The problem of drinking water access: A review of disinfection technologies with an emphasis on solar treatment methods

Assessing the Health Impact of Disinfection Byproducts in Drinking Water

This study provides a comprehensive investigation of the impact of disinfection byproducts (DBPs) on human health, with a particular focus on DBPs present in chlorinated drinking water, concentrating on three primary DBP categories (aliphatic, alicyclic, and aromatic). Additionally, it explores pivotal factors influencing DBP formation, encompassing disinfectant types, water source characteristics, and environmental conditions, such as the presence of natural materials in water. The main objective is to discern the most hazardous DBPs, considering criteria such as regulation standards, potential health impacts, and chemical diversity. It provides a catalog of 63 key DBPs alongside their corresponding parameters. From this set, 28 compounds are meticulously chosen for in-depth analysis based on the above criteria. The findings strive to guide the advancement of water treatment technologies and intelligent sensory systems for the efficient water quality surveillance. This, in turn, enables reliable DBP detection within water distribution networks. By enriching the understanding of DBP-associated health hazards and offering valuable insights, this research is aimed to contribute to influencing policy-making in regulations and treatment strategies, thereby protecting public health and improving safety related to chlorinated drinking water quality.

Conversion of locally available materials to biochar and activated carbon for drinking water treatment

For environmental sustainability and to achieve sustainable development goals (SDGs), drinking water treatment must be done at a reasonable cost with minimal environmental impact. Therefore, treating contaminated drinking water requires materials and approaches that are inexpensive, produced locally, and effortlessly. Hence, locally available materials and their derivatives, such as biochar (BC) and activated carbon (AC) were investigated thoroughly. Several researchers and their findings show that the application of locally accessible materials and their derivatives are capable of the adsorptive removal of organic and inorganic contaminants from drinking water. The application of locally available materials such as lignocellulosic materials/waste and its thermo-chemically derived products, including BC and AC were found effective in the treatment of contaminated drinking water. Thus, this review aims to thoroughly examine the latest developments in the use of locally accessible feedstocks for tailoring BC and AC, as well as their features and applications in the treatment of drinking water. We attempted to explain facts related to the potential mechanisms of BC and AC, such as complexation, co-precipitation, electrostatic interaction, and ion exchange to treat water, thereby achieving a risk-free remediation approach to polluted water. Additionally, this research offers guidance on creating efficient household treatment units based on the health risks associated with customized adsorbents and cost-benefit analyses. Lastly, this review work discusses the current obstacles for using locally accessible materials and their thermo-chemically produced by-products to purify drinking water, as well as the necessity for technological interventions.

Nanosized tubular clay minerals as inorganic nanoreactors for energy and environmental applications: A review to fill current knowledge gaps

Modern society pays further and further attention to environmental protection and the promotion of sustainable energy solutions. Heterogeneous photocatalysis is widely recognized as one of the most economically viable and ecologically sound technologies to combat environmental pollution and the global energy crisis. One challenge is finding a suitable photocatalytic material for an efficient process. Inorganic nanotubes have garnered attention as potential candidates due to their optoelectronic properties, which differ from their bulk equivalents. Among them, clay nanotubes (halloysite, imogolite, and chrysotile) are attracting renewed interest for photocatalysis applications thanks to their low production costs, their unique physical and chemical properties, and the possibility to functionalize or dope their structure to enhance charge-carriers separation into their structure. In this review, we provide new insights into the potential of these inorganic nanotubes in photocatalysis. We first discuss the structural and morphological features of clay nanotubes. Applications of photocatalysts based on clay nanotubes across a range of photocatalytic reactions, including the decomposition of organic pollutants, elimination of NOx, production of hydrogen, and disinfection of bacteria, are discussed. Finally, we highlight the obstacles and outline potential avenues for advancing the current photocatalytic system based on clay nanotubes. Our aim is that this review can offer researchers new opportunities to advance further research in the field of clay nanotubes-based photocatalysis with other vital applications in the future.

Interfacial Solar Evaporation: From Fundamental Research to Applications

In the last decade, interfacial solar steam generation (ISSG), powered by natural sunlight garnered significant attention due to its great potential for low-cost and environmentally friendly clean water production in alignment with the global decarbonization efforts. This review aims to share the knowledge and engage with a broader readership about the current progress of ISSG technology and the facing challenges to promote further advancements toward practical applications. The first part of this review assesses the current strategies for enhancing the energy efficiency of ISSG systems, including optimizing light absorption, reducing energy losses, harvesting additional energy, and lowering evaporation enthalpy. Subsequently, the current challenges faced by ISSG technologies, notably salt accumulation and bio-fouling issues in practical applications, are elucidated and contemporary methods are discussed to overcome these challenges. In the end, potential applications of ISSG, ranging from initial seawater desalination and industrial wastewater purification to power generation, sterilization, soil remediation, and innovative concept of solar sea farm, are introduced, highlighting the promising potential of ISSG technology in contributing to sustainable and environmentally conscious practices. Based on the review and in-depth understanding of these aspects, the future research focuses are proposed to address potential issues in both fundamental research and practical applications.

Safeguarding drinking water: A brief insight on characteristics, treatments and risk assessment of contamination

Water pollution stands as a critical worldwide concern, bearing extensive repercussions that extend to human health and the natural ecosystem. The sources of water pollution can be diverse, arising from natural processes and human activities and the pollutants may range from chemical and biological agents to physical and radiological contaminants. The contamination of water disrupts the natural functioning of the system, leading to both immediate and prolonged health problems. Various technologies and procedures, ranging from conventional to advanced, have been developed to eliminate water impurities, with the choice depending on the type and level of contamination. Assessing risks is a crucial element in guaranteeing the safety of drinking water. Till now, research is continuing the removal of contaminates for the sake of supplying safe drinking water. The study examined physical, inorganic, organic, biological and radiological contaminants in drinking water. It looked at where these contaminants come from, their characteristics, the impact they have and successful methods used in real-world situations to clean the contaminated water. Risk assessment methodologies associated with the use of unsafe drinking water as future directives are also taken into consideration in the present study for the benefit of public concern. The manuscript introduces a comprehensive study on water pollution, focusing on assessing and mitigating risks associated with physical, inorganic, organic, biological and radiological contaminants in drinking water, with a novel emphasis on future directives and sustainable solutions for public safety.

Advancement in nanomaterials for environmental pollutants remediation: a systematic review on bibliometrics analysis, material types, synthesis pathways, and related mechanisms

Environmental pollution is a major issue that requires effective solutions. Nanomaterials (NMs) have emerged as promising candidates for pollution remediation due to their unique properties. This review paper provides a systematic analysis of the potential of NMs for environmental pollution remediation compared to conventional techniques. It elaborates on several aspects, including conventional and advanced techniques for removing pollutants, classification of NMs (organic, inorganic, and composite base). The efficiency of NMs in remediation of pollutants depends on their dispersion and retention, with each type of NM having different advantages and disadvantages. Various synthesis pathways for NMs, including traditional synthesis (chemical and physical) and biological synthesis pathways, mechanisms of reaction for pollutants removal using NMs, such as adsorption, filtration, disinfection, photocatalysis, and oxidation, also are evaluated. Additionally, this review presents suggestions for future investigation strategies to improve the efficacy of NMs in environmental remediation. The research so far provides strong evidence that NMs could effectively remove contaminants and may be valuable assets for various industrial purposes. However, further research and development are necessary to fully realize this potential, such as exploring new synthesis pathways and improving the dispersion and retention of NMs in the environment. Furthermore, there is a need to compare the efficacy of different types of NMs for remediating specific pollutants. Overall, this review highlights the immense potential of NMs for mitigating environmental pollutants and calls for more research in this direction.

