Levels Of Disinfection By-products Research Articles

Drinking Water Quality in the Kingdom of Saudi Arabia

The production and transmission system of the Saudi Water Authority (SWA) faces a number of challenges in maintaining the high quality of potable water. Produced desalinated water is transmitted for long distances and is mixed with ground and surface waters of varying quality. The SWA is also in the process of converting from thermal desalination to seawater reverse osmosis which typically gives higher total dissolved solids, requiring better control of species with possible impacts on system integrity or human health. The results of monitoring across the desalination plants and transmission systems of the SWA in 2020–2022 confirm an overall high quality of water, with levels of disinfection by-products and heavy metals low in comparison to public water supplies in high-income countries dependent on surface and groundwater rather than seawater desalination. The results also indicate that continued operational improvements are required with the transition from thermal desalination technologies to reverse osmosis in order to maintain chloride at a level to avoid corrosion in the distribution system and to maintain boron and bromate within acceptable regulatory limits. Significant improvement in bromate control was observed over the course of the study, and recent innovations in post-treatment suggest that this will improve further.

Swimming benefits outweigh risks of exposure to disinfection byproducts in pools

Disinfection of swimming pool water is critical to ensure the safety of the recreational activity for swimmers. However, swimming pools have a constant loading of organic matter from input water and anthropogenic contamination, leading to elevated levels of disinfection byproducts (DBPs). Epidemiological studies have associated increased risks of adverse health effects with frequent exposure to DBPs in swimming pools. Zhang et al. (2023b) investigated the occurrence of trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and haloacetaldehydes (HALs) in eight swimming pools and the corresponding input water in a city in Eastern China. The concentrations of THMs, HAAs, HANs, and HALs in swimming pools were 1–2 orders of magnitude higher than those detected in the input water. The total lifetime cancer and non-cancer health risks of swimmers through oral, dermal, inhalation, buccal, and aural exposure pathways were assessed using the United States Environmental Protection Agency's (USEPA) standard model and Swimmer Exposure Assessment Model (SWIMODEL). The results showed that dermal and inhalation pathways were the most significant for the associated cancer and non-cancer risks. This article provides an overview and perspectives of DBPs in swimming pools, the benefits of swimming, the need to improve the monitoring of DBPs, and the importance of swimmers’ hygiene practices to keep swimming pools clean. The benefits of swimming outweigh the risks from DBP exposure for the promotion of public health.

Disinfection byproducts and their cytotoxicity contribution from dissolved black carbon in source water during chlor(am)ination

Dissolved black carbon (DBC), the soluble component of black carbon, which mainly comes from the incomplete combustion of fossil fuels or biomass, is widely spread in source water and significantly contributes to the formation of dissolved organic matter (DOM). However, the origin of DBC in different types of source water in China has not been well studied, as well as its subsequent transformation and toxicity contribution during disinfection of source water DOM by chlor(am)ine. In this study, DBC from 17 different source water in East China at different seasons was collected. The δ13C compositions indicated that straw burning was the main origin of DBC in source water. After simulated chlor(am)ination of DBC, 5 categories of aliphatic disinfection byproducts (DBPs) including trihalomethanes, haloacetic acids, haloacetonitriles, haloketones, halonitromethanes and 6 categories of aromatic DBPs including halophenols, halonitrophenols, halohydroxybenzaldehyde, halohydroxybenzoic acid, halobenzoquinones and haloaniline were detected. Compared with chlorination of DBC, higher levels of nitrogenous DBPs and aromatic DBPs were generated during chloramination. Detected DBPs accounted for 42 % of total organic halogen. What's more, Chinese hamster ovary cells cytotoxicity tests showed that the cytotoxicity of DBPs formed by chlor(am)ination of DBC was 4 times higher than that by chlor(am)ination of DOM. Haloacetonitriles contributed to the highest cytotoxicity in the chloramination of DBC, and haloacetic acids contributed to the highest cytotoxicity in chlorination. 67 % of the total cytotoxicity attributed to the undetected DBPs. As a result, DBPs generated from DBC contributed to 11.7 % of the total cytotoxicity in the chlor(am)ination of the source water DOM although DBC only took up 2 % of DOC in the source water. Results obtained from this study systematically revealed the DBPs formation from DBC and their potential cytotoxicity contribution in the chlor(am)ination of source water DOM, which should not be ignored in drinking water treatment.

