Figure 1. Seventeen chemically similar rare earth elements and their distribution by country (Canada, Greenland, Tanzania, and South Africa are included in “Other”) and end use. (7) Qieyuan Gao is now a Ph.D. student in the research division “Process Engineering for Sustainable Systems” within the department of Chemical Engineering at KU Leuven, starting his Ph.D. research in 2020. He has long been engaged in the research of industrial water treatment and advanced separation technology. He received a Master’s in engineering from the China University of Mining and Technology in 2020. To date, Qieyuan Gao has published 14 peer-reviewed journal articles. He is also a reviewer for internationally renowned journals Separation and Purification Technology, Journal of Colloid and Interface Science, Fuel, ACS ES&T Water, etc. He is also a member of the European Membrane Society (EMS) (from 2022). In addition, he was funded by the China Scholarship Council (CSC) to go to KU Leuven for doctoral research. Bart Van der Bruggen is a professor at the University of Leuven (KU Leuven) in Belgium, where he leads a group of 30 Ph.D. students in the research division “Process Engineering for Sustainable Systems” within the Department of Chemical Engineering. His expertise is in separation technologies for sustainable processes, with an emphasis on membrane science and technology. He has authored more than 700 publications in international journals (current h-factor: 93; >36 000 citations) and 30 book chapters. He has been the scientific promoter of 65 Ph.D. theses. He was the President of the European Membrane Society (EMS) from 2013 to 2017 and is the Founding President of the World Association of Membrane Societies (2017–2020). Since 2014, he has also been an Extraordinary Professor in Tshwane University of Technology (South Africa). He is Editor-in-Chief of Separation and Purification Technology (Q1, IF 9.1), Executive Editor of the Journal of Chemical Technology and Biotechnology (IF 3.7), Section Editor of Heliyon, and Associate Editor of Process Safety and Environmental Protection. Q.G. acknowledges the support provided by the China Scholarship Council (CSC) of the Ministry of Education, P. R. China (CSC 202006420004). This article references 10 other publications. This article has not yet been cited by other publications. Figure 1. Seventeen chemically similar rare earth elements and their distribution by country (Canada, Greenland, Tanzania, and South Africa are included in “Other”) and end use. (7) Qieyuan Gao is now a Ph.D. student in the research division “Process Engineering for Sustainable Systems” within the department of Chemical Engineering at KU Leuven, starting his Ph.D. research in 2020. He has long been engaged in the research of industrial water treatment and advanced separation technology. He received a Master’s in engineering from the China University of Mining and Technology in 2020. To date, Qieyuan Gao has published 14 peer-reviewed journal articles. He is also a reviewer for internationally renowned journals Separation and Purification Technology, Journal of Colloid and Interface Science, Fuel, ACS ES&T Water, etc. He is also a member of the European Membrane Society (EMS) (from 2022). In addition, he was funded by the China Scholarship Council (CSC) to go to KU Leuven for doctoral research. Bart Van der Bruggen is a professor at the University of Leuven (KU Leuven) in Belgium, where he leads a group of 30 Ph.D. students in the research division “Process Engineering for Sustainable Systems” within the Department of Chemical Engineering. His expertise is in separation technologies for sustainable processes, with an emphasis on membrane science and technology. He has authored more than 700 publications in international journals (current h-factor: 93; >36 000 citations) and 30 book chapters. He has been the scientific promoter of 65 Ph.D. theses. He was the President of the European Membrane Society (EMS) from 2013 to 2017 and is the Founding President of the World Association of Membrane Societies (2017–2020). Since 2014, he has also been an Extraordinary Professor in Tshwane University of Technology (South Africa). He is Editor-in-Chief of Separation and Purification Technology (Q1, IF 9.1), Executive Editor of the Journal of Chemical Technology and Biotechnology (IF 3.7), Section Editor of Heliyon, and Associate Editor of Process Safety and Environmental Protection. This article references 10 other publications.

Water quality monitoring at the point of consumption by consumers can improve the understanding of the microbial risk of drinking water. In this study, drinking water samples were collected by citizen science participants according to their normal drinking sources and behaviors. Among six different sample types, tap water received the most attention per sampling frequency (39%) and weighted importance score, followed by drinking fountain (38%) and personal container (21%). Enumeration of Escherichia coli and the total coliform as indicator organisms showed consistent and good quality in water samples from tap water and drinking fountains but significantly higher detection frequencies (90 and 90%, respectively) and median concentrations (14 and 252 CFU/100 mL, respectively) in water samples from personal containers. Microbial community analysis based on 16S rRNA gene amplicon sequencing showed that the microbial communities in water samples from personal containers were less diverse than microbial communities in the other water types, the latter of which showed high similarity in the microbial composition and α and β diversity. Several genera that include species of opportunistic pathogens were detected across samples from drinking water sources, while higher total relative abundances of these genera were detected in water samples from personal containers than others.

