOB produced insignificant amounts of DBP corresponding to 13% and 14% in the original samples, but they were collectively responsible for 50% of the DBPs yield. Much larger amounts of hydrophobic fractions were utilized than hydrophilic fractions after biodegradation. The increase in SUVA values indicating aromatic structures, except for HPOA fraction, was observed after biodegradation. The protein-like materials in both the HPOA and HPIA fractions and polycarboxylate-type humic acid in the HPIA fraction decreased but the enrichment of HPOA (MW 100 kDa) and TPIA (MW 1 kDa) was observed after biodegradation. The production of = C-H in HPIA fraction and the appearance of double peak at 1100 cm

Various types of dissolved organic matter (DOM) exist in the effluent of coking wastewater treatment plants. These can become precursors for disinfection by-products (DBPs) during chlorination in downstream drinking water treatment plants, representing a significant threat to the water supply. In this study, an O3 fluidized bed reactor (FBR) process is proposed to stabilize and reduce the number of precursors of haloacetonitriles (HANs) and trihalomethanes (THMs) in coking wastewater effluent. It was found that higher O3 concentrations resulted in lower amounts of precursors. Analysis of dissolved organic carbon (DOC) and total organic carbon (TOC), as well as three-dimensional excitation-emission matrix (3D EEM) fluorescence spectroscopy, showed that O3 preferentially decomposed DOM containing unsaturated and aromatic components. Ozonation also changed the species of organic compounds in the effluent. Furthermore, nitrogenous organic compounds such as nitrogen-containing heterocyclic compounds and nitrile were quickly oxidized. Amines were first increased then decreased, while the olefin and phenol, which contain unsaturated functional groups, were also selectively oxidized by ozonation. Organic acids and alkanes were formed during ozonation; however, these intermediate compounds showed relatively low formation potential for HANs and THMs. Therefore, the precursors can be mineralized or converted to organic compounds, which are less likely to form disinfection by-products. These results indicate that the ozonation treatment of coking wastewater effluent can effectively minimize disinfection by-product formation potential (DBPFP), reducing risks to the downstream water supply.

The presence of disinfection by-products (DBPs) increases the mutagenicity of water and may pose adverse health effects. Gut microbiota exerts a fundamental role on host physiology, and how extrinsic perturbations influence its composition has been increasingly examined. However, the effect of DBPs on gut microbiota is still poorly understood. In the present study, adult zebrafish were exposed to different concentrations of dichloroacetamide (DCAcAm, an emerging nitrogenous DBP) for 30 days. Sequencing of 16S rRNA amplicons revealed a significant change in the richness and diversity of microbiota in the gut of DCAcAm-exposed zebrafish. At the phylum level, the abundance of Proteobacteria decreased and the abundance of Fusobacteria and Firmicutes increased significantly in the gut after exposure to 100 and 500 μg/L DCAcAm. At the genus level, the abundances of several bacteria which are considered pathogens or opportunistic pathogens in fish and closely related to fish metabolism, disease and inflammation (Aeromonas, Stenotrophomonas, Bacteroides and Ralstonia) increased in the DCAcAm-treated groups. Our results reveal that DBPs in drinking water potentially affect gut microbiota composition, which may contribute to the toxicity assessment of DBPs in future and provide new insight into the complex interactions between the DBPs in drinking water and host health.

Soluble microbial products (SMPs) discharged into surface water may increase the formation of disinfection by-products (DBPs) in downstream drinking water treatment plants. In this study, ultrafiltration (UF) fractionation was used to separate SMPs into homogenous components. An aerobic microbial experiment was conducted to evaluate the bioavailability of individual molecular weight (MW) fractions of SMPs in surface water and the impact on their DBP formation, facilitating the interpretation of SMPs characterization and DBPs reactivity. For SMPs, organics with MW 1 kDa were the primary fraction, containing the most abundant humic substances. The 30 kDa MW 100 kDa fraction was the lowest in SMPs but had the highest SUVA values. After biodegradation, the bioavailability of physical fractions increased with the increasing MW size. However, the SUVA value, except for MW 1 kDa, increased in individual fraction after biodegradation. Low molecular weight SMPs fractions (MW10 kDa) were major precursors for DBP in which trichloromethane (TCM) was the most abundant. The 10 kDaMW 100 kDa fractions were found to be more active in formation of chloral hydrate (CH), and MW 100KDa had relative abundant dichloroacetonitrile (DCAN) formation. After biodegradation, TCM precursors with MW 1 kDa were removed by approximately 20%, whereas the increase of TCM formation was observed in 1 kDa MW 100 kDa fraction. CH formation from 1 kDa MW 10 kDa increased considerably, but those from 10 kDa MW 30 kDa decreased after biodegradation, as a result of the biotransformation of large organic acids to small organic acids. In terms of DBP reactivity, the TCM yield for the MW 1 kDa fraction had no significant change while the 30 kDaMW 100 kDa fraction exhibited the greatest increase (approximately 8 times) in TCM yield.

