Pharmaceuticals have received extensive scientific and socio-economic attention worldwide due to their acute and chronic toxic effects on plants, animals, and human health. However, the geographical distribution and seasonal variability of pharmaceutical mixtures in aquatic environments remain underexplored, especially in resource-deficient countries. The present review provides an in-depth analysis of the seasonal occurrence of pharmaceuticals, particularly antibiotics detected over the last five years in surface water, groundwater, and drinking water. The effectiveness of the conventional and advanced drinking water treatment processes is discussed with a focus on the adsorption and ozonation processes, commonly employed at drinking water treatment plants (DWTPs). Findings reveal median concentrations of antibiotics and other pharmaceuticals in drinking water worldwide, often exceeding their levels in groundwater. This underscores the urgent need for global-scale, long-term monitoring of antibiotics in aquatic systems, especially in DWTPs. Beyond targeted analysis, non-targeted analysis (NTA) should be integrated into routine water quality monitoring at DWTPs to identify novel contaminants, including fluorinated pharmaceuticals. Finally, this review provides an overview concerning the process-based and data-driven modelling of pharmaceutical occurrence, fate, and transport as a complementary approach to sampling and lab-scaled experiments, especially in resource-limited settings. Strengthening long-term monitoring, expanding treatment solutions, integrating modelling tools, and promoting green chemistry innovations are crucial to mitigating risks and safeguarding water quality.@en

This mini review explores the potential of visible light–driven bismuth vanadate (BiVO₄)-based photoanodes for removing trace organic pollutants from water. It highlights the advantages of using BiVO₄-based photoanodes over conventional UV-driven photoanodes in water treatment. The mechanism of reactive species generation through water oxidation is discussed. The review also highlights the role of sulfate and sulfite radicals in enhancing pollutant degradation. Furthermore, it evaluates how heterojunction formation improves the removal efficiency of BiVO₄-based photoanodes by reducing charge carrier recombination. Limited research on BiVO₄-based photoanodes for the simultaneous removal of multiple organic pollutants at low concentrations (<1 mg L⁻¹) from real wastewater is identified as a key knowledge gap. Addressing this gap could advance the application of BiVO₄-based photoanodes in photoelectrocatalytic-based advanced oxidation processes.

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Wastewater surveillance has been successfully employed to monitor pharmaceutical usage on a university campus. In this study, the usage patterns of antibiotics and disinfectants during the COVID-19 pandemic were evaluated. Firstly, the results showed that during COVID-19 waves, different pharmaceuticals correlated with normalized SARS-CoV-2 concentrations, suggesting that distinct medications may have been necessary to address the unique symptoms associated with each COVID-19 variant. Secondly, it was observed that both the total concentrations of antibiotics and disinfectants were higher during the peak of the COVID-19 pandemic compared to before the Delta Wave. Overall, this indicates an increased chemical usage associated with COVID-19, which raises concerns about its impact on the emergence of Antibiotic Resistance Genes (ARGs) during this period.@en

Predicting the hotspots of antimicrobial resistance (AMR) in aquatics is crucial for managing associated risks. We developed an integrated modeling framework toward predicting the spatiotemporal abundance of antibiotics, indicator bacteria, and their corresponding antibiotic-resistant bacteria (ARB), as well as assessing the potential AMR risks to the aquatic ecosystem in a tropical reservoir. Our focus was on two antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP), and on Escherichia coli (E. coli) and its variant resistant to sulfamethoxazole-trimethoprim (EC_SXT). We validated the predictive model using withheld data, with all Nash-Sutcliffe efficiency (NSE) values above 0.79, absolute relative difference (ARD) less than 25%, and coefficient of determination (R2) greater than 0.800 for the modeled targets. Predictions indicated concentrations of 1–15 ng/L for SMX, 0.5–5 ng/L for TMP, and 0 to 5 (log10 MPN/100 mL) for E. coli and −1.1 to 3.5 (log10 CFU/100 mL) for EC_SXT. Risk assessment suggested that the predicted TMP could pose a higher risk of AMR development than SMX, but SMX could possess a higher ecological risk. The study lays down a hybrid modeling framework for integrating a statistic model with a process-based model to predict AMR in a holistic manner, thus facilitating the development of a better risk management framework.@en

Plastic pollution has grown into an epidemic. Among them, plastics smaller than 5mm, defined as microplastics (MPs), have caused severe environmental pollution and emerged as the second major global environmental and ecological issue in the 21st century. As the major receptacles for land-based MPs, the aquatic systems in the urbanized region are considered to be one of the most widely polluted environments, where waterborne MPs can be transported and distributed through water flow; coherent strategies are required to segregate and control MPs pollution. This chapter reviews and describes MPs pollution in urbanized aquatic environments, where wastewater treatment plants and estuarine fronts (for coastal cities) can act as control points for the retention of MPs during transportation. Furthermore, waterborne MPs also undergo complex processes, including sedimentation, fragmentation, aging, and aggregation, further increasing the challenge of MPs pollution assessment and control. This chapter highlights that the Asiatic region displays greater MPs pollution in the aquatic environment. Hence, taking Asia as an example, we further explored the causes of increased MPs pollution and provided an outlook on plausible management strategies for pollution control.