Climate change hazards, including increased temperatures, drought, sea level rise, extreme precipitation, wildfires, and changes in freeze–thaw cycles, are expected to degrade drinking water utility system infrastructure and decrease the reliability of water provision. To assess how drinking water utility manager perceptions of these risks affect utility planning, 60 semistructured interviews were conducted with utilities of various sizes, source water supplies, and United States geographical regions. This study analyzes these interviews (1) to evaluate which climate hazards are of primary concern to drinking water managers, (2) to develop a mental model framework for assessing utility-level understanding of climate change risks to system reliability, and (3) to examine the status of current water utility adaptation planning. The results show that concern and awareness of climate hazard risks vary geographically and are grounded in historical exposure; some participants do not believe climate change will influence their system’s overall reliability. When considering climate change risks, utility managers tend to focus on effects to water supply and infrastructure, as opposed to changes in operations and maintenance, water quality, or business functions. Most surveyed utilities do not have comprehensive climate adaptation plans despite federal and professional recommendations. The range of beliefs and actions concerning climate adaptation planning indicates that utilities need directed guidance, and policymakers should consider including climate hazards and projections as part of required utility risk and resilience assessments.

Characterizing sorbent affinity for a target compound (described by sorbent–water distribution coefficient, Ksw) is a necessary step in the sorbent selection and performance-testing process in the process of capturing aquatic contaminants. However, no standardized procedure exists to measure Ksw, and studies display significant variations in setup and performance. For per- and polyfluoroalkyl substances (PFAS), most Ksw determinations employ batch experiments with small-scale water–sorbent mixtures, methanol-based spike of target compound(s), and analysis after assumed equilibrium, but methodological details of the above procedure differ and might cause artifacts in the determination of Ksw. We conducted several batch experiments systematically varying a general procedure to characterize the effects of suboptimal experimental design. Using a selection of PFAS (6-carbon fluorinated chain length with differing functional groups) and two sorbents, we tested variations of a solution/sorbent ratio, methanol content, and PFAS initial concentration and compared derived Ksw values. Each methodological component affected log(Ksw) usually by suppressing the value (by 0–48%) when compared with a “best design” procedure. Thus, we suggest (1) a reference procedure for PFAS and sorbents used here and (2) general guidelines for batch experiment design with different compounds and sorbents. Additionally, we report well-constrained Ksw values for 23 PFAS and two sorbents.

The concentration of heavy metals (HMs) in rivers continues to increase beyond regional background values, thereby impacting human health and disrupting ecological balance. In this context, an electrochemical sensing device to detect HM ions Zn(II) and Cd(II) in river waters is herein reported. It consists of graphite (G) decorated with 2-hydroxy-1,4-naphthoquinone (HNFQ) incorporated in a carbon paste electrode (CPE), and the G surface modification with HNFQ was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronocoulometry (CC). The electroanalytical behavior and detection of Zn(II) and Cd(II) were evaluated by square-wave voltammetry (SWV) and CV. The developed sensor exhibits excellent stability, reproducibility, repeatability, and selectivity in the presence of interferents. The optimal G/HNFQ-CPE sensitivity is reflected by the limits of detection (LOD, 0.28 ± 0.02 μmol L–1 for Zn and 0.21 ± 0.03 μmol L–1 for Cd), limits of quantification (LOQ, 0.95 ± 0.09 μmol L–1 for Zn and 0.70 ± 0.11 μmol L–1 for Cd), and linear working range (0.47–93.8 μmol L–1). DFT calculations were performed to obtain molecular insights into the electrode/electrolyte solution interface. Finally, the sensor was validated using the atomic absorption technique, which places G/HNFQ-CPE as a promising electrode for Zn(II) and Cd(II) SWV detection.

