Removal of precursors and disinfection by-products (DBPs) by membrane filtration from water; a review

Exposure to trichloromethane via drinking water promotes progression of colorectal cancer by activating IRE1α/XBP1 pathway of endoplasmic reticulum stress

Trichloromethane (TCM), a commonly recognized disinfection by-product formed during the chlorination of water, has been associated with the onset of colorectal cancer (CRC) in humans. Despite this, the impact of TCM on the progression of CRC remains uncertain. In this investigation, it was observed that exposure to TCM could augment the migratory capabilities of CRC cells and facilitate the advancement of colorectal tumors. To delve deeper into the mechanism responsible for TCM-induced CRC progression, we performed RNA-Seq analysis at cellular and animal levels after TCM exposure. Both the KEGG and GO enrichment analyses indicated the activation of endoplasmic reticulum stress (ERS) and the regulation of the cytoskeleton. Subsequently, we confirmed the activation of the IRE1α/XBP1 pathway of ERS through western blot and RT-qPCR. Additionally, we observed the aggregation of cytoskeletal proteins F-actin and β-tubulin at the cell membrane periphery and the development of cellular pseudopods using immunofluorescence following exposure to TCM in vitro. The downregulation of IRE1α and XBP1 through siRNA interference resulted in the disruption of cell cytoskeleton rearrangement and impaired cell migration capability. Conversely, treatment with TCM mitigated this inhibitory effect. Moreover, chronic exposure to low concentration of TCM also triggered CRC cell migration by causing cytoskeletal reorganization, a process controlled by the IRE1α/XBP1 axis. Our study concludes that TCM exposure induces cell migration through the activation of ERS, which in turn regulates cytoskeleton rearrangement. This study offers novel insights into the mechanism through which TCM facilitates the progression of CRC.

Removal of endocrine disruptors and pharmaceuticals by graphene oxide-based membranes in water: A review

Membrane-based water treatment has emerged as a promising solution to address global water challenges. Graphene oxide (GO) has been successfully employed in membrane filtration processes owing to its reversible properties, large-scale production potential, layer-to-layer stacking, great oxygen-based functional groups, and unique physicochemical characteristics, including the creation of nano-channels. This review evaluates the separation performance of various GO-based membranes, manufactured by coating or interfacial polymerization with different support layers such as polymer, metal, and ceramic, for endocrine-disrupting compounds (EDCs) and pharmaceutically active compounds (PhACs). In most studies, the addition of GO significantly improved the removal efficiency, flux, porosity, hydrophilicity, stability, mechanical strength, and antifouling performance compared to pristine membranes. The key mechanisms involved in contaminant removal included size exclusion, electrostatic exclusion, and adsorption. These mechanisms could be ascribed to the physicochemical properties of compounds, such as molecular size and shape, hydrophilicity, and charge state. Therefore, understanding the removal mechanisms based on compound characteristics and appropriately adjusting the operational conditions are crucial keys to membrane separation. Future research directions should explore the characteristics of the combination of GO derivatives with various support layers, by tailoring diverse operating conditions and compounds for effective removal of EDCs and PhACs. This is expected to accelerate the development of surface modification strategies for enhanced contaminant removal.

Molecular insight of dissolved organic matter and chlorinated disinfection by-products in reclaimed water during chlorination with permanganate preoxidation

Permanganate is a common preoxidant applied in water treatment to remove organic pollutants and to reduce the formation of disinfection by-products. However, the effect of permanganate preoxidation on the transformation of dissolved effluent organic matter (dEfOM) and on the formation of unknown chlorinated disinfection by-products (Cl-DBPs) during chlorination remains unknown at molecular level. In this work, the molecular changes of dEfOM during permanganate preoxidation and subsequent chlorination were characterized using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Permanganate preoxidation was found to decrease the DBE (double bond equivalent) and AImod (modified aromaticity index) of the dEfOM. The identity and fate of over 400 unknown Cl-DBPs during KMnO4-chlorine treatment were investigated. Most Cl-DBPs and the precursors were found to be highly unsaturated aliphatic and phenolic compounds. The Cl-DBPs precursors with lower H/C and lower O/C were preferentially removed by permanganate preoxidation. Additionally, permanganate preoxidation decreased the number of unknown Cl-DBPs by 30% and intensity of unknown Cl-DBPs by 25%. One-chlorine-containing DBPs were the major Cl-DBPs and had more CH2 groups and higher DBEw than Cl-DBPs containing two and three chlorine atoms. 60% of the Cl-DBPs formation was attributed to substitution reactions (i.e., +Cl-H, +2Cl-2H, +3Cl-3H, +ClO-H, +Cl2O3-2H). This work provides detailed molecular level information on the efficacy of permanganate preoxidation on the control of overall Cl-DBPs formation during chlorination.

The occurrence, ecological risk, and control of disinfection by-products from intensified wastewater disinfection during the COVID-19 pandemic

Increased disinfection of wastewater to preserve its microbiological quality during the coronavirus infectious disease-2019 (COVID-19) pandemic have inevitably led to increased production of toxic disinfection by-products (DBPs). However, there is limited information on such DBPs (i.e., trihalomethanes, haloacetic acids, nitrosamines, and haloacetonitriles). This review focused on the upsurge of chlorine-based disinfectants (such as chlorine, chloramine and chlorine dioxide) in wastewater treatment plants (WWTPs) in the global response to COVID-19. The formation and distribution of DBPs in wastewater were then analyzed to understand the impacts of these large-scale usage of disinfectants in WWTPs. In addition, potential ecological risks associated with DBPs derived from wastewater disinfection and its receiving water bodies were summarized. Finally, various approaches for mitigating DBP levels in wastewater and suggestions for further research into the environmental risks of increased wastewater disinfection were provided. Overall, this study presented a comprehensive overview of the formation, distribution, potential ecological risks, and mitigating approaches of DBPs derived from wastewater disinfection that will facilitate appropriate wastewater disinfection techniques selection, potential ecological risk assessment, and removal approaches and regulations consideration.

Advances and research needs for disinfection byproducts control strategies in swimming pools

The control of disinfection byproducts (DBPs) in swimming pools is of great significance due to the non-negligible toxicity and widespread existence of DBPs. However, the management of DBPs remains challenging as the removal and regulation of DBPs is a multifactorial phenomenon in pools. This study summarized recent studies on the removal and regulation of DBPs, and further proposed some research needs. Specifically, the removal of DBPs was divided into the direct removal of the generated DBPs and the indirect removal by inhibiting DBP formation. Inhibiting DBP formation seems to be the more effective and economically practical strategy, which can be achieved mainly by reducing precursors, improving disinfection technology, and optimizing water quality parameters. Alternative disinfection technologies to chlorine disinfection have attracted increasing attention, while their applicability in pools requires further investigation. The regulation of DBPs was discussed in terms of improving the standards on DBPs and their preccursors. The development of online monitoring technology for DBPs is essential for implementing the standard. Overall, this study makes a significant contribution to the control of DBPs in pool water by updating the latest research advances and providing detailed perspectives.

