Search Results (89)

This study focuses on optimizing the ozonation process in drinking water production from Lake Butoniga to ensure safe water quality while minimizing disinfection by-products (DBPs). Laboratory simulations were conducted using the Box–Behnken design to model the effects of ozone dose and treatment duration on bromate formation, trihalomethanes (THMs), haloacetic acids (HAAs) and specific UV absorption (SUVA). Two ozonation strategies were tested: Strategy 1 aimed to minimize all DBPs, while Strategy 2 focused on controlling bromate levels while keeping THMs, HAAs and SUVA below 80% of maximum contaminant levels. Results showed that Strategy 2 reduced ozone consumption while maintaining water quality within regulatory standards, providing a cost-effective and environmentally sustainable treatment approach. Seasonal and depth-dependent variations in water quality had a significant impact on treatment efficiency and required adjustments to operational settings. The study also addressed discrepancies between laboratory and real plant results and suggested recalibration methods that improved the accuracy of model predictions. These results highlight the potential for integrating predictive modelling and dynamic treatment strategies into large-scale water treatment processes. Full article

In this study, the sodium perborate (SP)-activated peroxymonosulfate (PMS) process was used to enhance the coagulation efficiency of cyanobacteria with polymeric aluminum chloride (PAC), aiming to efficiently mitigate the impact of algal blooms on the safety of drinking water production. The optimal concentrations of SP, PMS, and PAC were determined by evaluating the removal rate of OD₆₈₀ and zeta potential of the algae. Experimental results demonstrated that the proposed ternary PMS/SP/PAC process achieved a remarkable OD₆₈₀ removal efficiency of 95.2%, significantly surpassing those obtained from individual treatments with PMS (19.5%), SP (5.2%), and PAC (42.1%), as well as combined treatments with PMS/PAC (55.7%) and PMS/SP (28%). The synergistic effect of PMS/SP/PAC led to the enhanced aggregation of cyanobacteria cells due to a substantial reduction in their zeta potential. Flow cytometry was performed to investigate cell integrity before and after treatment with PMS/SP/PAC. Disinfection by-products (DBPs) (sodium hypochlorite disinfection) of the algae-laden water subsequent to PMS/SP/PAC treatment declined by 57.1%. Moreover, microcystin-LR was completely degraded by PMS/SP/PAC. Electron paramagnetic resonance (EPR) analysis evidenced the continuous production of ${\mathrm{S}\mathrm{O}}_4^{•-}$, •OH, ¹O₂, and ${\mathrm{O}}_2^{•-}$, contributing to both cell destruction and organic matter degradation. This study highlighted the significant potential offered by the PMS/SP/PAC process for treating algae-laden water. Full article

In this study, samples from the Yangtze River, Han River, and Liangzi Lake in Wuhan City were utilized to characterize the formation of disinfection by-products (DBPs) from chlorine-based disinfection residues in drinking water sources. The results indicated that the main DBPs in drinking water sources were trichloromethane (TCM) and trichloroacetic acid (TCAA). The generation of DBPs was significantly positively correlated with oxidative substances, aromatic compounds, pH, and ammonia nitrogen (NH₃-N) content in the water. The concentration of TCAA increased from 0 to 2.45 ± 0.31 mg/L when the reaction time increased to 72 h. As the NaClO concentration increased from 5 mg/L to 15 mg/L, the concentrations of TCAA, TBM, and DCAN increased from 2.03 ± 0.04 mg/L, 0 mg/L, and 0 mg/L to 2.49 ± 0.34 mg/L, 0.21 ± 0.07 mg/L, and 0.10 ± 0.04 mg/L before decreasing to 1.75 ± 0.19 mg/L, 0.17 ± 0.07 mg/L, and 0.04 ± 0.05 mg/L, respectively. The orthogonal experimental results showed that Br⁻, NH₃-N, and pH all had significant influences on the TCM generation, whereas temperature affected the formation of TCAA in the Han River. This work reveals the factors influencing the generation of DBPs from chlorine-based disinfection residues, offering a prevention and control method for DBPs in drinking water sources from a theoretical perspective. Full article