Biofiltration has been shown to be effective for disinfection by-product (DBP) precursor control, however few studies have considered its role in the potential formation of DBPs. Biofilm is composed of heterogeneous bacteria as well as extracellular polymeric substances (EPS). The objective of this study was to determine the contribution of biofilm-related materials such as EPS to form nitrogen-containing DBPs upon chloramination, and to determine the influence of cyclical (scheduled on-off) biofilter operation on DBP precursor removal. Biologically active media was sampled from a full-scale biofilter operating under cold-water conditions (3.6 ± 0.5 °C) and extracted using a cation exchange resin into a phosphate buffer solution. Biomass concentrations, as determined using adenosine triphosphate (ATP) measurements, remained stable at 298 ± 55 ng ATP/g media over the trial period. N-nitrosodimethylamine (NDMA) and haloacetonitrile (HAN4) formation potential (FP) tests conducted under uniform formation conditions (UFC) using extracted biofilm yielded 0.80 ± 0.27 ng NDMA/g media and 18.7 ± 3.3 ng dichloroacetonitrile (DCAN)/g media. Further analyses of extracted biofilm using fluorescence spectroscopy and liquid chromatography-organic carbon detection indicated the presence of proteins above 20 kDa and humic-like substances. Extracted proteins (93.5 ± 8.1 μg/g media) correlated well (R = 0.90) with UV 280 measurements, indicating that spectrophotometry may serve as a valuable tool to quantify proteins in extracted biofilms. While substances in biofilms can serve as NDMA and DCAN precursors, the full-scale cyclically-operated biofilter that was examined did not show release of NDMA precursors during start-up following stagnation periods of 6 h or more. These biofilters consistently removed 6.9 ± 4.3 ng/L of NDMA precursors; typical NDMA UFC-FP of biofilter effluent was 8.5 ± 2.6 ng/L.

Concerns regarding disinfection by-product (DBP) formation during drinking water treatment have led water utilities to apply treatment processes to reduce the concentration of DBP precursor natural organic matter (NOM). However, these processes often do not remove bromide, leading to high bromide to dissolved organic carbon (DOC) ratios after treatment, which can increase the formation of more toxic brominated DBPs. In the current study, we investigated the formation and effect of DBPs in a matrix of synthetic water samples containing different concentrations of bromide and DOC after disinfection with chlorine. Trihalomethanes and haloacetic acids were analysed by chemical analysis, while effect was evaluated using in vitro bioassays indicative of the oxidative stress response and bacterial toxicity. While the addition of increasing bromide concentrations did not alter the sum molar concentration of DBPs formed, the speciation changed, with greater bromine incorporation with an increasing Br:DOC ratio. However, the observed effect did not correlate with the Br:DOC ratio, but instead, effect increased with increasing DOC concentration. Water samples with low DOC and high bromide did not exceed the available oxidative stress response effect-based trigger value (EBT), while all samples with high DOC, irrespective of the bromide concentration, exceeded the EBT. This suggests that treatment processes that remove NOM can improve drinking water quality, even if they are unable to remove bromide. Further, iceberg modelling showed that detected DBPs only explained a small fraction of the oxidative stress response, supporting the application of both chemical analysis and bioanalysis for monitoring DBP formation.

Disinfection by-products (DBPs) in indoor swimming pool water and air have long been a critical human health risk concern. This study investigated the effects of several indoor swimming pool design and management factors (e.g. ventilation, water treatment, pool operations, pool type) on the concentrations of DBPs, such as trihalomethanes (THMs) and chloramines, in pool water and air. Two sampling campaigns, A and B, were carried out to measure the concentrations of DBPs under different conditions. In both campaigns, 46 pool water samples, seven tap water samples, and 28 ambient air samples were collected and analyzed. Regression models were also developed and validated for investigating the combined effects of design and management factors on total trihalomethanes (TTHM) and trichloramine. The model results show that pool water characteristics (e.g., total organic content, temperature, conductivity, pH and alkalinity) and management factors (e.g., the number of bathers and sprayers) have direct effects on DBP concentrations. Pool water characteristics such as UV absorbance, hardness, and oxidation-reduction potential and a management factor UV intensity have inverse effects on DBPs levels. Based on the correlation analysis, other factors such as fan speed, fresh air, pool age, and basin area were found to be correlated with the concentrations of individual THMs and trichloramine in both water and air. It was also observed that the concentration of THMs varies with pool type. It is note worthy that the effects of the number of sprayers was quantified for the first time. This study comprehensively assessed pool design and management factors and identified their effects on DBPs, providing indoor swimming pool facilities with useful information to control DBPs in the indoor swimming environment.