A comprehensive appraisal on status and management of remediation of DBPs by TiO2 based-photocatalysts: Insights of technology, performance and energy efficiency

Disinfection has been acknowledged as an inevitable technique in water treatment. However, an inadvertent consequence of generation of carcinogenic and mutagenic disinfection byproducts (DBPs) is associated with the reaction of disinfectants and natural organic matter (NOM) present in water. More than 700 DBPs have been identified in drinking water. The conventional processes carried out in WTPs do not optimally ensure NOM elimination, which evokes the need for the incorporation of other processes. In this context, several physicochemical and advanced oxidation processes (AOP), such as adsorption, membrane techniques, photocatalysis, etc., have been studied for the removal of NOM from water. Photocatalysis using semiconductors has been one of the most proficient technologies, which utilizes light energy for the degradation of recalcitrant organics. The present study aims to provide a comprehensive appraisal on the performance of titanium dioxide (TiO₂) based photocatalysts in the remediation of DBPs concerning the efficacy and energy requirements of the system. Furthermore, the effect of process parameters, such as pH, catalyst dose, light intensity, etc. on the efficacy of the process was also studied. It was observed that conventional P25-TiO₂ powders were efficient in the degradation of dissolved organic carbon (DOC) (up to 90%). However, low photocatalytic activity under visible light activation is one of its significant downsides. Several modifications on the catalyst surface in many studies exhibited advantages, such as high humic acid (HA) degradation under visible light. Furthermore, doped TiO₂ catalysts have shown high total organic carbon (TOC) degradation. The photocatalytic systems have achieved a better decrease in trihalomethane formation potential (THMFP) when compared to haloacetic acid formation potential (HAAFP). The energy requirements of the photocatalytic systems are determined by electrical energy per order (EE/O), which has been observed to be lesser for doped TiO₂ and engineered TiO₂ catalysts when compared with P25-TiO₂ powders. Carbon, iron, silver, etc., based catalysts can be a promising alternative to TiO₂-based photocatalysts for the degradation of NOM, although further research is required in this direction. The present review provides critical highlights on the uses, opportunities, and challenges of TiO₂-based photocatalytic techniques for the management of DBPs and their precursors pertaining to an emerging area of water treatment.

Characterization and chlorine reactivity of particulate matter released by bathers in indoor swimming pools

Disinfecting swimming pool water is essential for preventing waterborne diseases. An unforeseen consequence of treating water with disinfectants is the formation of disinfection by-products (DPBs) that can cause harmful effects to health through the interactions between the added disinfectant and organic matter in the water. The present work focuses on the chlorine reactivity with particles released by bathers. Such particles are collected in the filter backwash water of swimming pools and this study intends to distinguish DPBs generated from dissolved chemicals from those formed by particulate matter. Therefore, filtered and unfiltered backwash waters were collected from several swimming pools, analysed physicochemically and chemically, and then chlorinated as is (79 mgL^-1) and as diluted suspensions (36.2 and 11.9 mgL^-1) at varying concentrations of chlorine (1.2 mg and 24 mgCl₂L^-1). Utilizing a DPD colorimetric technique and GC-ECD, respectively, the kinetics of chlorine consumption and DPBs production have been investigated. Up to 25.7 μgL^-1 of chloroform was produced within 96 h at 1.2 mgCl₂L^-1, followed by haloacetic acids (HAAs) and haloacetonitriles (HANs). Within 96 h, the concentration of trichloroacetic acid reached a maximum of 231.8 μgL^-1 at a chlorine concentration of 231.8 μgL^-1. The formations of 0.13 μmol THMs, 0.31 μmol HAAs, and 0.04 μmol HANs per mg of dissolved organic carbon (DOC) were finally determined by correlating the organic content of particles with the nature of the DBPs generated. Comparing the quantities of DBPs generated in filtered and unfiltered samples helps us conclude that ∼50% of DBPs formed during the chlorination of swimming pool water are derived from particles brought by bathers.

Trihalomethanes in drinking water from three First Nation reserves in Manitoba, Canada

Previous research indicates that the water distribution system used has a significant impact on the microbial quality of tap water sampled in First Nations reserves in Canada. This study tested tap water from homes in three First Nations reserves to compare the concentrations of four trihalomethanes and related water quality parameters between homes receiving piped water from a water treatment plant (WTP) versus homes equipped with cisterns that are filled by a water truck. Of all the samples collected across time from household taps, 75% of piped samples and 70% of cistern samples had TTHM concentrations exceeding Health Canada's maximum acceptable concentration (MAC) of 100 µg L^-1 total trihalomethanes (TTHMs) in treated water. In all communities and across sampling times, trichloromethane (CHCl₃) was the dominant trihalomethane (42-96%) followed by bromodichloromethane (CHBrCl₂) (3-37%) and dibromochloromethane (CHClBr₂) (1-18%). Tribromomethane (CHBr₃) always accounted for < 5% of TTHMs. Within each of the three First Nations reserves, the water distribution system had no significant effect on TTHM concentration at the household level. Sampling month had a significant effect on TTHM concentration due to temporal changes in dissolved organic carbon of the source water. Results suggest that families in the studied First Nations reserves receive drinking water with high TTHM concentrations and that improvements to the water treatment plant might be the most effective way to minimize trihalomethane formation.

Current Developments in the Effective Removal of Environmental Pollutants through Photocatalytic Degradation Using Nanomaterials

Photocatalysis plays a prominent role in the protection of the environment from recalcitrant pollutants by reducing hazardous wastes. Among the different methods of choice, photocatalysis mediated through nanomaterials is the most widely used and economical method for removing pollutants from wastewater. Recently, worldwide researchers focused their research on eco-friendly and sustainable environmental aspects. Wastewater contamination is one of the major threats coming from industrial processes, compared to other environmental issues. Much research is concerned with the advanced development of technology for treating wastewater discharged from various industries. Water treatment using photocatalysis is prominent because of its degradation capacity to convert pollutants into non-toxic biodegradable products. Photocatalysts are cheap, and are now emerging slowly in the research field. This review paper elaborates in detail on the metal oxides used as a nano photocatalysts in the various type of pollutant degradation. The progress of research into metal oxide nanoparticles, and their application as photocatalysts in organic pollutant degradation, were highlighted. As a final consideration, the challenges and future perspectives of photocatalysts were analyzed. The application of nano-based materials can be a new horizon in the use of photocatalysts in the near future for organic pollutant degradation.