Viruses found in the effluent and on the membrane surface during ultrafiltration (UF) processes will introduce hidden biosecurity dangers to drinking water. Fe3+ coagulation coupled with H2O2 to create an in situ membrane cleaning method, and MS2 bacteriophage was used as a model to investigate virus removal by UF when humic acid (HA) was present. The results showed that MS2 was removed by HA based on size exclusion, hydrophobicity, and electrostatic repulsion. Meanwhile, HA slightly reduced MS2 accumulation on the membrane surface by inhibiting MS2 adsorption. Fe3+ pretreatment (0.08 mmol/L) eliminated MS2 in the effluent by the adsorption and size exclusion of iron flocs. MS2 retained on the membrane surface was reduced through electrostatic repulsion. Iron flocs-H2O2 cleaning destroyed viral protein capsids through HO· oxidation and eliminated all MS2. The mitigation efficiency of membrane fouling was greatly improved with a flux recovery of 97.8%. Moreover, the use of H2O2 was significantly saved (3%) compared to no Fe3+ pretreatment (12%). This study provides a potentially useful and economically enhanced membrane cleaning method for virus-containing water treatment by UF, which could not only eliminate viruses and mitigate membrane fouling in the UF system but also reduce the use of membrane cleaning agents to save costs.

Urban stormwater runoff is a major source of pollutants into receiving water bodies. The pollutant profile of stormwater samples collected from an Australian creek during a major storm event in 2020 was investigated using high-resolution mass spectrometry and chemometric tools. The samples were solid phase-extracted and analyzed by liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer (LC-QToF-MS/MS). The detected features were prioritized using two independent but complementary workflows to identify the highly abundant stormwater-related compounds. A total of 174 features were detected at elevated levels during the storm. Four compounds were identified to a confidence level of 1 and 11 at level 2, including nonpolymeric surfactants, plastic additives, rubber and resin-related products, and natural products. Forty two percent were characterized as oligomers such as poly(ethylene glycol) (PEG)-related compounds and octylphenol ethoxylates. Due to a lack of database experimental data, many compounds remained unidentified. Compounds belonging to the same class were clustered using Global Natural Product Social (GNPS) Molecular Networking analysis, highlighting the benefit of this platform in environmental analysis. The prioritization workflow used here is characterized as an effective tool for assessing key stormwater-related compounds and identifying which should receive attention in assessing the environmental effects of stormwater-related chemicals.

Complexed heavy metal (HM) in acidic wastewater is one of the toughest issues for environmental pollution control. Aimed at directly eliminating complexed HMs from acidic wastewater, a novel cost-effective oligo-dithiocarbamate (oligo-DTC) chelating precipitant was synthesized by a bottom-up method from ammonia and 1,2-dichloroethane (DCE). Synthesis conditions were systematically optimized based on Ni removal performance at pH 2 and pH 7. An NH3/DCE ratio of 3:1 or above at temperatures between 100 and 160 °C were suitable for amination, while a NaOH/DCE ratio of 0.5–1.0:1 and a CS2/DCE ratio of 1.0:1 were favorable for dithiocarbamylation. The theoretical S/Ni mole ratio of oligo-DTC, representing the theoretically required oligo-DTC dose for complete Ni removal, was 8.2–9.4 at pH 2 and 4.0–4.6 at pH 7. Oligo-DTC showed high removal efficiencies for various HMs and had advantages over similar DTCs with high synthesis costs. Oligo-DTC successfully removed complexed HMs from two typical acidic wastewaters with residual HMs below the stringent discharge limits. Oligo-DTC had an average molecular weight of 1150 Da based on LCHRMS. Characterizations (scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy) showed that oligo-DTC removed HMs by chelation with its NCS2– functional groups and also indicated that oligo-DTC suffered nonnegligible self-aggregation and decomposition in HM removal under strongly acidic conditions.

Positive and negative electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and 1H NMR revealed major compositional and structural changes of dissolved organic matter (DOM) after mixing two sets of river waters in Amazon confluences: the Solimões and Negro Rivers (S + N) and the Amazon and Tapajós Rivers (A + T). We also studied the effects of water mixing ratios and incubation time on the composition and structure of DOM molecules. NMR spectra demonstrated large-scale structural transformations in the case of S + N mixing, with gain of pure and functionalized aliphatic units and loss of all other structures after 1d incubation. A + T mixing resulted in comparatively minor structural alterations, with a major gain of small aliphatic biomolecular binding motifs. Remarkably, structural alterations from mixing to 1d incubation were in essence reversed from 1d to 5d incubation for both S + N and A + T mixing experiments. Heterotrophic bacterial production (HBP) in endmembers S, N, and S + N mixtures remained near 0.03 μgC L–1 h–1, whereas HBP in A, T, and A + T were about five times higher. High rates of dark carbon fixation took place at S + N mixing in particular. In-depth biogeochemical characterization revealed major distinctions between DOM biogeochemical changes and temporal evolution at these key confluence sites within the Amazon basin.

