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Seawater chlorination has three main industrial uses: disinfection of water and installations, control of biofouling, and preventing the transport of aquatic invasive species. Once in contact with seawater, chlorine reacts rapidly with water constituents (e.g. bromide ions, ammonia, and nitrogen-containing compounds) to form a range of oxidative species (e.g. bromine and N-haloamines), termed "chlorine-produced oxidants" (CPOs) or "total residual oxidants" (TRO). The chemical nature of CPOs and their concentration are a function of two categories of parameters related to treatment modality (e.g. chlorine dose) and water quality (e.g. temperature, pH, ammonia concentration, and organic constituents). The chlorination process may result in continuous or intermittent releases of CPOs in seawater. The reactivity and potential ecotoxicity of CPO species largely depend on their physical and chemical properties. Therefore, evaluation of the biocidal effectiveness of chlorination and its potential impacts requires not only determining the sum of CPOs (via a bulk parameter), but also their chemical speciation. The aim of this article – which is the first of a trilogy dedicated to the chemical speciation of CPOs in seawater – is to provide an overview of current knowledge about chlorine chemistry in seawater and to discuss the biocidal efficacy and the environmental fate of resulting CPOs. The 2nd and 3rd articles delineate a comprehensive and critical review of analytical methods and approaches for the determination of CPOs in seawater. [ABSTRACT FROM AUTHOR]

In this study, the effect of baffle configuration on the water disinfection efficiency of a planar photoreactor equipped with ultraviolet C light-emitting diodes (UV-C LEDs) was investigated. The results indicated that the configuration of the baffles influenced the hydrodynamics inside the flow channel and thus affected the microbial trajectory, and exposure time. Accordingly, a modified serpentine configuration was developed to enhance the UV light exposure of microbes in water and improve the reactor performance for microbial inactivation. According to the simulation results, the quarter-circle baffles used in the modified serpentine configuration increased the microbial path length along the flow channel. However, because the cross-sectional area of the flow channel decreased, this configuration increased the water velocity. A modified serpentine configuration with a baffle radius of 5 mm achieved the longest microbial exposure time and highest inactivation value for Escherichia coli. At a water flow rate of 160 mL/min, this configuration achieved a UV fluence of 15.2 mJ/cm2 and an inactivation value of 3.8 log, which were approximately 22% and 0.4 log higher than those obtained with the traditional serpentine configuration, respectively. In addition, the maximum water flow rate at which the UV reactor achieved an inactivation value of 4.0 log was 154 mL/min at a baffle radius of 5 mm. This flow rate was 11.5% higher than that obtained with the traditional serpentine configuration. These close agreements between the experimental and simulation results confirmed the strong capability of the proposed modified serpentine configuration to improve reactor performance. [ABSTRACT FROM AUTHOR]

Trihalomethanes, the main drinking water disinfection byproducts, may be carcinogenic and are regulated to amaximum total trihalomethanes (TTHM) of 80 µg/l in the US. We aimed to determine whether total and individual trihalomethanes in drinking water across the US are associated with higher cancer mortality in 6,260 adult participants to the National Health and Nutrition Examination Surveys from 1999 to 2008 followed for mortality until 2019 (median: 14.4 years). At baseline, the geometric mean (standard error) of TTHM in drinking water was 9.61 (0.85) µg/l. During follow-up, 873 deaths occurred, including 207 from cancer. In Cox proportional hazards regression adjusted for relevant covariates, drinking water TTHM (HR: 1.45, 95% CI: 1.16–1.82), chloroform (HR: 1.35, 95% CI: 1.12–1.64), and bromodichloromethane (HR: 1.30, 95% CI: 1.05–1.59) were associated with 30% to 45% higher cancer mortality. Therefore, drinking water trihalomethanes, especially chloroform and bromodichloromethane maybe risk factors for cancer mortality. [ABSTRACT FROM AUTHOR]

Proper disinfection treatment is the basic guarantee for safe utilisation of sewage. However, the commonly used disinfection methods are not suitable for nutrients containing reclaimed water. In this work, the microwave disinfection method assisted by a microwave-absorbing material in recycled water samples was investigated. Magnetic corn stalk biochar (MCSB), the microwave absorbing material, was prepared by high temperature carbonisation of corn stalk particles impregnated with ferrous sulfate. Escherichia coli and fecal coliforms were selected as target microorganisms to investigate the disinfection efficiency of MCSB assisted microwave radiation (MW/MCSB). The addition of microwave absorbing materials significantly improves the disinfection effect of water samples. Compared with the microwave radiation (MW) without MCSB, the bactericidal rate by using 107 CFU/L E. coli suspension increased from 63.5% to 100% at 480 W for 30 s after adding 4 g/L MCSB. Besides, the effects of MCSB dosage, microwave power, microwave radiation time, and initial bacterial concentration on disinfection efficiency were explored. Moreover, the bactericidal efficiency for actual sewage samples was also demonstrated by treating the effluent from septic tank sewage. The residual fecal coliforms in treated water samples met China's farmland irrigation water standard (GB 5084-2021). The result indicates that the proposed method of microwave disinfection strengthened by MCSB has a promising application prospect for reclaimed water disinfection. [ABSTRACT FROM AUTHOR]

It is important to find the estimation methodology with the highest accuracy in order to determine the parameters of water disinfection and to provide the most ideal disinfection. In this study, the usability of artificial neural networks in predicting response disinfection efficiency in electrochemical water disinfection processes was investigated. An artificial neural network model was developed using a total of 17 data sets and Response Disinfection Efficiency values were estimated from the model. Current density, treatment time and interelectrode spacing values are defined as input parameters in the network model, which has a multilayer perceptron architecture with 10 neurons in its hidden layer. The coefficient of determination value for the developed model was 0.98682 and the average deviation rate was −0.1%. The study findings showed that neural networks are an ideal tool that can be used to predict response disinfection efficiency in electrochemical water disinfection processes. [ABSTRACT FROM AUTHOR]

Dexamethasone (DEX) degradation was investigated using three UV-based advanced oxidation processes combined with sodium persulphate, hydrogen peroxide, and free chlorine in aqueous solutions in a bench-scale reactor. The goal was to determine which process would be the best option in terms of DEX degradation without the subsequent generation of toxic compounds. The process performance for DEX degradation followed the UV/S2O82−> UV/H2O2> UV/HOCl order under equal conditions. In the UV/S2O82− process, sulphate radicals led to a 70.4% DEX degradation. The experimental mineral inhibitory factors showed that nitrite and bicarbonate further decrease the efficiency of the UV/S2O82− process. In the optimal conditions, the UV/S2O8−2 process removed DEX by 100% and had a 74.1% mineralisation. Furthermore, the intermediates were detected using LC-MS/MS, and the cytotoxicity of the UV/S2O8−2 process effluent was evaluated using human embryonic kidney cultured cells. The treatment of DEX solution by the UV/S2O8−2 process significantly decreased the toxicity of the effluent. Therefore, it can be concluded that the UV/S2O8−2 process can be a reliable process for DEX degradation and detoxification in aqueous solutions. [ABSTRACT FROM AUTHOR]