Chloride ions readily react with organic matter and other ions, resulting in the formation of disinfection by-products (DBPs) that exhibit heightened levels of toxicity, carcinogenicity, and mutagenicity. This study creatively employed waste walnut shells as self-templates and low-cost magnesium bicarbonate as a rigid template to successfully synthesize multifunctional porous carbon derived from walnut shells. Employing a series of characterization techniques, it was ascertained that the porous carbon material (WSC/Mg) synthesized via the dual-template method exhibited a distinct layered microscopic surface structure, with a predominance of C and O elements on the surface. The material displayed a high degree of graphitization, significant specific surface area, and abundant oxygen-containing surface functional groups. The incorporation of magnesium bicarbonate as a hard template improved the structure of the walnut shell porous carbon, resulting in a significant enhancement in mass transfer efficiency for the target product on the adsorbent and a substantial improvement in removal efficiency. In comparison with walnut shell-derived carbon using only self-templating, WSC/Mg exhibited a 17.26-fold increase in adsorption capacity for 2,4-dichlorophenol. Furthermore, even after four adsorption–desorption cycles, WSC/Mg-12 maintained an adsorption efficiency above 90%. It is remarkable that WSC/Mg-12 demonstrated exceptional resistance to interference from natural organic matter and pH variations. Moreover, the adsorbed saturated WSC/Mg-12 effectively treated real coke wastewater, resulting in an 80% color removal rate, 20% COD removal rate, and 15% ammonia nitrogen removal rate. In conclusion, this study presents an innovative approach for cost-effective and versatile porous carbon materials with extensive applications in water environment purification and biomass utilization. Full article

The prevalence of disinfection by-products in drinking water supplies is a global concern due to their carcinogenicity. However, the monitoring of DBPs such as trihalomethanes (THMs) and haloacetic acids (HAAs) in drinking water supplies is non-existent in many developing Asian, South American, and African countries. The formation of THMs during disinfection arises from a reaction between the disinfectant and natural organic matter in the water, particularly, dissolved organic carbon (DOC). This reaction is hastened by increases in temperature, high levels of disinfectant doses or residual, elevated water pH, long disinfection contact times, and high DOC concentrations. However, the inclusion of a granular activated carbon adsorption process in the water treatment process is the most effective method for the removal of the main precursor (DOC) for the formation of THMs in treated water. The Barekese WTP, which disinfects with chlorine, has no adsorption process for DOC removal, and supplies over 80% of pipe-borne water to the city of Kumasi in Ghana, was assessed for the THM formation potential (THMFP). A THM predictive model was used to determine the potential THM concentration in the final water. The THMFP at the Barekese WTP ranged between 22.42 and 38.94 µg/L, which was below the 100 µg/L threshold set by the WHO. The lifetime average daily doses were 3.9494 × 10⁻⁴ µg/Kg/d and 3.9294 × 10⁻⁴ µg/Kg/d for male and female consumers, respectively. The lifetime integrative cancer risks associated with consumption of the water were 1.817 × 10⁻⁵ and 1.808 × 10⁻⁵ for males and females, respectively. The cancer risk posed was acceptably low. However, direct measurement of DBPs is required to corroborate these findings and verify the cancer risk posed to the consumers of treated water from the Barekese WTP to inform policies, regulations, public health interventions, and investment. Full article