Control of chlorination disinfection by-products in drinking water by combined nanofiltration process: A case study with trihalomethanes and haloacetic acids

Disinfection by-products (DBPs) are prevalent contaminants in drinking water and are primarily linked to issues regarding water quality. These contaminants have been associated with various adverse health effects. Among different treatment processes, nanofiltration (NF) has demonstrated superior performance in effectively reducing the levels of DBPs compared to conventional processes and ozone-biological activated carbon (O3-BAC) processes. In this experiment, we systematically investigated the performance of three advanced membrane filtration treatment schemes, namely "sand filter + nanofiltration" (SF + NF), "sand filter + ozone-biological activated carbon + nanofiltration" (SF + O3-BAC + NF), and "ultrafiltration + nanofiltration" (UF + NF), in terms of their ability to control disinfection by-product (DBP) formation in treated water, analyzed the source and fate of DBP precursors during chlorination, and elucidated the role of precursor molecular weight distribution during membrane filtration in relation to DBP formation potential (DBPFP). The results indicated that each treatment process reduced DBPFP, as measured by trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP), with the SF + O3-BAC + NF process being the most effective (14.27 μg/L and 14.88 μg/L), followed by the SF + NF process (21.04 μg/L and 16.29 μg/L) and the UF + NF process (26.26 μg/L and 21.75 μg/L). Tyrosine, tryptophan, and soluble microbial products were identified as the major DBP precursors during chlorination, with their fluorescence intensity decreasing gradually as water treatment progressed. Additionally, while large molecular weight organics (60–100,000 KDa) played a minor role in DBPFP, small molecular weight organics (0.2–5 KDa) were highlighted as key contributors to DBPFP, and medium molecular weight organics (5–60 KDa) could adhere to the membrane surface and reduce DBPFP. Based on these findings, the combined NF process can be reasonably selected for controlling DBP formation, with potential long-term benefits for human health.

Reconsider the burn: The transient effect of a chlorine burn on controlling opportunistic pathogens in a full-scale chloraminated engineered water system

Nitrification is a serious water-quality issue in chloraminated engineered water systems (EWSs). Nitrification is often remediated by a chlorine burn (i.e., a free‑chlorine conversion), a short-term switch from chloramination to chlorination in EWSs. Opportunistic pathogens (OPs) are the dominant infectious agents in EWSs. However, the responses of OPs to a chlorine burn are unknown. This study for the first time assessed how a chlorine burn affected OPs in a full-scale EWS. We determined the impact of a 1.5-month chlorine burn on four dominant OPs (Legionella, Mycobacterium, Pseudomonas, and Vermamoeba vermiformis) in a representative full-scale chloraminated EWS in the United States. Legionella and Mycobacterium were the most abundant OPs. In the water main, the summed concentration of the four OPs during the chlorine burn [3.27 ± 1.58 log10(GCN·L−1); GCN: genome or gene copy number] was lower (p ≤ 0.001) than before the burn [4.83 ± 0.50 log10(GCN·L−1)]. After the burn, the summed concentration increased to 4.27 ± 0.68 log10(GCN·L−1), comparable to before the burn (p > 0.05), indicating a transient effect of the chlorine burn in the water main. At the residential sites, the summed concentrations of the four OPs were comparable (p > 0.05) at 5.50 ± 0.84, 5.27 ± 1.44, and 5.08 ± 0.71 log10(GCN·L−1) before, during, and after the chlorine burn, respectively. Therefore, the chlorine burn was less effective in suppressing OP (re)growth in the premise plumbing. The low effectiveness might be due to more significant water stagnation and disinfectant residual decay in the premise plumbing. Indeed, for the entire sampling period, the total chlorine residual concentration in the premise plumbing (1.8 mg Cl2·L−1) was lower than in the water main (2.4 mg Cl2·L−1). Consequently, for the entire sampling period, the summed concentration of the four OPs in the premise plumbing [5.26 ± 1.08 log10(GCN·L−1)] was significantly higher (p < 0.001) than in the water main [4.04 ± 1.25 log10(GCN·L−1)]. In addition, the chlorine burn substantially increased the levels of disinfection by-products (DBPs) in the water main. Altogether, a chlorine burn is transient or even ineffective in suppressing OP (re)growth but raises DBP concentrations in chloraminated EWSs. Therefore, the practice of chlorine burns to control nitrification should be optimized, reconsidered, or even replaced.