Dissolved organic matter (DOM) is ubiquitous in natural water and reacts with disinfectants to form disinfection by-products (DBPs). The analysis of DOM in raw water is helpful in evaluating the formation potential of DBPs. However, there is relatively little research on the DOM identification of raw water in northern China. In this study, the sources and characteristics of DOM were investigated in the samples collected from the Manas River. Dissolved organic carbon (DOC), UV254, specific ultraviolet absorbance, and fluorescence indices (fluorescence index, humification index, and biological index) were measured to characterize the DOM, and trihalomethanes (THMs) were quantified following formation potential tests with free chlorine. The maximum amount of total trihalomethane formation potential (THMsFP) was 225.57 μg L−1. The DOM of the Manas River consisted of microorganisms and soil resources. The excitation–emission matrix combined with parallel factor analysis (EEM-PARAFAC) identified microbial humus (C1, 54%) and tryptophan-like protein (C2, 46%). PARAFAC components were evaluated as the precursor surrogate parameters of THMsFP. Additionally, the linear THMsFP correlation was stronger with C1 + C2 (r = 0.529, p < 0.01) than with C1 (r = 0.485, p < 0.01). Thus, C1 + C2 is an accurate THMsFP precursor surrogate parameter for the Manas River, and the use of fluorescence spectroscopy may be a robust alternative for predicting DOC removal.

Efforts to remove highly toxic haloacetonitriles (HANs) is an important step to reduce health risks associated with disinfection by product exposure. Zero valent iron (ZVI) is a versatile material, whose reductant, sorbent and coagulant role has been well understood. However, their catalytic role is less known. In this study, the degradation and transformation of HANs in ZVI system were investigated. Significant decreases of the four HANs in ZVI system were observed, and haloacetamides and haloacetic acids (hydrolysis products of HANs) were the dominant transformation products of HANs. However dehalogenated HANs, Fe (II) and Fe (III) were rarely detected after reaction, indicating that the ZVI acted as a catalyst to promote the hydrolysis of HANs, rather than other previously reported causes (dehalogenation or redox reaction). The HAN degradation rates were dramatically affected by the initial pH, ZVI doses and initial HAN concentration. Kinetic analysis indicated that HAN removal was enhanced with the increase of initial pH (5-9), ZVI doses (1-10 g/L), and initial HAN concentration (25-200 μg/L). ZVI induced the transformation of HANs to haloacetamides, haloacetic acids and other de-halogenated compounds, which reduced the cytotoxicity and genotoxicity by 88% and 85%, respectively. This study helped to understand the fate of HAN during the transmission in cast iron pipes, and provided a theoretical foundation for future HAN control and monitoring efforts.

To remove disinfection by-product (DBP) precursors and mitigate odor compounds, peroxide (peroxymonosulfate and persulfate)/Fe(II)-based process was applied as a combination of coagulation and oxidation. Compared with traditional Fe-based salt coagulation (FeSO4 and FeCl3), peroxide/Fe(II)-based process was more efficient in dissolved organic carbon, UV254 and turbidity removal, and peroxymonosulfate showed better performance than persulfate. The better coagulation performance arose from a combination of enhanced neutralization and different characteristics of flocs. Even though the combined process would increase the bromine substitution factor of DBPs, DBP formation and DBP-associated toxicity after peroxide/Fe(II)-based process were 9.2-38.8% and 5.2-27.2% lower than that after conventional Fe(III) coagulation. Both enhanced dissolved organic matter removal and oxidation of DBP precursors played vital roles in DBP control. Conventional Fe-based salt coagulation could hardly remove odor compounds (less than 10%, generally), whereas 28.2-84.9% of odor compounds were degraded during peroxide/Fe(II)-based process, due to free radical formation. This study demonstrated that PMS/Fe(II)-based process might be a promising treatment process for simultaneous DBP control and odor removal in source water.

This study investigated the role of microorganisms on the correlation between temperature changes and disinfection by-product formation in natural waters. Climate changes have resulted in an increase in the global surface temperature. Studies have revealed that increases in temperature may change the composition of dissolved organic matter (DOM), which may contain major disinfection by-product (DBP) precursors. This change in the DOM composition may affect DBP formation after conventional water treatment processes. Understanding the role of microorganisms in DOM composition as well as DBP formation and speciation is critical for controlling DBP formation. In this study, laboratory stimulatory experiments were conducted on water samples from various sources, at various temperatures, and with various microbial concentrations. The results revealed a decreasing trend of dissolved organic carbon (DOC), trihalomethane formation potential (THMFP), and haloacetic acid formation potential (HAAFP) at high temperature incubations irrespective of microbial concentrates. This result may be attributed to the fact that microorganism activities or concentrations in water increase at higher temperatures, which may result in higher DOC consumption and lower DBP formation. Water samples spiked with bacteria concentrates exhibited higher THMFP or HAAFP reduction than did samples without bacteria concentrates. A higher biomass in water may contribute to a higher consumption of DOC and consequently lower DBP formation potentials, especially at high incubation temperatures.

