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Inorganic arsenic (As), a known carcinogen and major contaminant in drinking water, affects over 140 million people globally, with levels exceeding the World Health Organization's (WHO) guidelines of 10 μg L−1. Developing innovative technologies for effluent handling and decontaminating polluted water is critical. This paper summarizes the fundamental characteristics of chitosan-embedded composites for As adsorption from water. The primary challenge in selectively removing As ions is the presence of phosphate, which is chemically similar to As(V). This study evaluates and summarizes innovative As adsorbents based on chitosan and its composite modifications, focusing on factors influencing their adsorption affinity. The kinetics, isotherms, column models, and thermodynamic aspects of the sorption processes were also explored. Finally, the adsorption process and implications of functionalized chitosan for wastewater treatment were analyzed. There have been minimal developments in water disinfection using metal-biopolymer composites for environmental purposes. This field of study offers numerous research opportunities to expand the use of biopolymer composites as detoxifying materials and to gain deeper insights into the foundations of biopolymer composite adsorbents, which merit further investigation to enhance adsorbent stability. [ABSTRACT FROM AUTHOR]

Recent advancements in membrane technologies and disinfection methods have enhanced drinking water quality significantly. However, microorganisms, including free-living amoebae (FLA), persist and pose potential threats to humans. FLA are linked to severe neuro-ophthalmic infections and serve as hosts of pathogenic bacteria. This study examined FLA presence in chlorinated and ultrafiltration drinking water and evaluated chlorine's disinfectant. Of 115 water samples, 21 tested positive for Acanthamoeba sp., Allovahlkampfia sp., and Vermamoeba vermiformis, originating from chlorinated sources. FLA trophozoites withstand temperatures up to 37 °C, while the cysts tolerate heat shocks of 60–70 °C. Trophozoites are susceptible to 5 mg L−1 chlorine, but cysts remain viable at concentrations up to 10 mg L−1. FLAs' survival in chlorinated waters is attributed to high cyst tolerance and lower residual chlorine concentrations. These findings highlight the need for ultrafiltration or enhanced chlorination protocols to ensure safer drinking water. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) is a mild, environmentally friendly, and versatile oxidizer. The current main production process, the anthraquinone method, has high energy consumption and pollution. However, the photocatalytic production of H2O2 is considered to be a green and sustainable process. In this paper, the research progress of photocatalytic production of H2O2 was reviewed. Firstly, the basic principle of photocatalytic production of H2O2 and the three production pathways, namely, oxygen reduction, water oxidation, and dual-channel were introduced. Then, advanced photocatalysts for H2O2 production were introduced with emphasis. From the reactants and products, several new reaction systems and improvement strategies were introduced, including the construction of a spontaneous system without a sacrifice agent, a gas–liquid–solid three-phase system, and inhibition of H2O2 decomposition. The in-situ applications of photocatalytic H2O2 production in the environmental field, including in-situ disinfection and in-situ degradation of pollutants are discussed. Finally, the research progress and future research directions in this field are summarized and prospected. [ABSTRACT FROM AUTHOR]

Chlorinated organic compounds (COCs) are typical refractory organic compounds, having high biological toxicity. These compounds are a type of pervasive pollutants that can be present in polluted soil, air, and various types of waterways, such as groundwater, rivers, and lakes, posing a significant threat to the ecological environment and human health. Bioelectrochemical systems (BESs) are an effective strategy for the degradation of bio-refractory compounds. BESs improve the waste treatment efficiency through the application of weak electrical stimulation. This review discusses the processes of BESs configurations and degradation performances in different environmental media including wastewater, soil, waste gas and groundwater. In addition, the degradation mechanisms and performance-enhancing additives are summarized. The future challenges and perspectives on the development of BES for COCs removal are briefly discussed. [ABSTRACT FROM AUTHOR]

Although, different plant species were utilized for the fabrication of polymorphic, hexagonal, spherical, and nanoflower ZnO NPs with various diameters, few studies succeeded in synthesizing small diameter ZnO nanorods from plant extract at ambient temperature. This work sought to pioneer the ZnO NPs fabrication from the aqueous extract of a Mediterranean salt marsh plant species Limoniastrum monopetalum (L.) Boiss. and assess the role of temperature in the fabrication process. Various techniques have been used to evaluate the quality and physicochemical characteristics of ZnO NPs. Ultraviolet–visible spectroscopy (UV–VIS) was used as the primary test for formation confirmation. TEM analysis confirmed the formation of two different shapes of ZnO NPs, nano-rods and near hexagonal NPs at varying reaction temperatures. The nano-rods were about 25.3 and 297.9 nm in diameter and in length, respectively while hexagonal NPs were about 29.3 nm. The UV–VIS absorption spectra of the two forms of ZnO NPs produced were 370 and 365 nm for nano-rods and hexagonal NPs, respectively. FT-IR analysis showed Zn–O stretching at 642 cm−1 and XRD confirmed the crystalline structure of the produced ZnO NPs. Thermogravimetric analysis; TGA was also used to confirm the thermal stability of ZnO NPs. The anti-tumor activities of the two prepared ZnO NPs forms were investigated by the MTT assay, which revealed an effective dose-dependent cytotoxic effect on A-431 cell lines. Both forms displayed considerable antioxidant potential, particularly the rod-shaped ZnO NPs, with an IC50 of 148.43 µg mL−1. The rod-shaped ZnO NPs were superior candidates for destroying skin cancer, with IC50 of 93.88 ± 1 µg mL−1 ZnO NPs. Thus, rod-shaped ZnO NPs are promising, highly biocompatible candidate for biological and biomedical applications. Furthermore, both shapes of phyto-synthesized NPs demonstrated effective antimicrobial activity against various pathogens. The outcomes highlight the potential of phyto-synthesized ZnO NPs as an eco-friendly alternative for water and wastewater disinfection. [ABSTRACT FROM AUTHOR]

It is well-known that the equilibrium isotope fractionation of mercury (Hg) includes classical mass-dependent fractionations (MDFs) and nuclear volume effect (NVE) induced mass-independent fractionations (MIFs). However, the effect of the NVE on these kinetic processes is not known. The total fractionations (MDFs + NVE-induced MIFs) of several representative Hg-incorporated substances were selected and calculated with ab initio calculations in this work for both equilibrium and kinetic processes. NVE-induced MIFs were calculated with scaled contact electron densities at the nucleus through systematic evaluations of their accuracy and errors using the Gaussian09 and DIRAC19 packages (named the electron density scaling method). Additionally, the NVE-induced kinetic isotope effect (KIE) of Hg isotopes are also calculated with this method for several representative Hg oxidation reactions by chlorine species. Total KIEs for 202Hg/198Hg ranging from − 2.27‰ to 0.96‰ are obtained. Three anomalous 202Hg-enriched KIEs (δ202Hg/198Hg = 0.83‰, 0.94‰, and 0.96‰,) caused by the NVE are observed, which are quite different from the classical view (i.e., light isotopes react faster than the heavy ones). The electron density scaling method we developed in this study can provide an easier way to calculate the NVE-induced KIEs for heavy isotopes and serve to better understand the fractionation mechanisms of mercury isotope systems. [ABSTRACT FROM AUTHOR]

Environmental pollution caused by toxic pharmaceutical ingredients and other human hazards is a sign of danger for the biological life on earth. Considering the importance of green revolution including the green pharmaceutical industries, the scientists and environmental protection agencies recently highlighted green chemical ingredients and biodegradable products as extreme protection line for our environment. An electronic search was conducted utilizing Science Finder, Medline, Scopus, and Google Scholar to gather English-language articles pertaining to chemical environmental hazards and green foot printing. Our study explored that environmental risks are majorly caused by emitted chemical pharma ingredients and non-biodegradable products such as antibiotics, analgesics, antidepressants, antihypertensive, contraceptives, steroids, hormones, and polychlorinated dioxins. Although the detected amounts of these ingredients are very small, however, such minute quantities are enough to be considered toxic for human, animal, and aquatic lives. Moreover, a significant number of drugs undergo incomplete metabolism in both humans and animals, contributing to environmental hazards alongside the substantial volume of non-biodegradable industrial waste. The current review highlights the impact of pharmaceutical waste on environmental safety, health of living world, and the recent achievements in adopting green pharma as an alternative strategy. Additionally, keeping in view the potential risk of production of toxic ingredients and emission by conventional chemical methods, this review further focuses on the footprint of green (plant source) synthesized ingredients for utilization in various pharma sectors and their possible implication in environmental protection. [ABSTRACT FROM AUTHOR]