Disinfection by-products (DBPs) such as chloroacetic acids (CAAs) and N-Nitrosodimethylamine (NDMA) are prevalent pollutants in surface waters, particularly with the increasing use of chlorine-based disinfectants. The entry of these DBPs into water bodies may increase accordingly, posing ecological risks to aquatic life. To assess the toxic effects of CAAs and NDMA on submerged macrophytes, Vallisneria natans was exposed to different concentrations of CAAs (1.0, 10.0, and 100.0 μg L⁻¹) and NDMA (0.1, 1.0, and 10.0 μg L⁻¹). A RI value of <1 indicates that simultaneous exposure to CAAs and NDMA can produce an antagonistic effect. Both CAAs and NDMA adversely affect the photosynthetic system of plants. In the NDMA treatment group, chlorophyll a content decreases with increasing concentration, accounting for 96.03%, 60.80%, and 58.67% of the CT group, respectively. Additionally, it effectively triggers the plant’s antioxidant response, with significant increases in SOD, POD, and GSH levels. Among these, the combined treatment group AN2 (10 + 1 μg L⁻¹) showed the most significant change in SOD activity, reaching 3.57 times that of the CT group. Ultrastructural changes also revealed stress responses in leaf cells and damage to organelles. Furthermore, metabolomics provided insights into the metabolic responses induced by CAAs or NDMA in V. natans leaves, where the composition and metabolism of lipids, fatty acids, cofactors and vitamins, amino acids, nucleotides, and some antioxidants were regulated, affecting plant growth. This study provides preliminary information for the ecological risk assessment of submerged plants by complex contamination with the disinfection by-products CAA and NDMA. Full article

Growing concerns over public health and environmental safety have intensified the focus on minimizing harmful disinfection byproducts (DBPs) in water treatment. Traditional methods like chlorination, while effective against pathogens, often lead to the formation of DBPs, which pose significant risks. This paper explores alternative strategies to reducing DBP formation while ensuring effective disinfection. The methodology involved a bibliographic study conducted through the Scopus platform, using appropriate keywords. The initial search yielded 9576 articles from the period 2020 to 2024. The key approaches identified include advanced oxidation processes (AOPs) such as UV/H₂O₂ and ozone, which mineralize natural organic matter (NOM) and minimize chemical use and sludge production; membrane-based filtration systems, like reverse osmosis, effectively removing contaminants without chemical disinfectants, reducing DBP risks. Furthermore, conventional processes, such as coagulation and filtration, serve as crucial pretreatment steps to lower NOM levels before disinfection. Additionally, optimizing chlorine dosing, using non-chlorine disinfectants, and employing post-disinfection methods like adsorption and biological filtration further mitigate DBP formation. Finally, the integration of artificial intelligence in process optimization is emerging as a promising tool for enhancing treatment efficiency and safety. This research contributes to the development of safer, more sustainable water treatment solutions, addressing regulatory demands and public health objectives. Full article

Drinking water disinfection by water utilities aims to ensure the safety and high quality of the provided water; however, it can pose a threat to human health due to the formation of disinfection byproducts (DBPs). The prediction and modeling of DBPs are challenging tasks due to the complex reactions within water distribution networks (WDN). To address this challenge, we introduce a virtual testbed based on a realistic WDN in Cyprus that utilizes the EPANET and EPANET-MSX engines to model multi-species reactions for the execution of simulation experiments under various conditions regarding the formation and fate of two families of DBPs within WDNs. Full article

With the rapid development of society, more and more unknown halogenated disinfection byproducts (DBPs) enter into drinking water and pose potential risks to humans. To explore the unknown halogenated DBPs in tap water, a selectively nontargeted analysis (SNTA) method was developed by conducting micro-liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (micro-LC-QTOFMS). In this method, two runs were employed: in the first run, the modes of TOFMS and precursor ion (the fragments were set as Cl³⁵/Cl³⁷, Br⁷⁹/Br⁸¹, and I^126.9) were performed, and the molecular ions or precursor ions of the halogenated organics could be obtained; in the second run, the product ion mode was conducted by setting the molecular ion screened above, and the MS/MS spectrums could be acquired to speculate concerning the structure. Two kinds of model DBPs (one kind had an aliphatic structure and the other was an aromatic compound) were used to optimize the parameters of the MS, and their MS characteristics were summarized. With this SNTA method, 15 halogenated DBPs were screened in two tap water samples and their structures were proposed. Of them, six DBPs had not been reported before and were assumed to be new DBPs. Overall, the detected halogenated DBPs were mostly acidic substances. Full article