This work investigated the removal efficiency of disinfection by-product (DBP) precursors by different drinking water treatment processes and evaluated the feasibility of using fluorescence components removal as an indicator. A four-component (including tryptophan-like, protein-bound, tyrosine-like, and humic-like components) parallel factor analysis model was developed basing on 288 fluorescence excitation-emission matrices. Among all treatment processes, coagulation-sedimentation process showed the best performance, with mean removal ratios of 30% in total fluorescence intensity and 31% in total formation potential (FP) of DBPs, respectively. It preferentially removed humic-like component C4 (43%). Advanced treatment processes were less effective in comparison. Ozone and biological activated carbon (BAC) combined process reduced 20% of total fluorescence intensity, while ultrafiltration process reduced 3%. Ozonation and BAC filtration preferentially removed free amino acids (i.e., C1 and C3) and protein-bound (i.e., C2) components, with mean removal ratios of 12% and 17%, respectively. Significant correlations (p 0.01, double-tailed) were observed between four fluorescence components removal and FPs reduction of three trihalomethanes, dichloroacetonitrile (DCAN), and 1,1-dichloropropanone (1,1-DCP). Specifically, the correlation coefficients for three trihalomethanes and 1,1-DCP followed the order of C4 C1 C2 C3, while the order for DCAN was C2 C4 C1 C3.

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.

Restoring woody vegetation to riparian zones helps to protect waterways from excessive sediment and nutrient inputs. However, the associated leaf litter can be a major source of dissolved organic matter (DOM) leached into surface waters. DOM can lead to the formation of disinfection by-products (DBPs) during drinking water treatment. This study investigated the DBPs formed during chlorination of DOM leached from leaf litter and assessed the potential toxicity of DBPs generated. We compared the leachate of two native Australian riparian trees, Casuarina cunninghamiana and Eucalyptus tereticornis, and a reservoir water source from a catchment dominated by Eucalyptus species. Leachates were diluted to dissolved organic carbon concentrations equivalent to the reservoir (~9 mg L-1). E. tereticornis leachates produced more trihalomethanes (THMs), haloacetic acids (HAAs), and haloketones after chlorination, while C. cunninghamiana produced more chloral hydrate and haloacetonitriles. Leachate from both species produced less THMs and more HAAs per mole of carbon than reservoir water. This may be because reservoir water had more aromatic, humic characteristics while leaf leachates had relatively more protein-like components. Using in vitro bioassays to test the mixture effects of all chemicals, chlorinated E. tereticornis leachate induced oxidative stress in HepG2 liver cells and bacterial toxicity more frequently and at lower concentrations than C. cunninghamiana and reservoir water. Overall, this study has shown that the DOM leached from litter of these species has the potential to generate DBPs and each species has a unique DBP profile with differing bioassay responses. E. tereticornis may pose a relatively greater risk to drinking water than C. cunninghamiana as it showed greater toxicity in bioassays. This implies tree species should be considered when planning riparian zones to ensure the benefits of vegetation to waterways are not offset by unintended increased DBP production and associated toxicity following chlorination at downstream drinking water intakes.

With the popularity of swimming activities across the world, the responsibility of the pool operators and managers to ensure the microbial and chemical safety of the pool participants becomes extremely significant. Disinfection by-products (DBPs) in swimming pool waters (SPWs) have attracted considerable public attentions due to their high frequency of occurrence, considerable concentrations and potent toxicity. This study explored the appropriateness of novel approaches for the control and treatment of DBPs. Chlorine/bromine stabilized disinfectants have been attempted to fulfil the dual requirements of sufficient disinfectants and less DBP formation. Reverse osmosis and nanofiltration have been used to remove haloacetic acids (HAAs, a group of prevalent DBPs) and the mechanism governing the rejection has been well interpreted. The effect of calcium ion (a ubiquitous species in SPWs) on HAA rejection has been systematically investigated. The fundamental understanding of these DBP control protocols offers good theoretical basis for future practical applications. Doctor of Philosophy (IGS)

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.