Excessive use of antibiotics causes their residues in the environment and food, seriously threatening ecosystem and human health. Designing a portable and sensitive sensor for on-site analysis of antibiotics is therefore in high demand. In this study, we have developed a smartphone-capable hydrogel colorimetric platform for ultrasensitive detection of kanamycin (KAN) based on aptamer-regulated nanozyme activity. The synthesized Fe/CeO2 hexagonal bipyramidal microcrystals (Fe/CeO2 HBs) exhibited excellent peroxidase-like activity, but it could be obviously inhibited by the aptamer, and the inhibition effect was further enhanced with the specific recognition between target and aptamer, making it possible to design a facile colorimetric method for KAN analysis. Moreover, the aptamer-functionalized Fe/CeO2 HBs (Fe/CeO2 HBs@Apt) were introduced into the hydrogel to fabricate a portable analytical tube, whose colorimetric signal was read out by a smartphone platform, realizing the on-site analysis of KAN. The linear response range was 0.05–48.45 ng mL–1 with an ultralow detection limit of 0.035 ng mL–1 and the recovery rate ranging from 99.57 to 103.76% for spiked real samples, demonstrating its superior accuracy and reliability. This work provides new insights into designing the solid-phase hydrogel-based colorimetric method for on-site analysis of antibiotic residues.

Contamination of water with bacterial, viral, and protozoan pathogens can cause human diseases. Both humans and nonhumans can release these pathogens through their feces. To identify the sources of fecal contamination in the water environment, microbial source tracking (MST) approaches have been developed; however, the relationship between MST markers and pathogens is still not well understood most likely due to the lack of comprehensive datasets of pathogens and MST marker concentrations. In this study, we developed a novel microfluidic quantitative PCR (MFQPCR) platform for the simultaneous quantification of 37 previously validated MST markers, two fecal indicator bacteria (FIB), 22 bacterial, 11 viral, and five protozoan pathogens, and three internal amplification/process controls in many samples. The MFQPCR chip was applied to analyze pathogen removal rates during the wastewater treatment processes. In addition, multiple host-specific MST markers, FIB, and pathogens were successfully quantified in human and avian-impacted surface waters. While the genes for pathogens were relatively infrequently detected, positive correlations were observed between some potential pathogens such as Clostridium perfringens and Mycobacterium spp., and human MST markers. The MFQPCR chips developed in this study, therefore, can provide useful information to monitor and improve water quality.

Organic matter dissolved in tertiary effluents (effluent organic matter, EfOM) is the predominant organic membrane foulant in tertiary wastewater reverse osmosis (RO) desalination, ultimately causing biofouling. The interrelated effects of EfOM fractions of different hydrophobicity and polarity on membrane performance were studied by (i) examining each fraction’s overall effect on membrane permeability; (ii) analyzing the intrinsic hydraulic resistance induced by each fraction; (iii) studying their adsorption on the active layer of an RO membrane using a quartz crystal microbalance with dissipation monitoring (QCM-D); (iv) assessing their “dry” molecular mass when adsorbed on polyamide using localized surface plasmon resonance (LSPR) sensing; (v) analyzing their hydrodynamic radii by dynamic light scattering (DLS); and (vi) characterization using excitation–emission matrix (EEM) analysis and parallel-factor (PARAFAC) modeling. Hydrophobic and transphilic neutral fractions (containing ∼12.5% total organic carbon) have the greatest effect on membrane flux reduction and the highest hydraulic resistance and adhere most strongly to polyamide surfaces, resulting in the highest adsorbed “dry” mass. Therefore, in terms of their effect on RO permeate flux reduction, these fractions are the most detrimental in the EfOM mix. EEM analysis and associated PARAFAC modeling indicate that the main components causing this effect are mixtures of protein-like compounds, together with humic-like substances. Novel LSPR-based analysis elucidated the role of the fractions most detrimental to membrane permeability through measurement of dry mass surface concentration on a polyamide mimetic sensor. This study provides valuable insights into the roles of different EfOM fractions in RO membrane fouling and enhances our understanding of fouling during tertiary wastewater desalination.

Biosurfactants are promising alternatives to chemical dispersants for combating marine oil spills; however, the impacts of biosurfactants on microbial community composition and oil biodegradation activities remain largely unknown. Here, we conducted a time-course microcosm experiment mimicking oil spill scenarios with surface seawater from the North Sea, amended with either the biosurfactant rhamnolipid or a dispersant (Corexit 9500 or Slickgone NS). Radioactive tracer assays to track hexadecane and naphthalene oxidation as well as bacterial production revealed the highest hydrocarbon oxidation rates and general microbial activities in the rhamnolipid-amended oil microcosms, followed by oil microcosms with Slickgone and Corexit. Impacts on the microbial community composition differed among treatments, and growth of oil-degrading Colwellia was stimulated remarkably in Corexit-amended oil and oil-only microcosms, while potential oil-degrading Oleispira were highly enriched in the presence of oil in combination with rhamnolipid or Slickgone. Furthermore, increased abundances of Colwellia and Oleispira, and stimulated bacterial production in microcosms with only rhamnolipid, Corexit, or Slickgone, indicated their involvement in biosurfactant/dispersant biodegradation. Our findings highlight varying microbial impacts resulting from rhamnolipid and chemical dispersants and suggest great promise for the application of biosurfactants in future marine oil spills.