Disinfection byproducts formed during drinking water treatment reveal an export control point for dissolved organic matter in a subalpine headwater stream

Changes in climate, season, and vegetation can alter organic export from watersheds. While an accepted tradeoff to protect public health, disinfection processes during drinking water treatment can adversely react with organic compounds to form disinfection byproducts (DBPs). By extension, DBP monitoring can yield insights into hydrobiogeochemical dynamics within watersheds and their implications for water resource management. In this study, we analyzed temporal trends from a water treatment facility that sources water from Coal Creek in Crested Butte, Colorado. These trends revealed a long-term increase in haloacetic acid and trihalomethane formation over the period of 2005-2020. Disproportionate export of dissolved organic carbon and formation of DBPs that exceeded maximum contaminant levels were consistently recorded in association with late spring freshet. Synoptic sampling of the creek in 2020 and 2021 identified a biogeochemical hotspot for organic carbon export in the upper domain of the watershed that contained a prominent fulvic acid-like fluorescent signature. DBP formation potential analyses from this domain yielded similar ratios of regulated DBP classes to those formed at the drinking water facility. Spectrometric qualitative analyses of pre and post-reacted waters with hypochlorite indicated lignin-like and condensed hydrocarbon-like molecules were the major reactive chemical classes during chlorine-based disinfection. This study demonstrates how drinking water quality archives combined with synoptic sampling and targeted analyses can be used to identify and understand export control points for dissolved organic matter. This approach could be applied to identify and characterize analogous watersheds where seasonal or climate-associated organic matter export challenge water treatment disinfection and by extension inform watershed management and drinking water treatment.

Groundwater-Based Drinking Water Supply in Sri Lanka: Status and Perspectives

Drinking water is largely from groundwater in Sri Lanka, so quality management is of great concern. In order to achieve the 6th goal of United Nations (UN) Sustainable Development Goals (SDG), more efforts are being undertaken to secure drinking water quality. In this paper, the current status, challenges and opportunities of groundwater quality management and improvement in Sri Lanka were reviewed and discussed, based on previous studies. There are Ca-HCO3 type, Ca–Mg-HCO3 type and Na–SO4–Cl type groundwater dominated in the wet zone, intermediate and the dry zone, respectively. Elevated levels of hardness, fluoride, DOC, and alkalinity, and salinity are reported in the groundwater in the dry zone controlled by geology and arid climate. Although groundwater in some regions contain significant levels of nitrates, arsenic, cadmium and lead, the majority remain at acceptable levels for drinking purposes. As for treatment technologies, existing membrane-based drinking water treatment technologies such as RO (Reverse Osmosis) stations can produce safe and clean drinking water to the community, but this has still a limited coverage. To achieve a safe drinking water supply for all, especially in rural communities of Sri Lanka under the 6th goal of the UN SDG, more efforts in building up the infrastructure and man power are needed to monitor and assess groundwater quality regularly so as to develop management strategies. Research and development can be directed towards more cost-effective water treatment technologies. Protection of groundwater from being polluted, and educational and awareness programs for the stakeholders are also essential tasks in the future.

Comparison of Disinfection By-Product Formation and Distribution during Breakpoint Chlorination and Chlorine-Based Disinfection in Drinking Water

Breakpoint chlorination (BC) and disinfection with chlorine-based disinfectant are widely used procedures in drinking water production. Both involve dosing chlorine into the raw water, where it can react with organic compounds, forming disinfection by-products (DBPs) of health concern. However, technological parameters (e.g., contact time, chlorine dosage, and bromide to residual free chlorine ratio) of the two chlorination procedures are different, which can lead to differences in DBP formation. To better understand this, a year-long sampling campaign was carried out at three waterworks in Hungary, where both BC and chlorine disinfection are used. To confirm the results of the field sampling, bench-scale experiments were carried out, investigating the impact of (a) bromide concentration in raw water, (b) residual free chlorine (bromide to residual chlorine ratio), and (c) contact time on DBP formation. The measured DBPs were trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), and chlorate. During BC, the DBPs were formed in higher concentration, with the exception of one waterwork having elevated bromide content in the raw water. Bromine substitution factors (BSFs) were significantly higher during disinfection than BC in both field and laboratory experiments. After BC, the chlorate concentration range was 0.15–1.1 mg/L, and 96% of the samples exceeded the European Union (EU) parametric value (0.25 mg/L), whereas disinfection contributed only slightly. Granular activated carbon (GAC) filters used to remove DBPs in waterworks were exhausted after 6–8 months of use, first for those chlorinated THMs, which are generated predominantly during BC. The biological activity of the filters started to increase after 3–6 months of operation. This activity helps to remove the biodegradable compounds, such as disubstituted haloacetic acid (DHAAs) and HANs, even if the adsorption capacity of the GAC filters are low.

Adsorption Behavior and Dynamic Interactions of Anionic Acid Blue 25 on Agricultural Waste

In this study, adsorption characteristics of a negatively charged dye, Acid Blue 25 (AB25), on pomelo pith (PP) was studied by varying the adsorption parameters, with the aim of evaluating the adsorption mechanism and establishing the role of hydrogen bonding interactions of AB25 on agricultural wastes. The kinetics, intraparticle diffusion, mechanism, and thermodynamics of the AB25 adsorption were systematically evaluated and analyzed by pseudo-first-order and pseudo-second-order kinetic models, the Weber-Morris intraparticle and Boyd mass transfer models, the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models, and the Van't Hoff equation. It was found that AB25 adsorption followed pseudo-second-order kinetics, governed by a two-step pore-volume intraparticle diffusion of external mass transfer of AB25 onto the PP surface. The adsorption process occurred spontaneously. The adsorption mechanism could be explained by the Langmuir isotherm model, and the maximum adsorption capacity was estimated to be 26.9 mg g-1, which is comparable to many reported adsorbents derived from agricultural wastes. Changes in the vibrational spectra of the adsorbent before and after dye adsorption suggested that AB25 molecules are bound to the PP surface via electrostatic and hydrogen bonding interactions. The results demonstrated that the use of pomelo pith, similar to other agricultural wastes, would provide a basis to design a simple energy-saving, sustainable, and cost-effective approach to remove negatively charged synthetic dyes from wastewater.