Designing materials capable of disinfecting water without releasing harmful by-products is an ongoing challenge. Here, we report a novel polycationic sponge material synthesized from chitosan derivatives and cellulose fibers, exhibiting antibacterial properties. The design of such material is based on three key principles. First, the formation of a highly porous structure through cryogelation for an extensive surface area. Second, the incorporation of cationic quaternary ammonium moieties onto chitosan to enhance bacterial adsorption and antibacterial activity. Lastly, the reinforcement of mechanical properties through integration of cellulose fibers. The presented sponge materials exhibit up to a 4-log (99.99%) reduction within 6 h against both gram-positive B. subtilis and gram-negative E. coli. Notably, QCHI90/Cell, with the highest surface charge, exhibits a 2–4.5 log reduction within 1 h of incubation time. The eco-friendly synthesis from water and readily available biomaterials, along with cost-effectiveness and simplicity, underscores its versatility and feasibility of upscaling. Together with its outstanding antibacterial activity, this macroporous biomaterial emerges as a promising candidate for water disinfection applications. [ABSTRACT FROM AUTHOR]

Inorganic chlorine is susceptible to water and soil salinization due to its non-degradability and high mobility. To clarify the environmental risks associated with the active inorganic chlorine in municipal solid waste (MSW), the specific characteristics and contributions of inorganic chlorine in different MSW categories were investigated in this study. MSW samples were collected from eight representative waste classification residential areas in Hangzhou, China. It was found that the inorganic chlorine content in different MSW categories varied significantly (0–113 mg/g). Perishable waste, paper, and plastic were found to be the main sources of inorganic chlorine in MSW. A four-category classification system was used to quantify the contribution of inorganic chlorine from each waste category. It was found that the misclassification of inorganic chlorine contributions from perishable waste and other waste accounted for 51.96% and 48.04%, respectively. However, when correctly classified into the four-category system, their contributions were reduced to 67.14% and 30.65%, respectively. Therefore, MSW classification showed a significant reduction in the overall contribution of inorganic chlorine. The misclassification reduces the contribution of inorganic chlorine to 48.04%, while correct classification increases the reduction to 69.35%. [ABSTRACT FROM AUTHOR]

Benzophenone-4 (BP-4) is one of the UV filters widely used in personal care products (PCPs). BP-4 has been identified as an emergent contaminant detected in influent and effluent of wastewater treatment plants (WWTPs) at high concentrations showing that conventional treatment is unable to remove it, subsequently, the presence of BP-4 in surface water is inevitable. In this study, we focus on the degradation of this compound by chlorine, and we report the efficiency of its removal from water by applying two advanced oxidation processes UV/TiO2 and UV/H2O2 aiming to achieve a superior mineralization result. The study was performed in purified water (pH = 6.5, temperature = 25 °C) with an initial concentration of BP-4 similar to that detected in WWTPs (10 mg/L). The results showed that 76% of BP-4 was degraded after 80 min of reaction with chlorine leading to the formation of one by-product persistent in the solution. The oxidation by UV/TiO2 and UV/H2O2 led to a total removal of BP-4 and their generated by-products after 50 and 10 min of reactions, respectively. The kinetic study showed that BP-4 degradation by UV/H2O2 and UV/TiO2 followed pseudo-first-order reaction kinetics and the apparent rate constants (kapp) were determined to be 0.48 min−1 and 0.08 min−1, respectively. The degradation of BP-4 by chlorine followed first-order reaction kinetics with kapp = 0.02 min−1. The identification of by-product structures was performed using liquid chromatography with electrospray ionization and tandem mass spectrometry (MS/MS. The fragmentation of BP-4 and by-product ions at different collision energies allowed to propose the pathways of degradation and to predict the toxicity using a silico toxicity program which confirmed a higher toxicity of all generated by-products. [ABSTRACT FROM AUTHOR]

Substitution reactions in carbocyanine dyes are used to determine nucleophilic compounds. The interaction of a chlorine-containing carbocyanine dye with a number of medicinal substances is studied. It is shown that, in the reaction with isoniazid in the presence of a surfactant, this dye selectively changes color from yellow-green to violet. The formation of a product of the substitution of chlorine for isoniazid is proven by chromatography–mass spectrometry. The reaction proceeds in 20 min in the presence of 1 mM cetyltrimethylammonium bromide. The limit of detection for isoniazid in water by the photometric method is 10 μg/mL and in diluted artificial urine using fluorimetry, 0.3 μg/mL. The procedure does not use full-spectrum equipment, which simplifies the determination. [ABSTRACT FROM AUTHOR]

A lab-scale reactor with a fixed-bed hematite catalyst for the effective decomposition of H2O2 and bacteria inactivation was designed. The bactericidal effect is the largest at a low initial bacterial count of 2·103 CFU/L, which is typical for natural surface waters. When using a 5 mM H2O2 solution and a residence time of 104 min, the reduction in the number of E. coli bacteria is about 3.5-log. At a higher initial bacterial count of 1-2·104 CFU/L, a 5 mM H2O2 solution reduces the bacteria number by about 4-log. The H2O2 decomposition follows the log-linear kinetics of a first-order reaction while the bacterial inactivation does not. The kinetics of bacterial inactivation was described using the Weibull model in the modified form: log10(N0/N) = b · tn. The values of the non-linearity parameter n were found to be lower than 1, indicating that bacterial inactivation slows down over time. With increasing initial H2O2 concentration, the rate parameter b increases while the non-linearity parameter n decreases. With increasing temperature, both parameters increase. The stability of the catalyst has been proved by XRD, FTIR, SEM, and ICP-OES. The concentration of iron leaching into water during disinfection is much lower than the limit declared by WHO for iron in drinking water. The results show that technical-grade hematite is a promising Fenton-like catalyst for water disinfection. The fixed-bed reactor can be the basis of the mobile installations for water purification in emergencies. [ABSTRACT FROM AUTHOR]

Water cleaning can be provided in batch mode or in continuous flow. For the latter, some kind of framework must withhold the cleaning agents from washout. Porous structures provide an ideal ratio of surface to volume for optimal access of the water to active sites and are able to facilitate rapid and efficient fluid transport to maintain a constant flow. When functionalized with suitable photoactive agents, they could be used in solar photocatalytic disinfection. In this study, we have used the sugar cube method to fabricate PDMS-based materials that contain three different classes of photosensitizers that differ in absorption wavelength and intensity, charge as well as in ability to generate singlet oxygen. The obtained sponges are characterized by scanning electron microscopy and digital microscopy. Archimede's method was used to measure porosity and density. We show that the materials can absorb visible light and generate Reactive Oxygen Species (ROS) that are required to kill bacteria. The disinfection ability was tested by examining how irradiation time and operation mode (batch vs. flow) contribute to the performance of the material. The current strategy is highly adaptable to other (medium) pressure-driven flow systems and holds promising potential for various applications, including continuous flow photoreactions. [ABSTRACT FROM AUTHOR]

Nitrogen-containing disinfection by-products (N-DBPs) produced in the process of drinking water disinfection are widely concerning due to the high cytotoxicity and genotoxicity. It is due to the difficulty of natural degradation of N-DBPs in water and the fact that conventional treatment systems do not effectively treat N-DBPs in drinking water. In this study, N-nitrosopyrrolidine (NPYR) in water was electrocatalytically degraded by a three-dimensional electrode reactor (3DER). This system applied graphite plates as anode and cathode. The granular activated carbon (GAC) was used as third electrode. The degradation of NPYR using a continuous flow three-dimensional electrode reactor was investigated by examining the effects of flow rate, current density, electrolyte concentration, and pollutant concentration on the degradation efficiency, energy consumption, and reaction kinetics of GAC particle electrodes. The results showed that the optimal operating conditions were flow rate = 0.45 mL/min, current density = 6 mA/cm2, Na2SO4 concentration = 0.28 mol/L, and NPYR concentration = 20 mg/L. Under optimal conditions, the degradation of NPYR exceeded 58.84%. The main contributor of indirect oxidation was deduced from free radical quenching experiments. NPYR concentration was measured by GC–MS with DB-5 capillary column, operating in full scan monitoring mode for appropriate quantification of NPYR and intermediates. Based on the identification of reaction intermediates, a possible pathway for the electrochemical oxidation of NPYR on GAC particle electrodes was proposed. [ABSTRACT FROM AUTHOR]