Iodine (I2) in the form of iodide ions (I–) is an essential chemical element in the human body. Iodine is a nonmetal that belongs to the VIIA group (halogens) in the periodic table. Over the last couple of centuries, the exponential growth of human society triggered by industrialization coincided with the use of iodine in a wide variety of applications, including chemical and biological processes. However, through these processes, the excess amount of iodine eventually ends up contaminating soil, underground water, and freshwater sources, which results in adverse effects. It enters the food chain and interferes with biological processes with serious physiological consequences in all living organisms, including humans. Existing removal techniques utilize different materials such as metal–organic frameworks, layered double hydroxides, ion-exchange resins, silver, polymers, bismuth, carbon, soil, MXenes, and magnetic-based materials. From our literature survey, it was clear that absorption techniques are the most frequently experimented with. In this Review, we have summarized current advancements in the removal of iodine and iodide from human-made contaminated aqueous waste.

Molecular docking has been used for the high-throughput screening of chemical interactions with target proteins in pharmaceutical and environmental applications. We determined the in silico binding affinity, protein–chemical interactions, toxic potential, and hormone equivalents of 96 organic Unregulated Contaminant Monitoring Rule (UCMR 1–4) organic contaminants and agonist/antagonist standards with 10 nuclear receptors associated with environmental endocrine disruption. Endocrine-active pollutants and their toxic potentials were mapped across United States Public Water Systems (PWS). The percent of inactive UCMR chemicals varied greatly, from ∼38% for the thyroid system (TRα and TRβ) up to ∼70% for the estrogen system (ERα and ERβ), due to the presence of charged amino acid residues within the receptor’s ligand binding domains. Further, a majority of UCMR-detectable public water systems (4,900/5,229) contained thyroid-active chemicals, including perfluoroalkyl and polyfluoroalkyl substances (PFAS), haloacetic acids, and herbicide degradates. Most UCMR chemical classes were modeled with low toxic potential in monitored PWSs serving populations that varied between a few thousand and 100 million people. Insecticides, pesticides, herbicides, hormones, and PFAS had moderate toxic potential impacting a population of 10,000–20 million people. The potential for endocrine disruption by unregulated chemicals in public water systems calls for a further risk analysis of cumulative exposures.

In this study, adsorption modeling of a model organic dye, methylene blue (MB), onto cellulose nanocrystal-alginate (CNC-ALG) hydrogel beads in a fixed bed column until full breakthrough was performed. A method for the in-situ production and loading of CNC-ALG hydrogel beads in a fixed bed column adsorption process was proposed for the first time. Fixed bed column adsorption experiments using MB and 0.5 wt % ALG and 2 wt % CNC beads were conducted using various initial dye concentrations, influent flow rates and adsorbent mass. The results were evaluated using a mathematical model with axial dispersion, film and pore diffusion to predict the fluid and particle phase continuity, and good agreement with the experimental data was observed. Experiments conducted using the spent hydrogel beads in a fixed bed column suggested that these adsorbents could be regenerated to 81% of its original adsorption capacity upon elution with 1 M hydrochloric acid:ethanol (1:1 v:v), and a subsequent adsorption cycle indicated that these adsorbents could achieve 96% of the renewed adsorption capacity. Furthermore, both batch and fixed bed column adsorption experiments displayed the maximum adsorption capacities of 401.8 and 410.5 mg MB/g adsorbent, respectively, and these similar values signify the reproducibility of the adsorption capacity of the adsorbents when operated under batch and continuous modes.

In recent years, there have been increasing initiatives undertaken worldwide to employ alternative per- and polyfluoroalkyl substances (PFAS) molecules in order to minimize the environmental and health effects associated with legacy PFAS molecules. Hexafluoropropylene oxide dimer acid (HFPO-DA), commonly known as GenX, is one of the important replacements currently used for PFOA. However, growing investigations suggest that GenX is identified in natural settings, including soils and groundwater, thus emphasizing the need to understand their sorption behavior in these environments. This study provides molecular-level insights into the impact of three different common soil constituents, namely, clay minerals, that vary in mineralogical composition and surface charge distribution in dictating the adsorption and transport characteristics of GenX on a fundamental molecular level for the first time using molecular dynamics simulations. The surface complexation of GenX varies significantly between the three clay minerals, and the factors that dictate the complexation are completely different. Depending upon the clay minerals, both surface-adsorbed and solution-phase GenX are observed. Importantly, the interfacial structure, nearest neighbor coordination, and dynamic behavior of GenX and their correlation with legacy PFAS in minerals systems are presented.