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Solid Waste Management for Resource-Efficient Systems: Circularity in Action promotes innovation and shares best practices based on the principles of the circular economy and resource conservation on different aspects of sustainable solid waste management. The book also explains sources, impacts, and recycling potential of emerging wastes. It presents management strategies, including emerging green infrastructure and digitalization for recycling and gainful application of waste. In addition, sections highlight various environmental and health hazards while providing different management strategies based on the principle of resource recovery and circular economy that can help to minimize the environmental impacts.@en

Antimicrobial resistance (AMR) is a global challenge that has impacted aquaculture and surrounding marine environments. In this study, a year-long monitoring program was implemented to evaluate AMR in two different aquaculture settings (i.e., open cage farming, recirculating aquaculture system (RAS)) and surrounding marine environment within a tropical coastal region. The objectives of this study are to (i) investigate the prevalence and co-occurrence of antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARGs), antibiotics (AB) and various associated chemical compounds at these study sites; (ii) explore the contributing factors to development and propagation of AMR in the coastal environment; and (iii) assess the AMR risks from different perspectives based on the three AMR determinants (i.e., ARB, ARGs and AB). Key findings revealed a distinct pattern of AMR across the different aquaculture settings, notably a higher prevalence of antibiotic-resistant Vibrio at RAS outfalls, suggesting a potential accumulation of microorganisms within the treatment system. Despite the relative uniform distribution of ARGs across marine sites, specific genes such as qepA, blaCTX−M and bacA, were found to be abundant in fish samples, especially from the RAS. Variations in chemical contaminant prevalence across sites highlighted possible anthropogenic impacts. Moreover, environmental and seasonal variations were found to significantly influence the distribution of ARGs and chemical compounds in the coastal waters. Hierarchical cluster analysis that was based on ARGs, chemical compounds and environmental data, categorized the sites into three distinct clusters which reflected strong association with location, seasonality and aquaculture activities. The observed weak correlations between ARGs and chemical compounds imply that low environmental concentrations may be insufficient for resistance selection. A comprehensive risk assessment using methodologies such as the multiple antibiotic resistance (MAR) index, comparative AMR risk index (CAMRI) and Risk quotient (RQ) underscored the complexity of AMR risks. This research significantly contributes to the understanding of AMR dynamics in natural aquatic systems and provides valuable insights for managing and mitigating AMR risks in coastal environments.@en

Waste-to-Energy: Sustainable Approaches for Emerging Economies presents the latest developments and applications for the conversion of waste into biofuels and other energy products. Divided into two parts, Section I reviews the major sources of solid waste and their management strategies in developing countries, and includes the collection, composition, segregation, and dispersal of various waste streams, as well as the generation of biogas and other value-added products. Section II examines the transformation of waste into biofuels and the management strategies required to efficiently implement waste-to-energy processes. Methods for the production of hydrogen, biomethane, biofuels, and bioenergy, as well as resource recovery are discussed in depth, and mathematical models are provided for anaerobic digestion techniques. The benefits and challenges of waste-to-energy as a waste management strategy are explored through dedicated chapters on the techno-economics, environmental and social regulation, and the operation of WtE plants. The final chapter of the book presents a lifecycle assessment and environmental impact analysis of the technologies and strategies discussed.

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Liquid crystal monomers pose rising environmental risks. Discover their impact, health concerns, and global efforts to manage and mitigate these effects.@en

Quaternary ammonium compounds (QACs) are commonly used in many products, such as disinfectants, detergents and personal care products. However, their widespread use has led to their ubiquitous presence in the environment, posing a potential risk to human and environmental health. Several methods, including direct and indirect photodegradation, have been explored to remove QACs such as benzylalkyldimethyl ammonium compounds (BACs) and alkyltrimethyl ammonium compounds (ATMACs) from the environment. Hence, in this research, a systematic review of the literature was conducted using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) method to understand the fate of these QACs during direct and indirect photodegradation in UV/H2O2, UV/PS, UV/PS/Cu2+, UV/chlorine, VUV/UV/chlorine, O3/UV and UV/O3/TiO2 systems which produce highly reactive radicals that rapidly react with the QACs, leading to their degradation. As a result of photodegradation, several transformation products (TPs) of QACs are formed, which can pose a greater risk to the environment and human health than the parent QACs. Only limited research in this area has been conducted with fewer QACs. Hence, quantum mechanical calculations such as density functional theory (DFT)-based computational calculations using Gaussian09 software package were used here to explain better the photo-resistant nature of a specific type of QACs, such as BACs C12-18 and ATMACs C12-C18, and their transformation pathways, providing insights into active sites participating in the phototransformation. Recognizing that different advanced oxidation processes (AOPs) come with pros and cons in the elimination of QACs, this review also highlighted the importance of implementing each AOP concerning the formation of toxic transformation products and electrical energy per order (EEO), especially when QACs coexist with other emerging contaminants (ECs).@en