With the fast development of peroxymonosulfate (PMS)-dominating processes in drinking water and wastewater treatment, residual PMS is easy to come across chlorine as these processes are usually followed by secondary chlorine disinfection. The synergistic effect of PMS and chlorine on the degradation of micro-organic pollutants is investigated by selecting acetaminophen (ACT) as a reference compound for the first time in this study. Unlike conventional PMS or chlorine activation which generates reactive species such as hydroxyl radical (HO•), sulfate radical (SO4•-), chlorine radical (Cl•), and singlet oxygen (1O2), the efficient ACT removal is attributed to the direct catalytic chlorination by PMS due to the significantly enhanced consumption of chlorine along with negligible change of PMS concentration at neutral condition, and the same reaction pathways in both PMS/chlorine and chlorine processes. The kinetic study demonstrates that ACT oxidation by PMS/chlorine follows second order reaction, and the degradation efficiency can be promoted at alkaline conditions with peak rate constants at pH 9.0-10.0. The presence of chloride can enhance the removal of ACT, while ammonium and humic acid significantly retard ACT degradation. Higher formation of selected disinfection by-products (DBPs) is observed in the PMS/chlorine process than in the sole chlorination. This study highlights the important role of PMS in organic pollutants degradation and DBPs formation during the chlorination process.

The current study compared the impact of three different unit processes, coagulation, granular activated carbon (GAC), and a novel suspended ion exchange (SIX) technology, on disinfection by-product formation potential (DBPFP) from two UK lowland water sources with medium to high bromide content. Specific attention was given to the influence of the organic molecular weight (MW) fraction on DBPFP as well as the impact of bromide concentration. Whilst few studies have investigated the impact of MW fractions from Liquid Chromatography with Organic Carbon Detection (LC-OCD) analysis on dissolved organic carbon (DOC) removal by different processes, none have studied the influence of DOC MW fractions from this analysis on DBP formation. The impact of higher bromide concentration was to decrease the total trihalomethane (THM) and haloacetic acid (HAA) mass concentration, in contrast to previously reported studies. Results indicated that for a moderate bromide concentration source (135 μg/L), the THM formation potential was reduced by 22% or 64% after coagulation or SIX treatment, respectively. For a high bromide content source (210 μg/L), the THM formation potential removal was 47% or 69% following GAC or SIX treatment, respectively. The trend was the same for HAAs, albeit with greater differences between the two processes/feedwaters with reference to overall removal. A statistical analysis indicated that organic matter of MW > 350 g/mol had a significant impact on DBPFP. A multiple linear regression of the MW fractions against DBPFP showed a strong correlation (R2 between 0.90 and 0.93), indicating that LC-OCD analysis alone could be used to predict DBP formation with reasonable accuracy, and offering the potential for rapid risk assessment of water sources.

The purpose of this study is to develop a modeling framework to assess the impact of drinking water distribution system water-age dynamics on population-weighted disinfection by-product (DB...

Ozonation has been applied in water treatment for more than a century, first for disinfection, later for oxidation of inorganic and organic pollutants. In recent years, ozone has been increasingly applied for enhanced municipal wastewater treatment for ecosystem protection and for potable water reuse. These applications triggered significant research efforts on the abatement efficiency of organic contaminants and the ensuing formation of transformation products. This endeavor was accompanied by developments in analytical and computational chemistry, which allowed to improve the mechanistic understanding of ozone reactions. This critical review assesses the challenges of ozonation of impaired water qualities such as wastewaters and provides an up-to-date compilation of the recent kinetic and mechanistic findings of ozone reactions with dissolved organic matter, various functional groups (olefins, aromatic compounds, heterocyclic compounds, aliphatic nitrogen-containing compounds, sulfur-containing compounds, hydrocarbons, carbanions, beta-diketones) and antibiotic resistance genes.

Although granular activated carbon (GAC) has been broadly applied in ozone-biologically activated carbon filtration (O3/BAC) systems for potable reuse of municipal wastewater, the mechanisms of various pollutant removal remain largely unknown as the regenerated GAC develops microbial populations resulting in biofiltration but loses significant adsorption capacity as it becomes spent GAC. Therefore, pilot-scale parallel performance comparisons of spent and regenerated GAC, along with a range of pre-oxidant ozone doses, were used to shed light on the mechanisms responsible for the removal of various types of treatment byproduct precursors and trace organic compounds. It was confirmed from this pilot-study that ozone alone can effectively degrade chlorinated trihalomethane (THM) and haloacetic acid (HAA) precursors, chloramine-reactive N-nitrosodimethylamine (NDMA) precursors, and 29 PPCPs. In contrast, biodegradation by microbial population on spent or regenerated GAC can remove NDMA and 22 PPCPs, while the adsorption by regenerated GAC can remove chlorinated THM and HAA precursors, PFAS, flame retardants, and 27 PPCPs. The results of this pilot study are intended to provide those interested in potable reuse with an example of the simultaneous removal capabilities and mechanisms that can be anticipated for treating a complex mixture of organics present in real municipal wastewater effluent.