This article discusses the effect of UV-C radiation on two types of cured polymer resins, epoxy and polyester, intended for use in disinfection chambers. The exposure of the samples to UV-C rays lasted 168 h. Our evaluation covered two aspects: the effect of UV-C rays on the flammability and flame retardancy of the resins, and the effect of UV-C rays on the adhesion of the resins to the steel substrate. It was found that the applied halogen and halogen-free organophosphate agents can be used for the tested resins under UV-C conditions (e.g. disinfection chambers), and no negative impact of UV-C radiation on the performance of these flame retardants was found. The use of the tested types of resins in the form of thin coatings on a steel substrate is feasible in disinfection chambers under UV-C radiation conditions, as the obtained results indicate that the radiation did not affect the adhesion of the coating. The visible effect of UV-C radiation on both the tested resins was discoloration, giving yellow and brown colors. Our results suggest that further studies, probably involving longer UV-C exposure, would be advisable. [ABSTRACT FROM AUTHOR]

Water treatment plants (WTPs) in developing countries play an important role in providing potable water to rural and urban areas. However, they often face many challenges, making them unable to produce quality water for consumers. We surveyed the performance of two rural WTPs from the Vhembe District Municipality, South Africa for eight months using secondary water quality data from each plant. Turbidity at the WTPs and most points of use (POU) exceeded the aesthetic (5 NTU) and operational (1 NTU) risk guidelines. Fluoride, iron, and manganese were within the regulated limits of < 1 mg/L, <3 mg/L and < 4 mg/L, respectively), but with signs of post-treatment change in the concentration of iron and manganese in the distribution system. At both WTPs, the free chlorine residual was below limits (<5 mg/L,), posing a risk of proliferation of pathogens in the distribution system. The results indicated problems with water disinfection at both WTPs. The study suggested the existence of challenges with the integrity, good operation, and maintenance of the water treatment system and distribution network. It is necessary to continuously monitor the performance of WTPs and POU to ensure public health and safety. [ABSTRACT FROM AUTHOR]

Numerous tons of hazardous wastes containing persistent organic pollutants (POPs) are stored in an unsafe manner in the petrochemical industries. The planetary ball mill causes the formation of mineral Cl compounds during the degradation of polychlorinated compounds in the presence of various reagents. In addition, the planetary ball mill has been applied for the synthesis of diverse organic-inorganic hybrid nanomaterials. In the present study, Fe-metal organic framework was prepared using a planetary ball mill, and then Fe@C nanocomposite with core/shell structure was synthesised by carbonisation. X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) were utilised to study the synthesised materials. The nanocomposite was used as a reagent to degrade persistent organic pollutants in the sludge of a petrochemical wastewater treatment plant by a planetary ball mill. CaO was also used to compare the effect of nanocomposites on system performance. Ion chromatography (IC) analysis was carried out to determine chlorine mineralisation. Furthermore, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were applied to determine chemical bonds. The results illustrated a zero-valent iron nanoparticle in the core protected by carbon shell in a synthesised nanocomposite with a core/shell structure. Hence, nanocomposite was the most efficient additive, with 97% dechlorination efficiency in the first hour while the efficiency of the planetary ball mill in the presence of CaO was only 76% after 12 hours of milling. Furthermore, major changes occurred in the organic phases, carbon and chlorine bonds. Simultaneously, graphite and amorphous carbon were produced in the final products after milling. This indicates that aromatic structures and C-Cl bonds were broken down into inorganic compounds. Thus, this study presented a practical method of producing materials while degrading hazardous pollutants in petrochemical wastewater sludge through a planetary ball mill. [ABSTRACT FROM AUTHOR]

The efficient removal of 2-Methylisoborneol (2-MIB), a typical odour component, in water treatment plants (WTPs), poses a great challenge to conventional water treatment technology due to its chemical stability. In this study, the combination of ultraviolet light-emitting diode (UV-LED) and chlorine (UV-LED/chlorine) was exploited for 2-MIB removal, and the role of ultraviolet (UV) wavelength was investigated systematically. The results showed that UV or chlorination alone did not degrade 2-MIB effectively, and the UV/chlorine process could degrade 2-MIB efficiently, following the pseudo-first-order kinetic model. The 275 nm UV exhibited higher 2-MIB degradation efficiency in this UV-LED/chlorine system than 254 nm UV, 265 nm UV and 285 nm UV due to the highest mole adsorption coefficient and quantum yield of chlorine in 275 nm UV. ·OH and ·Cl produced in the 275 nm UV/chlorine system played major roles in 2-MIB degradation. HCO3− and Natural organic matter (NOM), prevalent in water, consumed ·OH and ·Cl, thus inhibiting the 2-MIB degradation by UV-LED/chlorine. In addition, NOM and 2-MIB could form a photonic competition effect. The degradation of 2-MIB by UV-LED/chlorine was done mainly through dehydration and demethylation, and odorous intermediates, such as camphor, were produced. 2-MIB was degraded through the α bond fracture and six-membered ring opening to form saturated or unsaturated hydrocarbons and aldehydes. Four DBPs, chloroform (CF), trichloroacetaldehyde (TCE), trichloroacetone (TCP) and dichloroacetone (DCP), were mainly generated, and CF was the most significant by-product. [ABSTRACT FROM AUTHOR]

The photocatalytic technology for indoor air disinfection has been broadly studied in the last decade. Selecting proper photocatalysts with high disinfection efficiency remains to be a challenge. By doping with the incorporation of metals, the bandgap can be narrowed while avoiding the recombination of photogenerated charge. Three photocatalysts (Ag-TiO2, MnO2-TiO2, and MnS2-TiO2) were tested in photocatalytic sterilization process. The results revealed that Ag-TiO2 had the best antibacterial performance. Within 20 min, the concentration of Serratia marcescens (the tested bacteria) decreased log number of ln 4.04 under 640 w/m2 light intensity with 1000 µg/mL of Ag-TiO2. During the process of inactivating bacteria, the cell membranes of bacterial was destructed and thus decreasing the activity of enzymes and releasing the cell contents, due to the generation of reactive oxygen species (O2•– and •OH) and thermal effect. Spectral regulation has the greatest impact on the sterilization efficiency of MnO2-TiO2, which reduces the probability of photocatalytic materials being excited. [ABSTRACT FROM AUTHOR]

The presence of heavy metals and/or harmful bacteria in drinking water represents significant risks to human health. This study aimed to develop a low-cost water treatment technology using synthesized nanocomposites with metal nanoparticles supported on activated carbon (AC) for bacteria and heavy metal removal. In addition, the performance of the developed nanomaterials was compared with that of commercial materials – carbon fibers of three different typologies. The chemical and textural properties of all tested materials were characterized. To simulate a technology to be applied in a water outlet point, removal tests were carried out in a continuous system using suspensions of Escherichia coli and/or Staphylococcus aureus, wherein the contact time with the two phases was minimal (1 min). The obtained results revealed that iron and copper oxides supported on AC with a calcination treatment (CuFeO/AC-C) was the nanocomposite with the best performance, achieving a 6 log reduction for both bacteria in the same suspension up to 9 h operation. A mix of bacteria and heavy metals, simulating a real water, was treated with CuFeO/AC-C obtaining a 6 log reduction of bacteria, a Pb2+ removal >99.9% and Cd2+ removal between 97 and 98% over 180 passage times. [ABSTRACT FROM AUTHOR]