Water Quality Trade-offs for Risk Management Interventions in a Green Building.

Premise plumbing water quality degradation has led to negative health impacts from pathogen outbreaks (e.g., Legionella pneumophila and non-tuberculous mycobacteria), as well as chronic effects from exposure to heavy metals or disinfection by-products (DBP). Common water quality management interventions include flushing, heat shock (thermal disinfection), supplemental disinfection (shock or super chlorination), and water heater temperature setpoint change. In this study, a Legionella pneumophila- colonized Leadership in Energy and Environmental Design (LEED) certified building was monitored to study health-relevant water quality changes before and after three controlled management interventions: (1) flushing at several points throughout the building; (2) changing the water heater set point; and (3) a combination of interventions (1) and (2) by flushing during a period of elevated water heater set point (incompletely performed due to operational issues). Microbial (culturable L. pneumophila, the L. pneumophila mip gene, and cATP) and physico-chemical (pH, temperature, conductivity, disinfectant residual, disinfection by-products (DBPs; total trihalomethanes, TTHM), and heavy metals) water quality were monitored alongside building occupancy as approximated using Wi-Fi logins. Flushing alone resulted in a significant decrease in cATP and L. pneumophila concentrations (p = 0.018 and 0.019, respectively) and a significant increase in chlorine concentrations (p = 0.002) as well as iron and DBP levels (p = 0.002). Copper concentrations increased during the water heater temperature setpoint increase alone to 140°F during December 2022 (p = 0.01). During the flushing and elevated temperature in parts of the building in February 2023, there was a significant increase in chlorine concentrations (p = 0.002) and iron (p = 0.002) but no significant decrease in L. pneumophila concentrations in the drinking water samples (p = 0.27). This study demonstrated the potential impacts of short term or incompletely implemented interventions which in this case were not sufficient to holistically improve water quality. As implementing interventions is logistically- and time-intensive, more effective and holistic approaches are needed for informing preventative and corrective actions that are beneficial for multiple water quality and sustainability goals.

Comparative effectiveness of sequential and synergistic (VUV/)UV and chlorine disinfection on DBPs and humic acid reduction

The widespread use of chlorine during disinfection has led to the problems of disinfection by-products (DBPs). Recently, the combination of ultraviolet (UV, 254 nm) and vacuum ultraviolet (VUV, 185 nm) with chlorine has been considered a promising strategy to mitigate the formation of DBPs. This study systematically evaluated the efficacy of six different disinfection methods in abating humic acid (HA), a common precursor of DBPs (UV-Chlorine, VUV/UV-Chlorine, Chlorine-UV, Chlorine-VUV/UV, UV/Chlorine, and VUV/UV/Chlorine). Under 40 mJ/cm2 UV fluence and 3 mg/L chlorine dose, the synergistic processes yielded DBP levels below 20 μg/L, whereas sequential disinfection resulted in DBP levels exceeding 100 μg/L. Additionally, there was no significant difference in the formation of DBPs between the two methods of chlorination followed by irradiation. However, for irradiation followed by chlorination, the addition of VUV led to an increase of 50 μg/L in trihalomethanes (THMs). As the irradiation time increased, the inclusion of VUV demonstrated enhanced control of DBP levels in the sequential disinfection process. Moreover, compared to UV/Chlorine, at 13 mg/L chlorine dose in VUV/UV/Chlorine process, the inclusion of VUV expedited the appearance of peak DBPs by two minutes and reduced the peak value by 25.6 %, but the DBP yield was 12.9 times higher than that at a chlorine dose of 3 mg/L. This study, comparing six combination disinfection methods, will provide deeper insights into precursor abatement and DBP control during drinking water disinfection.