Removal of Emerging Contaminants from Wastewater Streams Using Membrane Bioreactors: A Review

Water is a very valuable natural resource. As the demand for water increases the presence of emerging contaminants in wastewater has become a growing concern. This is particularly true when one considers direct reuse of wastewater. Obtaining sufficient removal of emerging contaminants will require determining the level of removal for the various unit operations in the wastewater treatment process. Membrane bioreactors are attractive as they combine an activated sludge process with a membrane separation step. They are frequently used in a wastewater treatment process and can operate at higher solid loadings than conventional activated sludge processes. Determining the level of removal of emerging contaminants in the membrane bioreactor step is, therefore, of great interest. Removal of emerging contaminants could be by adsorption onto the biomass or membrane surface, biotransformation, size exclusion by the membrane, or volatilization. Given the fact that most emerging contaminants are low molecule weight non-volatile compounds, the latter two methods of removal are usually unimportant. However, biotransformation and adsorption onto the biomass are important mechanisms of removal. It will be important to determine if the microorganisms present at given treatment facility are able to remove ECs present in the wastewater.

A Review on the Use of Membrane Technology Systems in Developing Countries

Fulfilling the demand of clean potable water to the general public has long been a challenging task in most developing countries due to various reasons. Large-scale membrane water treatment systems have proven to be successful in many advanced countries in the past two decades. This paves the way for developing countries to study the feasibility and adopt the utilization of membrane technology in water treatment. There are still many challenges to overcome, particularly on the much higher capital and operational cost of membrane technology compared to the conventional water treatment system. This review aims to delve into the progress of membrane technology for water treatment systems, particularly in developing countries. It first concentrates on membrane classification and its application in water treatment, including membrane technology progress for large-scale water treatment systems. Then, the fouling issue and ways to mitigate the fouling will be discussed. The feasibility of membrane technologies in developing countries was then evaluated, followed by a discussion on the challenges and opportunities of the membrane technology implementation. Finally, the current trend of membrane research was highlighted to address future perspectives of the membrane technologies for clean water production.

Tailored design of nanofiltration membranes for water treatment based on synthesis-property-performance relationships

Tailored design of high-performance nanofiltration (NF) membranes is desirable because the requirements for membrane performance, particularly ion/salt rejection and selectivity, differ among the various applications of NF technology ranging from drinking water production to resource mining. However, this customization greatly relies on a comprehensive understanding of the influence of membrane fabrication methods and conditions on membrane properties and the relationships between the membrane structural and physicochemical properties and membrane performance. Since the inception of NF, much progress has been made in forming the foundation of tailored design of NF membranes and the underlying governing principles. This progress includes theories regarding NF mass transfer and solute rejection, further exploitation of the classical interfacial polymerization technique, and development of novel materials and membrane fabrication methods. In this critical review, we first summarize the progress made in controllable design of NF membrane properties in recent years from the perspective of optimizing interfacial polymerization techniques and adopting new manufacturing processes and materials. We then discuss the property-performance relationships based on solvent/solute mass transfer theories and mathematical models, and draw conclusions on membrane structural and physicochemical parameter regulation by modifying the fabrication process to improve membrane separation performance. Next, existing and potential applications of these NF membranes in water treatment processes are systematically discussed according to the different separation requirements. Finally, we point out the prospects and challenges of tailored design of NF membranes for water treatment applications. This review bridges the long-existing gaps between the pressing demand for suitable NF membranes from the industrial community and the surge of publications by the scientific community in recent years.

Nanofiltration for drinking water treatment: a review

In recent decades, nanofiltration (NF) is considered as a promising separation technique to produce drinking water from different types of water source. In this paper, we comprehensively reviewed the progress of NF-based drinking water treatment, through summarizing the development of materials/fabrication and applications of NF membranes in various scenarios including surface water treatment, groundwater treatment, water reuse, brackish water treatment, and point of use applications. We not only summarized the removal of target major pollutants (e.g., hardness, pathogen, and natural organic matter), but also paid attention to the removal of micropollutants of major concern (e.g., disinfection byproducts, per- and polyfluoroalkyl substances, and arsenic). We highlighted that, for different applications, fit-for-purpose design is needed to improve the separation capability for target compounds of NF membranes in addition to their removal of salts. Outlook and perspectives on membrane fouling control, chlorine resistance, integrity, and selectivity are also discussed to provide potential insights for future development of high-efficiency NF membranes for stable and reliable drinking water treatment.

Molecular Insight into AC Electric Field Enhanced Removal of Protein Aggregates from a Material Surface

Biofouling, caused by unwanted accumulation of the biological molecules on the material surface, is a common problem when medical devices are planted in the human body. Application of an electric field was first suggested in the 1960s along with many other approaches to deactivate the biofouling process. There are experiments showing a higher efficiency in reducing the biofouling using the alternating current (AC) compared to the direct current (DC). Here, using molecular dynamics (MD) simulations, we compared the binding stability of a single protein molecule on a graphene surface with either an AC or a DC field was applied. We first showed that the protein molecule, initially attached to the graphene surface, will spontaneously be desorbed by the applied AC electric field, while it remains intact under the DC field of the same voltage. We then revealed that the desorption of the protein by the AC electric field is kinetically controlled. As the orientation of the protein changed alongside the reversing electric field, the protein-graphene interface would be destabilized the most if the AC frequency was close to that of the relaxation of the protein dipole moment (i.e., resonance).

Antibacterial and corrosion protection properties of SA-CuZnO@ODA-GO composite in circulating cooling water

The suitable temperature of circulating cooling water is conducive to the reproduction of bacteria, which will cause corrosion to the pipe and form slime on its surface. Therefore, the sterilization of circulating cooling water is an essential step. In this work, a new type of SA-CuZnO@ODA-GO composite antibacterial material with hydrophobic properties was prepared by ultrasonic treatment method. The composite was characterized and analyzed by SEM, TEM, XPS, XRD, and FT-IR. Then, the CuZnO@ODA-GO@PU hydrophobic and antibacterial coating was prepared. The antibacterial properties and mechanism of the composite were investigated by gram-positive bacteria S. aureus and gram-negative bacteria E. coli. The result shows that the best antibacterial rate of SA-CuZnO@ODA-GO composite antibacterial material is up to 99.10%. As for the SA-CuZnO@ODA-GO@PU composite antibacterial coating, the corrosion resistance of the antibacterial coating is up to 99.99%. The anticorrosion property is due to the hydrophobic modification of the composite, which can insulate the steel sheet from water. Secondly, due to the rigidity of the SA-CuZnO@ODA-GO, it combines with epoxy resin to form a compact structure.