Systematic analysis of the scientific-technological production on the use of the UV, H2O2, and/or Cl2 systems in the elimination of bacteria and associated antibiotic resistance genes

This study presents a systematic review of the scientific and technological production related to the use of systems based on UV, H2O2, and Cl2 for the elimination of antibiotic-resistant bacteria (ARB) and genes associated with antibiotic resistance (ARGs). Using the Pro Know-C (Knowledge Development Process-Constructivist) methodology, a portfolio was created and analyzed that includes 19 articles and 18 patents published between 2011 and 2022. The results show a greater scientific-technological production in UV irradiation systems (8 articles and 5 patents) and the binary combination UV/H2O2 (9 articles and 4 patents). It was emphasized that UV irradiation alone focuses mainly on the removal of ARB, while the addition of H2O2 or Cl2, either individually or in binary combinations with UV, enhances the removal of ARB and ARG. The need for further research on the UV/H2O2/Cl2 system is emphasized, as gaps in the scientific-technological production of this system (0 articles and 2 patents), especially in its electrochemically assisted implementation, have been identified. Despite the gaps identified, there are promising prospects for the use of combined electrochemically assisted UV/H2O2/Cl2 disinfection systems. This is demonstrated by the effective removal of a wide range of contaminants, including ARB, fungi, and viruses, as well as microorganisms resistant to conventional disinfectants, while reducing the formation of toxic by-products.

Emerging Applications of Nanobiosensors in Pathogen Detection in Water and Food

Food and waterborne illnesses are still a major concern in health and food safety areas. Every year, almost 0.42 million and 2.2 million deaths related to food and waterborne illness are reported worldwide, respectively. In foodborne pathogens, bacteria such as Salmonella, Shiga-toxin producer Escherichia coli, Campylobacter, and Listeria monocytogenes are considered to be high-concern pathogens. High-concern waterborne pathogens are Vibrio cholerae, leptospirosis, Schistosoma mansoni, and Schistosima japonicum, among others. Despite the major efforts of food and water quality control to monitor the presence of these pathogens of concern in these kinds of sources, foodborne and waterborne illness occurrence is still high globally. For these reasons, the development of novel and faster pathogen-detection methods applicable to real-time surveillance strategies are required. Methods based on biosensor devices have emerged as novel tools for faster detection of food and water pathogens, in contrast to traditional methods that are usually time-consuming and are unsuitable for large-scale monitoring. Biosensor devices can be summarized as devices that use biochemical reactions with a biorecognition section (isolated enzymes, antibodies, tissues, genetic materials, or aptamers) to detect pathogens. In most cases, biosensors are based on the correlation of electrical, thermal, or optical signals in the presence of pathogen biomarkers. The application of nano and molecular technologies allows the identification of pathogens in a faster and high-sensibility manner, at extremely low-pathogen concentrations. In fact, the integration of gold, silver, iron, and magnetic nanoparticles (NP) in biosensors has demonstrated an improvement in their detection functionality. The present review summarizes the principal application of nanomaterials and biosensor-based devices for the detection of pathogens in food and water samples. Additionally, it highlights the improvement of biosensor devices through nanomaterials. Nanomaterials offer unique advantages for pathogen detection. The nanoscale and high specific surface area allows for more effective interaction with pathogenic agents, enhancing the sensitivity and selectivity of the biosensors. Finally, biosensors' capability to functionalize with specific molecules such as antibodies or nucleic acids facilitates the specific detection of the target pathogens.

Disinfection by-product precursors introduced by sandstorm events: Composition, formation characteristics and potential risks

Sandstorms, a natural meteorological event, occur repeatedly during the dry season and can accumulate large amounts of natural/anthropogenic pollutants during the deposition process, potentially introducing disinfection by-product (DBP) precursors into surface waters. In this study, the characteristics of sandstorm-derived dissolved organic matter (DOM) and its DBP formation potential were elucidated. Overall, sandstorm-derived DOM mainly consisted of low-molecular-weight, low-aromaticity, high-nitrogen organic matter, with a dissolved organic carbon (DOC) release yield of 14.4 mg-DOC/g. The halogenated DBP formation potential (calculated as total organic halogen) of sandstorm-derived DOM was comparable to that of surface water, while the normalized DBP-associated toxicity was 1.96 times higher. Similar to DOM introduced by other depositional pathways, sandstorm-derived DOM also had higher yields of highly cytotoxic DBPs (haloacetaldehydes [HALs], haloacetonitriles [HANs] and halonitromethanes [HNMs]). The average atmospheric deposition flux for DOM during the sandstorm event (50.4 ± 2.1 kg km-2 day-1) was 6.95 times higher than that of dry deposition, indicating a higher probability of contaminant input. Simultaneously, the estimation revealed that the sandstorm will increase the formation potential of toxicity forcing agents, such as HALs, HANs and HNMs, in surface water by 3.87%, 2.39% and 9.04%, respectively. Considering the high frequency of sandstorm events and the sorption of other organic pollutants by sand and dust, the impact of sandstorms on surface water quality should be of concern.

An insights of organochlorine pesticides categories, properties, eco-toxicity and new developments in bioremediation process

Organochlorine pesticides (OCPs) have been used in agriculture, increasing crop yields and representing a serious and persistent global contaminant that is harmful to the environment and human health. OCPs are typically bioaccumulative and persistent chemicals that can spread over long distances. The challenge is to reduce the impacts caused by OCPs, which can be achieved by treating OCPs in an appropriate soil and water environment. Therefore, this report summarizes the process of bioremediation with commercially available OCPs, considering their types, impacts, and characteristics in soil and water sources. The methods explained in this report were considered to be an effective and environmentally friendly technique because they result in the complete transformation of OCPs into a non-toxic end product. This report suggests that the bioremediation process can overcome the challenges and limitations of physical and chemical treatment for OCP removal. Advanced methods such as biosurfactants and genetically modified strains can be used to promote bioremediation of OCPs.

Chlorination of L-tyrosine and metal complex: degradation kinetics and disinfection by-products generation

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.

Surface-modified activated carbon for N-nitrosodimethylamine removal in the continuous flow biological activated carbon columns

The carcinogenic nitrogenous disinfection by-product, N-nitrosodimethylamine (NDMA), is challenging to adsorb due to its high polarity and solubility. Our previous research demonstrated that the adsorptive removal of NDMA can be improved using surface-modified activated carbon (AC800). The current study evaluated the efficacy of AC800 in removing NDMA in a continuous-flow column over 75 days, using both granular activated carbon (GAC) and biologically activated carbon (BAC) columns. The AC800 GAC column demonstrated extended breakthrough and exhaustion times of 10 days and 22 days, respectively, compared to the conventional GAC column at 4 days and 10.5 days. The surface modification effect persisted for 25 days before the removal trends became indistinguishable. The AC800 BAC column outperformed the conventional BAC column with a longer breakthrough time of 11.3 days compared to 7.4 days. BAC columns consistently showed greater NDMA removal, emphasizing the role of biodegradation in NDMA removal on carbon. The higher NDMA removal in the inoculated columns was attributed to increased microbial diversity and the dominance of six specific genera, Methylobacterium, Phyllobacterium, Curvibacter, Acidovorax, Variovorax, and Rhodoferax. This study provides new insights into using modified activated carbon as GAC and BAC media in a real-world continuous-flow setup.