Leafy vegetables contain nutritious levels of vitamin C. Good postharvest management and food safety are the focus of reducing food loss. This study aims to evaluate the effectiveness of superoxide water in stabilizing the Vitamin C level and simultaneously prolonging the storage period for bok choy (Brassica rapa var. chinensis). The bok choy samples were immersed in superoxidised water [100 ppm Active chlorine concentration, neutral pH] and sodium bicarbonate solution for three different soaking periods: 5, 10, and 15 minutes and stored at 4°C. Weight loss, vitamin C, and chlorophyll content were evaluated during the 12 days of storage. The shelf life of bok choy treated with superoxidised water was extended from 3 days at room temperature to 8 days at 4°C. The results indicated that superoxidised water with a 5-minute treatment time could maintain a better quality of bok choy, which provides a cost-effective and sustainable alternative for chemical washing agents in the food industry compared to market-available sodium bicarbonate. [ABSTRACT FROM AUTHOR]

Electro-catalytic technology is a promising approach for wastewater treatment, owing to its easy operation, minimal generation of secondary pollution, small foot-print and rapid start-up. In this work, the chlorine evolution potential of the Pd-Sn modified ruthenium(Ru)-iridium(Ir) electrode was investigated for the electro-catalytic treatment of high chlorine ammonia-nitrogen wastewater. The effect of reaction conditions on the removal of ammonia-nitrogen, kinetics and apparent activation energy of ammonia-nitrogen removal were studied. The possible denitrification process of high chlorine ammonia-nitrogen wastewater was discussed. The results indicated that the chlorine evolution potential of the Pd-Sn modified Ru-Ir electrode was 1.0956 V(vs. SCE). The electro-catalytic treatment of high chlorine ammonia-nitrogen conformed to zero-order kinetic law, and the apparent activation energy of removal process was 14.089 kJ/mol. With a current was 0.5 A, the removal efficiency of ammonia-nitrogen could achieve 100% at a reaction time of 40 min. Indirect oxidation played an essential role in the electro-catalytic ammonia-nitrogen removal using the Pd-Sn modified Ru-Ir electrode. This paper demonstrated that the electro-catalytic technology was a promising approach for efficiently treating the high chlorine ammonia-nitrogen wastewater. [ABSTRACT FROM AUTHOR]

In this study, Escherichia coli (E. coli) was used as an indicator bacterium treated with five different concentrations of chlorine (0.1; 0.5; 1.0; 2.0, and 5.0 mg/L) and without chlorine (0.0 mg/L) to evaluate the changes in the DOM characteristics. The dissolved organic carbon (DOC) concentration initially increased along with the chlorine concentrations and decreased after 24 h (0.0 and 0.1 mg/L) and 168 h (0.5; 1.0; 2.0 and 5.0 mg/L). Ultra-violet absorbance at 260 nm (UV260) showed that the absorbance decreased for control without chlorine (0.0 mg/L) and 0.1 mg/L chlorine, while increased for other concentrations of chlorine within 120 h. The DOC and UV260 results indicated that the high concentrations of chlorine initiated high contents of DOM which contained more humic-like molecules than the DOM released from E. coli without chlorine. Fluorescence excitation–emission matrix (EEM) analysis suggested that the DOM released from E. coli without chlorine enriched with protein-like substances, whereas the fulvic-like and humic-like substances more intensified in the DOM for the high concentrations of chlorine (>1.0 mg/L). The molecular weight distribution of DOM showed that the intensity of high molecular weight substances and polydispersity increased along with chlorine concentration and contact time, whereas the low molecular weight substances were relatively higher in the DOM for control without chlorine. The obtained results of this study would be useful for a better understanding of the variation of DOM during treatment and could be used as an important reference for optimizing the operation condition of the water treatment plants. [ABSTRACT FROM AUTHOR]

Natural activities and industrial emissions can lead to high bromide and iodide concentrations in surface water, and potentially pollute drinking water sources. During drinking water disinfection process, bromide and iodide can transform into brominated disinfection by-products (Br-DBPs) and iodinated disinfection by-products (I-DBPs), which are more toxic than chlorinated disinfection by-products (Cl-DBPs). Therefore, studying bromide and iodide removal from water is of great significance to the ecological environment, human health and resource recovery. In this work, we reviewed the techniques for bromide and iodide removal from water and unprecedently classified the techniques into four types: membrane techniques, adsorption techniques, electrochemical techniques and chemical oxidation techniques. It is worth mentioning that chemical oxidation is not covered in other reviews before. The halide removal performance, mechanism, applications, merit and demerit of each technique were discussed and compared. Finally, we proposed research priorities in the context of existing and future halide removal from water. Most of these methods have been studied in depth, but still have some problems and challenges. Electrolysis and chemical oxidation are mostly used in the field of bromine and iodine production, and less attention is paid to the remaining bromide and iodide in water. The research on electrolysis and chemical oxidation for halide removal is potential but lacking. It is hoped that this review will provide theoretical support and guidance for the development of new halide removal technologies and decision-making of environmental management. [ABSTRACT FROM AUTHOR]

Chlorine concentrations in water distribution systems are generally predicted by combined models of reactions in bulk water and at pipe walls. The structure of the widely used EPANET wall-reaction models is questioned, as they do not reproduce the variation in wall-reaction rate with decreasing chlorine observed in real pipelines. The microbially mediated wall-reaction model (EXPBIO) is structurally valid. EXPBIO was extended to calculate the mass-transfer coefficient in individual pipes, rather than using a single fitted value. Smooth- and rough-pipe versions were formally validated against observed chlorine data from the Mirrabooka pipeline, where rough-pipe predictions better matched lower observed chlorine concentrations. In a medium-sized rough pipe, the mass-transfer coefficient doubled between 10 and 30°C. In the real pipeline, chlorine concentration decreased much faster with distance downstream at higher temperature, due to increasing microbial activity and mass-transfer of chlorine. System simulations to search for improved seasonal chlorine dosing strategies need to include these effects. [ABSTRACT FROM AUTHOR]

Nowadays water pollution is a major problem in the world threatening human health and ecosystems. Nanocomposites (NCs), as a very large group of promising nanomaterials, demonstrate high performance in the water treatment process. In this paper, the green synthesis of zinc oxide (ZnO)-NPs stabilized on eggshell (ES) powder particles by Ferulago macrocarpa (F. macrocarpa) extract, as a new natural reducing agent, was considered to produce ZnO/ES-NCs. Different characterization techniques such as SEM, TEM, EDS, XRD, and IR were used for the characterization of the nanocomposites. The results confirmed the synthesis of pure ZnO-NPs with an average particle size of 25 nm, uniformly stabilized on the ES matrix. Further, this structure was a promising material for photocatalytic degradation of diazinon with high antibacterial efficiency against fish and human bacterial pathogens and could be employed as an eco-friendly product for disinfection in aqueous media. [ABSTRACT FROM AUTHOR]

The utilization of DMSO or Ph2SO/(COBr)2 or (COCl)2 for the bromination or chlorination of arenes has been explored. Notably, monobromination of activated arenes can be achieved with high regioselectivity using the combination of dimethyl sulfoxide and oxalyl bromide. Bromodimethylsulfonium bromide generated in situ was proposed to be the active species for bromination. In contrast, the practicality of chlorination of arenes with DMSO or Ph2SO/(COCl)2 is limited due to production of the formation of by-products such as aryldimethylsulfonium chlorides or dichlorinated arenes. [ABSTRACT FROM AUTHOR]