Changes in structural characteristics of humic and fulvic acids under chlorination and their association with trihalomethanes and haloacetic acids formation

The effects of chlorination on 16 humic and fulvic acids (HAs and FAs, respectively) extracted from six different soil samples from Korea and two purchased soil samples (Canadian peat moss, Elliott Silt Loam Soil) were investigated to identify the changes in their structural characteristics and their effects on trihalomethane formation potential (THMFP) and haloacetic acid formation potential. The effect of chlorination was also investigated in fractionated samples (Aldrich HA, F₁-F₅) based on molecular weight (MW). Total organic carbon (TOC), specific UV absorbance (SUVA), fulvic-like fluorescence (%FLF), terrestrial humic-like fluorescence (%THLF), weight-average molecular weight (MW_w), and carbon structures (¹³C NMR) were measured for each sample before and after chlorination, and factors relating to the chlorination mechanism were examined using principal component analysis (PCA). The results showed that the changes in the structural characteristics and the disinfection by-product formation of chlorinated HA and FA differed critically. For chlorinated HA, TOC and %FLF decreased due to oxidation, whereas %THLF was reduced via incorporation; MW also affected the structural changes and THMFP generation. In the PCA results, high SUVA, low MW, low N/C, and low O groups of aromatic C were associated with high THMFP production in HA, whereas low O groups of aliphatic C in FA were associated with both oxidation and incorporation in terms of THMFP. These results elucidate the mechanisms associated with the effects of chlorination in HA and FA and will support the prediction of THMFP generation in HA and FA based on their specific structural characteristics.

Recent Advances in Biopolymer-Based Dye Removal Technologies

Synthetic dyes have become an integral part of many industries such as textiles, tannin and even food and pharmaceuticals. Industrial dye effluents from various dye utilizing industries are considered harmful to the environment and human health due to their intense color, toxicity and carcinogenic nature. To mitigate environmental and public health related issues, different techniques of dye remediation have been widely investigated. However, efficient and cost-effective methods of dye removal have not been fully established yet. This paper highlights and presents a review of recent literature on the utilization of the most widely available biopolymers, specifically, cellulose, chitin and chitosan-based products for dye removal. The focus has been limited to the three most widely explored technologies: adsorption, advanced oxidation processes and membrane filtration. Due to their high efficiency in dye removal coupled with environmental benignity, scalability, low cost and non-toxicity, biopolymer-based dye removal technologies have the potential to become sustainable alternatives for the remediation of industrial dye effluents as well as contaminated water bodies.

Recent Advances of Photocatalytic Application in Water Treatment: A Review

Photocatalysis holds great promise as an efficient and sustainable oxidation technology for application in wastewater treatment. Rapid progress developing novel materials has propelled photocatalysis to the forefront of sustainable wastewater treatments. This review presents the latest progress on applications of photocatalytic wastewater treatment. Our focus is on strategies for improving performance. Challenges and outlooks in this promising field are also discussed. We hope this review will help researchers design low-cost and high-efficiency photocatalysts for water treatment.

Producing and storing self-sustaining drinking water from rainwater for emergency response on isolated island

Drinking water on isolated islands includes treated rainwater, water shipped from the mainland, and desalinated seawater. However, marine transportation and desalination plants are vulnerable to emergencies, such as extreme weather, making self-sustaining stand-by water for emergency response essential. Rainwater is ideal for producing the stand-by water, and rainwater harvesting is sustainable and clean, and prolonged biostability can be ensured by managing biological and chemical parameters. The present study applied a stand-by drinking water purification system (primarily including nanofiltration and low-dose chlorination) to explore the feasibility of producing and storing cleaner drinking water from rainwater and the following conclusions were drawn. First, treatment of rainwaters ensures biosafety for seven days, which is longer than that for untreated rainwater; the proportion of opportunistic pathogens decreased from 23.40-7.77% after nanofiltration, and it was proposed that the microbial community converges after advanced water treatment. Second, chemical qualities were improved. Local resource coral sand prevents pH in rainwater from decreasing below 6.5, and treated rainwater had lower disinfection by-product potential and higher disinfection efficiency, allowing periodical rainwater recycling. Third, harvesting rainwater was extremely cost-effective, with an operation cost of 1.5-2.5 RMB/m³. From biosafety, chemical safety, and economic cost perspectives, self-sustaining water from rainwater can contributes to the development of sustainable and cost-effective water supply systems on isolated islands. Mixing treated rainwater and desalinated seawater reasonably guarantees sufficiency and safety.

The Role of Catalytic Ozonation Processes on the Elimination of DBPs and Their Precursors in Drinking Water Treatment

Formation of disinfection byproducts (DBPs) in drinking water treatment (DWT) as a result of pathogen removal has always been an issue of special attention in the preparation of safe water. DBPs are formed by the action of oxidant-disinfectant chemicals, mainly chlorine derivatives (chlorine, hypochlorous acid, chloramines, etc.), that react with natural organic matter (NOM), mainly humic substances. DBPs are usually refractory to oxidation, mainly due to the presence of halogen compounds so that advanced oxidation processes (AOPs) are a recommended option to deal with their removal. In this work, the application of catalytic ozonation processes (with and without the simultaneous presence of radiation), moderately recent AOPs, for the removal of humic substances (NOM), also called DBPs precursors, and DBPs themselves is reviewed. First, a short history about the use of disinfectants in DWT, DBPs formation discovery and alternative oxidants used is presented. Then, sections are dedicated to conventional AOPs applied to remove DBPs and their precursors to finalize with the description of principal research achievements found in the literature about application of catalytic ozonation processes. In this sense, aspects such as operating conditions, reactors used, radiation sources applied in their case, kinetics and mechanisms are reviewed.

Antibacterial properties of recoverable CuZnO@Fe3O4@GO composites in water treatment

The growth of bacteria will lead to water quality deterioration and equipment damage. Therefore, it is necessary to control the growth and reproduction of microorganisms in water treatment. A new type of magnetic recoverable CuZnO@Fe3O4@GO composites was prepared by ultrasonic method, and the composites were characterized and analyzed by SEM, TEM, XPS, and other methods. The optimum mass ratio of composites was determined by orthogonal experiment, and the antibacterial properties and mechanism of the composite were investigated by gram-positive bacteria Staphylococcus aureus and gram-negative bacteria Escherichia coli. Finally, the antibacterial properties of the composites in the effluent of the secondary sedimentation tank were researched. It was shown that the optimum mass ratio of the composites was GO:Fe3O4:CuZnO =1:2:3. When the dosage of composites was 180 mg L-1 and the action time was 100 min, the antibacterial rate against S. aureus and E. coli reached more than 99.5%. The composites could destroy the cell structure of two kinds of bacteria, increase the content of active oxygen in bacteria cells, and enhance the leakage rate of protein by more than 9 times in 150 min, thereby causing the death of the bacteria. And the antibacterial rate of the composites in effluent of the secondary sedimentation tank could reach 99%, and the magnetic recovery rate could reach more than 98%. After 5 cycles of use, the antibacterial rate could still exceed 90%.