The impact of potassium peroxymonosulphate and chlorinated cyanurates on biofilms of Stenotrophomonas maltophilia: effects on biofilm control, regrowth, and mechanical properties

The activity of two chlorinated isocyanurates (NaDCC and TCCA) and peroxymonosulphate (OXONE) was evaluated against biofilms of Stenotrophomonas maltophilia, an emerging pathogen isolated from drinking water (DW), and for the prevention of biofilm regrowth. After disinfection of pre-formed 48 h-old biofilms, the culturability was reduced up to 7 log, with OXONE, TCCA, and NaDCC showing more efficiency than free chlorine against biofilms formed on stainless steel. The regrowth of biofilms previously exposed to OXONE was reduced by 5 and 4 log CFU cm-2 in comparison to the unexposed biofilms and biofilms exposed to free chlorine, respectively. Rheometry analysis showed that biofilms presented properties of viscoelastic solid materials, regardless of the treatment. OXONE reduced the cohesiveness of the biofilm, given the significant decrease in the complex shear modulus (G*). AFM analysis revealed that biofilms had a fractured appearance and smaller bacterial aggregates dispersed throughout the surface after OXONE exposure than the control sample. In general, OXONE has been demonstrated to be a promising disinfectant to control DW biofilms, with a higher activity than chlorine. The results also show the impact of the biofilm mechanical properties on the efficacy of the disinfectants in biofilm control.

Practical approach of As(V) adsorption by fabricating biochar with low basicity from FeCl3 and lignin

One of the main challenges of biochar application for environmental cleanup is rise of pH in water or soil due to high ash and alkali metal contents in the biochar. While this intrinsic property of biochar is advantageous in alleviating soil and water acidity, it severely impairs the affinity of biochar toward anionic contaminants such as arsenic. This study explored a technical approach that can reduce the basicity of lignin-based biochar by utilizing FeCl₃ during production of biochar. Three types of biochar were produced by co-pyrolyzing feedstock composed of different combinations of lignin, red mud (RM), and FeCl₃, and the produced biochar samples were applied to adsorption of As(V). The biochar samples commonly possessed porous carbon structure embedded with magnetite (Fe₃O₄) particles. The addition of FeCl₃ in the pyrolysis feedstock had a notable effect on reducing basicity of the biochar to yield significantly lower solution pH values than the biochar produced without FeCl₃ addition. The extent of As(V) removal was also closely related to the final solution pH and the greatest As(V) removal (>77.6%) was observed for the biochar produced from co-pyrolysis of lignin, RM, and FeCl₃. The results of adsorption kinetics and isotherm experiments, along with x-ray spectroscopy (XPS), strongly suggested adsorption of As(V) occurred via specific chemical reaction (chemisorption) between As(V) and Fe-O functional groups on magnetite. Thus, the overall results suggest the use of FeCl₃ is a feasible practical approach to control the intrinsic pH of biochar and impart additional functionality that enables effective treatment of As(V).

Near dissolved organic matter microfiltration (NDOM MF) coupled with UVC LED disinfection to maximize the efficiency of water treatment for the removal of Giardia and Cryptosporidium

Microfiltration (MF) membranes with a mean pore size same as or smaller than 0.45 µm have been typically used to separate pathogenic protozoa in water since materials larger than 0.45 µm are considered particulates. However, 0.45 µm is too small to separate protozoa which are 4-6 µm (Cryptosporidium oocyst) or 8-15 µm (Giardia cyst) in size. In this study, we optimized the mean pore size of MF membranes to maximize the producibility and guarantee a high removal rate simultaneously and proposed the membrane filtration using an MF membrane with an optimum mean pore size larger than but close to dissolved organic matter (DOM), which is called near DOM MF (NDOM MF). According to the MF test using polystyrene surrogate beads with diameters of 3 and 8 µm, an MF membrane with a 0.8 µm mean pore size was the best in that it showed 52% to 146% higher water fluxes than a 0.45 µm MF membrane while maintaining the removal rate at 3-4 log. It was also the case for a low-temperature MF test, revealing the NDOM MF is highly effective regardless of temperature changes. Lastly, we tried to find the possibility of combining the NDOM MF with disinfection by an ultraviolet light emitting diode (UVC LED) to further guarantee the high quality of treated water while providing high process efficiency.

Chitosan-based hollow nanofiber membranes with polyvinylpyrrolidone and polyvinyl alcohol for efficient removal and filtration of organic dyes and heavy metals

Due to their large specific surface area and numerous diffusion channels, hollow fibers are widely used in wastewater treatment. In this study, we successfully synthesized a chitosan (CS)/polyvinylpyrrolidone (PVP)/polyvinyl alcohol (PVA) hollow nanofiber membrane (CS/PVP/PVA-HNM) via coaxial electrospinning. This membrane demonstrated remarkable permeability and adsorption separation. Specifically, the CS/PVP/PVA-HNM had a pure water permeability of 4367.02 L·m^-2·h^-1·bar^-1. The hollow electrospun nanofibrous membrane exhibited a continuous interlaced nanofibrous framework structure with the extraordinary advantages of high porosity and high permeability. The rejection ratios of CS/PVP/PVA-HNM for Cu²⁺, Ni²⁺, Cd²⁺, Pb²⁺, malachite green (MG), methylene blue (MB) and crystal violet (CV) were 96.91 %, 95.29 %, 87.50 %, 85.13 %, 88.21 %, 83.91 % and 71.99 %, and the maximum adsorption capacities were 106.72, 97.46, 88.10, 87.81, 53.45, 41.43, and 30.97 mg·g^-1, respectively. This work demonstrates a strategy for the synthesis of hollow nanofibers, which provides a novel concept for the design and fabrication of highly efficient adsorption separation membranes.

Strategies for safe management of hospital wastewater during the COVID-19 pandemic

Management of hospital wastewater is a challenging task, particularly during the situations like coronavirus 2019 (COVID-19) pandemic. The hospital effluent streams are likely to contain many known and unknown contaminants including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) along with a variety of pollutants arising from pharmaceuticals, life-style chemicals, drugs, radioactive species, and human excreta from the patients. The effluents are a mixed bag of contaminants with some of them capable of infecting through contact. Hence, it is essential to identify appropriate treatment strategies for hospital waste streams. In this work, various pollutants emerging in the context of COVID-19 are examined. A methodical review is conducted on the occurrence and disinfection methods of SARS-CoV-2 in wastewater. An emphasis is given to the necessity of addressing the challenges of handling hospital effluents dynamically involved during the pandemic scenario to ensure human and environmental safety. A comparative evaluation of disinfection strategies makes it evident that the non-contact methods like ultraviolet irradiation, hydrogen peroxide vapor, and preventive approaches such as the usage of antimicrobial surface coating offer promise in reducing the chance of disease transmission. These methods are also highly efficient in comparison with other strategies. Chemical disinfection strategies such as chlorination may lead to further disinfection byproducts, complicating the treatment processes. An overall analysis of various disinfection methods is presented here, including developing methods such as membrane technologies, highlighting the merits and demerits of each of these processes. Finally, the wastewater surveillance adopted during the COVID-19 outbreak is discussed.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13762-023-04803-1.

Photocatalytic Inactivation of Co-Culture of E. coli and S. epidermidis Using APTES-Modified TiO2

The presented work shows the antibacterial activity of TiO₂ photocatalysts modified by 3-aminopropyltriethoxysilane (APTES). The APTES-functionalized TiO₂ samples were obtained by the solvothermal process followed by calcination. The antibacterial activity of APTES/TiO₂ samples was evaluated with two species of bacteria, Escherichia coli and Staphylococcus epidermidis, under artificial solar light (ASL) irradiation. The used bacteria are model organisms characterized by negative zeta potential (approx. -44.2 mV for E. coli and -42.3 mV for S. epidermidis). For the first time, the antibacterial properties of APTES-functionalized TiO₂ were evaluated against mono- and co-cultured bacteria. The high antibacterial properties characterized the obtained APTES-modified nanomaterials. The best antibacterial properties were presented in the TiO₂-4 h-120 °C-300 mM-Ar-300 °C sample (modified with 300 mM of APTES and calcined at 300 °C). The improvement of the antibacterial properties was attributed to a positive value of zeta potential, high surface area, and porous volume.