Cyanotoxins, produced from cyanobacteria-dominated harmful algal blooms (cHABs), pose a threat to ecosystems, as well as drinking water systems. Disinfection via chlorine is the last step in a conventional drinking water treatment plant (DWTP) to remove any extracellular toxins present in the water. This research investigated the impact of pH on the oxidation of different saxitoxin (STX) and anatoxin-a (ANTX-a) concentrations in the post-filtration water collected from two DWTPs. STX degradation was the most efficient at higher pH levels. For instance, pH 6 resulted in 13–43% degradation and pH 9 resulted in 56–74% degradation of STX. The presence of microcystin-LR (MC-LR) did not significantly inhibit the removal of STX, with STX removal (at pH 6–8) higher than when MC-LR was not present. A dose of 1.8 mg/L chlorine and 235-min contact achieved 38% removal of ANTX-a while the dose of 3.2 mg/L chlorine and the contact time of 118 min removed 75% of ANTX-a at pH 6. [ABSTRACT FROM AUTHOR]

Water treatment for most public pools involves disinfection with active chlorine leading to the formation of disinfection by-products (DBPs). Among them, nitrogen-containing compounds (N-DBPs) having increased toxicity and adverse effects on human health are of the greatest concern. Being the major component of various body washers for swimmers, cocamidopropyl betaine (CAPB) represents a potential and still underestimated anthropogenic precursor of N-DBPs in pool water. The purpose of this study was to investigate CAPB transformation pathways and mechanisms under the aqueous chlorination conditions. High-performance liquid and two-dimensional gas chromatography hyphenated with high-resolution mass spectrometry were used for the search and tentative identification of the primary and final CAPB transformation products. A wide range of DBPs containing up to five chlorine atoms including these in combination with hydroxyl and additional carbonyl groups has been revealed in model chlorination experiments for the first time. The proposed mechanism of their formation involves nucleophilic substitution of the secondary amide hydrogen atom at the first stage with subsequent free radical and electrophilic addition reactions resulting in non-selective introduction of halogen atoms and hydroxyl groups in the alkyl chain. The deep transformation products include short-chain chlorinated hydrocarbons and their oxidation products as well as dimethylcarbamoyl chloride possessing high toxicity and carcinogenic properties. Targeted analysis of real swimming pool water samples confirmed the results of model experiments enabling semi-quantitative determination of CAPB (0.8 µg L–1) and 18 primary DBPs, including 10 chlorine-containing compounds with the total concentration of 0.1 µg L–1. Among them, monochloro (50%) and hydroxydichloro (25%) derivatives predominate. The toxicity and health of the main DBPs has been estimated using QSAR/QSTR approach. Thus, the possibility of formation of new classes of potentially toxic chlorine-containing DBPs associated with the widespread use of detergents and cosmetics was shown. [ABSTRACT FROM AUTHOR]

One novel method for disinfecting water is the use of silver nanoparticles. The aim of this work was to prepare a granular antibacterial composite based on chitosan boehmite, enhanced with silver nanoparticles (Ag-CHB), and evaluate its antibacterial activity. The composite was prepared by the sol-gel method and characterized by FTIR, AFM, FESEM, EDS, and UV-VIS techniques. The topographical study using the AFM revealed a clear change in the surface shape of the composite after it was reinforced with silver nanoparticles. Additionally, FESEM images displayed that the particles of chitosan-boehmite supported with silver nanoparticles are polygonal granules with an average size of 61.93 nm. The EDX analysis showed that the percentage of silver atoms in the composite is about 1.24 wt%. The results of FTIR indicated that chitosan's functional groups have specific interactions with silver and aluminum. According to XRD analysis, boehmite nanocrystals are orthorhombic, with a mean crystal size of 30 nm was confirmed. Optical characterization of the colloidal silver nanoparticles by UV-VIS technique revealed the presence of a clear surface plasmon band, with a peak wavelength of 389 nm. The stability in the water of the prepared composite was verified by the swelling test, and the swelling index was about 11.82%. The ability of the composite to kill bacteria was also verified before and after being reinforced with silver nanoparticles by the agar well diffusion method. The composite reinforced with silver nanoparticles showed antibacterial activity against E. coli, with a 10 mm inhibition zone diameter. Overall, these results indicated that the Ag-CHB composite has the potential for water disinfection and incorporation into household filtration systems. Highlights: Chitosan-boehmite, enhanced with silver nanoparticles, is synthesized by the sol-gel method. The successful formation of the composite was corroborated through several techniques. The composite exhibits full stability in water and demonstrates antibacterial properties. Chitosan-boehmite enhanced with silver nanoparticles granules, can be used in multimedia household filters. [ABSTRACT FROM AUTHOR]

Production and processing of oil and gas are associated with the formation of a huge volume of wastewater of complex composition disposed in different ways after thorough treatment. Environmental control of the composition and degree of purification of oil- and gas-bearing wastewater requires using effective methods for determining various pollutants, including chloride and fluoride. The object of the study was a sample of wastewater from the largest gas field Mustakillikning 25 yilligi in the Surkhandarya region of the Republic of Uzbekistan. It was shown that the sample was salty (dry residue was 34.1–31.7 g/dm3) and had a neutral reaction. The method of atomic emission analysis of water revealed high concentrations of potassium, sodium, and sulfur, a significant amount of calcium and magnesium, and a significantly smaller amount of a number of other elements contained in water. Study of various methods of sample preparation for ionometric measurements of chloride ion shows that a significant proportion of chlorine is bound with organic components of water. It is shown that boiling (~100°C) or fusing at 800–850°C with NaOH eliminates the interfering effect of accompanying components (sulfur, iodine, and organic matter) on the chloride determination. The results obtained provide quantitative determination of the total content of chlorine in water both in the form of a free chloride ion and in a bound state, probably in the composition of organochlorine compounds. The presence of fluorine in the organic part of the sample has not been revealed. The possibility of using a single sample preparation (boiling or fusing) for the determination of both chloride and fluoride ions has been shown. The interfering effect of the accompanying elements upon fluorine determination is masked by a buffer solution regulating the total ionic strength. The developed procedures are easy to use, selective, and cost-effective. The trueness and precision of the developed techniques have been evaluated and proved using a method of varying the sample volume. [ABSTRACT FROM AUTHOR]

By the method of laboratory modeling, it was found that 4-chloraniline transformation in natural water at a concentration of 10 mg/L is described by a first-order equation. The activation parameters of this reaction indicate in favor of its biochemical mechanism, and the chemical (non-enzymatic) mechanism does not play a significant role in this process. The results of IR spectroscopic examination of the decomposition products of 4-chloraniline in natural water indicate the absence of an amino group in them and the preservation of most chlorine atoms. [ABSTRACT FROM AUTHOR]

The study of groundwater hydrogeochemistry is of great significance to the development, utilization and protection of regional groundwater resources. In this paper, a complete and comprehensive analysis of three runoff zones is carried out in the Fengfeng mining area of Handan City, Hebei Province, China. The Piper trilinear diagram is used to analyze the types of karst groundwater hydrochemistry, the ionic proportionality coefficient method is used to analyze the sources of groundwater chemistry and the formation process, the chlorine-alkali index is used to react to the exchange reactions between cations, and PHREEQC software is also used to invert the groundwater simulation. The results are: the type of karst water hydrochemical in the study area is mainly HCO3·SO4–Ca·Mg; the ions are mainly influenced by rock halite, carbonate, sulphate, silicate and cation exchange; in the groundwater runoff zone, aragonite, calcite and dolomite are in saturated state, while gypsum and rock halite are in unsaturated state. The study of karst groundwater hydrochemical types, analysis of water-rock interaction and exploration of hydrogeochemical evolution mechanisms are intended to provide reference for karst water supply security and water resources utilization. [ABSTRACT FROM AUTHOR]