Effects of microbubble pre-ozonation time and pH on trihalomethanes and haloacetic acids formation in pilot-scale tropical peat water treatments for drinking water purposes

The high concentrations of dissolved organic matter (DOM), chloride, and bromide in tropical peat water have a significant impact on the formation of carcinogenic disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs), especially during the chlorination process. Therefore, other pretreatment methods to effectively remove these harmful substances in the water during treatment are needed. The aim of this study was to determine the effects of microbubble pre-ozonation pH on the reduction of THM4 and HAA5 formed during the peat water treatment process and to determine the best conditions for microbubble pre-ozonation to reduce the formation of these two classes of DBPs. The microbubble pre-ozonation was conducted at a pH of 5.5, 7, and 8.5. Furthermore, the primary treatments applied after this pretreatment were coagulation and activated carbon adsorption before post-chlorine disinfection. The coagulation process using aluminum sulfate and activated carbon adsorption succeeded in reducing the formation of THM4 after chlorination, to a level below USEPA standards, but the concentration of HAA5 was still high. However, the use of microbubble pre-ozonation significantly reduced the formation of both classes of compounds during the chlorination process of the peat water. Also, the concentration of THM4 increased during the pre-ozonation process in all pH conditions, but HAA5 decreased except in alkaline state. Furthermore, the ideal conditions for microbubble pre-ozonation on peat water were at pH 7 (neutral) after 30 min, with the total THM4 concentration at 33.73 ± 0.40 μg/L, and that of HAA5 at 49.89 ± 0.09 μg/L, falling below the USEPA standard.

Bottled water safety evaluations in IRAN: determination of bromide and oxyhalides (chlorite, chlorate, bromate) by ion chromatography

Bottled water is most well liked within the world and attention is drawn due to its health issues. Oxyhalides is one amongst the foremost important by-products in bottled water which is produced by disinfection process such as "ozonation". International standards have been set and justified to permissible levels for chlorate, chlorite and bromate as 700, 700 and 10 μg/l. Thereafter, 168 samples of bottled water (mineral and drinking water) from Iran market obtained with the optimal working conditions and analyzed by ion chromatography (IC) with conductivity detector. The results actuated that 23 and 17 out of 168 samples as mineral and drinking water revealed bromate content in charge of the national permissible level, found as the mean level of 37.04 and 33.58 μg/l, respectively. According to risk assessment results, the average of hazard quotient (HQ) and lifetime excess cancer (ELCR) were calculated 6.955 × 10^-3 and 0.25 × 10^-3, respectively. Thereupon, it is indispensable to control as well as make consumers aware of oxyholides hazard especially bromate following governmental authorities with an insight to health sectors monitoring guidelines due to its obvious harmful effects and aspects on health issues.

Precursors of typical nitrogenous disinfection byproducts: Characteristics, removal, and toxicity formation potential

The emergence of nitrogenous disinfection byproducts (N-DBPs) in drinking water has become a widespread concern. In this study, dichloroacetonitrile (DCAN), dicholoacetamide (DCAcAm) and trichloronitromethane (TCNM) were chosen as representatives to clarify the characteristics of N-DBP precursors in the raw waters of Taihu Lake, the Yangtze River, and Gaoyou Lake. Removal of DCAN and DCAcAm precursors must focus on nonpolar and positively charged organics, but more attention should be paid to micromolecular, polar and non-positively charged organics as TCNM precursors. Compared to molecular weight (MW) and hydrophilicity fractionation, polarity and electrical classification have higher selectivity to intercept N-DBP precursors. The properties of N-DBP precursors are relatively fixed and traceable in water systems, which could contribute to their targeted removal. Based on investigation of their characteristics, the removal efficiency and preferences of organic precursors under different processes were studied in three drinking water treatment plants (DWTPs). The TCNM precursors produced in preozonation can be effectively removed during coagulation. The cumulative removal efficiency of conventional processes on N-DBP precursors was approximately 20-30%, but O₃/BAC process improved removal by about 40%. The key to improving the removal efficiency of N-DBP precursors by O₃/BAC is that it can significantly remove low-MW, nonpolar, positively charged, hydrophilic and transphilic organics. In combined toxicity trials, both cytotoxicity and genotoxicity showed a synergistic effect when DCAN, DCAcAm, and TCNM coexisted, which means that low-level toxicity enhancement in the actual water merits attention. DCAN precursors dominated in the toxicity formation potential (TFP), followed by TCNM precursors. In addition, the removal rate of total N-DBP precursors may be higher than that of TFP, leading to overly optimistic evaluation of precursor removal in water treatment practice. Therefore, the removal effect on TFP must also be considered.

Nanoceramics and novel functionalized silicate-based magnetic nanocomposites as substitutional disinfectants for water and wastewater purification

Herein, we successfully synthesized nano-porous Co₂O₃/Cu₂O₃: Al₂O₃: SiO₂ ((0, 5, 7, 9) Co-CAS) using the acidic sol-gel approach and calcined at 800 °C for 4 h. The crystallization behavior and spectroscopic properties were investigated using X-ray diffraction, field emission-scanning electron microscopy, and Fourier-transform infrared absorption spectra analysis. The antibiotic properties of the nano-porous CAS, 5Co-CAS, and 9Co-CAS magnetic nanocomposites was studied against some potentially pathogenic bacteria in water and wastewater samples. The bacteria tested included Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus, Enterococcus faecalis, and Bacillus subtilis. Incorporating Co₂O₃ resulted in the identification of three peaks at 2θ = 10.2°, 13.4°, and 15°. The introduction of cobalt nanoparticles created a ferromagnetic behavior in the CAS nanoceramic, with the magnetic moment and saturation values increasing with increased Co₂O₃ doping. 9Co-CAS was most potent against all the tested pathogens with minimum inhibitory concentrations of 25 mg/L within 40 min for E. coli and P. aeruginosa and 50 mg/L within 10 min for S. enterica; the lowest antibacterial activity was observed with the unmodified CAS. The findings revealed that the manufactured nanocomposite materials were potent disinfectants with a promising application for water and wastewater treatment.