Systematic literature review of solar-powered landfill leachate sanitation: Challenges and research directions over the past decade

Researchers have documented the negative effects of refractory chemicals and emergent pollutants in landfill leachate (LL) that cannot be degraded using conventional methods. The propagation, invasion, and deleterious effects of several LL hazards affect aquatic species, the environment, and food outlets, causing significant safety issues. These include cancer risks, chronic exposure, and reproductive consequences. Alternatively, solar energy is a sustainable solution for treating landfill leachate to benefit humans and the environment. In this work, a thorough bibliometric and systematic analysis of studies that employed solar energy for landfill leachate remediation over the past decade was conducted in order to determine trends, and future research areas. In addition to the energy demand, the economic aspect and the advantages of using solar power to treat landfill leachate were discussed. Additionally, the study gives specific suggestions for future research purposes and important problems. The reviewed literature revealed that combining solar-based physical-chemical and biological processes has proven to be the most efficient method for landfill leachate degradation. It also appears from the bibliometric study that more collaboration and contribution are needed to develop solar-based landfill leachate treatment. This study concludes that solar-powered landfill leachate remediation techniques would considerably increase the effectiveness of treated leachate reutilization, advancing the cause of environmental sustainability.

Advanced photocatalytic sterilization for recalcitrant Enterococcus sp. contaminated water by newly developed Z-scheme Bi2WO6 based composites under solar light

Pathogenic contamination is one of the major causes of clean water shortage, which poses great risk to human health. Herein, g-C₃N₄ (CN) was firstly introduced to Ag/Ag₂O/BiPO₄/Bi₂WO₆ (Ag/P/BWO) to construct a novel Z-scheme composite CN-Ag/P/BWO for disinfecting Enterococcus sp. contaminated water. CN-Ag/P/BWO showed excellent disinfection performance toward recalcitrant Enterococcus sp. under simulated solar light irradiation, achieving complete inactivation of 1.5 × 10⁷ cfu mL^-1 of bacterial cells only within 60 min, which was mainly attributed to the improved light absorption ability, charge carries separation/transfer efficiency and surface wettability. Additionally, the disinfection mechanism of CN-Ag/P/BWO toward Enterococcus sp. was systematically investigated. Photogenerated active species h⁺, ·OH and ·O₂^- worked together and played crucial roles in photocatalytic inactivation. The antioxidant system enabled Enterococcus sp. self-protection ability at the beginning of disinfection through secreting more antioxidant enzymes. However, with accumulation of active species, bacterial cell membrane and energy system were damaged, which further led to leakage of intracellular components and decomposition of bacteria. Besides, CN-Ag/P/BWO exhibited high practicability for different environmental factors and also performed well for real lake water disinfection. The high stability further confirmed its practicability for water disinfection. This work not only systematically revealed the disinfection mechanism toward Enterococcus sp., but also provided an efficient method for water disinfection.

Thermoresponsive Ionic Liquid with Different Cation-Anion Pairs as Draw Solutes in Forward Osmosis

We synthesized various phosphonium- and ammonium-based ionic liquids (ILs), using benzenesulfonate (BS) and 4-methylbenzenesulfonate (MBS) to establish the criteria for designing an ideal draw solute in a forward osmosis (FO) system. Additionally, the effects of monocationic, dicationic, and anionic species on FO performance were studied. Monocationic compounds ([P₄₄₄₄][BS], [P₄₄₄₄][MBS], [N₄₄₄₄][BS], and [N₄₄₄₄][MBS]) were obtained in one step via anion exchange. Dicationic compounds ([(P₄₄₄₄)₂][BS], [(P₄₄₄₄)₂][MBS], [(N₄₄₄₄)₂][BS], and [(N₄₄₄₄)₂][MBS]) were prepared in two steps via a Menshutkin SN₂ reaction and anion exchange. We also investigated the suitability of ILs as draw solutes for FO systems. The aqueous [P₄₄₄₄][BS], [N₄₄₄₄][BS], [N₄₄₄₄][MBS], and [(N₄₄₄₄)₂][BS] solutions did not exhibit thermoresponsive behavior. However, 20 wt% [P₄₄₄₄][MBS], [(P₄₄₄₄)₂][BS], [(P₄₄₄₄)₂][MBS], and [(N₄₄₄₄)₂][MBS] had critical temperatures of approximately 43, 33, 22, and 60 °C, respectively, enabling their recovery using temperature. An increase in IL hydrophobicity and bulkiness reduces its miscibility with water, demonstrating that it can be used to tune its thermoresponsive properties. Moreover, the FO performance of 20 wt% aqueous [(P₄₄₄₄)₂][MBS] solution was tested for water flux and found to be approximately 10.58 LMH with the active layer facing the draw solution mode and 9.40 LMH with the active layer facing the feed solution.

Challenges on solar oxidation as post-treatment of municipal wastewater from UASB systems: Treatment efficiency, disinfection and toxicity

The application of solar photo-Fenton as post-treatment of municipal secondary effluents (MSE) in developing tropical countries is the main topic of this review. Alternative technologies such as stabilization ponds and upflow anaerobic sludge blanket (UASB) are vastly applied in these countries. However, data related to the application of solar photo-Fenton to improve the quality of effluents from UASB systems are scarce. This review gathered main achievements and limitations associated to the application of solar photo-Fenton at neutral pH and at pilot scale to analyze possible challenges associated to its application as post-treatment of MSE generated by alternative treatments. To this end, the literature review considered studies published in the last decade focusing on CECs removal, toxicity reduction and disinfection via solar photo-Fenton. Physicochemical characteristics of effluents originated after UASB systems alone and followed by a biological post-treatment show significant difference when compared with effluents from conventional activated sludge (CAS) systems. Results obtained for solar photo-Fenton as post-treatment of MSE in developed countries indicate that remaining organic matter and alkalinity present in UASB effluents may pose challenges to the performance of solar advanced oxidation processes (AOPs). This drawback could result in a more toxic effluent. The use of chelating agents such as Fe³⁺-EDDS to perform solar photo-Fenton at neutral pH was compared to the application of intermittent additions of Fe²⁺ and both of these strategies were reported as effective to remove CECs from MSE. The latter strategy may be of greater interest in developing countries due to costs associated to complexing agents. In addition, more studies are needed to confirm the efficiency of solar photo-Fenton on the disinfection of effluent from UASB systems to verify reuse possibilities. Finally, future research urges to evaluate the efficiency of solar photo-Fenton at natural pH for the treatment of effluents from UASB systems.

Recent advances in aqueous virus removal technologies

The COVID-19 outbreak has triggered a massive research, but still urgent detection and treatment of this virus seems a public concern. The spread of viruses in aqueous environments underlined efficient virus treatment processes as a hot challenge. This review critically and comprehensively enables identifying and classifying advanced biochemical, membrane-based and disinfection processes for effective treatment of virus-contaminated water and wastewater. Understanding the functions of individual and combined/multi-stage processes in terms of manufacturing and economical parameters makes this contribution a different story from available review papers. Moreover, this review discusses challenges of combining biochemical, membrane and disinfection processes for synergistic treatment of viruses in order to reduce the dissemination of waterborne diseases. Certainly, the combination technologies are proactive in minimizing and restraining the outbreaks of the virus. It emphasizes the importance of health authorities to confront the outbreaks of unknown viruses in the future.