Water heating and disinfection with reduced energy and CO2 footprint demands new and efficient materials for solar-thermal conversion technologies. Here, we demonstrate nanostructured porous hard-carbon florets (NCF) as effective solar absorber coating achieving excellent photon thermalization efficiency (87%). Functional NCF coating on three-dimensionally tapered helical solar receivers generate high surface temperatures (up to 95 °C). Such 'green-heat' is channeled to heat water up to 82 °C that simultaneously results in water disinfection through thermal shock. Untreated lake-water with high turbidity (5 NTU), high bacterial load (106 CFU mL−1) and pathogenic fungi is effectively disinfected in a continuous flow process. Translating this, a fully automated SWAP prototype (solar water antimicrobial purifier), delivers bacteria free hot water at an output capacity of 42 L m−2 day−1 with the lowest CO2 footprint (5 kg L−1) in comparison to all other existing approaches (>40 kg L−1). [ABSTRACT FROM AUTHOR]

The effect of UVC light (λ = 254 nm) on chlorine generation through a sequential combination of three wastewater treatments was evaluated to disinfect and mineralize carwash wastewater. Electrocoagulation, electrooxidation, and catalysis processes were sequentially performed in the presence and absence of UVC radiation. Toxicity changes during the photoEC process were detected using Artemia salina as a model organism, which improves the LD50 of the raw carwash effluent from 13.4 to 52.1. Disinfection trials showed a colony-forming unit decrease by approximately 90%; however, the mineralization degree was only 7%. The subsequent electrooxidation treatment showed that the IrO2-RuO2 anode generated the highest concentration of active chlorine species (400 mg L−1 at pH = 3). However, during UVC irradiation, a better efficiency in producing •OH radicals was observed. Thus, the total organic carbon abatement using photoelectrocoagulation followed by photoelectrooxidation of carwash wastewater was 57%. As a final step, photocatalysis using crystalline TiO2 increased the mineralization degree, reaching 80% at the end of the tandem protocol. Thus, it was proposed that the sequential UVC-based treatments degrade organic matter and reduce pathogens in a raw carwash effluent in the presence of chloride ions. [ABSTRACT FROM AUTHOR]

Most people in developing countries live in rural areas where getting clean, drinkable water is difficult. The hygienic state of the water supplies used for a drink is contaminated with pathogenic bacteria, protozoa, or viruses. Water quality at the point of delivery is not always optimal, and the amount of chlorine concentration in the water is not proportional to the water volume. The low amount of chlorine in the water makes re-contamination very likely to occur. Despite receiving well-treated water from supply reservoirs, the water storage tank (jerrycan) used for storing water at their home grows pathogens over time. Thus, the main goal of this research was to find a solution for giving people access to clean drinking water. This paper explains the measures taken to treat water by designing small-scale automated water disinfection systems for the rural community. The system disinfects the water with chlorine in an appropriate amount depending on the water volume without human intervention. A two-pilot village around Hawassa city was selected, and the water quality in 200 households was tested by measuring the content of the free residual chlorine. The test result is below average, and the societies in these villages are vulnerable to pathogenic diseases. However, after piloting the designed automated disinfection system, the water quality test showed a satisfactory result. Numerous microbiological tests carried out have shown a 99% decrease in coliforms if water is treated with the automated disinfection system. [ABSTRACT FROM AUTHOR]

An effective, polysaccharide-based water-soluble disinfectant was produced by chemically modifying gum arabic (GA) through various substitution reactions. This food-grade and non-toxic plant polysaccharide was subjected to tosylation, azidation and reduction to substitute the hydroxyl functionality with amino groups via the formation of tosyl and azide derivatives of GA. The reactions were followed by C, H, N and S analysis, FT-IR, 1H- and 13C-NMR spectroscopy. The degrees of substitution in the prepared gum derivatives, DSTos (= 1.02), DSAzi (= 0.97) and DSAmi (= 0.77) were calculated from the elemental compositions. The amino-functionalized gum was quaternized with different amounts of iodomethane to produce polycationic GA derivatives with degrees of quaternization (DQ) calculated to be 35.2 and 58.3%. The N-trimethyl ammonium iodide derivatives of GA (QrGA) showed significant antibacterial activity against Escherichia coli, Staphylococcus aureus and Bacillus subtilis. The minimum inhibitory concentration values of QrGA derivatives varied with bacterial species and decreased as DQ increased. The disinfection efficiency of the produced quaternized gum derivatives was also evaluated by determining the Riedeal-Walker phenol coefficient that was found to be higher than unity (1.4–1.6) indicating a good bactericidal efficacy. The developed quaternary ammonium iodide derivative of gum arabic has the potential to be used as an effective disinfectant in aqueous medium. [ABSTRACT FROM AUTHOR]

One of the innovative approaches to supplying water demands for irrigation and recreational purposes is the treatment and reuse of greywater. However, during the coronavirus pandemic, greywater has the potential to be polluted by SARS-CoV-2. Therefore, it is unsafe to reuse it during the peak of the COVID-19 outbreak. In this research, a membrane bioreactor combined with an ultraviolet disinfection system is applied to treat the greywater and remove the SARS-CoV-2 virus up to the required quality for irrigation or flush tank purposes. The results showed membrane bioreactor could remove 94.3 ± 1.2% of initial chemical oxygen demand and be partially successful in virus removal. Fifty percent of secondary treated effluent samples were still positive for SARS-CoV-2 RNA. The results also illustrated that ultraviolet disinfection could reduce faecal and total coliform by more than 99% and eliminate the SARS-CoV-2 virus. The tertiary treated effluent biochemical oxygen demand, chemical oxygen demand, and total coliform were 1.7 ± 0.2 mg/l, 18 ± 1.2 mg/l, and below 3 MPN/100 mL, respectively. Moreover, all of the samples of the tertiary treated effluent were negative for coronavirus RNA. Therefore, the tertiary treated effluent characteristic satisfied Iran's standards for wastewater reuse in irrigation. [ABSTRACT FROM AUTHOR]

Water disinfection is conventionally achieved by oxidation or irradiation, which is often associated with a high carbon footprint and the formation of toxic byproducts. Here, we describe a nano-structured material that is highly effective at killing bacteria in water through a hydrodynamic mechanism. The material consists of carbon-coated, sharp Cu(OH)2 nanowires grown on a copper foam substrate. We show that mild water flow (e.g. driven from a storage tank) can efficiently tear up bacteria through a high dispersion force between the nanotip surface and the cell envelope. Bacterial cell rupture is due to tearing of the cell envelope rather than collisions. This mechanism produces rapid inactivation of bacteria in water, and achieved complete disinfection in a 30-day field test. Our approach exploits fluidic energy and does not require additional energy supply, thus offering an efficient and low-cost system that could potentially be incorporated in water treatment processes in wastewater facilities and rural communities. Common methods for water disinfection involve oxidation or irradiation, and are often associated with a high carbon footprint and formation of toxic byproducts. Here, the authors describe a nano-structured material that is highly effective at killing bacteria in water through a hydrodynamic mechanism driven by mild water flow, in the absence of additional energy supply. [ABSTRACT FROM AUTHOR]

The emerging global problem of antimicrobial resistance needs immediate attention. In this regard, this work demonstrates the use of expanded polystyrene waste in the synthesis of immobilized photocatalytic films for the treatment of antibiotics as well as for bacterial disinfection. A boron–cerium codoped TiO2 catalyst (of specific composition: B0.8Ce0.2TiO2) was immobilized in an expanded polystyrene (EPS) film prepared from waste EPS beads. These films were studied for the degradation of ciprofloxacin (CIP) and disinfection of E. coli under sunlight. The film with a catalyst loading of 20 wt% showed a maximum degradation of 89% in 240 min with a corresponding TOC reduction of 84%. A 7.4 and 6.3 log reduction from the bacterial inactivation studies in the presence and absence of antibiotics, respectively, was obtained. The EPS film was stable after five times of reuse, and no significant chemical changes in the used film were observed from FTIR analysis. The average thickness of the prepared film was found from FESEM analysis to be 1.09 mm. These EPS films were also tested for degradation of other antibiotics, such as norfloxacin, levofloxacin and moxifloxacin. The EPS films were tested in two different reactor volumes at optimum conditions. Also, the effectiveness of B0.8Ce0.2TiO2/EPS film in real water samples indicates its potential in large-scale and real-world applications. Thus, these B0.8Ce0.2TiO2/EPS films can be effectively employed for both degradation of ciprofloxacin and the disinfection of E. coli under solar light to solve the increasing problem of antimicrobial resistance. [ABSTRACT FROM AUTHOR]