The presence of metal ions in drinking water treatment and distribution systems may affect the disinfection process of organic matter, which had aroused people's concern. L-tyrosine can complex with metal ions through carboxyl, carbonyl, and amino groups and affect its chemical reactions. In this paper, the complexation of L-tyrosine with common metal ions was studied and the influence of complexation on chlorination with different experimental factors was investigated. It was inferred that L-tyrosine complexed with metal ions by single dentate ligand or double dentate chelation in a ratio of 2:1. The degradation of L-tyrosine-metal complex followed the pseudo-first-order reaction kinetic. TCM, DCAA, and TCAA were the main species DBPs in the chlorination of L-tyrosine. Compared with L-tyrosine, the reaction rate constants of complex increased by 5.6%, the formation of trihalomethane production decreased by 21.5% and the formation of haloacetic acids production increased by 26.9% at the state of metal complexation. The effect of metal complexation on chlorination was more obvious than that of metal coexistence. For different metal complexation, the order of inhibition on trihalomethane production was Ca2+> Fe3+> Mn2+ and the order of promotion on haloacetic acids production was Mn2+> Fe3+> Ca2+. Moreover, it was found that alkaline conditions were favorable for the formation of DBPs due to the hydroxyl radical. The combination of ultraviolet and chlorine disinfection promoted L-Tyrosine degradation and DBPs generation, and the promotion efficiency follow the order: UV/Cl2> UV-Cl2> Cl2. [ABSTRACT FROM AUTHOR]

The use of ultraviolet-C (UV-C) light-emitting diodes (LEDs) as a water sterilization light source poses a serious challenge in heat dissipation. High junction temperatures reduce the radiant power and lifespan of UV-C LEDs. In this study, a novel self-cooling water disinfection reactor was developed to dissipate Joule heat from UV-C LEDs. The advantage of the self-cooling design is that cooling can be achieved without requiring additional power consumption and cooling liquid. The effects of the water flow rate and driving current of UV-C LEDs on the sterilization of Escherichia coli were investigated for a traditional flow-through reactor and a reactor with self-cooling. The experimental results indicated that an increase in driving current resulted in a considerable increase in the LED temperature of the flow-through reactor but only a marginal increase in the LED temperature of the self-cooling reactor. Under a driving current of 150 mA, the LED temperature of the self-cooling reactor was 55.5°C less than that of the flow-through reactor. The time required by the self-cooling reactor to reach the steady state decreased as the water flow rate increased. Under a flow rate of 100 mL/min, the self-cooling reactor reached the steady state within 62 and 70 s when the driving current was 100 and 150 mA, respectively. Moreover, the average irradiance and inactivation values of the self-cooling reactor were up to 16.5% and 26.0% higher than those of the flow-through reactor, respectively. [ABSTRACT FROM AUTHOR]

One of the requirements for the treatment of drinking water is the removal of pathogenic microorganisms. Typically, the most used techniques apply inorganic nanoparticles or chlorine release precursors to inactivate bacteria. While these treatments are very effective, they tend to show a decrease in antimicrobial activity over time, releasing potentially toxic ions and contributing to bacterial resistance. In this sense, the development of hydrogel-based materials has become a potential alternative for water disinfection. The synthesis and functionalization of hydrogels have been proven to improve the global performance of microorganism retention. Our work provides an overview of the synthesis and functionalization of hydrogel-based materials, their advantages and limitations, and the latest research on the use of hydrogels for water disinfection. The future panorama of hydrogel-based materials applicability for water treatment is also provided. The main challenge to expand the use of hydrogels in water treatment is the lack of research assessing the feasibility of large-scale applicability of these materials, considering real systems. Most of the studies carried out experiments at laboratory scale with controlled situations, in which interactions between microorganisms and real world contaminants were not considered. [ABSTRACT FROM AUTHOR]

COVID-19 is a global health threat with a large number of confirmed cases and deaths worldwide. Person-to-person transmission through respiratory droplets and contact with aerosol-infected surfaces are the main ways in which the virus spreads. However, according to the updated literature, the new coronavirus (SARS-CoV-2) has also been detected in aqueous matrices, with the main route of transmission being feces and masks from patients diagnosed with the disease. Given the emergence of public health and environmental protection from the presence of lethal viruses and bacteria, this review article aims to report the major challenges associated with the application of ozonation in water contaminated with viruses and bacteria, in order to clarify whether these communities can survive or infect after the disinfection process and if it is efficient. Available data suggest that ozonation is able to increase the inactivation effect of microorganisms by about 50% in the logarithmic range, reducing infectivity. In addition, the evidence-based knowledge reported in this article is useful to support water and sanitation safety planning and to protect human health from exposure to cited contaminants through water. [ABSTRACT FROM AUTHOR]

Antimicrobial coatings are designed to inhibit the growth of pathogens and have been used to reduce foodborne illness bacteria on food processing equipment. Novel N-halamine based antimicrobial coatings are highly advantageous due to their unique properties and low cost, and are being investigated for applications in food safety, health care, water and air disinfection, etc. In this study, we evaluated the chemical safety of a novel N-halamine antimicrobial polymer coating (Halofilm) for use on food processing equipment. Migration tests were performed on stainless steel tiles prepared with four different treatment groups: negative control, positive control, Halofilm coating without chlorination, and Halofilm coating with chlorination. An LC-MS/MS method was developed and validated for four formulation components: polyethylenimine (PEI), Trizma® base, hydantoin acrylamide (HA) and dopamine methacrylamide (DMA), followed by stability and recovery tests. Migration tests were conducted at 40 °C with three food simulants (10, 50 and 95% ethanol/water) to mimic various food properties, and aliquots of migration extracts were analyzed at 2, 8, 72, 240 and 720 h. In general, measured concentration levels were consistent among simulant types for the four tested chemicals. Chlorinated tiles had non-detects for three analytes (PEI, HA and DMA), and less than 0.05 mg/kg of HA migration over 30 days. A chlorination step could possibly change the measured mass (m/z) hence leading to non-detects in targeted LC-MS/MS. In non-chlorinated tiles, all four compounds were detected during the migration test. This suggests that addition of the chlorination step may have a stabilizing effect on the polymer. Additionally, full scan high resolution mass spectrometry (HRMS) analysis was employed to screen for migration of other extractable and leachable (E&L) chemicals, which led to the identification of eight common E&L chemicals. To our knowledge, this is the first report evaluating chemical migration from an N-halamine antimicrobial polymer coating product. [ABSTRACT FROM AUTHOR]

Occurrence of trimethoprim (TMP), recalcitrant antibiotic, and its adverse effect on ecosystem have been reported in several countries. The study aims to remove the TMP and its phytotoxicity via a UV/chlorine process, compared with chlorination and UV irradiation alone. Various treatment conditions including chlorine doses, pHs, and TMP concentrations was conducted with synthetic waters and effluent waters. The UV/chlorine process exhibited a synergistic effect on the TMP removal, compared with chlorination and UV irradiation alone. The UV/chlorine process was the most effective in removing TMP, followed by chlorination. The UV irradiation slightly affected the TMP removal (less than 5%). The UV/chlorine process completely removed TMP by 15 min contact time, while chlorination for 60 min could achieve 71% of TMP removal. The TMP removal fitted well with the pseudo first-order kinetics, and the rate constant (k′) increased with higher chlorine doses, lower TMP concentrations and low pH. HO• was the major oxidant affecting the TMP removal and its degradation rate, compared with other reactive chlorine species (e.g., Cl•, OCl•). The TMP exposure increased the phytotoxicity by decreasing a germination rate of Lactuca sativa and Vigna radiata seeds. The use of UV/chlorine process could effectively detoxify the TMP, resulting in the phytotoxicity level of treated waters equivalent or lower than those of TMP-free effluent water. The detoxification level depended on the TMP removal, and it was about 0.43–0.56 times of TMP removal. The findings indicated the potential use of UV/chlorine process in removing TMP residual and its phytotoxicity. [ABSTRACT FROM AUTHOR]