Temporal and spatial variations of disinfection by-products in South Taihu's drinking water, Zhejiang Province, China.

Some disinfection by-products (DBPs) in drinking water present a potential safety concern. This study focuses on the elements influencing DBPs formation. A total of 120 water samples were collected from 10 different drinking water facilities spanning 5 counties within Huzhou, Zhejiang Province, China. Concentrations of trihalomethanes (THMs) and haloacetic acids (HAAs) were observed to be 14.5 and 27.4 μg/L, respectively, constituting 34 and 64% of the total DBPs. Seasonal fluctuations demonstrated that HAAs, THMs, halonitromethanes (HNMs), and haloacetonitriles (HANs) followed a similar pattern with higher levels in summer or autumn compared to spring. Importantly, the concentrations of HAAs and THMs were markedly higher in Taihu-sourced water compared to other sources. Geographically, Nanxun exhibited the highest levels of total DBPs, HAAs, and THMs, while Deqing and Changxing demonstrated significantly lower levels. Correlation studies between water quality parameters and DBPs revealed that factors such as chloride content, temperature, and residual chlorine positively influenced DBPs formation, whereas turbidity negatively affected it. Principal component analysis suggested similar formation processes for HANs, haloketones (HKs), HNMs, and THMs. Factors such as temperature, chemical oxygen demand (COD), and residual chlorine were identified as significant contributors to the prevalence of HAAs.

The combination of multiple linear regression and adaptive neuro-fuzzy inference system can accurately predict trihalomethane levels in tap water with fewer water quality parameters

Artificial Neural Network (ANN) models are accurate in predicting the levels of disinfection by-products (DBPs) in drinking water. However, these models are not yet practical due to the large number of parameters involved, which should take a significant amount of time and cost to detect. Developing accurate and reliable prediction models of DBPs with fewest parameters is essential in the management of drinking water safety. This study used the adaptive neuro-fuzzy inference system (ANFIS) and radial basis function artificial neural network (RBF-ANN) to predict the levels of trihalomethanes (THMs), the most abundant DBPs in drinking water. Two water quality parameters identified by multiple linear regression (MLR) models were used as model inputs, and the quality of the models was assessed based on criteria such as correlation coefficient (r), mean absolute relative error (MARE), and the percentage of predictions with absolute relative error less than 25% (NE<25%) and over than 40% (NE>40%), etc. The results showed that the ANFIS models had higher correlation coefficients (r = 0.853–0.898) and prediction accuracy (NE<25% = 91%–94%) compared to RBF-ANN models (r = 0.553–0.819; NE<25% = 77%–86%) and traditional MLR models (r = 0.389–0.619; NE<25% = 67%–77%). Conversely, the prediction error, as indicated by MARE and NE>40%, showed the opposite trend: ANFIS models (MARE = 8%–11%; NE>40% = 0–5%) < RBF-ANN models (MARE = 15%–18%; NE>40% = 5%–11%) < MLR models (MARE = 19%–21%; NE>40% = 11%–17%). The present study provided a novel approach for constructing high-quality prediction models of THMs in water supply systems using only two parameters. This method holds promise as a viable alternative for monitoring THMs concentrations in tap water, thereby contributing to the improvement of water quality management strategies.

Novel insights into impacts of the “7.20” extreme rainstorm event on water supply security of Henan Province, China: Levels and health risks of tap water disinfection by-products

Spatial distributions, levels, and comprehensive assessments of post-flood tap water disinfection by-products (DBPs) were first studied in Henan Province after the “7.20” Extreme Rainstorm Event in 2021. DBPs levels and health risks in tap water were higher in areas flooded (waterlogged) by storm or upstream flood discharge (WA) and rainstorm-affected areas (RA) compared with other areas (OA), suggesting that extreme rainstorm and flooding events may somehow exacerbate DBPs contamination of tap water through disinfection. WA sites were characterized as contamination hotspots. The results revealed high haloacetic acids (HAAs) levels in WA (Avg: 57.79 μg·L−1) and RA (Avg: 32.63 μg·L−1) sites. Compared with normal period, DBPs-caused cancer risk increased by 3 times, exceeding the negligible risk level. Cancer risk came primarily from the ingestion of trihalomethanes (THMs) (>80%), children were the sensitive group. Those between 30 and 69 showed approximately 1.7 times higher disability-adjusted life yearsper person-yearthan other age groups. Apart from regulated DBPs, bromochloracetic acid (BCAA) and dibromoacetonitrile (DBAN) appear to be the main toxicity contributors in these samples. Our results provide a scientific basis for preventing and controlling health risks from tap water DBPs and for assessing the social benefits and burdens of emergency disinfection.