Electrochemical chlorine evolution reaction is of central importance in the chlor-alkali industry, but the chlorine evolution anode is largely limited by water oxidation side reaction and corrosion-induced performance decay in strong acids. Here we present an amorphous CoOxCly catalyst that has been deposited in situ in an acidic saline electrolyte containing Co2+ and Cl- ions to adapt to the given electrochemical condition and exhibits ~100% chlorine evolution selectivity with an overpotential of ~0.1 V at 10 mA cm−2 and high stability over 500 h. In situ spectroscopic studies and theoretical calculations reveal that the electrochemical introduction of Cl- prevents the Co sites from charging to a higher oxidation state thus suppressing the O-O bond formation for oxygen evolution. Consequently, the chlorine evolution selectivity has been enhanced on the Cl-constrained Co-O* sites via the Volmer-Heyrovsky pathway. This study provides fundamental insights into how the reactant Cl- itself can work as a promoter toward enhancing chlorine evolution in acidic brine. Achieving stable and selective chlorine production is of high interest yet challenging. Here the authors report an amorphous CoOxCly catalyst prepared by in situ electrodeposition in acidic saline electrolyte which shows ~100% chlorine evolution selectivity with low overpotential and high stability over 500 h. [ABSTRACT FROM AUTHOR]

Parabens are ubiquitous, being found in surface waters around the world. Although little is known about the release of paraben transformation products and fate of transformation products in surface water. This study evaluates both parabens and paraben transformation products in the Brazos River upstream and downstream of a wastewater facility located in Waco, Texas. Concentrations of thirteen compounds were reported in this study, five parent parabens and eight paraben disinfection by-products. Analyte concentrations were spatially evaluated to determine if release of wastewater effluent affects their concentrations in the river. Two Brazos River tributaries were also sampled to determine if they released parabens and related compounds to the Brazos. Sampling occurred weekly for one year with at least 40 samples collected at each site. Analyses were completed for both yearly and seasonal data. Sites downstream of wastewater treatment outfalls had lower concentrations of methyl paraben during the yearly analysis and across multiple seasons in the seasonal analysis with average yearly annual methyl paraben concentrations decreasing from 0.83 ng/L at site 3 to 0.09 ng/L at site 4. Para-hydroxybenzoic acid was the compound present in greatest concentration at most sites across most seasons, with the highest average annual concentration of 10.30 ng/L at site 2. Spatial changes in para-hydroxybenzoic acid varied by season, with seasonal trends only identifiable after normalization by flow. Dichlorinated paraben concentrations increased in the river at sites downstream of wastewater treatment with a yearly average dichlorinated methyl paraben concentration of 0.490 ng/L at site 3 to 1.53 at site 4, just downstream of the major wastewater treatment plant. Concentration increases indicate that wastewater effluent contains sufficiently high dichlorinated paraben concentrations to effect concentrations downstream of effluent discharges. Dichlorinated species also persisted in the environment, with no significant decreases at sites further downstream during any season with an annual average dichlorinated methyl paraben concentration of 1.23 ng/L at site 6. Methyl paraben concentrations decreased at the site furthest downstream to a concentration of 0.081 ng/L, while dichlorinated methyl paraben concentrations remained stable with a concentration of 1.10 ng/L at the site furthest downstream. Due to the dichlorinated species being released in higher concentrations in effluent than parents and being more resistant to degradation, the dichlorinated parabens are more likely to be environmentally relevant than are parent parabens. [ABSTRACT FROM AUTHOR]

In this research, a strong anionic resin was prepared to remove chloride ions. This study was performed in a laboratory pilot to evaluate effective parameters such as temperature, amine flow rate, pH, chloride ion concentration and concentration of resin caustic. The purpose of this work is to determine kinetics of the resin reaction and determination of the optimal operating conditions in order to achieve maximum saturation. This study shows that volume of distilled water passing through resin to eliminate alkalinity at temperatures 40 °C, 50 °C and 60 °C is equal to 5500 ml, 5000 ml and 7000 ml, respectively. This work states that a temperature 50 °C is more appropriate than other temperatures. The results of this research show that volume of caustic for resin recovery is 8.5 L at a temperature of 50 °C. This study shows that amount of distilled water to eliminate alkalinity of the resin is equal to 5 L. Results show that the order of reaction to chloride ion concentration is equal to 0.794 and reaction constant is equal to exp (−1.8753). [ABSTRACT FROM AUTHOR]

With the increased use of microplastics and antibiotics in modern society, a large number of microplastics and antibiotics are being found in natural and water treatment systems. In this paper, the effect of polypropylene (PP), polyethylene (PE), and polystyrene (PS) microplastics (MPs) on the chlorination of ciprofloxacin (CIP) and subsequent production of disinfection byproducts (DBPs) was investigated using sodium hypochlorite (NaClO) as the disinfectant and trichloromethane (CHCl3) and dichloroacetonitrile (DCAN) as typical carbon- and nitrogen-containing disinfection byproducts. Disinfection byproducts (DBPs) were investigated. The results showed that the mass concentrations of CHCl3 and DCAN generated after CIP chlorination were higher, reaching 160.1 μg/L and 2.5 μg/L, respectively, than those generated after the chlorination of microplastics (0.49~41 μg/L). Considering the effect of microplastics on the chlorination of ciprofloxacin to generate disinfection byproducts, it was found that the increase in the production of CHCl3 and DCAN was not significant and that production even tended to decrease. There was a slight contribution to the generation of CHCl3 with increasing microplastic concentration. There was almost no effect on DCAN, and the generation of DCAN was even inhibited. Increases in pH, NaClO dose, and chlorination time promoted the generation of CHCl3, but DCAN showed a decreasing trend due to its instability and easy decomposition. This study provides a theoretical basis for understanding the generation of disinfection byproducts in water sources contaminated by microplastics and antibiotics. [ABSTRACT FROM AUTHOR]

Haloacetonitriles (HANs) are hazardous water disinfection by-products due to their adverse health effects. In this study, the interaction and adsorption of the key HAN pollutants on the fullerene C20 surface were investigated by density functional theory (DFT). Thus, the pristine structures of fullerene, four HANs, and their complexes were geometrically optimized at the B3LYP/6-31G* level of theory with the help of ORCA software package. Natural bond orbital (NBO) results indicate that interaction between the surface of the C20 adsorbent and adsorbate could be chemical in nature. Infrared (IR) frequency computations exhibited that the studied structures are experimentally feasible showing no imaginary frequency. The HANs adsorbed on the surface of C20 confer a greater dipole moment than corresponding unabsorbed compounds. The adsorption energy, Gibbs free energy (ΔGad), and enthalpy (ΔHad) values revealed that the adsorption of HANs on the fullerene C20 surface is exothermic, spontaneous, and irreversible. The calculated chemical potential values are negative for all structures affirming that the scrutinized structures are thermodynamically stable. The increasing trend of adsorption efficiency for fullerene-HANs complexes is C2HBr2N―C20 > C2HBrClN―C20 > C2HCl2N―C20 > CCl3CN―C20. The results demonstrate that fullerene C20 is a proficient adsorbent in removing of HAN contaminants from aqueous media. Besides, C20 provides a proper sensing capability during adsorption due to its increased specific heat capacity and decreased bandgap. To verify the adsorption behavior of considered fullerene, other significant properties such as band gap, chemical hardness, electrophilicity, chemical potential, and charge capacity were also discussed in detail. The molecular electrostatic potential surface (ESP) of haloacetonitriles (HANs), by-products of water disinfection, fullerene C20 adsorbent, and HANs―C20 complexes in aqueous phase using DFT approach [ABSTRACT FROM AUTHOR]