Due to the high recurrence of microbial infections, developing new technologies for preventing the dissemination of pathogens is essential, especially to prevent infection in humans. Thus, devices for the decontamination of surfaces reduce not only the spread of pathogens in the environment, but provide greater security and protection for communities. Ozone (O3) is a substance capable of reducing or eliminating several types of microorganisms owing to its biocidal capacity, including when it is dissolved in water. The objective of this study was to develop an instant decontamination device using ozonated water. To confirm its biocidal action and verify the device's efficacy, the reduction of the microbial load of important pathogens on personal protective equipment (PPE) was assessed. In addition, in order to confirm the biocidal action of ozonated water against SARS-CoV-2, in vitro tests on a viral model of Gammacoronavirus were performed. The results showed the efficacy of ozonated water in the disinfection device at concentration ranges of 0.3–0.6 mg/L and 0.7–0.9 mg/L of ozonated water, with growth reductions above 2 log10 for both concentration ranges tested and inactivation fractions above 60% (0.3–0.6 mg/L) and 80% (0.7–0.9 mg/L), with a high proportion of the tested PPE showing 100% microbial reduction. In vitro results for the evaluation of ozonated water in a viral model showed a 99.9% reduction percentage in the concentration range of 0.3 to 0.5 mg/L and a 99% reduction in the concentration range of 0.6 to 0.8 mg/L, with a 5.10 log EDI50/mL and 6.95 log EDI50/mL reduction, respectively. The instant decontamination system developed in this study proved effective for microbial reduction, and we confirmed the potential of ozonated water as a biocidal agent. Therefore, the proposed decontamination device could be considered as a tool for reducing contamination on surfaces using ozonated water. [ABSTRACT FROM AUTHOR]

The adsorption of chlorinated aromatic compounds (CACs) on pristine biochar was often limited. Surface modification can greatly improve the adsorption capacity of biochar. In this work, by pyrolysis activation of rubber-seed shell wastes, nitrogen auto-doped biochar (RSS-NBC) was synthesized and used for purifying CACs-containing wastewater. Systematic characterization results showed that after proper treatment, the as-prepared RSS-NBC had high specific surface area, abundant surface oxygen- and nitrogen-containing functional groups, and nano-scale pore structure. Batch adsorption experiments were conducted with using three typical CACs probing pollutants, i.e. 1,2-dichlorobenzene (1,2-DCB), 2,4-dichlorophenol (2,4-DCP) and 2,4-dichlorobenzoic acid (2,4-DCBA). The adsorption experiments results showed that the maximum adsorption amounts of 1, 2-DCB, 2,4-DCP, and 2,4-DCBA could reach 2284, 1921, and 1142 mg/g at 298.15 K. Moreover, 90% of the equilibrium adsorption amount can be reached within 0.5 h. The adsorption kinetic results showed that the adsorption processes of the three CACs followed the pseudo-second-order rate model and were dominated by chemisorption. Also, the adsorption isotherms of 1, 2-DCB and 2, 4-DCP belonged to the Freundlich model and were valid for multilayer adsorption, while the adsorption of 2,4-DCBA followed Langmuir model and single-layer adsorption. The thermodynamics data indicated that the spontaneous adsorption process of 1, 2-DCB and 2, 4-DCP was endothermic while that of 2,4-DCBA was exothermic. After 5 cycles of adsorption-regeneration, the removal efficiency of RSS-NBC particles still remained more than 80% for the three typical CACs, indicating that it could be reused as an effective and retrievable adsorbent in the treatment of CACs-containing effluents. [ABSTRACT FROM AUTHOR]

In response to the pandemic of COVID-19, various unexpected environmental impacts in many countries have been rising. Millions of gloves and masks are used and thrown away daily around the globe. Incorrect disposal of COVID-19 waste without disinfection preparation could expose people and healthcare personnel to the possibility of spreading the infection of coronaviruses. This article finds an appropriate way to disinfect the waste of coronavirus-infected items by involving various physical factors, chemical and biological or physiological factors. Policymakers must immediately adopt disinfection technology to achieve green recovery of covid-19 waste that encourages development and sustains climate change. Regarding previously published papers and research results, this article intends to investigate the plastic pollution research status before and during the COVID-19 pandemic and outline safely disinfecting COVID-19 plastic waste. [ABSTRACT FROM AUTHOR]

Chlorine is a widely used disinfectant in developing countries due to its efficiency and affordability. Millions of people in these countries receive water intermittently through piped networks. However, very little is known about chlorine decay in intermittent networks. In this work, field chlorine decay measurements were carried out in adjoining continuous and intermittent networks. Hydraulic modelling was done to determine the water velocity in networks using EPANET. Overall chlorine decay rates were estimated using field measurements and showed a good first-order fit. Decay rates in continuous and intermittent networks were compared, considering the influence of pipe velocity, material and diameter. The average overall decay rate for ductile and cast-iron pipes in intermittent network (1.7 h r − 1 ) was 1.5 times higher than that in continuous network (1.1 h r − 1 ). These results indicate that intermittency has a long-term effect on the overall chlorine decay in supply networks and its implications are discussed in this study. [ABSTRACT FROM AUTHOR]

This study compares the Canadian Council Water Quality Index (CCME WQI) and the Arithmetic Water Quality Index (WAWQI) methodologies for determining the quality of water in the city of Azogues (Ecuador). Additionally, a drinking water quality risk index (IRCA) was determined to evaluate the degree of risk of disease occurrence related to water consumption. The data generated came from the analyses of twelve physicochemical parameters (pH, turbidity, colour, total dissolved solids, electrical conductivity, total hardness, alkalinity, nitrates, phosphates, sulfates, chlorides, residual chlorine) from 172 samples of water over six months. The calculated average value of CCME WQI (97.59 ± 1.08) indicates that 100% of the drinking system was of 'excellent' quality. The WAWQI average value was calculated to be 26.36 ± 1.13 indicating that 16.67% of the distribution system was of 'excellent' quality and 83.33% of the distribution water was of 'good' quality. The IRCA calculated in all the distribution zones is between 0 and 5% and therefore, the distributed water is considered suitable for human consumption and is rated at the no-risk level. Furthermore, WAWQI is influenced by parameters with low maximum allowed concentration (for example, turbidity value 1 NTU in the Ecuadorian standard was used instead of 5 NTU recommended by the WHO); conversely, CCME-WQI is influenced by parameters with a high maximum allowed concentration (no parameter exceeded the norm in this study). The IRCA is a support instrument to guarantee that the water supplied by the provider companies complies with the characteristics established for drinking water. [ABSTRACT FROM AUTHOR]

Drinking water quality is one of the greatest factors affecting human health. The drinking water production process was investigated in 30 factories in Sakon Nakhon province, Thailand using hazard analysis and critical control points (HACCP) and water quality analysis. The results showed that the major hazards were pollution of the raw water source, final disinfection, personal hygiene of workers and drinking water quality. Overall, 28 samples contained total coliform bacteria, 23 samples were positive for fecal coliform bacteria and 16 samples contained Escherichia coli. These results suggested poor hygienic conditions in the water production process. To safeguard public health, more effort is required regarding a community program and strict regulation. [ABSTRACT FROM AUTHOR]