Effects of physicochemical parameters of water on byproduct formation during electrolysis of ballast water

Introduction: Disinfection byproducts (DBPs) generated during ballast water treatment using active substances have gained increasing interest owing to their potential impact on the marine environment. This study aimed to investigate the occurrence and distribution of DBPs, which are secondary products generated during electrolysis, using land-based tests.Methods: DBP levels were compared under various water conditions, including chloride and bromide ion compositions, hold time, and organic matter-related parameters.Results: After electrolysis, trihalomethane (THM) and haloacetic acid (HAA) levels increased from day 0 to day 5 under all salinities, whereas haloacetonitrile (HAN) level decreased. THMs were found to be the most dominant DBP group, followed by HAAs and HANs. In marine water and brackish water, brominated DBPs were dominant owing to high levels of bromide ions, while chlorinated DBP concentrations were relatively high in fresh water.Discussion: After electrolysis, the specific ultraviolet absorption of the treated water was &amp;gt;4, indicating a high likelihood of generating carbonaceous DBPs such as THMs and HAA. These findings contribute to a better understanding of the general mechanisms through which physicochemical factors affect the formation of DBPs during electrolysis treatment of ballast water. This understanding is valuable in addressing issues related to the treatment and release of treated ballast water into the marine environment, which is an emerging environmental concern.

Algae impacted drinking water: Does switching to chloramination produce safer drinking water?

Harmful algal (cyanobacterial) blooms (HABs) are increasing throughout the world. HABs can be a direct source of toxins in freshwater sources, and associated algal organic matter (AOM) can act as precursors for the formation of disinfection by-products (DBPs) in drinking water. This study investigated the impacts of algae on DBP formation using treatment with chloramine, which has become a popular disinfectant in the U.S. and in several other countries because it can significantly lower the levels of regulated DBPs formed. Controlled laboratory chloraminations were conducted using live field-collected algal biomass dominated by either Phormidium sp. or Microseira wollei (formerly known as Lyngbya wollei) collected from Lake Wateree and Lake Marion, SC. Sixty-six priority, unregulated or regulated DBPs were quantified using gas chromatography (GC)-mass spectrometry (MS). The presence of HAB-dominated microbial communities in source waters led to significant increases in more toxic nitrogen-containing DBPs (1.5–5 fold) relative to lake waters collected in HAB-free waters. Compared to chlorinated Phormidium-impacted waters, chloraminated waters yielded lower total DBP levels (up to 123 μg/L vs. 586 μg/L for low Br−/I− waters), but produced a greater number of brominated, iodinated, and mixed halogenated DBPs in high Br−/I− waters. Among the DBPs formed in Phormidium-impacted chloraminated waters, dichloroacetic acid, trichloromethane, chloroacetic acid, chloropropanone, and dichloroacetamide were dominant. For Microseira wollei-impacted chloraminated waters, total DBP concentrations ranged from 33 to 145 μg/L (approximately 3–5 times lower than chlorination), with dichloroacetic acid, dichloroacetamide, and trichloromethane dominant. Overall, chloramination significantly reduced calculated cytotoxicity and genotoxicity in low Br− and I− waters, but produced 1.3 fold higher calculated cytotoxicity (compared to chlorine) with high Br−/I− waters due to increased formation of more toxic iodo- and mixed halogenated DBPs.