Hydrodynamic cavitation (HC) was a kind of advanced oxidation mode. There were defects in the common HC devices, such as high energy consumption, low efficiency, and easy plugging. In order to effectively utilize HC, it was urgent to research new HC devices and used them together with other traditional water treatment methods. Ozone was widely used as a water treatment agent that does not produce harmful by-products. Sodium hypochlorite (NaClO) was efficient and cheap, but too much chlorine will be harmful to water. The combination of ozone and NaClO with the HC device of propeller orifice plate can improve the dissolution and utilization rate of ozone in wastewater, reduce the use of NaClO, and avoid the generation of residual chlorine. The degradation rate reached 99.9% when the mole ratio γ of NaClO to ammonia nitrogen (NH3-N) was 1.5 and the residual chlorine was near zero. As for the degradation rate of NH3-N or COD of actual river water and real wastewater after biological treatment, the ideal mole ratio γ was also 1.5 and the ideal O3 flow rates were 1.0 L/min. The combined method has been preliminarily applied to actual water treatment and was expected to be used in more and more scenarios. [ABSTRACT FROM AUTHOR]

The final and most crucial step in obtaining clean water is disinfection. More innovative methods of water disinfection have recently been sought. Water disinfection is a promising application for nanoparticles as disinfectants. As a contribution to the literature, biofilm and metal-containing nanoparticles as antiadhesion inhibitors were used in conjunction with ultrasound in this study. The microbroth dilution test was used to reveal the microbiological antibacterial activities of different concentrations of AgNO3 and CuCl2 containing nanoparticles against the Escherichia coli ATCC 25,922 strain, which is an indicator bacterium in water systems. Antibiofilm activities were then investigated using biofilm attachment and biofilm inhibition tests. The inhibitory effect of nanoparticle ultrasonic waves on biofilm contamination was determined using a novel approach. Human keratinocyte cells (HaCaT cell line) were used in cell culture studies after water disinfection, and their cytotoxic effects were demonstrated using the MTT assay. The findings suggest that the nanoparticles utilized might be a viable choice for water disinfection applications. Furthermore, employing ultrasound at low doses with nanoparticles resulted in greater results. One feasible option is to employ nanoparticles to cleanse water without producing cytotoxicity. [ABSTRACT FROM AUTHOR]

Contamination with pathogens degrades water quality and is a major cause of many waterborne diseases. The aim of this research is to reduce the global disease burden by presenting an efficient, durable, and low-cost ceramic filter impregnated with actinomycetes-mediated silver nanoparticles (AgNPs) for water disinfection in rural areas. This marks the first report on the simultaneous biosynthesis of AgNPs utilizing cell-free supernatants obtained from terrestrial actinomycetes. An easy and efficient method was used to impregnate AgNPs onto a ceramic filter using 3-aminopropyltriethoxysilane (APTES). The APTES linker is anchored to the ceramic surface through Si–O–Si bridges, while the terminal amino groups coordinate with AgNPs. Notably, the observed inhibition zone around the filter with AgNPs was ~ 18 mm, suggesting that the silver ions were responsible for the antibacterial activity. After 30 min of sonication, only insignificant traces of AgNPs were released from the filter, making it stable for long-term antibacterial activity when treating water. According to the laboratory simulation experiments, the untreated filter can reject about 99% of spiked bacteria, while the antibacterial efficiency of the filter coated with AgNPs was 100% due to the synergistic effect between filtration and disinfection with AgNPs. In addition, the average concentration of dissolved silver in the outlet water of the ultrafiltration system during three months was 33.7 μg/L, far below the permissible limit (100 μg/L) for drinking water. Overall, this work offers a suitable and affordable water treatment strategy for low-income, isolated, and rural societies in developing countries. [ABSTRACT FROM AUTHOR]

Trichloroacetic acid is known as one of the harmful disinfection byproducts with chlorine of tap water and is regulated according to legally binding standards in Japanese Drinking Water Quality Standards. We developed a high-purity trichloroacetic acid reference material, NMIJ CRM 4074-a, with certified purity as a traceability source of standard solution supplied under the Japan Calibration Service System (JCSS). As trichloroacetic acid is hygroscopic, water could be the main impurity. Although all impurities in the sample can be possibly detected by the freezing point depression method (FPD), it was unclear for trichloroacetic acid whether water was detected by FPD owing to evaporation of water from the sample during fusion. Therefore, we confirmed that water in trichloroacetic acid was detected as an impurity by FPD. The procedure was validated from an increment of purity by FPD due to reduction of water content and an agreement of purity by FPD with those by neutralization titrimetry (NT) and mass balance approach (MBA), both methods were based on different measurement principles from FPD. The certified value was determined to be (0.999 ± 0.003) kg kg−1 from the purity assay by FPD and NT, and uncertainties due to the homogeneity and stability of the CRM were included in the expanded uncertainty. The reliability of the certified value was verified by the agreement of purities by FPD, NT, and MBA. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) water disinfection method has emerged as an alternative to chemical methods of disinfection. In typical UV photoreactors for water treatment, water flows in the space between the lamp's sleeve and outer shell. The contact of water and sleeve causes fouling, which reduces the effectiveness of UV. To clean the photoreactor, the quartz sleeve must be replaced; this may lead to quartz or lamp breakage and mercury leakage into water during cleaning. In this study, a novel type of multi-lamp UV photoreactors is proposed, in which the UV lamps are placed out of the water channel and their UV irradiation is redirected into the channel using an outer cylindrical reflector. This allows for the installment of a self-cleaning mechanism for the water channel. A well-validated three-dimensional CFD model is utilized to model the performance of this photoreactor for microbial inactivation. The impacts of several geometrical and optical parameters are investigated on the inactivation of microorganisms. The results revealed that the difference in log reduction values (LRV) between fully specular and fully diffuse reflector ranges from 10 to 47% as the lamp-to-channel distance increases. For the volumetric flow rate of 25 GPM, the LRV of a photoreactor with fully diffuse reflector can be 46% higher than a fully specular one. In addition, the performance of the proposed photoreactor is compared against a classic L-shaped annular photoreactor. The results show that the new design can provide equal or better microbial performance compared to the classic photoreactor, but it removes many of their common issues such as quartz fouling, lamp overheating at low flow rates, and sleeve breakage during lamp replacement. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to explore the adsorption behaviors and mechanisms of chlorobenzene compounds (CBs; monochlorobenzene (MCB); 1,2-dichlorobenzene (1,2-DCB); pentachlorobenzene (PeCB); and hexachlorobenzene (HCB)) on corn straw-based biochar. Materials and methods: The adsorption kinetics and isotherms of the four CBs were investigated in mono- or multi-CB adsorption experiments with the corn straw–based biochar which was pyrolyzed at 500 °C and modified with 1 mol/L HCl. Moreover, the surface morphology and porosity of the biochar were characterized. The molecular orbitals, electron cloud distribution, and configuration of the CBs were calculated by the quantum chemical method. The relationships were investigated among the adsorption behaviors and quantum chemical parameters of the CBs as well as the morphology characteristics of the biochar to explore the adsorption mechanisms of the CBs on the biochar. Results and discussion: The results showed that in both mono- and multi-adsorbate systems, the adsorption of the CBs was well fitted by the pseudo-second-order, Elovich, and the Freundlich model. The adsorption rates, affinities, and amounts indicated that the biochar preferably absorbed highly chlorinated CBs (PeCB and HCB) over low-chlorinated CBs (MCB and 1,2-DCB). The absolute electronegativity (χ), electrophilicity index (ω), polarizability (α), and molecular volume (Vm) followed the increasing order MCB < 1,2-DCB < PeCB < HCB. The values of energy gap of molecular frontier orbitals (ΔEGap) and molecular hardness (η) decreased with increasing halogen number of the CBs. The lower energy gap of molecular frontier orbitals, the less molecular stability, and higher deformability could favor the adsorption of highly chlorinated CBs (PeCB and HCB) on the biochar. Conclusions: During the adsorption process of the CBs on the biochar, physisorption and pore filling might be the two associated mechanisms. The biochar with properties (aromatization and porosity) matchable to the CBs in energy gap of molecular frontier orbitals, electrophilicity, and polarizability is available to enhance adsorption capacity to the greatest extent. The competitive adsorption might enhance the risk of CB mobility and bioavailability by reducing the adsorption amount and delaying the equilibrium time. [ABSTRACT FROM AUTHOR]