Enzyme-mimetic metal-based catalysts have received extensive attention for the efficient catalytic applications. These catalysts can be adapted to complex environmental circumstances, thus becoming one of the effective ways to deal with refractory pollutants. In previous research, the K+-intercalated FeOCl (KxFeOCl) catalyst can produce Fe(IV)═O intermediate species through heterocleavage of H2O2 in a similar way as natural peroxidases. In this study, the detailed kinetics and surface reaction mechanisms of KxFeOCl were comprehensively investigated using 2-methoxyphenol (2-MeOP) as the model contaminant and at pH 7. 2-MeOP molecules are oxidized to organic radicals, which further oxidize 2-MeOP for direct radical–radical coupling. Based on the kinetics, the Langmuir–Hinshelwood model was used to describe the oxidative coupling of 2-MeOP on the KxFeOCl/H2O2 system. The competitive adsorption of H2O2 and downstream catalase activity of H2O2 decomposition were also proposed. The substrate oxidation rate of high-valent iron species reached 9.25 × 105 mM–1 min–1. These results clarified the intrinsic kinetic principle and interfacial reaction mechanism of 2-MeOP oxidative coupling catalyzed by KxFeOCl, offering valuable insights for optimizing reaction performance and scaling up the process.

Low-micrometer microplastics (LMMPs), typically in the size range, 1–10 μm, are emerging contaminants ubiquitously present in aquatic systems. However, the quantification of LMMP mixtures in environmental waters is hindered by the limitations of current analytical methods. In this study, we developed a novel analytical method that couples a fractionated membrane filtration with Raman microspectroscopy (μ-Raman) to reliably quantify LMMPs in lake water. The fractionated membrane filtration system recovered >90% of the mixed polystyrene (PS) and poly(methyl methacrylate) (PMMA) LMMPs (i.e., 1.5, 3, 5, and 8 μm) from water. By separating LMMPs into 1–5 and 5–10 μm size fractions, the quality of the Raman images of small LMMPs (i.e., 1.5 and 3 μm particles) acquired directly on the membrane filters improved substantially. The reliability of LMMP Raman imaging was further improved by tracking the sum and product of their three characteristic Raman bands. In this way, the interferent Raman signals from the lake water matrix and membrane filters were significantly suppressed. This method provides a reliable tool to recover, separate, and quantify LMMP mixtures in complex water matrices, paving the way toward a deeper understanding of their environmental implications.