Parallel factor (PARAFAC) analysis of fluorescence excitation-emission matrices (EEMs) was used to investigate the organic matter and DBP formation characteristics of untreated, primary treated (enhanced coagulation; EC) and secondary treated synthetic waters prepared using a Suwannee River natural organic matter (SR-NOM) isolate. The organic matter was characterised by four different fluorescence components; two humic acid-like (C1 and C2) and two protein-like (C3 and C4). Secondary treatment methods tested, following EC treatment, were; powdered activated carbon (PAC), granular activated carbon (GAC), 0.1% silver-impregnated activated carbon (SIAC), and MIEX® resin. Secondary treatments were more effective at removing natural organic matter (NOM) and fluorescent DBP-precursor components than EC alone. The formation of a suite of 17 DBPs including chlorinated, brominated and iodinated trihalomethanes (THMs), dihaloacetonitriles (DHANs), chloropropanones (CPs), chloral hydrate (CH) and trichloronitromethane (TCNM) was determined after chlorinating water sampled before and after each treatment step. Regression analysis was used to investigate the relationship between peak component fluorescence intensity (FMAX), DBP concentration and speciation, and more commonly used aggregate parameters such as DOC, UV254 and SUVA254. PARAFAC component 1 (C1) was in general a better predictor of DBP formation than other aggregate parameters, and was well correlated (R ≥ 0.80) with all detected DBPs except dibromochloromethane (DBCM) and dibromoacetonitrile (DBAN). These results indicate that the fluorescence-PARAFAC approach could provide a robust analytical tool for predicting DBP formation, and for evaluating the removal of NOM fractions relevant to DBP formation during water treatment.

The aim of this study was to optimize the dispersive liquid–liquid microextraction (DLLME) parameters for simultaneous analysis through DLLME-gas chromatography–mass spectrometry (GC–MS) of six iodo-trihalomethanes, four haloacetonitriles, and one halonitromethane, which are residual disinfection products found in drinking water. Eleven disinfection by-product (DBPs) remaining in aqueous samples were extracted and concentrated using a simple, rapid, and environmentally friendly DLLME method, and then analyzed simultaneously by GC–MS. The optimized DLLME parameters were a sample volume of 5 mL, 100 μL of dichloromethane as the extraction solvent, 1 mL of methanol as the dispersion solvent, an extraction time of 60 s, and 1.5 g of sodium chloride for the salting out effect. The enrichment factor values obtained using the established DLLME-GC–MS method were 19.8–141.5, and the limit of detection and limit of quantification were 0.22–1.19 μg/L and 0.75–3.98 μg/L, respectively. The calibration curves had correlation coefficients (r2) of 0.9958–0.9992 in the concentration range of 0.5–40 μg/L, and they exhibited good linearity in quantitative analysis. This new method could be useful for analyzing eleven DBPs that remain in drinking water.

The degradation kinetics of chlorimuron-ethyl during chlorination was analyzed, and the effects of the influencing factors of pH, bromide and ammonium concentrations and reaction temperature on degradation kinetics were evaluated. Regarding degradation kinetics, the chlorination of chlorimuron-ethyl followed second-order kinetics, first-order kinetics when the chlorine concentration was changed, and first-order kinetics when the chlorimuron-ethyl concentration was changed. The apparent second-order rate constant was calculated, which significantly decreased increasing pH. The rate constant of the reaction between chlorimuron-ethyl− and HOCl was calculated as 3.25 (±1.14) × 103 M−1 min−1, and under the acid-catalyzed condition, the rate constant significantly increased to 6.41 (±1.62) × 107 M−1 min−1. The degradation rate of chlorimuron-ethyl decreased with increasing bromide (at pH 5.5–7.0) and ammonium concentrations (≤6 μM). Chlorimuron-ethyl chlorination is an endothermic reaction, with an activation energy estimated as 22.46 kJ mol−1 using the Arrhenius equation. During chlorimuron-ethyl chlorination, chloroform was the major volatile degradation product during chlorimuron-ethyl chlorination, and its concentration increased with the increasing reaction time and pH level. The distribution of disinfection by-products (DBPs) formed at different solution pH levels was quite distinct. In the presence of bromide, the concentration and species of brominated DBPs increased with the increasing bromide concentration. Notably, carcinogenicity and mutagenicity of brominated DBPs were higher than their chlorinate analogs.