Silver-silver chloride nanoparticles (Ag-AgCl NPs) have bactericidal activity and are widely used for water disinfection. The rapid, facile and green method was proposed for the synthesis of Ag-AgCl NPs which are nontoxic and cost effective. The present study highlights the use of water extract of Ehretia laevis leaf as a reducing agent for Ag-AgCl NPs synthesis from silver nitrate by a green synthesis route. The formation of Ag-AgCl NPs was analyzed by UV-Vis spectrophotometer, a characteristic absorbance peak at 450–500 nm with a color change in reaction solution was observed. Further, it was confirmed by XRD and EDX technique. The transmission electron microscopy reveals the synthesized Ag-AgCl NPs were spherical to oval shape with an approximately size of 20–80 nm. The X-ray diffraction confirms face-centered cubic structure of synthesized Ag-AgCl and the element composition by energy dispersive X-ray analysis. Interaction between leaf extract and the synthesized Ag-AgCl was studied by Fourier transform infrared spectroscopy. The synthesized Ag-AgCl NPs show bactericidal activity against Staphylococcus aureus, Listeria monocytogenes and Escherichia coli bacteria and also shows the photocatalytic degradation of methyl orange by Ag-AgCl NPs in combination with Fenton's reagent with 98% maximum degradation efficiency. [ABSTRACT FROM AUTHOR]

Many studies consider the contamination of dental unit waterlines (DUWLs), but few of them have studied the possible presence of antibiotic resistant Pseudomonas aeruginosa in the DUWLs. Investigation of the presence of P. aeruginosa and Pseudomonas spp. strains in DUWLs and evaluation of their resistance to six antibiotics (ceftazidime, netilmicin, piperacillin/tazobactam, meropenem, levofloxacin, colistin sulfate) at a public dental clinic in Milan, Italy. Dental units were contaminated by P. aeruginosa with loads of 2–1,000 CFU/L and were mainly located on the mezzanine floor, with a range of 46–54%, while Pseudomonas spp. were primarily found on the first and second floors, ranging from 50 to 91%. P. aeruginosa was antibiotic resistant in 30% of the strains tested, andPseudomonas spp. in 31.8%. Cold water from controls was also contaminated by these microorganisms. Monitoring antibiotic resistance in the water and adopting disinfection procedures on DUs are suggested within the Water Safety Plan. [ABSTRACT FROM AUTHOR]

N-Nitrosamines, well-known human carcinogens, are widely considered to be formed through the disinfection of waters containing compounds with amine moieties. The formation mechanisms of nitrosamines during the disinfection of drinking water and wastewater have been previously reviewed in the literature. However, no study to date has reviewed the effects of inorganic ions on nitrosamines formation during disinfection. Inorganic ions are ubiquitous in the environment and are present at significant concentrations in water and wastewater. Their presence influences aqueous nitrosamines formation, depending on the type, concentration, and environmental conditions. In this review, we have critically reviewed nitrosamines' precursors and occurrence, disinfection processes associated with nitrosamines' formation/destruction, and the impact of inorganic ions on the formation or removal of nitrosamines during disinfection of water and wastewater. The disinfectants reviewed in the study were chlorine, chloramine, chlorine dioxide, ozone, and radicals generated through advanced oxidation processes (AOPs). N-Nitrosodimethylamine formation pathways, in the presence and absence of inorganic ions, were also reviewed to summarize our current understanding. Although chloramination has been associated with the formation of nitrosamines, many ozonation studies have also shown significant levels of nitrosamines formation. Pre-oxidation and AOPs have been reported as the most promising mitigation strategies for controlling nitrosamines formation, requiring prolonged exposure of precursors for effective mineralization. [ABSTRACT FROM AUTHOR]

An onboard zero-discharge water treatment process, aimed at the well-boat industry, is described and demonstrated as an alternative to current techniques. Two live-fish holding trials were carried out with Arctic char for 8 days (84 kg/m3) and 6 days (154 kg/m3). The trials were conducted in a zero-discharge pilot system with a unique water treatment unit relying on electrochemical water-treatment for oxidizing ammonia into N2(g), disinfecting the water, removing fine particles/organic matter and chlorine-species via activated-carbon filtration. No professional skills are required to operate the system. The TAN excretion rate of adult Arctic char under starvation at 5°C amounted to ~22 mgN/(kg·d). Sensory evaluation showed that Arctic char could be successfully held in a system based on the suggested technology without adverse effects relating to mortality and product quality. The costs of operating the system were assessed at 0.30 USD per one ton of standing stock per 24-h journey. [ABSTRACT FROM AUTHOR]

The overuse of chemicals has been causing serious global pollution. Toxicity assessment and screening of chemicals effectively contribute to individualised management and control of toxic and harmful chemicals that are released into the environment. Moreover, they can protect the ecological environment and human health from the effect of these substances. This study is researching for A Textile Company in Suzhou, China, and uses the USEtox consensus model to calculate the toxic effects of pollution emissions on the ecological environment. In addition, the pollutants that should be controlled first are screened and identified through comprehensive analysis of accounting results. Results show that heavy metals are a major source of potential ecotoxicity and pollutants to be prioritised. Considering the total ecotoxicity ranking, category ranking and rankings within categories of pollutants discharged by A company, copper, nickel and manganese in heavy metals; tetrachlorophenol and pentachlorophenol in chlorinated chemicals; and nonylphenol/branched-4-nonylphenol and 4-octylphenol in alkylphenols should be primarily controlled. From the perspective of terminal control, the study puts forward that the objects of corporate environmental management should be transformed from 'medium management (wastewater, waste gas and waste residue)' to 'substance management (chemical)' and provides empirical evidence for the management and control of toxic and hazardous substances from 'comprehensive pollutant management' to 'single pollutant management'. The research results can provide theoretical basis and practical guidance for scientific decision-making in order to achieve priority management and control of pollutants and reduce the ecotoxic effects of chemical pollutants. [ABSTRACT FROM AUTHOR]

A novel approach to chlorine isotope analysis is presented to overcome many drawbacks of existing methods. Contemporary methods often require several laborious off-line procedures prior to instrumental determination; interfering ions (SO42- and NO3-) in real samples are difficult to completely remove, especially when the concentrations of those ions are equal to that of the Cl- ion. This study was aimed to develop an automatic sample preparation method with chromatographic purity for determination of chlorine isotopes using isotopic preparative chromatography (IPC), which was a modified ion chromatograph and a fraction collector. An AS19 chromatographic column was employed to separate chlorine from interference ions using an eluent, flow rate, and suppressor current of 30 mM NaOH, 1 mL/min, and 70 mA, respectively. After the original solutions introduced into the IPC, eluted pure chlorine in the form of HCl was collected in an automated procedure from the outlet of the detector for 6 to 10 mins. The recoveries of chlorine were more than 95% with the relative standard deviation (RSD) of the separation less than 1.8%. After transforming the HCl into CsCl with a resin and concentration in a super-clean laboratory, the samples were sent to the thermal ionization mass spectrometer. The present method was validated by certified reference materials and real samples. The precision of 37Cl/35Cl ratio value was generally below 0.20 ‰. This method provides a potential approach for the analysis of samples with low chlorine concentrations. [ABSTRACT FROM AUTHOR]