This article is part of the Water Challenges and Solution Opportunities in South Asia, a Rapidly Developing Region of the World special issue. The geographical location, climate change, rising population, and unplanned urbanization simultaneously probe a considerable water challenge in South Asia. The discharge of heavy metals such as chromium, manganese, lead, and mercury from industries, the release of organic compounds from wastewater treatment plants, the use of dyes in the textile industry, the disposal of pharmaceutical waste by pharmaceutical companies, and the seepage of pesticides, herbicides, insecticides, and fertilizers from agricultural land all contribute to water pollution. It then propagates via irrigation, drinking, and domestic usage, adversely affecting humans and the aquatic ecosystem. Apart from scientific advancements in wastewater treatment technologies, another aspect of remediation comprising the spatiotemporal analysis of water pollution and originating water crisis is less explored. So, it becomes crucial to integrate water resources, the origin of water pollution by natural (e.g., flooding) and artificial (e.g., industrialization) means, and the role of researchers and society in effectively tackling the water challenges. We are pleased to launch “Water Challenges and Solution Opportunities in South Asia, a Rapidly Developing Region of the World “ as a special issue in ACS ES&T Water. There are 22 publications, comprising 14 research articles, 2 viewpoint/perspective, and 6 review papers. The topics covered can be broadly categorized into two major aspects: (1) aquatic ecosystem surveys and (2) strategies to treat emerging water pollutants. The aquatic ecosystem surveys across different parts of South Asia are essential to include in this special issue. They will help us understand the location-dependent reasons for water pollution and their effects on human beings and aquatic ecosystems. These papers include case studies on (a) spatiotemporal groundwater analysis, recharging mechanisms, and evaluation for drinking and irrigation purposes, (b) impacts on groundwater intermixing with seawater in coastal regions, (c) anthropogenic activities affecting water quality, and (d) correlating climate change impacts using remote sensing with public health management. The impacts of spatial and depth-dependent determinants on groundwater level (GWL) projections are considered and correlated with the agriculturally intensive regions of South Asia. These considerations may be implemented in various regions, bringing attention to the relevance of spatiotemporal to multidepth aspects in GWL forecasting. Apart from GWL projections, Karangoda and Nanayakkara explored georeferencing and spatial interpolation techniques to determine the groundwater quality in the Ratnapura District, Sri Lanka. The study provides the spatial distribution of hardness, pH, and electrical conductivity, along with their causes governed by the climate and geological conditions. Also considered is the release of heavy metals from rocks, such as quaternary alluvial sediments, which has significantly damaged the water quality. The arsenic and manganese inclusions in the groundwater are studied by Mueller et al. and Rahman et al., respectively. Furthermore, Rajendran et al. provided insights about treating the formation water from hydrocarbon reservoirs as it pollutes the groundwater, surface water, and soil. Nepal’s federal, provincial, and municipal administrations are all described by Shrestha et al. in their efforts to recognize the threats posed by climate change to water, sanitation, and hygiene (WASH) infrastructure. Since Bangladesh uses both surface and groundwater for agriculture and drinking, Gulfam-E-Jannat et al. deduced that the contamination of these resources is devastating. They discussed future problems and solutions to treat industrial wastewater. Water shortages in Sri Lanka are examined, and its root causes determined in research by Chandrasekara et al. As water shortages increase in Sri Lanka, this research examines the measures to counteract the problem. Indika et al. studied the water supply possibilities to ensure long-term viability in Sri Lanka’s North Central Province. They suggested that reverse osmosis technology pretreated with softening and activated carbon would be the most effective way to deal with very salty groundwater in many parts of North Central Province. The second category of papers focuses on sustainable strategies to treat emerging water pollutants and provide a path for large-scale water treatment. Examples of pollutants studied include Indigo carmine, benzotriazoles, benzothiazoles, benzophenones, p-phenylenediamines, manganese, chromium, and arsenic, alongside many others. Samriti et al. discuss the scientific ways to utilize nanomaterials and develop methods to treat wastewater. These include photocatalytic/adsorptive removal, disinfection, tracing, and sensing. For more emphasis on sustainable approaches, Mao et al. developed manganese-oxidizing bacteria to treat wastewater from acid mines using continuous stirred tank bioreactors. Different materials, including CdS-doped glucose-derived carbon nanoflakes photocatalysts and Ti/RuO2-stainless steel, have been explored using photodegradation and ultrasound enhanced electro-Fenton mineralization, respectively. As guest editors in this special issue of ACS ES&T Water, we sincerely acknowledge all the authors, reviewers, and associate editors who helped present an informed and intuitive picture of South Asia’s water concerns to a broader and more general audience. Combating water contamination, raising public awareness about the alarming situation, and finding practical solutions are crucial in the current scenario. Different infrastructure, financial, and policy challenges must be carefully addressed. This special issue builds a foundation to state and solve these critical problems. Dr. Raju Kumar Gupta is a Professor in the Department of Chemical Engineering, Indian Institute of Technology Kanpur, India. Dr. Gupta has made important contributions to the area of sustainable materials, green synthesis, nanostructured materials for wastewater treatment and energy storage applications. His current research interests are photocatalysis for water remediation and CO2 conversion to fuels, perovskite solar cells, and energy storage devices based on batteries. Dr. Gupta has been recipient of several fellowships and awards for his outstanding career in academic and research fields e.g. Distinguished Young Alumnus Awards 2021 and Fellowship of the Royal Society of Chemistry 2022. He has authored more than 115 research articles in international journals, 4 patents, 3 edited books, and 18 book chapters and guest edited special issues for several international journals, and his work has been cited more than 8500 times. Dr. Gupta is an editorial board member of several international journals, as well as a member of scientific bodies e.g. associate editor for Solar Energy; editorial board member for Scientific Reports, Journal of Polymer Science and Current Opinion in Green and Sustainable Chemistry. Dr.