A review on disinfection methods for inactivation of waterborne viruses

Water contamination is a global health problem, and the need for safe water is ever-growing due to the public health implications of unsafe water. Contaminated water could contain pathogenic bacteria, protozoa, and viruses that are implicated in several debilitating human diseases. The prevalence and survival of waterborne viruses differ from bacteria and other waterborne microorganisms. In addition, viruses are responsible for more severe waterborne diseases such as gastroenteritis, myocarditis, and encephalitis among others, hence the need for dedicated attention to viral inactivation. Disinfection is vital to water treatment because it removes pathogens, including viruses. The commonly used methods and techniques of disinfection for viral inactivation in water comprise physical disinfection such as membrane filtration, ultraviolet (UV) irradiation, and conventional chemical processes such as chlorine, monochloramine, chlorine dioxide, and ozone among others. However, the production of disinfection by-products (DBPs) that accompanies chemical methods of disinfection is an issue of great concern due to the increase in the risks of harm to humans, for example, the development of cancer of the bladder and adverse reproductive outcomes. Therefore, this review examines the conventional disinfection approaches alongside emerging disinfection technologies, such as photocatalytic disinfection, cavitation, and electrochemical disinfection. Moreover, the merits, limitations, and log reduction values (LRVs) of the different disinfection methods discussed were compared concerning virus removal efficiency. Future research needs to merge single disinfection techniques into one to achieve improved viral disinfection, and the development of medicinal plant-based materials as disinfectants due to their antimicrobial and safety benefits to avoid toxicity is also highlighted.

The Role of Conventional Methods and Artificial Intelligence in the Wastewater Treatment: A Comprehensive Review

Water pollution is a severe health concern. Several studies have recently demonstrated the efficacy of various approaches for treating wastewater from anthropogenic activities. Wastewater treatment is an artificial procedure that removes contaminants and impurities from wastewater or sewage before discharging the effluent back into the environment. It can also be recycled by being further treated or polished to provide safe quality water for use, such as potable water. Municipal and industrial wastewater treatment systems are designed to create effluent discharged to the surrounding environments and must comply with various authorities’ environmental discharge quality rules. An effective, low-cost, environmentally friendly, and long-term wastewater treatment system is critical to protecting our unique and finite water supplies. Moreover, this paper discusses water pollution classification and the three traditional treatment methods of precipitation/encapsulation, adsorption, and membrane technologies, such as electrodialysis, nanofiltration, reverse osmosis, and other artificial intelligence technology. The treatment performances in terms of application and variables have been fully addressed. The ultimate purpose of wastewater treatment is to protect the environment that is compatible with public health and socioeconomic considerations. Realization of the nature of wastewater is the guiding concept for designing a practical and advanced treatment technology to assure the treated wastewater’s productivity, safety, and quality.

A modified flower pollen-based photothermocatalytic process for enhanced solar water disinfection: Photoelectric effect and bactericidal mechanisms

Solar disinfection (SODIS) is regarded as an affordable and effective point-of-use (POU) water disinfection treatment urgently needed in rural developing world. This work developed an enhanced SODIS scheme that utilized a novel flower pollen-based catalyst (Te-TRP). The bench-scale experiments demonstrated 100% photothermocatalytic inactivation of approximately 7-log E. coli K-12, Spingopyxis sp. BM1-1, or S. aureus bacterium by Te-TRP within 40-60 min. Moving toward practical device design, we constructed a flow-through reactor and demonstrated the outstanding water disinfection performance of Te-TRP. The in-depth mechanistic study revealed the synergetic effect between photocatalysis and photothermal conversion and identified the bacterial inactivation pathway. ¹O₂ and ·O₂^¯ were verified to be the dominant reactive oxygen species involved in the bacterial inactivation. The damage to bacterial cells caused by photothermocatalytic reactions was systematically investigated, demonstrating the cell membrane destruction, the loss of enzyme activity, the increased cell membrane permeability, and the complete inactivation of bacteria without the viable but nonculturable state cells. This work not only affords a facile approach to preparing biomaterial-based catalysts capable of efficient photothermocatalytic bacterial inactivation, but also proposes a prototype of POU water treatment, opening up an avenue for sustainable environmental remediation.

Recent advances on inactivation of waterborne pathogenic microorganisms by (photo) electrochemical oxidation processes: Design and application strategies

Compared with other conventional water disinfection processes, (photo) electrochemical oxidation (P/ECO) processes have the characteristics of environmental friendliness, convenient installation and operation, easy control and high efficiency of inactivating waterborne pathogenic microorganisms (PMs), so that more and more research work has been focused on this topic, but there is still a huge gap between the research and practical application. Here, the research network of inactivating PMs by P/ECO processes has been comprehensively summarized, and the electrode/reactor/process design strategies based on strengthening direct and indirect oxidation, enhancing mass transfer efficiency and electron transfer efficiency, and improving the effective dose of electrogenerated oxidants are discussed. Furthermore, the factors affecting the inactivation of PMs and the issues regarding to stability and lifetime of the electrode are discussed respectively. Finally, the important research priorities and possible research challenges of P/ECO processes are put forward to make significant progress of this technology.

Sustainable groundwater treatment technologies for underserved rural communities in emerging economies

Worldwide, about one out of two people depend on groundwater resources to satisfy their drinking water needs. While groundwater typically is of higher quality than surface water, pollution and geologic conditions may require treating groundwater to meet safe water quality criteria. Herein, a critical overview is presented of water treatment technologies for rural and underserved communities in emerging economies that depend on groundwater. Given that small to medium sized rural communities in emerging economies often lack the financial resources to support technologically complex and expensive centralized public water treatment systems, the focus is on proven technologies that are sustainable and acceptable by the rural population. After an overview of the underlying treatment mechanisms and the principal groundwater contaminants targeted by the traditional, advanced, and experimental water treatment technologies, we identify the groundwater quality parameters that may impact or interfere with the technology performance. We also introduce enabling environmental factors that might govern the implementation of water treatment technologies in the target communities and a brief discussion of safe storage of water after treatment to underline the importance of protecting the water from re-contamination. Our overview is further supported by tabulated summaries of the principal (dis)advantages of each technology covered herein, including cost considerations and social acceptance. Overall, our review suggests that underserved rural communities have sustainable and affordable options for cases where the quality of local groundwater resources requires treatment.

Chlorinated cyanurates and potassium salt of peroxymonosulphate as antimicrobial and antibiofilm agents for drinking water disinfection

The understanding of microbial susceptibility to disinfectants is an important step to provide drinking water (DW) of adequate microbiological quality. In drinking water distribution systems (DWDS) the application of disinfectants is the main approach to control microorganisms. Although chlorine has been commonly used for DW treatment, the increase of microbial resistance and the production of harmful disinfection by-products promote the necessity to seek new alternatives. This study evaluated the antimicrobial activity of sodium dichloroisocyanurate (NaDCC), trichloroisocyanuric acid (TCCA), and pentapotassium bis(peroxymonosulphate) bis(sulphate) (OXONE) against two emerging pathogens isolated from DW, Acinetobacter calcoaceticus and Stenotrophomonas maltophilia. Free chlorine from calcium hypochlorite was used for comparison. The dose and time-responses against planktonic bacteria were performed as well as the assessment of the effects on membrane integrity. Moreover, the effects against 48 h-old biofilms formed on polyvinyl chloride and stainless steel were evaluated in terms of biofilm culturability and removal. Minimum bactericidal concentrations of 2.1 and 3.1 mg/L for NaDCC, 2.5 and 3.8 mg/L for TCCA, 340 and 690 mg/L for OXONE, and 0.80 and 1.0 mg/L for free chlorine alone were obtained against S. maltophilia and A. calcoaceticus, respectively. The kinetic modeling revealed that NaDCC and TCCA caused similar inactivation rates and the time for first log reduction by OXONE was less than 10 min, for both bacteria. All the disinfectants triggered significant bacterial cytoplasmic membrane destabilization, even at sub-lethal concentrations. A 30 min treatment with the disinfectants allowed a reduction in the biofilm culturability up to 5 log. OXONE was the disinfectant with the best efficiency against both bacterial biofilms. However, none of the disinfectants caused significant biofilm removal (reduction < 1 log cells/cm²). This study highlights NaDCC, TCCA, and OXONE as promising alternatives to free chlorine for DW disinfection, particularly for planktonic growth control and biofilm culturability reduction.