Household Water Treatment and Safe Storage (HWTS) are recommended to supply the demand for drinking water in communities without conventional water supply systems. However, there is a lack of long-term laboratory studies regarding such technologies. We evaluated the contributions of each step of a multi-barrier system with pretreatment (sedimentation and fabric filtration), filtration in Household Slow Sand Filters (HSSFs) and disinfection (sodium hypochlorite) treating surface water for more than 14 consecutive months. Removal of turbidity, colour, organic matter, coliform group bacteria and protozoa were evaluated. Two HSSF models were compared, one with a diffuser vessel (HSSF-d) and one with a gravity float equipped vessel (HSSF-f). Correlations between efficiency and operational parameters were assessed. Overall, the multi-barrier system removed more than 90% of turbidity and more than 3.5 log of Escherichia coli. HSSF removed up to 3.0 log of Giardia spp. and 2.4 log of Cryptosporidium spp. HSSF-f presented significantly higher removal rates for turbidity, apparent colour and E. coli. Disinfection resulted in water with E. coli concentration lower than 1 CFU 100mL−1, however it was not able to inactivate protozoa. The evaluated system was able to reduce microbiological risks from water and could indeed be an alternative to communities that depend on surface water as their main source of supply. Nevertheless, further studies are recommended to include a low-cost disinfectant for protozoa inactivation. [ABSTRACT FROM AUTHOR]

This study reports the synthesis of sunlight-active zinc oxide-tungstate-kaolinite photocatalytic composite prepared via a green process (solvent-free mechano-thermal process) at an optimum temperature of 500°C for 1 h in a furnace. Electron Paramagnetic Resonance (EPR) study suggests the presence of W5+ defect states in the prepared photocatalytic composite (ZnWK-5), which is responsible for its photoactivity in visible light. Results from further analysis show that hole (h+) and superoxide radical (.O2−) are the major contributors to the photocatalytic efficiency of ZnWK-5 photocatalytic composite. This photocatalytic composite was used to treat water containing an antibiotic chemical-ampicillin (AMP) under sunlight. Mass spectrometry analysis of the treated water suggests that the mechanism of photodegradation of AMP is via several bond and ring cleavages, including amide bond, phenyl ring, and β-lactam ring cleavages. These cleavage reactions were followed by subsequent mineralization of ca. 98% after 5 h without the formation of toxic products. The introduction of phosphate and carbonate anions had a serious negative impact on the photocatalytic activity of the composite. However, the photocatalytic composite completely disinfected water contaminated with gram-(−ve) and gram-(+ve) bacteria. Even after five re-use cycles, the photocatalytic composite maintained a 90% photodegradation efficiency of ampicillin in water. [ABSTRACT FROM AUTHOR]

Disinfection contact tanks facilitated in urban water treatment plants suffer from low hydraulic and mixing efficiencies, which may result in high chemical and energy usage to yield the required disinfection levels. Porous baffle design can effectively remedy the adverse effects of solid baffles by creating momentum exchange between neighbouring chambers with controllable porosity in the flow direction. Although previously developed baffle has been proved to enhance the efficiency of the contact system, porous baffle design has not yet been optimized. A simulation-optimization framework is developed by means of Computational Fluid Dynamics (CFD) simulations and employed for single and multi-objective optimization of the porosity. The optimized design of tripartite baffle improved hydraulic and mixing efficiencies by 50% and 56%, respectively. The integrated optimization framework developed in this study can effectively be used for the multi-objective optimization of porous baffle in the design of disinfection contact tanks. [ABSTRACT FROM AUTHOR]

Chlorine is a widely used water disinfectant in humanitarian emergency water supply. However, its effective application can be limited by the uncertainty in initial dose determination. The target free chlorine residual in water should achieve both health objectives and aesthetic considerations, but the varying field conditions and changing source water quality may affect the performance of chlorination strategies. A chlorine dose predictive tool could assist in initial dose determination. To this end, an accurate chlorine decay kinetic model can serve as a strong foundation for developing such a tool. In this study, a literature search identified 7 basic chlorine decay kinetic models that were subsequently tested with 610 different chlorine decay test data (from a semi-systematic literature search and laboratory-generated results). The models were then ranked based on their goodness of fit (R2) and root mean square error. An empirical model, power models and parallel models were found able to fit most decay data with more than half of the regressions resulting in R2 value over 0.97. First order models can achieve R2 value above 0.95 when the data points in the rapid phase are excluded from the model fitting. The power models and parallel models can form a strong basis for developing a chlorine dose predictive tool if the power term and the ratio term (model parameters) can be controlled. An essential next step is to evaluate the relationships between easily obtainable water parameters in the field and the decay term in the models to allow rapid model calibration. [ABSTRACT FROM AUTHOR]

In this study, we synthesized and modified titanate nanotubes (TNTs) under different conditions of acid rinsing and calcination. The produced materials were then characterized by transmission electron microscopy, X-ray diffraction, ultraviolet–visible spectroscopy, temperature programmed desorption, inductively coupled plasma atomic emission spectroscopy, and Brunauer–Emmett–Teller analysis. The activity of material was evaluated via its application for disinfection of Coliforms and removal of natural organic matters (NOMs) in river water. Results showed that TNTs rinsed at pH 1.6 and calcined at 500°C had the highest removal efficiency for the treatment of Coliforms and NOMs in Sai Gon river water, possibly due to its high surface area, crystallinity, and surface acidity. The application of this TNTs material for the treatment of waters from Dong Nai River and Mekong River also show high removal efficiency, which could meet the quality standard for supply water, suggesting the potential of TNTs for practical drinking water treatment. [ABSTRACT FROM AUTHOR]

The application of chemical disinfectants in postharvest food processing facilities is important for the control of foodborne pathogen outbreaks. Similar to drinking water disinfection, food processors will need to optimize disinfectant exposures to balance pathogen inactivation against exposure to potentially toxic disinfection byproducts (DBPs). Since most disinfection research has focused on drinking water, this review summarizes research related to disinfection in food washing facilities, particularly by chlorination and ozonation. Although these disinfectants are also used for drinking water, the conditions are significantly different at food processing facilities. After a brief summary of foodborne pathogen outbreaks, this review describes food processing treatment trains, particularly the critical differences in conditions encountered relative to drinking water disinfection (e.g., short disinfectant contact times and high and variable disinfectant demands). The review discusses research related to pathogen inactivation and DBP formation by chlorine and ozone during washing of produce, meat and seafood. In particular, the research highlights the difficulty of inactivating pathogens on food, but the efficacy of these disinfectants for controlling pathogen cross-contamination through the washwater. While most research on food-associated DBPs has focused on the same, low molecular weight DBPs of interest in drinking water, these DBPs partition to the washwater. This review highlights the need for research on the initial transformation products of disinfectant reactions with biomolecules, since these products may present a risk for consumer exposure by remaining within the food. [ABSTRACT FROM AUTHOR]