Challenges of point-of-use devices in purifying tap water: The growth of biofilm on filters and the formation of disinfection byproducts

Currently, polypropylene (PP) and granular activated carbon (GAC) are widely used as the filters in point-of-use devices (POUs). However, the effect of biofilms formation in aged filters and subsequent formation/removal of disinfection byproducts (DBPs) during the use of POUs on purifying tap water remains unclear. In this study, the influence of filter replace event and filter usage time on the removal of DBPs by pristine or aged filters, such as trihalomethanes (THMs) and haloacetic acids (HAAs), was investigated. Additionally, the effect of biofilms-attached PP filters and GAC filters on DBPs concentration in treated water was explored. The results showed that POUs effectively removed over 60% of THMs and HAAs from tap water, while the removal efficiency decreased with the operation time. The increase in usage time of PP filters led to elevated levels of DBPs. Moreover, the pristine pre-GAC filters removed 12.31% of THMs and 6.62% of HAAs, respectively, while aged GAC filters enhanced the removal of HAAs. SEM and high-throughput sequencing analysis confirmed the attached growth of biofilms on aged PP and GAC filters. The biofilms growth on PP filters led to the formation of THMs and HAAs, and the formed DBPs increased with increasing influent chlorine concentration, lengthened filters usage time and stagnation time. Nevertheless, the DBPs in effluent of biofilms-attached GAC filters increased with increasing influent chlorine concentration and filter usage time while decreased with stagnation time. These results indicated that growth of biofilms commonly observed in filters of POUs leads to the formation of DBPs and increases the risk of DBPs exposure to users of POU devices.

New methods based on a genetic algorithm back propagation (GABP) neural network and general regression neural network (GRNN) for predicting the occurrence of trihalomethanes in tap water

Monitoring trihalomethanes (THMs) levels in water supply systems is of great significance in ensuring drinking water safety. However, THMs detection is a time-consuming task. Developing predictive THMs models using parameters that are easier to obtain is an alternative. To date, there is still no application of optimization algorithms and general regression neural networks in predicting disinfection by-products levels. This study was to explore the feasibility of back propagation neural network (BPNN), genetic algorithm back propagation (GABP) neural network and general regression neural network (GRNN) for predicting THMs occurrence in real water supply systems. The results showed that the BPNN models' prediction ability was limited (test rp = 0.571–0.857, N25 = 61.5 %–91.5 %). Optimized by the genetic algorithm (GA), GABP models were generated and exhibited better prediction performance (test rp = 0.573 and 0.696–0.863, N25 = 68.2 %–93.6 %). However, GABP models took a lot of time and their prediction performance was unstable. A GRNN was then used to generate simpler neural network models, and the resulting prediction performance was excellent (total trihalomethanes and bromodichloromethane: test rp = 0.657–0.824, N25 = 81.8 %–100 %). In general, GRNN was the best at predicting THMs concentrations among the three models. However, it is worth noting that the prediction accuracy of bromodichloromethane (BDCM) was not high, which may be due to the absence of key parameters affecting BDCM formation. Accurate predictions of THMs by GRNN with these nine water parameters made THMs monitoring in real water supply systems possible and practical.

Investigation of the correlation between trihalomethane concentrations and socioeconomic factors in NY State

Recent environmental justice studies have found associations between low drinking water quality and socioeconomic indicators such as income and race. Trihalomethanes, probable human carcinogens, are commonly found disinfection by-products (DBPs) in public water systems (PWS). Although trihalomethanes are correlated with socioeconomic indicators, there is a knowledge gap regarding how the level of contaminants correlates with socioeconomic indicators and other physicochemical factors in specific regions. Therefore, we investigated the correlation between trihalomethane concentrations and socioeconomic factors in New York State with more practical and insightful data analysis and interpretation compared to those in previous studies by providing more detailed city-level data and water system characteristics affecting the correlation. We found a negative correlation between median household income and trihalomethane concentrations in the state. The communities served by PWS using groundwater sources had lower trihalomethane concentrations and higher household income, suggesting that water quality parameters contribute to the negative correlation between trihalomethanes and income levels. The inverse association between trihalomethanes and household income may indicate socioeconomic disparity regarding drinking water quality and the need for improved efforts to assist small- and medium-sized community water systems to lower DBP levels in New York State because small- or medium-sized systems may have fewer resources to apply DBP control and removal technologies compared to large systems.

Anthracite Releases Aromatic Carbons and Reacts with Chlorine to Form Disinfection Byproducts in Drinking Water Production.