A membrane bioreactor (MBR) acclimatized with wastewater organic matter was employed for surface water treatment, and the feasibility of the MBR for the removal of disinfection by-product (DBP) precursors was studied. With a low pressure microfiltration hollow-fiber membrane module, a hydraulic retention time of 1.5 hours and a solids retention time of 180 days, the MBR was able to achieve 35% removal of trichloroacetic acid precursors and 21% removal of dichloroacetic acid precursors. The removal of trichloromethane (TCM) and brominated DBP precursors was unsatisfactory. The TCM yield and bromine substitution factors for trihalomethanes and dihaloacetic acids increased. The phenomena could be attributed to an extended treatment time for hydrophobic dissolved organic matter (DOM), production of soluble microbial products from biomass activities, and an increased Br/DOM ratio by the MBR. Since the MBR treatment would lead to the production of some new DBP precursors and a change of DOM composition, the toxic potency of the DBPs formed needs to be taken into consideration if this process is employed for surface water treatment.

National and international regulations require that ships' ballast water is treated to minimize the risk of introducing potentially invasive species. A common approach employed by commercial ballast water management systems is chlorination. This study presents the algal toxicity findings for three chlorination-based BWMS and their implications to environmental safety of port waters receiving treated ballast water from ships. Discharged treated ballast water from all three BWMS was toxic to algae with IC25s (25% growth inhibition) ranging from 9.9% to 17.9%, despite having total residual oxidant concentrations below 0.02 mg/l, based on Whole Effluent Toxicity assays. When held at 4 °C, some of the ballast water samples continued to exhibit toxic effects with no observed effect concentrations as low as 18% after a 134 day holding time. Thirteen individual disinfection by-products were measured above the detected limit at the time of discharge. No correlation between DBPs and algal toxicity was observed.

Algogenic organic matter (AOM) in eutrophic waters is a well-known precursor to disinfection by-product (DBP) formation in drinking water. This purpose of this study is (i) to characterize the optical properties of AOM origins, including intra- (IOM) and extra-cellular organic matter (EOM), derived from Chlorella sp. growth as precursors to two major carbonaceous DBPs (C-DBPs), trihalomethanes (THMs) and haloacetic acids (HAAs) and (ii) to correlate these optical properties with THM and HAA formation potential (FP) in order to predict DBP formation. The results show that both EOM and IOM had low UV254 and UV280 absorbance during their entire growth phase. While IOM chiefly comprised of aromatic proteins and soluble microbial products-like substances (80% of average fluorescent intensity–AFI), EOM spectra were rich in humic- and fulvic-like substances (60% AFI). However, its chemical nature likely differed from terrestrial humics. In DBPFP tests, IOM was a higher-yielding precursor of THMs and HAAs compared to EOM, regardless its growth status. Consequently, C-DBPFP of IOM was always higher than EOM during four growth phases. Results from DBP tests also showed insignificant variation of EOM-derived THMFP and HAAFP during the algal growth phase, while the algal growth status strongly influenced the yields of IOM-derived THMFP and HAAFP. From correlation analysis, our results showed no correlation between UV absorbance with THMFP and HAAFP. Conversely, the regional AFI showed a good correlation with HAAFP and C-DBPFP. Predicting models based on AFI for the formation of HAAs and C-DBPs consequently yielded great predictability for laboratory AOM-containing water samples, with a coefficient of determination R2 = 0.879, p

The electro-peroxone (E-peroxone) process is an emerging ozone-based electrochemical advanced oxidation process that combines conventional ozonation with in-situ cathodic hydrogen peroxide (H2O2) production for oxidative water treatment. In this study, the effects of the E-peroxone pretreatment on disinfection by-product (DBP) formation from chlorination of a synthetic surface water were investigated and compared to conventional ozonation. Results show that due to the enhanced transformation of ozone (O3) to hydroxyl radicals ( OH) by electro-generated H2O2, the E-peroxone process considerably enhanced dissolved organic carbon (DOC) abatement and significantly reduced bromate (BrO3−) formation compared to conventional ozonation. However, natural organic matter (NOM) with high UV254 absorbance, which is the major precursors of chlorination DBPs, was less efficiently abated during the E-peroxone process than conventional ozonation. Consequently, while both conventional ozonation and the E-peroxone process substantially reduced the formation of DBPs (trihalomethanes and haloacetic acids) during post-chlorination, higher DBP concentrations were generally observed during chlorination of the E-peroxone pretreated waters than conventional ozonation treated. In addition, because of conventional ozonation or the E-peroxone treatment, DBPs formed during post-chlorination shifted to more brominated species. The overall yields of brominated DBPs exhibited strong correlations with the bromide concentrations in water. Therefore, while the E-peroxone process can effectively suppress bromide transformation to bromate, it may lead to higher formation of brominated DBPs during post-chlorination compared to conventional ozonation. These results suggest that the E-peroxone process can lead to different DBP formation and speciation during water treatment trains compared to conventional ozonation.