Comprehensive review of polycyclic aromatic hydrocarbons in water sources, their effects and treatments

Polycyclic aromatic hydrocarbons (PAHs) are principally derived from the incomplete combustion of fossil fuels. This study investigated the occurrence of PAHs in aquatic environments around the world, their effects on the environment and humans, and methods for their removal. Polycyclic aromatic hydrocarbons have a great negative impact on the humans and environment, and can even cause cancer in humans. Use of good methods and equipment are essential to monitoring PAHs, and GC/MS and HPLC are usually used for their analysis in aqueous solutions. In aquatic environments, the PAHs concentrations range widely from 0.03 ng/L (seawater; Southeastern Japan Sea, Japan) to 8,310,000 ng/L (Domestic Wastewater Treatment Plant, Siloam, South Africa). Moreover, bioaccumulation of ∑16PAHs in fish has been reported to range from 11.2 ng/L (Cynoscion guatucupa, South Africa) to 4207.5 ng/L (Saurida undosquamis, Egypt). Several biological, physical and chemical and biological techniques have been reported to treat water contaminated by PAHs, but adsorption and combined treatment methods have shown better removal performance, with some methods removing up to 99.99% of PAHs.

Response surface methodological (RSM) approach for optimizing the removal of trihalomethanes (THMs) and its precursor's by surfactant modified magnetic nanoadsorbents (sMNP) - An endeavor to diminish probable cancer risk

Response surface methodology (RSM) approach was used for optimization of the process parameters and identifying the optimal conditions for the removal of both trihalomethanes (THMs) and natural organic matter (NOM) in drinking water supplies. Co-precipitation process was employed for the synthesis of magnetic nano-adsorbent (sMNP), and were characterized by field emission scanning electron microscopy (SEM), trans-emission electron microscopy (TEM), BET (Brunauer-Emmett-Teller), energy dispersive X-ray (EDX) and zeta potential. Box-Behnken experimental design combined with response surface and optimization was used to predict THM and NOM in drinking water supplies. Variables were concentration of sMNP (0.1 g to 5 g), pH (4–10) and reaction time (5 min to 90 min). Statistical analysis of variance (ANOVA) was carried out to identify the adequacy of the developed model, and revealed good agreement between the experimental data and proposed model. The experimentally derived RSM model was validated using t-test and a range of statistical parameters. The observed R² value, adj. R², pred. R² and “F-values” indicates that the developed THM and NOM models are significant. Risk analysis study revealed that under the RSM optimized conditions, a marked reduction in the cancer risk of THMs was observed for both the groups studied. Therefore, the study observed that the developed process and models can be efficiently applied for the removal of both THM and NOM from drinking water supplies.

Removal of mutagen X "MX" from drinking water using reduced graphene oxide coated sand particles

PURPOSE

Mutagen X is a hazardous by-product of disinfection by chlorine, which is responsible for most of the mutagenicity in chlorinated drinking water. It has the cancer potency value of 100-fold higher than bromodichloromethane and 6000-fold higher than chloroform, In this study, Mutagen X was removed from aqueous media by a thermally reduced graphene oxide bonded on the surface of amino-functionalized sand particles.

METHOD

A Box-Behnken design was applied to optimize the adsorption process. Characterization of the adsorbent and graphene oxide was accomplished using scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman analysis. The effects of three independent parameters, including initial concentration (20-200 μg L^-1), temperature (5-30 °C), and adsorbent dose (2-80 g L^-1) were examined using batch experiments.

RESULTS

Characterization results confirmed that the graphene oxide was successfully coated on the surface of sand particles. Regression analysis of experimental results showed a great fit with a quadratic polynomial model with the R² = 0.999. Optimum conditions (initial concentration: 20 μg L^-1, temperature: 30 °C, and adsorbent dose: 80 g L^-1) with the desirability of 1.0 resulted in the minimum residual concentration of Mutagen X (2 μg L^-1). Equilibrium study results depicted that the experimental data were fitted well to the Freundlich and UT isotherm models.

Synthesis and characteristics of a novel FeNi3/SiO2/TiO2 magnetic nanocomposites and its application in adsorption of humic acid from simulated wastewater: study of isotherms and kinetics

The presence of natural organic matter such as humic acid in water creates various problems in water purification. Humic acid can react with chlorine in the disinfection step and lead to the production of trihalomethanes and haloacetic acids that these compounds have carcinogenic and mutagenic properties; therefore, they must be removed before arriving to the disinfection stage. The purpose of this research was adsorption of humic acid from simulated wastewater by synthesized FeNi₃/SiO₂/TiO₂ magnetic nanocomposites. FeNi₃/SiO₂/TiO₂ magnetic nanocomposites were synthesized by sol-gel procedure and its characteristics were determined by TEM, VSM, BET, FESEM, and XRD techniques. Then, the effects of such pH (3-11), FeNi₃/SiO₂/TiO₂ dosage (0.005-0.1 g/L), contact time (0-200 min), and initial concentration (2-15 mg/L) were studied on humic acid adsorption using FeNi₃/SiO₂/TiO₂. The results of adsorption experiments revealed that the highest percentage of humic acid removal (94.4%) was achieved at pH 3, initial concentration of 5 ppm, FeNi₃/SiO₂/TiO₂ dose of 0.1 g/L, and contact time of 90 min. The analyses of experimental isotherm data showed that the humic acid adsorption was described by Langmuir model and also the kinetic studies represented that the process of adsorption of humic acid on FeNi₃/SiO₂/TiO₂ was followed by the pseudo-second kinetic. According to the results, it can be concluded that FeNi₃/SiO₂/TiO₂ magnetic nanocomposites have a high ability to absorb humic acid from simulated wastewater.

Public Water Supply and Sanitation Authorities for Strategic Sustainable Domestic Water Management. A Case of Iringa Region In Tanzania

Water supply is a mandatory service for the majority from respective legal public water utilities, and its sustainability reflects implementations of best management strategies at a local level. The objectives of this study were (i) to assess current approaches used in water quality and quantity management and (ii) propose a sustainable domestic water management strategy. This was achieved through secondary water data trends, on-site water quality assessments, visits of water supply and sanitation authorities, and assessment of their performances. It was observed that water supplied in rural-based authorities was quite different from that supplied in an urban setting as far as quality and quantity are concerned; urban-based supplies are more affordable to users than rural ones. A new strategy on water management is presented for sustainable water supply; it is based on controlling groundwater abstractions and preference of surface water in public water supplies. Rural water supply management must learn several practices realized in urban supplies for the betterment of services for the majority of the users.