Anthracite is globally used as a filter material for water purification. Herein, it was found that up to 15 disinfection byproducts (DBPs) were formed in the chlorination of anthracite-filtered pure water, while the levels of DBPs were below the detection limit in the chlorination of zeolite-, quartz sand-, and porcelain sandstone-filtered pure water. In new-anthracite-filtered water, the levels of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and ammonia nitrogen (NH3-N) ranged from 266.3 to 305.4 μg/L, 37 to 61 μg/L, and 8.6 to 17.1 μg/L, respectively. In aged anthracite (collected from a filter at a DWTP after one year of operation) filtered water, the levels of the above substances ranged from 475.1 to 597.5 μg/L, 62.1 to 125.6 μg/L, and 14 to 28.9 μg/L, respectively. Anthracite would release dissolved substances into filtered water, and aged anthracite releases more substances than new anthracite. The released organics were partly (around 5%) composed by the μg/L level of toxic and carcinogenic aromatic carbons including pyridine, paraxylene, benzene, naphthalene, and phenanthrene, while over 95% of the released organics could not be identified. Organic carbon may be torn off from the carbon skeleton structure of anthracite due to hydrodynamic force in the water filtration process.

Multi-omics signatures of exposure to disinfection by-products in swimming

Background and aims: Untargeted HRMS metabolomics provides an agnostic global profiling of small molecules in a biological system capturing an overview of exposure to exogenous compounds, and their effects on metabolic pathways, rendering an essential tool for characterising the exposome. Disinfection by-products (DBPs) are a complex mixture of halogenated organic compounds present in drinking and swimming pool water. Although several epidemiological studies have pointed their potential to induce adverse health outcomes such as bladder cancer, their mixture effect and the downstream molecules perturbed by their exposure have been poorly explored. In this work, we aim to identify molecular signatures of exposures to mixtures of DBPs in individuals with measured exposures. Methods: In PISCINA-II study, metabolomics, transcriptomics, proteomics in serum, and levels of DBPs in exhaled breaths, were measured in 60 subjects before and after swimming. Pre-processing of HRMS data from PISCINA-II study was customised to include more halogenated compounds. Multivariate normal (MVN) and partial least square (PLS) models were used to identify metabolic features associated with DBP exposures. Conditional correlation networks were constructed to understand the holistic relationship amongst the metabolic features and their relationship with proteomics and transcriptomics. Results: 98 metabolic features were identified to be associated with exposure to DBP mixture, of which 39 were not identified in the previous analysis without specific reprocessing and inclusion of halogenated compounds. In conditional network analysis, the 98 features showed cluster structures, suggesting they could contribute to different downstream biological pathways. Multi-omic networks showed that transcriptomic and proteomic signals were differentially connected to the different clusters of the metabolic signatures. Conclusions: New data processing approach allowed identification of novel metabolic signatures of DBP mixture exposure. Conditional correlation network implied the functional proximity of these signatures with other measured omic signals. Keywords: Disinfection by-products, PLS, network analysis, omics, exposome, statistical analysis

Innovative polymeric inorganic coagulant-flocculant for wastewater purification with simultaneous microbial reduction in treated effluent and sludge

The current work introduces polymeric inorganic coagulant-flocculants; poly-ferric chloride (POFC) which prepared using iron-containing waste. Different POFCs were produced according to Fe/basicity ratio. Likewise, the efficiency of POFC for purification and microbial decontamination of domestic wastewater was evaluated using various doses of POFC coagulant-flocculants. The solid content of the prepared POFCs was ranged from 11.1 to 29.9%, and density was varied from 1.13 to 1.24 kg/L with the varying iron/basicity ratios. Analyses results of XRD, FTIR and SEM confirm formation of a new inorganic polymeric ferric chloride that it is not assumed simple mixture of components. Moreover, the prepared POFCs showed coagulant-flocculant characteristics; therefore it is employed for treating wastewater without introducing organic polymer. Both POFCs coagulant-flocculants showed removal efficiencies of 99, 99 and 91% for total suspended solids (TSS), turbidity and chemical oxygen demand (COD) from domestic wastewater. Also, a complete deactivation of the tested waterborne species in wastewater was achieved at 100 ppm dose of POFCs. At POFC dose of 150 ppm, it was found that the anaerobic microbes and sulfate-reducing bacteria in sludge were reduced by 99.9 and 98%, respectively. The deactivation anaerobic micobes and sulfate-reducing bacteria in the produced sludge by using POFC will result in odor reduction generated from sludge. Moreover, the integration between POFC-based coagulation and rapid sand filtration (RSF) lowers POFC dose use and showed a good efficiency for domestic wastewater purification and microbial decontamination. Finally, POFC-based treatment aids in the decrease organic and bacterial load that results in reducing disinfection use and declining disinfection by-products levels. Moreover, POFC-based treatment/rapid sand filtration is considered a well-located cost-effective train for purification of domestic wastewater and microbial decontamination in treated effluent and sludge and which can be reused for safe agricultural purpose.