The rapid expansion of urban areas and the increasing demand for water resources necessitate substantial investments in technologies that enable the reuse of municipal wastewater for various purposes. Nonetheless, numerous challenges remain, particularly regarding disinfection by-products (DBPs), especially carcinogenic compounds such as N-nitrosamines (NTRs). To tackle the ongoing issues associated with reverse osmosis (RO) membranes, this study investigated the rejection of NTRs across a range of commercially available RO membranes. In addition, the research aimed to improve rejection rates by integrating molecular plugs into the nanopores of the polyamide (PA) layer. Hexylamine (HEX) and hexamethylenediamine (HDMA), both linear chain amines, have proven to be effective as molecular plugs for enhancing the removal of NTRs. Given the environmental and human health concerns associated with linear amines, the study also aimed to assess the feasibility of diamine molecules as potential alternatives. The application of molecular plugs led to changes in pore size distribution (PSD) and effective pore number, resulting in a decrease in membrane permeability (from 5 to 33%), while maintaining levels suitable for RO processes. HEX and HDMA exhibited a positive effect on NTR rejection with ACM1, ACM5 and BW30LE membranes. In particular, NDMA rejection, the smallest molecule of the tested NTRs, with ACM1 was improved by 65.5% and 70.6% after treatment with HEX and HDMA, respectively. Full article

Humic acid (HA) is an organic compound naturally present in aquatic environments. It has been found to have detrimental effects on water color, the transport of heavy metals, and the elimination of disinfection by-products (DBPs), thereby exerting an impact on human health. This study introduced four synergistic ultraviolet/advanced oxidation processes (UV/AOPs) systems aimed at eliminating HA from water. The research explored the effect of solution pH, duration of illumination, initial reactant concentration, and oxidant concentration on the degradation of HA. The results indicated that the mineralization rate achieved by individual UV or oxidant systems was less than 15%, which is significantly lower compared to UV/AOPs systems. Among these methods, the UV/peroxymonosulfate (UV/PMS) process demonstrated the highest effectiveness, achieving a mineralization rate of 94.15%. UV/peroxydisulfate (UV/PDS) and UV/sodium percarbonate (SPC) were subsequently implemented, with UV/sulfite (S(IV)) demonstrating the lowest effectiveness at 19.8%. Optimal degradation efficiency was achieved when the initial concentration of HA was 10 mg/L, the concentration of PMS was 3 mmol/L, and the initial pH was set at 5, with an illumination time of 180 min. This experimental setup resulted in high degradation efficiencies for chemical oxygen demand (COD), UV₂₅₄, and HA, reaching 96.32%, 97.34%, and 92.09%, respectively. The energy efficiency of this process (EE/O) was measured at 0.0149 (kWh)/m³, indicating the capability of the UV/PMS system to efficiently degrade and mineralize HA in water. This offers theoretical guidance for the engineered implementation of a UV/PAM process in the treatment of HA. Full article

Microplastics that adsorb various toxic contaminants in water may be transported into cells and organs, possibly posing toxicological risks in the aquatic environment. Disinfection byproducts (DBPs), which are ubiquitous in chlorinated drinking water and wastewater, may have some potential to sorb onto microplastics (MPs) through hydrophobic or electrostatic interactions. However, DBP adsorption on microplastics has not yet been closely examined. This work investigated the adsorption behavior of trihalomethanes (THMs)—a regulated and ubiquitous DBP class in chlorinated water—onto virgin and weathered polyvinyl chloride (PVC) microplastics, the most widely used plastic material in drinking water distribution and sewer systems. A comparative analysis of kinetic and isotherm test results indicated that the adsorption mechanisms mainly involved hydrophobic interactions from a combination of weak and strong physisorption behavior and possibly chemisorption. The adsorption coefficients from all the models examined suggested that the adsorption of THMs, and perhaps chemically similar DBPs, onto virgin PVC microplastics can be 10–20 µg g⁻¹. However, the weathered PVC microplastics contained more polar functional groups, which led to a decreased hydrophobicity and reduced THM adsorption capacity by approximately 10%. These findings offer novel insights into the possible adsorption characteristics of disinfection byproducts (DBPs) onto microplastics and will assist in targeting more toxic DBPs for future investigations. Full article