Magnetic covalent-organic frameworks for the simultaneous extraction of eleven emerging aromatic disinfection byproducts in water samples coupled with UHPLC-MS/MS determination

A simple method based on magnetic solid-phase extraction (MSPE) was developed for the simultaneous extraction of eleven emerging aromatic disinfection byproducts (DBPs) in water samples coupled with ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) determination. A magnetic covalent-organic framework (COF) material, namely, Fe₃O₄ @TpBD, was facilely synthesized and fully characterized, followed by an MSPE process. Several important MSPE parameters, such as the magnetic ratio, Fe₃O₄ @TpBD amount and sample pH, were systematically investigated. Under optimal conditions, the limits of detection and quantification of this COF-MSPE-UHPLC-MS/MS method were as low as 0.07-1.81 ng/L and 0.24-5.99 ng/L, respectively. Good precision was obtained with relative standard deviations (RSDs) of 1.3-10.9% (intraday) and 4.3-15.9% (interday). Furthermore, the validated method was proven applicable to real water samples; for example, the recoveries were 86.8-115.1% for the secondary effluent, and several DBPs in swimming pool water were detected. Notably, the MSPE process required only 7 min, ensuring that the DBPs were relatively stable during the whole analysis process and that Fe₃O₄ @TpBD demonstrated excellent reusability. The COF-based MSPE method with simplicity, rapidity and efficiency provided an ideal sample pretreatment alternative to determine trace DBPs in complex matrices.

High efficiency electrochemical disinfection of Pseudomons putida using electrode of orange peel biochar with endogenous metals

The electrochemical disinfection efficiency of Pseudomons putida was studied using ruthenium iridium coated titanium (RICT) electrode as anode and carbonized orange peel biochar (OPB) or graphite as the cathode. The results indicated that RICT/OPB system induced 6.5 and 7.0 log of P. putia inactivation after 60 s at 2 V and 45 s at 10 V, respectively. RICT/OPB system showed better efficiency than RICT/graphite system. The energy consumption of OPB cathode (17.5 Wh m^-3 per log) was significantly lower than that of graphite cathode (23.09 Wh m^-3 per log). Both anode and cathode played great roles on the disinfection. The anode absorbed electric energy to generate electrical hole, which can oxidize chloride ions to chlorine free radicals. The continuous porous structure of OPB can provide more adsorption sites and reduce electrolyte transport resistance, resulting in more Cl· production. Moreover, P. putia was much easier adsorbed to the anode surface in the RICT/OPB system because of the stronger electrostatic repulsion between cells and OPB cathode. As a result, P. putia was more easily inactivated by the Cl· produced on the anode. Besides chlorine active species, superoxide radical (O₂·﹣) produced on surface of cathode may also result in P. putia inactivation. The endogenous CuO in OPB can induce persistent free radicals (PFRs) production during pyrosis process. O₂·﹣ can be produced by O₂ activation through the function of Cu₂O/CuO and PFRs existed in OPB cathode. The more superoxide radical production led to the better disinfection effect than the graphite cathode. As a consequence, OPB electrode showed high efficiency electrochemical disinfection of P. putida.

The Visible light photodegradation of methyl orange and Escherichia coli O157:H7 in wastewater

Water pollution due to dyes and pathogens is problematic worldwide, and the disease burden is higher in low-income countries where water treatment facilities are usually inadequate. Thus the development of low-cost techniques for the removal of dyes and pathogens in aquatic systems is critical for safeguarding human and ecological health. In this work, we report the fabrication and use of a photocatalyst derived from waste from coal combustion in removing dyes and pathogens from wastewater. Higher TiO2 loading of the photocatalyst increased the removal efficiency for methyl orange (95.5%), and fluorine-doping improved the disinfection efficacy from 76% to 95% relative to unmodified material. Overall, the work effectively converted hazardous waste into a value-added product that has potential in point-of-use water treatment. Future research should focus on upscaling the technique, investigating the fate of the potential of the photocatalysts for multiple reuse, and the recovery of TiO2 in treated water.

Headwater-to-consumer Drinking Water Security Assessment Framework and Associated Indicators for Small Communities in High-income Countries

Drinking water insecurity in small and rural, remote, or otherwise marginalized communities in Canada is pervasive and complex with multiple dimensions and impacts. These communities face challenges such as variable source water quality, lack of resources, inappropriate treatment technologies, lack of access to training, difficulties retaining qualified personnel, and ineffective governance structures. Currently, there is a gap in the academic literature with respect to drinking water security assessment frameworks or tools for small and rural, remote, or otherwise marginalized communities, particularly in high income countries. Thus, the objective of this study is to introduce a framework for assessing drinking water security, from headwater to consumer, in the context of small and rural, remote, or otherwise marginalized communities.

An indicator-based framework has been developed to evaluate drinking water security, prioritize actions and investments, and support decision-making. The framework builds on expert knowledge and a critical review of security, sustainability, and performance indices of water supply and treatment processes obtained from the literature. The framework is organised into four dimensions of drinking water security from headwaters to consumer: upstream watershed security; source water security; community needs and engagement; and treatment and distribution infrastructure. A list of relevant indicators for each dimension has been compiled to support framework application in a format that is accessible to decision-makers in small and rural, remote, or otherwise marginalized communities.

Disinfectant-induced hormesis: An unknown environmental threat of the application of disinfectants to prevent SARS-CoV-2 infection during the COVID-19 pandemic?

Massive additional quantities of disinfectants have been applied during the COVID-19 pandemic as infection preventive and control measures. While the application of disinfectants plays a key role in preventing the spread of SARS-CoV-2 infection, the effects of disinfectants applied during the ongoing pandemic on non-target organisms remain unknown. Here we collated evidence from multiple studies showing that chemicals used for major disinfectant products can induce hormesis in various organisms, such as plants, animal cells, and microorganisms, when applied singly or in mixtures, suggesting potential ecological risks at sub-threshold doses that are normally considered safe. Among other effects, sub-threshold doses of disinfectant chemicals can enhance the proliferation and pathogenicity of pathogenic microbes, enhancing the development and spread of drug resistance. We opine that hormesis should be considered when evaluating the effects and risks of such disinfectants, especially since the linear-no-threshold (LNT) and threshold dose-response models cannot identify or predict their effects.

Flow Cytometric Analysis of Bacterial Protein Synthesis: Monitoring Vitality After Water Treatment

Bacterial vitality after water disinfection treatment was investigated using bio-orthogonal non-canonical amino acid tagging (BONCAT) and flow cytometry (FCM). Protein synthesis activity and DNA integrity (BONCAT–SYBR Green) was monitored in Escherichia coli monocultures and in natural marine samples after UV irradiation (from 25 to 200 mJ/cm²) and heat treatment (from 15 to 45 min at 55°C). UV irradiation of E. coli caused DNA degradation followed by the decrease in protein synthesis within a period of 24 h. Heat treatment affected both DNA integrity and protein synthesis immediately, with an increased effect over time. Results from the BONCAT method were compared with results from well-known methods such as plate counts (focusing on growth) and LIVE/DEAD™ BacLight™ (focusing on membrane permeability). The methods differed somewhat with respect to vitality levels detected in bacteria after the treatments, but the results were complementary and revealed that cells maintained metabolic activity and membrane integrity despite loss of cell division. Similarly, analysis of protein synthesis in marine bacteria with BONCAT displayed residual activity despite inability to grow or reproduce. Background controls (time zero blanks) prepared using different fixatives (formaldehyde, isopropanol, and acetic acid) and several different bacterial strains revealed that the BONCAT protocol still resulted in labeled, i.e., apparently active, cells. The reason for this is unclear and needs further investigation to be understood. Our results show that BONCAT and FCM can detect, enumerate, and differentiate bacterial cells after physical water treatments such as UV irradiation and heating. The method is reliable to enumerate and explore vitality of single cells, and a great advantage with BONCAT is that all proteins synthesized within cells are analyzed, compared to assays targeting specific elements such as enzyme activity.