Chlorination is the most common method of water disinfection of pathogens before discharged into receiving streams, rivers, or oceans. This study evaluates chlorination efficiency in improving microbiological and physicochemical parameters in water samples available in the Sheble Bernta district, Amhara region, from May 2020 to June 2020. Water samples were collected from selected five sampling points from unprotected springs, groundwater, hand-dug well, and river in five kebele from the district. All samples were undergone sample preparation. The chlorination process was made by calcium hypochlorite and then analyzed for bacteriological and physicochemical parameters before and after chlorination using standard procedures. The results of this study before chlorination showed that total coliform (TC) of water ranged between 71 and 127,000 (CFU)/100 ml, pH = 6.89-.35, turbidity = 196–270 NTU, and total dissolved solid (TDS) = 315–404 mg/l. Then the result of the microbiological and physicochemical parameters of water after chlorination was changed into total coliform ranging between1 50 (CFU)/100 ml, pH = 7.25–8.10, and turbidity = 2.9–5.6 NTU, TDS = 93–134 mg/l. Finally, the result confirmed that the removal efficiency of chlorination in total coliform (TC), turbidity, and TDS was ranged between 98.29 and 99.99%, 97 and 92-98.61%, and 62.03 and 73.31%, respectively. It was observed that there is a significant difference in removing turbidity, electrical conductivity, and total dissolved solids (TDS) before and after chlorination, but the pH test did not show a significant difference (p < 0.05). The efficiency of chlorination in removing total coliform and impurity of water is very efficient. It plays a vital role in the bactericide effect, reducing turbidity, and water's total dissolved solids. However, chlorinated compounds' (Ca(OCl)2) increased the pH of water after treatments. This study concluded that the efficiency of chlorination in improving the quality of water is highly significant (p < 0.05) and made water under permeable level compared to the World Health Organization standard. Hence, the chlorination water treatment process in a household can be granted to get quality water at the household level. [ABSTRACT FROM AUTHOR]

Although ultraviolet (UV) and persulfate (PS) have been widely used in water disinfection process, their incompleteness of disinfection, such as inducing the production of viable but non-culturable cells (VBNC), has attracted extensive attention. In this study, the disinfection effect of combined UV and PS was evaluated, and the roles of SO4•− and HO• radicals in UV/PS disinfection were also analyzed. UV/PS more effectively inactivated cells and reduced the number of culturable cells. Also, the test of bacterial dark activation suggested that UV/PS disinfection inhibited the recovery of VBNC bacteria. The mechanisms of UV/PS disinfection were the increase of membrane permeability and oxidative stress, where SO4•− radicals played more role than HO• radicals. Furthermore, UV/PS disinfection more significantly perturbed the metabolism of Pseudomonas aeruginosa (p < 0.05), mainly involving glyoxylate and dicarboxylic acid metabolism, aminoacyl-tRNA biosynthesis, Alanine, aspartate and glutamate metabolism, and citric acid cycle (TCA cycle). In short, UV/PS disinfection can not only significantly reduce the number of culturable bacteria (kill bacteria) but also inhibits the recovery of VBNC bacteria. [ABSTRACT FROM AUTHOR]

Alginate-based silver nanoparticles were prepared using a simple and efficient one-pot synthesis method and their antimicrobial activity evaluated. The prepared nanocomposites were characterised with scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and powder X-ray diffraction. Morphological analysis confirmed the successful formation of the nanocomposites with well-dispersed AgNPs throughout the alginate matrix. The antimicrobial activity was evaluated using the growth inhibition zone method and batch studies. The antimicrobial results showed that the nanocomposites were effective to inhibit growth of the tested bacteria; Staphylococcus aureus (45 mm), Salmonella (44 mm) and Escherichia coli (42 mm). Batch results also showed effective inactivation of bacteria with more contact time, where no bacteria were detected in all the water samples after 8 h. Noteworthy, the ICP results showed a very slow release of Ag concentration (1.529 ppb after 24 h), which might be the reason more contact time was required for effective inactivation. After 24 h, there was still no bacteria detected in the water which shows the long performance of the nanocomposites. These results indicate that the prepared nanocomposites are promising and can effectively be utilised for water disinfection. [ABSTRACT FROM AUTHOR]

In this work, chloride ions were used as conservative tracers and supplemented with conservative amounts of chloroethenes (PCE, TCE, Cis-DCE, 1,1-DCE), chloroethanes (1,1,1-TCA, 1,1-DCA), and the carbon isotope ratios of certain compounds, the most representative on the sites studied, which is a novelty compared to the optimization methods developed in the scientific literature so far. A location of the potential missing sources is then proposed in view of the balances of the calculated mixing fractions. A test of the influence of measurement errors on the results shows that the uncertainties in the calculation of the mixture fractions are less than 11%, indicating that the source identification method developed is a robust tool for identifying sources of chlorinated solvents in groundwater. [ABSTRACT FROM AUTHOR]

Non-steroidal anti-inflammatory drugs (NSAIDs) act as antipyretics, analgesics and anti-inflammatories. Among them, diclofenac and ibuprofen are the most consumed drugs worldwide. During the COVID-19 pandemic, some NSAIDs, such as dipyrone and paracetamol, have been used to alleviate the symptoms of the disease, causing an increase in the concentrations of these drugs in water. However, due to the low concentration of these compounds in drinking water and groundwater, few studies have been carried out on the subject, especially in Brazil. Thus, this study aimed to evaluate the contamination of the surface water, groundwater, and water treated with diclofenac, dipyrone, ibuprofen, and paracetamol at 3 cities (Orocó, Santa Maria da Boa Vista and Petrolândia) in the Brazilian semiarid region, in addition to analyzing the removal of these drugs by conventional water treatment (coagulation, flocculation, sedimentation, filtration and disinfection) in stations to each city. All drugs analyzed were detected in surface and treated waters. In groundwater, only dipyrone was not found. Dipyrone was seen in surface water with a maximum concentration of 1858.02 μg.L−1, followed by ibuprofen (785.28 μg.L−1), diclofenac (759.06 μg.L−1) and paracetamol (533.64 μg.L−1). The high concentrations derive from the increased consumption of these substances during the COVID-19 pandemic. During the conventional water treatment, the maximum removal of diclofenac, dipyrone, ibuprofen and paracetamol was 22.42%; 3.00%; 32.74%; and 1.58%, respectively, which confirms the inefficiency of this treatment in removing drugs. The variation in removal rate of the analyzed drugs is due to the difference in the hydrophobicity of the compounds. [ABSTRACT FROM AUTHOR]

Pollution of water sources by pathogens is a significant concern worldwide. In the present study, a pilot-scale once-through reactor was fabricated to investigate bacteria's inactivation and the degradation of organic matter present in municipal wastewater using an iron-mediated TiO2 catalyst in fixed mode. The catalyst was fabricated (in a spherical shape) using waste material such as foundry sand and fly ash and coated with TiO2 for a combined hybrid effect. The influence of H2O2 concentration and the flow rate of the reactor were examined. 4.1 log reductions of bacteria with 52% and 39% of BOD and COD reductions in 45 min of treatment were observed. The catalyst was also found to be highly durable, with only a 12.5% of reduction in catalyst activity observed after 200 recycles. Therefore, this pilot-scale research indicates the ability of waste materials to be employed as a practical approach for water disinfection applications. [ABSTRACT FROM AUTHOR]

Reverse osmosis (RO) is widely used in wastewater reclamation to alleviate the increasingly global water shortage. However, it has an inconvenient defect of biofouling. Some disinfection processes have been reported to select certain undesirable disinfection-residual bacteria (DRB), leading to severe long-term biofouling potential. To provide constructive guidance on biofouling prevention in RO systems, this study performed a 32-day experiment to parallelly compared the biofouling characteristics of RO membranes of DRB after five mature water disinfection methods (NaClO, NH2Cl, ClO2, UV, and O3) and two recently developed water disinfection methods (K2FeO4 and flow-through electrode system). As a result, the DRB biofilm of K2FeO4 and O3 caused a slight normalised flux drop (22.4 ± 2.4% and 23.9 ± 1.7%) of RO membrane compared to the control group (non-disinfected, ~27% normalised flux drop). FES, UV, NaClO and ClO2 caused aggravated membrane flux drop (29.1 ± 0.3%, 33.3 ± 7.8%, 34.6 ± 6.4%, and 35.5 ± 4.0%, respectively). The biofouling behaviour showed no relationship with bacterial concentration or metabolic activity (p > 0.05). The thickness and compactness of the biofilms and the organics/bacterial number ratio in the biofilm, helped explain the difference in the fouling degree between each group. Moreover, microbial community analysis showed that the relative abundance of typical highly EPS-secretory and biofouling-related genera, such as Pseudomonas, Sphingomonas, Acinetobacter, Methylobacterium, Sphingobium, and Ralstonia, were the main reasons for the high EPS secreting ability of the total bacteria, resulting in aggravation of biofouling degree (p < 0.05). All types of disinfection except for NaClO and ClO2 effectively prevented pathogen reproduction in the DRB biofilm. [ABSTRACT FROM AUTHOR]