CDs@ZIF-8 Modified Thin Film Polyamide Nanocomposite Membrane for Simultaneous Enhancement of Chlorine-Resistance and Disinfection Byproducts Removal in Drinking Water

Reverse osmosis (RO) is an emerging membrane technology for disinfection byproducts (DBPs) removal. However, the chlorine-resistance and DBPs removal performance of thin film composite (TFC) polyamide membranes should be simultaneously improved when used in chlorinated drinking water. This study was dedicated to synthesize a novel nanoparticle of ZIF-8 with carbon dots (CDs@ZIF-8) and then modify thin film nanocomposite (TFN) membranes to enhance their performance in removing four trihalomethanes (THMs), four haloacetonitriles (HANs), and two haloketones (HKs) in chlorinated drinking water. The fabricated CDs@ZIF-8 nanoparticles and TFN membranes were characterized by FESEM, AFM, XPS, water contact angle, membrane surface potential, and a three-dimensional excitation-emission matrix (EEM) to investigate the influences of CDs@ZIF-8 on TFN membranes. After chlorination, percentage reduction in salt rejection of the CDs@ZIF-8 TFN membranes was lower than that of the TFC membranes due to hydrogen bonding between CDs and polyamide, replacing amidic hydrogen with chlorine, rendering the membrane less susceptible to chlorine attack and enhancing chlorine-resistance. Results also showed that the rejection of DBPs in chlorinated drinking water by CDs@ZIF-8 TFN membranes was more than 95%. The large surface area and abundant oxygen-containing groups of CDs@ZIF-8 made the nanoparticle act as a nanocarbon filler with high adsorption capacity of DBPs. The enhanced performances of chlorine-resistance and DBPs removal by CDs@ZIF-8 TFN membranes determined in this study provided valuable insights on the DBPs control in chlorinated drinking water by RO membranes.

New Insights in the Natural Organic Matter Fouling Mechanism of Polyamide and Nanocomposite Multiwalled Carbon Nanotubes-Polyamide Membranes

Polyamide (PA) membranes comprise most of the reverse osmosis membranes currently used for desalination and water purification. However, their fouling mechanisms with natural organic matter (NOM) is still not completely understood. In this work, we studied three different types of PA membranes: a laboratory made PA, a commercial PA, and a multiwalled carbon nanotube (CNT-PA nanocomposite membrane during cross-flow measurements by NaCl solutions including NOM, humic acid (HA), or alginate, respectively). Molecular dynamic simulations were also used to understand the fouling process of NOM down to its molecular scale. Low molecular weight humic acid binds to the surface cavities on the PA structures that leads to irreversible adsorption induced by the high surface roughness. In addition, the larger alginate molecules show a different mechanism, due to their larger size and their ability to change shape from the globule type to the uncoiled state. Specifically, alginate molecules either bind through Ca²⁺ bridges or they uncoil and spread on the surface. This work shows that carbon nanotubes can help to decrease roughness and polymer mobility on the surfaces of the membranes at the molecular scale, which represents a novel method to design antifouling membranes.

Predicting the cytotoxicity of disinfection by-products to Chinese hamster ovary by using linear quantitative structure-activity relationship models

A suitable model to predict the toxicity of current and continuously emerging disinfection by-products (DBPs) is needed. This study aims to establish a reliable model for predicting the cytotoxicity of DBPs to Chinese hamster ovary (CHO) cells. We collected the CHO cytotoxicity data of 74 DBPs as the endpoint to build linear quantitative structure-activity relationship (QSAR) models. The linear models were developed by using multiple linear regression (MLR). The MLR models showed high performance in both internal (leave-one-out cross-validation, leave-many-out cross-validation, and bootstrapping) and external validation, indicating their satisfactory goodness of fit (R² = 0.763-0.799), robustness (Q²_LOO = 0.718-0.745), and predictive ability (CCC = 0.806-0.848). The generated QSAR models showed comparable quality on both the training and validation levels. Williams plot verified that the obtained models had wide application domains and covered the 74 structurally diverse DBPs. The molecular descriptors used in the models provided comparable information that influences the CHO cytotoxicity of DBPs. In conclusion, the linear QSAR models can be used to predict the CHO cytotoxicity of DBPs.

Green sol-gel synthesis of novel nanoporous copper aluminosilicate for the eradication of pathogenic microbes in drinking water and wastewater treatment

We used a green sol-gel synthesis method to fabricate a novel nanoporous copper aluminosilicate (CAS) material. Nanoporous CAS was characterized using X-ray powder diffraction (XRD), field emission transmission and scanning electron microscopies (FE-TEM/FE-SEM), Fourier transform infrared (FTIR) spectroscopy, and optical analyses. The CAS was also evaluated for use as a promising disinfectant for the inactivation of waterborne pathogens. The antimicrobial action and minimum inhibitory concentration (MIC) of this CAS disinfectant were determined against eight microorganisms (Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa, Listeria monocytogenes, Staphylococcus aureus, Enterococcus faecalis, Candida albicans, and Aspergillus niger). An antimicrobial susceptibility testing of CAS was measured. Results of disc diffusion method pointed out that the diameters of the zone using well diffusion were wider than disc diffusion methods, and the findings also showed that the MIC of the CAS disinfectant against E. coli, S. enterica, and P. aeruginosa was 100 mg/L within 20 min of contact time. Meanwhile, the MIC of the CAS disinfectant was 100 mg/L within 40 min of contact time for the other strains. The efficacy of antimicrobial action (100%) reached within 20 to 40 min against all tested microbes. Herein, the antimicrobial susceptibility testing of CAS disinfectant showed no toxicity for human and bacterial cells. It can be concluded that nanoporous CAS is a promising, economically, and worthy weapon for water disinfection.

Integrating MFT-qPCR techniques in constructed wetland faecal bacterial purification monitoring; a case of a typical tropical hybrid constructed wetland system

The sanitation control of pathogens in the tropical effluents needs much more attention to ensure ecosystem health integrity and the safety of human health. The common use of chemicals in achieving this in wastewater treatment has remained unsustainable due to much health concern. Indeed, based on the numerous challenges associated with faecal pathogenic bacteria in wastewaters, the focus is now on achieving higher purification efficiencies in the elimination of the human pathogens from wastewater through eco-sustainable systems such as constructed wetlands (CWs). Hence, the need to explore the application of constructed wetlands in wastewater treatment under specific local environmental conditions for accurate understanding and improved treatment efficiency. This study therefore aimed at monitoring constructed wetlands faecal bacteria purification efficiency through integrated non-molecular membrane filtration technique and molecular quantitative polymerase chain reaction (MFT-qPCR) technique. The results showed some shortfall in the treatment system and also proved that integrating MFT-qPCR in faecal bacterial purification monitoring within a constructed wetland system provides a more accurate and reliable outcome. Additionally, the wetland purification efficiency was low (<80%) with the dissolved oxygen posing the strongest influence on faecal pathogenic bacterial purification trend across the wetland. Hence, the need to regularly carry out dredging and macrophyte harvesting as well as the use of holistic and more integrative approaches such as MFT-qPCR in managing and monitoring the performance of CWs in faecal pathogen eradication for improved CWs purification efficiency.