Desalination and Detoxification of Textile Wastewater by Novel Photocatalytic Electrolysis Membrane Reactor for Ecosafe Hydroponic Farming

In this study, a novel photoelectrocatalytic membrane (PECM) reactor was tested as an option for the desalination, disinfection, and detoxification of biologically treated textile wastewater (BTTWW), with the aim to reuse it in hydroponic farming. The anionic ion exchange (IEX) process was used before PECM treatment to remove toxic residual dyes. The toxicity evaluation for every effluent was carried out using the Vibrio fischeri, Microtox^® test protocol. The disinfection effect of the PECM reactor was studied against E. coli. After PECM treatment, the 78.7% toxicity level of the BTTWW was reduced to 14.6%. However, photocatalytic desalination during treatment was found to be slow (2.5 mg L^-1 min^-1 at 1 V potential). The reactor demonstrated approximately 52% COD and 63% TOC removal efficiency. The effects of wastewater reuse on hydroponic production were comparatively investigated by following the growth of the lettuce plant. A detrimental effect was observed on the lettuce plant by the reuse of BTTWW, while no negative impact was reported using the PECM treated textile wastewater. In addition, all macro/micronutrient elements in the PECM treated textile wastewater were recovered by hydroponic farming, and the PECM treatment may be an eco-safe wastewater reuse method for crop irrigation.

Combined Application of Citric Acid and Cr Resistant Microbes Improved Castor Bean Growth and Photosynthesis while It Alleviated Cr Toxicity by Reducing Cr+6 to Cr3

Chromium is highly harmful to plants because of its detrimental effects on the availability of vital nutrients and secondary metabolites required for proper plant growth and development. A hydroponic experiment was carried out to analyze the effect of citric acid on castor bean plants under chromium stress. Furthermore, the role of two chromium-resistant microorganisms, Bacillus subtilis and Staphylococcus aureus, in reducing Cr toxicity was investigated. Different amounts of chromium (0 µM, 100 µM, 200 µM) and citric acid (0 mM, 2.5 mM, and 5 mM) were used both alone and in combination to analyze the remediation potential. Results showed that elevated amounts of chromium (specifically 200 µM) minimized the growth and biomass because the high concentration of Cr induced the oxidative markers. Exogenous citric acid treatment boosted plant growth and development by improving photosynthesis via enzymes such as superoxide dismutase, guaiacol peroxidase, catalase, and ascorbate peroxidase, which decreased Cr toxicity. The application of citric acid helped the plants to produce a high concentration of antioxidants which countered the oxidants produced due to chromium stress. It revealed that castor bean plants treated with citric acid could offset the stress injuries by decreasing the H₂O₂, electrolyte leakage, and malondialdehyde levels. The inoculation of plants with bacteria further boosted the plant growth parameters by improving photosynthesis and reducing the chromium-induced toxicity in the plants. The findings demonstrated that the combination of citric acid and metal-resistant bacteria could be a valuable technique for heavy metal remediation and mediating the adverse effects of metal toxicity on plants.

The Fenton-like reaction for Arsenic removal from groundwater: Health risk assessment

In this paper, the heterogeneous Fenton like-reaction for Arsenic-contaminated groundwater remediation based on the performance of FeSO₄ as an efficient and green catalyst and CaO₂ as a source of H₂O₂ was investigated. To intensify the heterogeneous Fenton process, three oxidants were tested: sodium percarbonate (SPC), sodium persulfate (SPS), and calcium peroxide (CP). The results showed that CP and SPC had a synergetic effect on the rate of Arsenic degradation, while SPS had an antagonistic effect. On the other hand, inorganic ions such as Na⁺, Mg²⁺ have a very low impact on the Arsenic removal efficiency, while the anions Cl^- and NO₃^- exhibited significant inhibition of Arsenic degradation. This effect may be imputed to the reaction and conversion of hydroxyl (HO^•) radicals to less reactive. Thus, HCO₃^- and humic acid dramatically raised the degradation rate. Also, the response Surface method based on Box-Behnken design was applied to examine the suitable modeling, and optimized condition of the Fenton like-reaction process, the maximum Arsenic removal efficiency of 94.91% is obtained when [Fe³⁺]₀ = 1.97 mM, [CaO₂]₀ = 1.74 mM and initial pH = 4.67. The obtained results showed that the Fenton-like reaction is an effective and reliable process for arsenic removal from groundwater with low non-carcinogenic risk (HQ) and carcinogenic risk (CR) values.

Solar disinfection (SODIS) technologies as alternative for large-scale public drinking water supply: Advances and challenges

Gastrointestinal waterborne diseases, continue to stand out among the most lethal diseases in developing countries, because of consuming contaminated water taken from unsafe sources. Advances made in recent decades in methods of solar water disinfection (SODIS) have shown that SODIS is an effective and inexpensive method of providing drinking water, capable of substantially reducing the prevalence and mortality of waterborne diseases. The increased impact of SODIS in communities lacking drinking water services depends on a successful upgrade from conventional SODIS (based on PET bottle reactors) in high flow continuous flow systems for solar water disinfection (CFSSWD). This review aimed to identify the main limitations of conventional SODIS that hinder its application as a large-scale drinking water supply strategy, and to propose ways to overcome these limitations (without making it economically inaccessible) based on the current frontier of advances technological. It was found that the successful development of the CFSSWD depends on overcoming the current limitations of conventional SODIS and the development of systems whose configurations allow combining the properties of solar pasteurization (SOPAS) and SODIS. Different improvements need to be made to the main components of the CFSSWD, such as increasing the performance of solar radiation collectors, photo and thermal reactors and heat exchangers. The integration of disinfection technologies based on photocatalytic and photothermal nanomaterials also needs to be achieved. The performance evaluation of the CFSSWD should be made considering resistant microorganisms, such as the environmental resistance structures of bacteria or protozoa (spores or (oo)cysts) as targets of disinfection approaches.

Insights into Solar Disinfection Enhancements for Drinking Water Treatment Applications

Poor access to drinking water, sanitation, and hygiene has always been a major concern and a main challenge facing humanity even in the current century. A third of the global population lacks access to microbiologically safe drinking water, especially in rural and poor areas that lack proper treatment facilities. Solar water disinfection (SODIS) is widely proven by the World Health Organization as an accepted method for inactivating waterborne pathogens. A significant number of studies have recently been conducted regarding its effectiveness and how to overcome its limitations, by using water pretreatment steps either by physical, chemical, and biological factors or the integration of photocatalysis in SODIS processes. This review covers the role of solar disinfection in water treatment applications, going through different water treatment approaches including physical, chemical, and biological, and discusses the inactivation mechanisms of water pathogens including bacteria, viruses, and even protozoa and fungi. The review also addresses the latest advances in different pre-treatment modifications to enhance the treatment performance of the SODIS process in addition to the main limitations and challenges.