The characteristics of dissolved organic matter (DOM) and bromide ion concentration have a significant influence on the formation of disinfection by-products (DBPs). In order to identify the main DBP precursors, DOM was divided into five fractions based on molecular weight (MW), trihalomethane formation potential and haloacetic acid formation potential were determined for fractions, and the change in contents of different fractions and total DBPs during treatment processes (pre-chlorination, coagulation, sand filtration, disinfection) were studied. Moreover, the relationship between bromide concentration and DBP generation characteristics in processes was also analyzed. The results showed that the main DBP precursors were the fraction with MW

Volatile organic compounds (VOCs) present in drinking water, have a negative impact on human health and environment especially that formed during chlorination step in the treatment process, they classified as possible human carcinogens, when exceed the permissible limits. The identification and quantification of VOCs performed by purge & trap GC/MS instrument, using reference analytical method (EPA 524.2, 1995). A monthly monitoring comparative study established during 2016 in both input and output of Shubra El-Kheima (Water Treatment Plants WTP) (1 km far from Nile River on Al-Sharqawia canal at the northern border of capital Cairo) and South Alamein WTP (270 km downstream far from the Nile River on Alhamam canal at North Coast of Egypt). The study investigated and recorded the presence of disinfection by-product of Volatile Organic Compounds (DBPs-VOCs) (CHCl3, CHCl2Br, CHClBr2 and CHBr3) which exceeded the permissible limits in the produced Water of South Alamein WTP and its boosters. The study succeeded in estimating the amount of granular activated carbon GAC required to reduce (DBPs-VOCs) values from (178 µg/l) to (94 µg/l) in the produced water of South Alamein WTP, The duration frequency for changing (GAC)would be approximately (581 ton)/(17 days).

Algal growth strongly affects the change in characteristics of algal organic matter (AOM) in algae-laden water. AOM has adverse effects on algal cell removal from natural water by coagulation-sedimentation, frequently results in the significant formation of disinfection by-products (DBPs), such as trihalomethanes (THMs) and haloacetic acids (HAAs). This study aimed to investigate the effects of pre-chlorination on Microcystis aeruginosa (MA)-laden water collected in exponential and decline phases and the corresponding in-situ formed carbonaceous DBPs (C-DBPs) within 10 min exposure time. An automated fluorescent cell counter was used to determine the changes in cell degradation and viability, and fluorescent organic matters were characterized. The results have shown that MA cells suffer a faster and stronger degradation in chlorination at the exponential phase to cause more pronounced viability loss (>70%) than that at the decline phase, resulting in more significant released AOM degradation and C-DBPs formation, especially for THMs formation. In chlorination, a significant degradation in SMP-like and HA-like substances occurs at the exponential phase, while AP-like and SMP-like organics are predominantly degraded at the decline phase. Both THM and HAA precursors play an important role towards in-situ formation of C-DBPs at the exponential phase while THM precursors are dominant at the decline phase. THMs formation decreases with increasing HAAs formation over time during chlorination at the exponential phase, but stagnant THMs and HAAs formation occurs at the decline phase. Intensified pre-chlorination at high dosing ratio (Cl2:DOC = 1:1) favors to facilitate in-situ formation of THMs. It is concluded that algal growth phase impact on cell removal and C-DBPs formation should be concerned for intensified pre-chlorination towards MA-laden water for drinking water treatment.

The components and characteristics of dissolved organic matter (DOM), the main precursor of toxic disinfection by-products (DBPs), have attracted increasing attention in water sources. In this study, fluorescence excitation-emission matrix (EEM) coupled with parallel factor (PARAFAC) analysis was used to investigate the DOM fluorescence characteristics of river water along the Huangpu River, China. Four fluorescence components were identified, including two protein-like components (C1 and C2) and two humic-like components (C3 and C4). The fluorescence characteristics showed spatial and temporal variations with the highest total fluorescence intensities observed in autumn, and the increased relative abundance of humic-like substance in the metropolitan area of Shanghai. Fluorescence index and biological index indicated that the DOM of Huangpu River water had both terrestrial and microbial origins and mainly autochthonous characteristic. Moreover, the formation potentials (FPs) of DBP for Huangpu River water were determined, and trihalomethanes were the predominant species formed in all samples. The correlation analysis further showed that PARAFAC C4 (microbial humic-like fluorescence) significantly correlated with the FP of N-DBPs, providing an insight for drinking water treatment to control specific DBPs precursor. In addition, the humic-like components also correlated with the concentrations of triazole and organophosphate pesticides detected in the Huangpu River. These results indicated that fluorescence-PARAFAC analysis is a promising tool to assess the DBPFPs and pesticide occurrence in surface waters.

Differential UV absorbance (ΔA) has been proposed as a method for estimating disinfection by-products (DBP) concentrations in drinking water at a lower cost and at higher frequencies than the sampl...