Comparative analysis of adaptive neuro-fuzzy inference system (ANFIS) and RSRM models to predict DBP (trihalomethanes) levels in the water treatment plant

Since disinfection by-products are a growing concern, it is important to know their quantities in water treatment plants before they are released to the public. As a result, there is a requirement for constant monitoring of disinfection by-products (DBPs), which can have major consequences for human health and productivity. Consequently, in previous studies, several models for predicting disinfection byproduct formation in drinking water have been developed which were either linear/log-linear, hybrid or neural network (radial basis function). In this study, an adaptive neuro-fuzzy inference system (ANFIS) is proposed for predicting trihalomethane levels in real distribution systems. To train and verify the proposed model, 24 sets of data were used, including THMs levels (TCM, BDCM, DBCM and T-THM levels) and five parameters (pH, temperature, UVA254, residual chlorine, and dissolved organic carbon). As compared to response surface modeling (RSRM) coefficient of determination, R2 is between 0.727 < R2 < 0.886, average absolute deviation, AAD = 4.07–10.99 %), MAE = 0.01 – 0.978, and RMSE = 0.017 – 1.449. Further, ANFIS for THMs (T-THMs, TCM, BDCM, and DBCM) prediction consistently show higher regression coefficients between 0.956 < R2 < 0.989, average absolute deviation, AAD = 0.350 – 1.977 %), MAE = 0.002 – 0.133, and RMSE = 0.007 – 0.401, Consequently, based on the statistical indices obtained, ANFIS, on the other hand, proved to be effective for predicting the formation of THMs, and thus allowed improved DBPs monitoring in water treatment systems.

How well does XAD resin extraction recover halogenated disinfection byproducts for comprehensive identification and toxicity testing?

Halogenated disinfection byproducts (DBPs) are an unintended consequence of drinking water disinfection, and can have significant toxicity. XAD resins are commonly used to extract and enrich trace levels of DBPs for comprehensive, nontarget identification of DBPs and also for in vitro toxicity studies. However, XAD resin recoveries for complete classes of halogenated DBPs have not been evaluated, particularly for low, environmentally relevant levels (ng/L to low µg/L). Thus, it is not known whether levels of DBPs or the toxicity of drinking water might be underestimated. In this study, DAX-8/XAD-2 layered resins were evaluated, considering both adsorption and elution from the resins, for extracting 66 DBPs from water. Results demonstrate that among the 7 classes of DBPs investigated, trihalomethanes (THMs), including iodo-THMs, were the most efficiently adsorbed, with recovery of most THMs ranging from 50%-96%, followed by halonitromethanes (40%-90%). The adsorption ability of XAD resins for haloacetonitriles, haloacetamides, and haloacetaldehydes was highly dependent on the individual species. The adsorption capacity of XAD resins for haloacetic acids was lower (5%-48%), even after adjusting to pH 1 before extraction. Recovery efficiency for most DBPs was comparable with their adsorption, as most were eluted effectively from XAD resins by ethyl acetate. DBP polarity and molecular weight were the two most important factors that determine their recovery. Recovery of trichloromethane, iodoacetic acid, chloro- and iodo-acetonitrile, and chloroacetamide were among the lowest, which could lead to underestimation of toxicity, particularly for iodoacetic acid and iodo-acetonitrile, which are highly toxic.