The formation, analysis, and control of chlor(am)ination-derived odor problems: A review

Odors and tastes have become universal problems related to drinking water quality. In addition to the typical odor problems caused by algae or microorganisms, the occurrence of odors derived from drinking water disinfection have attracted attention. The chlor(am)ination-derived odor substances have certain toxicity and odor-causing characteristics, and would enter the tap water through water distribution systems, directly affecting drinking water safety and customer experience. This study provided a comprehensive overview of the occurrence, detection, and control of odor substances derived from drinking water chlor(am)ination disinfection. The occurrence and formation mechanisms of several typical types of disinfection derived odor substances were summarized, including haloanisoles, N-chloroaldimines, iodotrihalomethanes, and halophenoles. They are mainly derived from specific precursors such as halophenols, anisoles, and amino acids species during the disinfection or distribution networks. In addition, the change of disinfectant during chlor(am)ination was also one of the causes of disinfection odors. Due to the extremely low odor threshold concentrations (OTCs) of these odor substances, the effective sample pre-enrichment for instrument identification and quantification are essential. The control strategies of odor problems mainly include adsorption, chemical oxidation, and combined processes such as ozonation and biological activated carbon processes (O₃/BAC) and ultraviolet-based advanced oxidation processes (UV-AOPs). Finally, the challenges and possible future research directions in this research field were discussed and proposed.

Proteomic analysis reveals the mechanism of different environmental stress-induced tolerance of Pseudomonas aeruginosa to monochloramine disinfection

Although drinking water disinfection proved to be an effective strategy to eliminate many pathogens, bacteria can still show disinfection tolerance in drinking water distribution systems. To date, the molecular mechanisms on how environmental stress affects the tolerance of Pseudomonas aeruginosa to monochloramine are not well understood. Here, we investigated how three stress conditions, namely starvation, low temperature, and starvation combined with low temperature, affected the monochloramine tolerance of Pseudomonas aeruginosa, an opportunistic pathogen commonly found in drinking water distribution systems. All stress conditions significantly promoted monochloramine tolerance, among which starvation had the most drastic effects. Proteomic analyses suggested that the three conditions not only triggered a positive antioxidant defense against oxidative damages but also prepared the bacteria to employ a passive defense mechanism against disinfectants via dormancy. Moreover, the expression of antioxidant enzymes reached the maximum under the starvation condition and further low temperature treatment had little effect on bacterial response to oxidative stress. Instead, we found further treatment of the starved cells with low temperature decreased the osmotic stress response and the stringent response, which generally play pivotal roles in disinfection tolerance. Taken together, these findings shed light on how abiotic factors influence the bacterial disinfection tolerance and will aid design of efficient strategies to eliminate Pseudomonas aeruginosa from drinking water.

The influence of UV irradiation on PAHs in wastewater

Studies were carried out on the impact of UV radiation contact time and UV/chlorination processes on changes in polycyclic aromatic hydrocarbons (PAHs) content in treated wastewater in order to obtain environmentally safe water. The research showed that the optimal time of UV irradiation for both processes was 30 min. After irradiation, the total concentration of PAH decreased by 66%, and after the UV/chlorination process by 78%. Following UV irradiation, the reduction ranged from 74% to 81% for 3-ring PAHs, 4-ring benzo(a)anthracene and 5-ring dibenzo(a,h)anthracene. Using the UV/chlorination process, the greatest changes were observed for acenaphthene (93 ± 4%), anthracene (90 ± 4%), pyrene (87% ± 3) and acenaphthylene (83 ± 4%). Due to limited information on the mechanisms which can be responsible for the observed decrease in PAH content in wastewater after the UV and UV/chlorination processes, it cannot be clearly stated to what extent the methods used affect the actual reduction of the concentration, therefore further research is required.

The Pathway towards Photoelectrocatalytic Water Disinfection: Review and Prospects of a Powerful Sustainable Tool

Photoelectrocatalysis is a hybrid photon/electron-driven process that benefits from the synergistic effects of both processes to enhance and stabilize the generation of disinfecting oxidants. Photoelectrocatalysis is an easy to operate technology that can be scaled-up or scaled-down for various water treatment applications as low-cost decentralized systems. This review article describes the fundamentals of photoelectrocatalysis, applied to water disinfection to ensure access to clean water for all as a sustainable development goal. Advances in reactor engineering design that integrate light-delivery and electrochemical system requirements are presented, with a description of photo-electrode material advances, including doping, nano-decoration, and nanostructure control. Disinfection and cell inactivation are described using different model microorganisms such as E. coli, Mycobacteria, Legionella, etc., as well the fungus Candida parapsilosis, with relevant figures of merit. The key advances in the elucidation of bacterial inactivation mechanisms by photoelectrocatalytic treatments are presented and knowledge gaps identified. Finally, prospects and further research needs are outlined, to define the pathway towards the future of photoelectrocatalytic disinfection technologies.

Characterization of Two New Shiga Toxin-Producing Escherichia coli O103-Infecting Phages Isolated from an Organic Farm

Shiga toxin-producing Escherichia coli (STEC) O103 strains have been recently attributed to various foodborne outbreaks in the United States. Due to the emergence of antibiotic-resistant strains, lytic phages are considered as alternative biocontrol agents. This study was to biologically and genomically characterize two STEC O103-infecting bacteriophages, vB_EcoP-Ro103C3lw (or Ro103C3lw) and vB_EcoM-Pr103Blw (or Pr103Blw), isolated from an organic farm. Based on genomic and morphological analyses, phages Ro103C3lw and Pr103Blw belonged to Autographiviridae and Myoviridae families, respectively. Ro103C3lw contained a 39,389-bp double-stranded DNA and encoded a unique tail fiber with depolymerase activity, resulting in huge plaques. Pr103Blw had an 88,421-bp double-stranded DNA with 26 predicted tRNAs associated with the enhancement of the phage fitness. Within each phage genome, no virulence, antibiotic-resistant, and lysogenic genes were detected. Additionally, Ro103C3lw had a short latent period (2 min) and a narrow host range, infecting only STEC O103 strains. By contrast, Pr103Blw had a large burst size (152 PFU/CFU) and a broad host range against STEC O103, O26, O111, O157:H7, and Salmonella Javiana strains. Furthermore, both phages showed strong antimicrobial activities against STEC O103:H2 strains. The findings provide valuable insight into these two phages’ genomic features with the potential antimicrobial activities against STEC O103.

Solar Water Disinfection to Produce Safe Drinking Water: A Review of Parameters, Enhancements, and Modelling Approaches to Make SODIS Faster and Safer

Solar water disinfection (SODIS) is one the cheapest and most suitable treatments to produce safe drinking water at the household level in resource-poor settings. This review introduces the main parameters that influence the SODIS process and how new enhancements and modelling approaches can overcome some of the current drawbacks that limit its widespread adoption. Increasing the container volume can decrease the recontamination risk caused by handling several 2 L bottles. Using container materials other than polyethylene terephthalate (PET) significantly increases the efficiency of inactivation of viruses and protozoa. In addition, an overestimation of the solar exposure time is usually recommended since the process success is often influenced by many factors beyond the control of the SODIS-user. The development of accurate kinetic models is crucial for ensuring the production of safe drinking water. This work attempts to review the relevant knowledge about the impact of the SODIS variables and the techniques used to develop kinetic models described in the literature. In addition to the type and concentration of pathogens in the untreated water, an ideal kinetic model should consider all critical factors affecting the efficiency of the process, such as intensity, spectral distribution of the solar radiation, container-wall transmission spectra, ageing of the SODIS reactor material, and chemical composition of the water, since the substances in the water can play a critical role as radiation attenuators and/or sensitisers triggering the inactivation process.