Among several existing technologies, solar pasteurization is widely accepted as a reliable and cost-effective method for the removal of microbial pathogens from water. This work reports nanophotonics-triggered thermally enhanced solar water disinfection bottles (nano-SODIS) designed rationally by coating plasmonic carbon nanoparticles (CNP) on the outer surface for the targeted pathogen inactivation from water. The cost-effective CNP nanophotonic material used in this work has high efficiency in harvesting solar radiation and dissipating the heat locally. It has broad absorption efficiency to cover the entire solar spectrum; hence, it is capable to generate multiple scattering. It has also properties of boosting of photon absorption and focusing the light within a constrained spatial region, resulting in powerful and targeted heating that inactivates microorganisms in near proximity. These CNPs were used to coat the nano-SODIS water bottles that achieved the highest temperature of 65–70 °C within 90 min of exposure to solar radiation with a consequent six-log reduction. The disinfection period was reduced by a factor of 3 compared to the conventional solar disinfection system. The treated water was further assessed for 7 days, which confirmed the complete absence of bacteria and no sign of regeneration after storing for a longer period. The SODIS bottles coated with CNP thus overcome the problem of limited solar absorption by acquiring higher broadband absorption potential and thus achieving comparatively high disinfection efficiency. The broad band absorption of CNP was confirmed through UV-DRS absorption spectra. The nano-SODIS bottles designed and constructed in this work are simple, durable, and user friendly in nature and have been deployed in the rural and slums areas of Nagpur, Delhi, and Mumbai, India to provide pathogen-free potable water and to improve the health of local poor communities. [ABSTRACT FROM AUTHOR]

A two-step electrochemical process including electrooxidation (EO) and electrocoagulation (EC) was proposed for the tertiary treatment of bio-treated landfill leachate (BTLL). The operating conditions of sole EO and EC technology were optimized via batch tests. Batch tests indicate that EO displayed superior removal efficiency towards color (89%) and UV254 (64%) under optimal experimental conditions. EC with the electrode combinations Fe–Fe-Fe–Fe (four plates, anode–cathode-anode–cathode) performed better than the other electrode combinations (Fe-Al–Fe-Al, Al–Fe-Al–Fe, Al-Al-Al-Al) and showed excellent removal efficiency towards COD (60%) and color (85%). In continuous-flow tests of 13 h, compared to sequential EC-EO process, the sequential EO-EC process was more effective than the sequential EC-EO process in reducing organic matters (COD, TOC) and residual chlorine. The sequential EO-EC process could remove 50% COD, 55% TOC, 72% UV254, and 96% color. The average concentration of residual chlorine in the final effluent of EO-EC process (147 mg/L) was significantly lower than that of EC-EO process (463 mg/L). UV–vis and GC–MS analyses indicate that the BTLL mainly contained humic acid and fulvic acid-like substances with unsaturated bonds. Conjugated unsaturated organics could be degraded into organic of small molecular weight after the sequential EO-EC process. EEM spectroscopic analysis revealed that soluble microbial byproducts became the predominant organics in the final effluent. This work verifies the synergism between EO and EC and provides some insights into the removal and degradation performance of organic substances in BTLL during the sequential EO-EC treatment. [ABSTRACT FROM AUTHOR]

Background: Chlorine substitution has been considered as one of the key steps of polychlorinated dibenzodioxin/furan (PCDD/Fs) generation. The introduction of oxygen carriers (OCs), especially in chemical looping combustion (CLC), provides the platform of directed regulation for the chlorine substitution process. Methods: Density functional theory (DFT) calculations with code VASP 5.4 were employed to investigate the free energy of PCDD/Fs adsorption on different surfaces. 12378-PCDD, which is the product of a one-step chlorine substitution for toxic 2378-PCDD, has been selected as the calculation case, and the regulation mechanisms on the inter-isomeric conversion of 12378-PCDD were identified by calculating the energy barrier and action angle. Results: It was found that the chlorine substitution of 12378-PCDD, particularly in 4# position, 9# position, and 6# position, emerged a tendency to increase the difficulty in turn, which conforms to the principle of distal preference. Besides, the influence from CaO adsorption on the crystalline surface of the iron-based oxygen carrier (OC) has been analyzed and it was verified that CaO adsorption can significantly increase the energy barrier for the chlorine substitution of 12378-PCDD. Meanwhile, the action angle was proposed to evaluate the parameters of adsorption process, and the adsorption of CaO can not only change the action angle between the 12378-PCDD molecule and the lattice surface, but also can modulate the energy barrier order of chlorine substitution among PCDD isomers. In addition, the loading component modulation was carried out to further confirm the feasibility of modulating the chloride substitution pathway, which proved the influence degree of loading component. And accordingly, the stretching analysis of the inactive component provides a theoretical basis for the subsequent study of the directional regulation of the PCDDs isomer generation pathway. Finally, the chlorine substitution rules and directed regulation mechanisms of PCDD/Fs isomers were obtained, which provides a modification direction for the structural components of OCs. [ABSTRACT FROM AUTHOR]

In a semi-arid region of Maadher, central Hodna (Algeria), groundwater is the main source for agricultural and domestic purposes. Anthropogenic activities and the presence of climate change's effects have a significant impact on the region's groundwater quality. This study's goals were to use water quality indices to evaluate the groundwater's quality and its suitability for drinking and irrigation, as well as to identify contaminated wells using a geographic information system (GIS) and the spatial interpolation techniques of ordinary kriging and inverse distance weighting (IDW). The results reveal that all water samples exceeded the World Health Organization's standards for nitrate ions and had alarming concentrations of calcium, chlorine, and sulfate (WHO). According to Piper's diagram, the groundwater hydrochemical facies is composed of the elements sulfate–chloride-nitrate-calcium (SO42−-Cl—NO3−-Ca2+ water type). The majority of samples fall into the poor water category, slightly more than 10% fall into the very poor water category, and less than 10% fall into the good to the excellent quality category, per the water quality indices, which classify samples in a similar manner. According to irrigation water indices, every sample is suitable for irrigation. Depending on the direction of groundwater flow, the spatial distributions of Ca2+, Na+, Mg2+, SO42−, and Cl− show that their concentrations are high north of the area and relatively low south of Maadher village (Fig. 3). Nitrate concentrations are high in the majority of samples, particularly those close to the Bousaada wadi. In most samples, particularly those close to the Bousaada wadi, nitrate levels are high. Various water quality models were described, and GIS spatial distribution maps were created using standard kriging and inverse distance weighting (IDW) techniques through selected semi-variograms predicted against measurements. To determine the origin of mineralization and the chemical processes that take place in the aquifer—which include the precipitation and dissolution of dolomite, calcite, aragonite, gypsum, anhydrite, and halite—the groundwater saturation index was calculated. [ABSTRACT FROM AUTHOR]

Pd-Ni bimetallic nano-catalyst supported on activated carbon was prepared by ultrasonic enhanced impregnation method with lower energy consumption compared to traditional impregnation method and characterized by x-ray diffraction and high-resolution transmission electron microscopy. The catalytic hydrodechlorination properties of the obtained catalyst for bleached shellac were also investigated. The optimal parameters of the main factors and levels affecting the catalytic hydrodechlorination of the catalyst were further optimized using response surface methodology and Box–Behnken design; a quadratic polynomial model of the catalytic hydrodechlorination process of bleached shellac by the prepared Pd-Ni/AC catalyst is achieved. Results indicated that the optimal parameters for catalytic hydrodechlorination reaction of bleached shellac are catalyst dosage of 1.80 g, reaction time of 83 min, and reaction temperature of 80°C and that the predicted chlorine content in the bleached shellac after catalytic hydrodechlorination with the prepared catalyst under the optimal conditions is 0.0992 wt.%. [ABSTRACT FROM AUTHOR]