During the pandemic of COVID-19, the amounts of quaternary ammonium compounds (QACs) used to inactivate the virus in public facilities, hospitals and households increased, which raised concerns about the evolution and transmission of antimicrobial resistance (AMR). Although QACs may play an important role in the propagation of antibiotic resistance gene (ARGs), the potential contribution and mechanism remains unclear. Here, the results showed that benzyl dodecyl dimethyl ammonium chloride (DDBAC) and didecyl dimethyl ammonium chloride (DDAC) significantly promoted plasmid RP4-mediated ARGs transfer within and across genera at environmental relevant concentrations (0.0004–0.4 mg/L). Low concentrations of QACs did not contribute to the permeability of the cell plasma membrane, but significantly increased the permeability of the cell outer membrane due to the decrease in content of lipopolysaccharides. QACs altered the composition and content of extracellular polymeric substances (EPS) and were positively correlated with the conjugation frequency. Furthermore, transcriptional expression levels of genes encode for mating pairing formation (trbB), DNA replication and translocation (trfA), and global regulators (korA, korB, trbA) are regulated by QACs. And we demonstrate for the first time that QACs decreased the concentration of extracellular AI-2 signals, which was verified to be involved in regulating conjugative transfer genes (trbB, trfA). Collectively, our findings underscore the risk of increased disinfectant concentrations of QACs on the ARGs transfer and provide new mechanisms of plasmid conjugation.@en

Explore the challenges faced by developing nations in dealing with PFAS contamination, a class of persistent chemicals affecting drinking water safety. How can these countries navigate these complex issues to ensure clean water for all?@en

Turbulence generated within the vegetated confluence system is important for water quality and river management. In this study, we conducted a series of experiments to explore the extent to which emergent rigid vegetation in the confluence channel influences hydrodynamic characteristics and contaminant transport. First, a series of tests with increasing discharge ratios (from 0.35, 0.5, and 1) was conducted to quantify the effects of the discharge ratio on hydrodynamic conditions within the vegetated confluence. Then, tests with different discharge ratios were also set up to explore how contaminants released locations and modes (line and point source) influence the transport and mixing of contaminants. The results showed that increasing the discharge ratio induced larger momentum in the confluence area. The increase in discharge ratio rendered the circulation stronger, and its position came earlier in the non-vegetative area. In addition, the dimensionless turbulent kinetic energy peaked near the interface of the non/vegetated zone. With the increase in the discharge ratio, the dimensionless turbulent kinetic energy was found to be smaller. In the contaminants transport tests, the results revealed larger discharge ratio could speed up contaminants transport and mixing. The applications from this study would be helpful to pollutant transport management in natural confluences.@en

Amplified hygiene and precautionary measures are of utmost importance to control the spread of COVID-19 and future infection; however, these changes in practice are projected to trigger a rise in the purchase, utilisation and hence, discharge of many disinfectants into the environment. While alcohol-based, hydrogen peroxide-based, and chlorine-based compounds have been used widely, quaternary ammonium compounds (QACs) based disinfectants are of significant concern due to their overuse during this pandemic. This review presents the classification of disinfectants and their mechanism of action, focusing on QACs. Most importantly, the occurrence, fate, toxicity and antimicrobial resistance due to QACs are covered in this paper. Here we collated evidence from multiple studies and found rising trends of concern, including an increase in the mass load of QACs at a wastewater treatment plant (WWTP) by 331% compared to before the COVID-19 pandemic, as well as an increases in the concentration of 62% in residential dust, resulting in high concentrations of QACs in human blood and breast milk and suggesting that these could be potential sources of persistent QACs in infants. In addition to increased toxicity to human and aquatic life, increased use of QACs and accelerated use of antibiotics and antimicrobials during the COVID-19 pandemic could multiply the threat to antimicrobial resistance.@en

In this study, we report the implementation of a comprehensive wastewater surveillance testing program at a university campus in Singapore to identify Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infected individuals and the usage of pharmaceuticals and personal care products (PPCPs) as well as other emerging contaminants (ECs). This unique co-monitoring program simultaneously measured SARS-CoV-2 with chemical markers/contaminants as the COVID-19 situation evolved from pandemic to endemic stages, following a nationwide mass vaccination drive. SARS-CoV-2 RNA concentrations in wastewater from campus dormitories were measured using real-time reverse transcription-polymerase chain reaction (RT-qPCR) and corroborated with the number of symptomatic COVID-19 cases confirmed with the antigen rapid test (ART). Consistent results were observed where the concentrations of SARS-CoV-2 RNA detected in wastewater increased proportionately with the number of COVID-19 infected individuals residing on campus. Similarly, a wide range of ECs, including disinfectants and antibiotics, were detected through sensitive liquid chromatography with tandem mass spectrometry (LC-MS/MS) techniques to establish PPCPs consumption patterns during various stages of the COVID-19 pandemic in Singapore. Statistical correlation of SARS-CoV-2 RNA was observed with few ECs belonging to disinfectants, PCPs and antibiotics. A high concentration of disinfectants and subsequent positive correlation with the number of reported cases on the university campus indicates that disinfectants could serve as a chemical marker during such unprecedented times.@en