Ozonation is a widely applied water treatment process, used for oxidation of contaminants, as well as for the disinfection of water. However, the conventional ozonation process demands a high energy requirement and deep tanks to ensure effective mass transfer and oxidation. Microbubble technologies have emerged which have the potential to improve gas-liquid contacting. Microbubbles have diameters of 1–100 µm, while conventional bubbles used in ozonation are between 2 and 6 mm. Microbubbles have many favorable characteristics that make them suitable for ozonation. In this review, the attributes of microbubbles for ozonation have been compared with those of conventional bubbles. The higher interfacial area and lower rise velocity of microbubbles compared with conventional bubbles means that ozone in the gas phase can be more efficiently transferred into the liquid phase. This is due to a higher contact time and increased contact area of the bubble with the bulk liquid. The analysis reveals that the volumetric mass transfer coefficient can be significantly enhanced through the use of microbubbles. In addition, the steady state dissolved ozone concentration was positively impacted by the use of microbubbles. Microbubbles were shown to be able to oxidize a broader range of organic compounds more quickly than for conventional bubbles. However, the review highlighted that comparison of microbubbles with conventional bubbles is not always carried out in a fair and consistent way with respect to reactor configuration. Requirements for future research, more consistent experimental comparisons and the steps needed to enable implementation of microbubbles have been discussed. Extensive comparison of microbubbles with conventional bubbles for ozonation. Ozone mass transfer enhanced through the use of microbubbles. Improved micropollutant removal when using microbubble ozonation. Opportunities for more efficient ozone reactor design using microbubbles. [ABSTRACT FROM AUTHOR]

Photocatalysis has attracted great attention because of its direct utilisation of sunlight to obtain various chemical reactions, causing water splitting, organic pollutant degradation, and water disinfection. Nanophotocatalysts can be employed for various applications, including hydrogen storage, green diesel production, fuel cell applications, industrial manufacturing methods, pharmaceutical industries, and catalytic degradation of contaminants/hazardous materials. Photocatalytic inactivation and removal of pathogenic viruses, antibiotic-resistant bacteria and antibiotic resistance genes can be considered as simple and effective technique with low-cost, eco-friendliness, and low energy consumption features. The high specific surface areas, abundant functional groups, large amounts of active sites are some advantages of the nanostructures for photocatalytic activity with high efficiency. However, some important limitations/drawbacks of nanophotocatalysts for industrial and commercial applications such as the low selectivity, aggregation/sedimentation, difficult separation, low-usage of visible light, fast charge recombination, and low migration potential of photogenerated electrons/holes are need to be comprehensively and analytically investigated and addressed by researchers. This critical review highlighted the recent advancements in photocatalytic disinfection of pathogenic viruses and antibiotic-resistant bacteria, focussing on the development of highly efficient nanophotocatalysts and their underlying mechanisms of inactivation/removal of these pathogens. [ABSTRACT FROM AUTHOR]

In this work, we developed a simple spectrophotometric strategy for BrO3− ions determination as a major water disinfection constituents in the mice's liver tissues by using pararosaniline (PRA). Mice were divided into seven main groups (6 doses): lowest dose KBrO3 (G1 0.01 mg L−1, G2 0.025 mg L−1 and G3 0.1 mg L−1), highest dose KBrO3 (G4 1 mg L−1, G5 10 mg·L−1 and G6 30 mg L−1) and control. All these groups maintained a dose-specific feeding for one month, just before the bromate assessment in mice's liver samples. The results revealed that groups of exposure to lower doses of drinking water did not detect the presence of BrO3− accumulated in the liver tissue during the study period (1–2 months). While, the BrO3− was detected in higher dosages for samples analyzed in first, second, third, fourth and fifth weeks (W1, W2, W3, W4, and W5). These results confirmed that the higher BrO3− dosages (1, 10, and 30 mg L−1) were fatal if introduced in drinking water and could accumulate in the liver tissues both for mice and for human. Detection the accuracy of the method for recovery of bromate ions in liver samples (N = 5) was found to be more than 95%. Relative standard deviations (RSDs) were found to be less than 2.0% confirming the reproducibility of the assay technique. [ABSTRACT FROM AUTHOR]

Diarrheal illnesses claim the lives of hundreds of thousands of children each year, most of whom live in rural and low-income communities. Ceramic Water Filters (CWF) are widely regarded as one water treatment technology with the potential to increase access to safe drinking water. While physical filtration mechanisms are a key contributor to improving the water safety, silver is commonly added to improve disinfection performance. Therefore, a thorough review of silver disinfection efficacy and disinfection mechanisms in relation to CWFs are critically important. This paper reviews filter mechanisms and efficacy for bacteria removal for cases with and without silver addition. Method of silver application (dipping, painting, or co-firing) is assessed. Silver release and retention is discussed. The findings from this paper illustrate that eluted silver contributes to filter bacterial disinfection. However, more research is needed on the impact of silver on preventing a "slime layer" on the filter surface and receptacle. Silver application method, water quality and particle characteristics were demonstrated to impact release. For instance, co-firing results in the most consistent elution over time but at lower concentrations than other methods. Finally, research into alternative metals to silver for enhanced disinfection present emerging opportunities within the CWF field. [ABSTRACT FROM AUTHOR]

Water disinfection processes such as sedimentation, filtration, and chemical or biological degradation are not fully capable of destroying emerging contaminants or certain types of bacteria. Nanotechnology can potentially be employed to address these challenges posed by various contaminants and microorganisms. This paper highlights the advanced nanomaterials and approaches for the removal of pollutants and contaminant from aqueous solutions, functionalized nanostructured materials and processes in water and wastewater treatment technologies, removal/recovery of heavy metals by amorphous metal oxide nanoparticles, nanoparticle-assisted nanofiltration, and development of innovative and natural-based nanosorbents for water treatment. In this review, recent nanotechnological advances and deployment of polymeric nanoadsorbents for the removal of toxic contaminants/pollutants from wastewater streams are discussed. Nanomaterials and nano-based strategies are summarized for water treatment [ABSTRACT FROM AUTHOR]

While chlorination is critical for water disinfection, a knowledge gap includes the nature of free residual chlorine (FRC) decay, which was investigated using four physical methods (SSA, SSR with and without a lid, heating, and incubator shaker). Keeping water samples in SSA and SSR methods for 24 h resulted in the FRC decline by 62% and 51%, respectively. The heterotrophic plate count (HPC) increased significantly between initial (3.17 ± 2.6–3.82 ± 1.1 CFU/mL) and final samples (6.7 ± 1.5–94.7 ± 4.72 CFU/mL) for both SSA and SSR methods. Thermodynamic behavior (ΔH versus ΔG) of FRC decay of the different methods was characterized. [ABSTRACT FROM AUTHOR]

Water disinfection using visible light-active photocatalyst has recently attracted more attention due to its potential to inactivate microbes. In this study, we have investigated the efficiency of photocatalysis (TiO2/UVA) on the inactivation of Pseudomonas aeruginosa and the attenuation of its virulence factors. For this aim, the photocatalytic effects of TiO2/UVA on the cultivability and viability of P. aeruginosa were investigated. Furthermore, during the photocatalysis, the morphology of the bacterial cells was examined by atomic force microscopy (AFM) while the virulence factors were assessed by protease and lipase activities in addition to the mobility and communication of cells. The results revealed that during the photocatalysis the bacterial cells lost their cultivability and viability on agar under the action of the reactive oxygen species generated by the photocatalytic reaction. In addition, AFM observations have shown a damage of the bacterial membrane and a total disruption of the bacterial cells. Moreover, the major virulence factors such as biofilm, lipase and protease expression have been markedly inhibited by TiO2/UVA treatment. In addition, the bacteria lost their ability of communication 'quorum sensing' and mobility with twitching and swarming types after 60 min of photocatalytic treatment. Accordingly, TiO2/UVA is an effective method to reduce P. aeruginosa virulence and to prevent biofilm formation. [ABSTRACT FROM AUTHOR]