-Ing. Fazlullah Akhtar serves as a Senior Researcher at the Center for Development Research (ZEF) of the University of Bonn, Germany. He specializes in the field of water resources management, with a specific focus on the challenges faced in developing countries. Dr. Shameen Jinadasa is Professor in Civil Engineering at the Department of Civil Engineering, University of Peradeniya, Sri Lanka. He is an award-winning water engineer with international experience. Dr Jinadasa has coordinated multinational and multisectoral research teams with experts from Singapore, Japan, Australia, the United States, New Zealand, and Sri Lanka with a range of disciplinary backgrounds such as agriculture, social science, economics, water resources management, and wastewater management to address complex water-related problems. His work has received recognition in Japan, Singapore, China, and the United States, where he has held prestigious fellowships and grants. Dr Jinadasa was educated at the University of Peradeniya, National University of Singapore, and Saitama University Japan. Dr. Jinadasa has published extensively with over 100 publications and is currently engaged in research fellowships with the United States and China. Shukra Raj Paudel is an Associate Professor of Environmental Engineering at the Department of Civil Engineering, Pulchowk Campus, Institute of Engineering, Tribhuvan University, Nepal, working in the area of water quality and treatment technologies. He is actively involved in teaching and research in environmental engineering at the university. He is a member of editorial advisory board in the journal Renewable Energy Focus and serves as editor and associate editor of domestic journals. M. Feisal Rahman is a Post Doctoral Research Associate in the Department of Geography and Environmental Sciences at Northumbria University, UK. His current work focuses on enhancing resilience in the Asian Deltas and ensuring trans-disciplinarity and coproduction in sustainable development research. He received his Ph.D. from the University of Waterloo, Canada, a Master’s degree from the University of Western Ontario, Canada, and a Bachelor’s degree from the Bangladesh University of Engineering and Technology, Dhaka, Bangladesh. R.K.G. acknowledges financial assistance from the Department of Science and Technology (DST), India, through Grant No. DST/TM/WTI/2K16/23(G), and from Science and Engineering Research Board, Department of Science & Technology, Government of India (Project no. CRG/2021/007464). This article has not yet been cited by other publications. Dr. Raju Kumar Gupta is a Professor in the Department of Chemical Engineering, Indian Institute of Technology Kanpur, India. Dr. Gupta has made important contributions to the area of sustainable materials, green synthesis, nanostructured materials for wastewater treatment and energy storage applications. His current research interests are photocatalysis for water remediation and CO2 conversion to fuels, perovskite solar cells, and energy storage devices based on batteries. Dr. Gupta has been recipient of several fellowships and awards for his outstanding career in academic and research fields e.g. Distinguished Young Alumnus Awards 2021 and Fellowship of the Royal Society of Chemistry 2022. He has authored more than 115 research articles in international journals, 4 patents, 3 edited books, and 18 book chapters and guest edited special issues for several international journals, and his work has been cited more than 8500 times. Dr. Gupta is an editorial board member of several international journals, as well as a member of scientific bodies e.g. associate editor for Solar Energy; editorial board member for Scientific Reports, Journal of Polymer Science and Current Opinion in Green and Sustainable Chemistry. Dr.-Ing. Fazlullah Akhtar serves as a Senior Researcher at the Center for Development Research (ZEF) of the University of Bonn, Germany. He specializes in the field of water resources management, with a specific focus on the challenges faced in developing countries. Dr. Shameen Jinadasa is Professor in Civil Engineering at the Department of Civil Engineering, University of Peradeniya, Sri Lanka. He is an award-winning water engineer with international experience. Dr Jinadasa has coordinated multinational and multisectoral research teams with experts from Singapore, Japan, Australia, the United States, New Zealand, and Sri Lanka with a range of disciplinary backgrounds such as agriculture, social science, economics, water resources management, and wastewater management to address complex water-related problems. His work has received recognition in Japan, Singapore, China, and the United States, where he has held prestigious fellowships and grants. Dr Jinadasa was educated at the University of Peradeniya, National University of Singapore, and Saitama University Japan. Dr. Jinadasa has published extensively with over 100 publications and is currently engaged in research fellowships with the United States and China. Shukra Raj Paudel is an Associate Professor of Environmental Engineering at the Department of Civil Engineering, Pulchowk Campus, Institute of Engineering, Tribhuvan University, Nepal, working in the area of water quality and treatment technologies. He is actively involved in teaching and research in environmental engineering at the university. He is a member of editorial advisory board in the journal Renewable Energy Focus and serves as editor and associate editor of domestic journals. M. Feisal Rahman is a Post Doctoral Research Associate in the Department of Geography and Environmental Sciences at Northumbria University, UK. His current work focuses on enhancing resilience in the Asian Deltas and ensuring trans-disciplinarity and coproduction in sustainable development research. He received his Ph.D. from the University of Waterloo, Canada, a Master’s degree from the University of Western Ontario, Canada, and a Bachelor’s degree from the Bangladesh University of Engineering and Technology, Dhaka, Bangladesh.