Eutrophication in water reservoirs releases algal organic matter (AOM), a key precursor to the formation of disinfection by-products (DBPs) during the disinfection process. Typical drinking water treatment is not efficient for AOM removal, and advanced treatments are necessary for the removal of residual AOM before chlorination. UV-based technology with PS and TiO₂ is widely used as a pre-oxidation step in water treatment; however, no publications have focused on them for AOM degradation. In this context, this work investigated the effect of oxidant concentration (0.1 to 0.5 g∙L⁻¹) and pH (6 to 10) on AOM degradation with TiO₂/UV and persulfate (PS)/UV using response surface methodology. In general, PS/UV was more effective in removing protein, while TiO₂/UV was more effective in carbohydrate degradation. TiO₂/UV removals varied from 27 to 57% for protein and from 48 to 86% for carbohydrates. The optimal condition (57% for protein and 86% for carbohydrates) was obtained using 0.5 g∙L⁻¹ TiO₂ at pH 10. PS/UV removals varied from 33 to 81% for protein and from 24 to 53% for carbohydrates. The optimal condition (81% for protein and 53% for carbohydrates) was obtained using 0.5 g∙L⁻¹ PS concentration at pH 8. Degradation kinetics showed a good fit to the pseudo-first-order model (R² > 95%) for both processes. The DBP formation reductions observed with TiO₂/UV—trihalomethane (THM) (85 to 86%) and chloral hydrate (CH) (94 to 96%)—were similar to the efficiencies observed for PS/UV—THM (87 to 89%) and CH (83 to 88%). These results show the efficiency of UV-based technology for AOM degradation and the control of DBP formation. Full article

Algal blooms are caused by excessive levels of nitrogen, phosphorus, and other plant nutrients in water. Algae and algal organic matter (AOM) pose a great threat to the quality of drinking water. This manuscript offers a systematic review of algal removal by ferrate (Fe(VI)) oxidation, including the conditions for the removal of different algae by Fe(VI) and the factors affecting the removal efficiency. On this basis, the oxidation and coagulation mechanisms of algae removal by Fe(VI) are discussed. Then, the review introduces the process combining Fe(VI) pre-oxidation with aluminum sulfate action. The addition of aluminum sulfate can further enhance the coagulation effect and reduce the formation of disinfection byproducts (DBPs) in the subsequent chlorination process by effectively removing AOM, which is recognized as a precursor of DBPs. In addition, recent studies on the combined application of Fe(VI) and Fe(II) are also reviewed. In a reasonable dose range, the synergistic effect of Fe(VI) and Fe(II) can significantly improve the removal of algae and algal toxins. Finally, this review provides a comprehensive evaluation of the applicability of Fe(VI) in removing algal material, offers guidance for the harmless treatment of algae with Fe(VI), and identifies future research questions. Full article

Bromhexine and ambroxol are among the mucolytic drugs most widely used to treat acute and chronic respiratory diseases. Entering the municipal wastewater and undergoing transformations during disinfection with active chlorine, these compounds can produce nitrogen- and bromine-containing disinfection by-products (DBPs) that are dangerous for aquatic ecosystems. In the present study, primary and deep degradation products of ambroxol and bromhexine obtained in model aquatic chlorination experiments were studied via the combination of high-performance liquid and gas chromatography with high-resolution mass spectrometry. It was shown that at the initial stages, the reactions of cyclization, hydroxylation, chlorination, electrophilic ipso-substitution of bromine atoms with chlorine, and oxidative N-dealkylation occur. Along with known metabolites, a number of novel primary DBPs were tentatively identified based on their elemental compositions and tandem mass spectra. Deep degradation of bromhexine and ambroxol gives twenty-four identified volatile and semi-volatile compounds of six classes, among which trihalomethanes account for more than 50%. The specific class of bromhexine- and ambroxol-related DBPs are bromine-containing haloanilines. Seven of them, including methoxy derivatives, were first discovered in the present study. One more novel class of DBPs associated with bromhexine and ambroxol is represented by halogenated indazoles formed through dealkylation of the primary transformation products containing pyrazoline or tetrahydropyrimidine cycle in their structure. Full article