Environmental Science: Water Research & Technology最新文献

In eastern and southern Africa, faecal sludge emptying and transport is the dominant urban sanitation solution, mainly delivered by a diverse and largely informal private sector. While regulation is advancing, there is limited evidence on how to build compliance among service providers at scale. This article explores learning from six analogous sectors - street food vending, informal transport, artisanal mining, alternative water supply, construction waste management, and municipal waste pickers - to inform effective regulatory practices. A rapid literature review (220 publications) and expert input (24 sector specialists) were combined with 19 key informant interviews with regional sanitation regulators. The findings highlight emerging good practices: making compliance clear, simple, visible, and valued; understanding service providers' economic and social and normative drivers; and using participatory, adaptive regulation. Key insights include the need to move beyond binary views of informality, tailor policies to diverse provider types, and work effectively through associations. Limitations of information-based tools like vehicle tracking were also noted. Recommendations for a more inclusive regulatory approach are proposed.

A key challenge in microbiologically influenced corrosion (MIC) laboratory-based research is the limited comparability of test results generated across different laboratories. This is due, in part, to variations in experimental protocols, including differences in how oxygen levels are controlled in test solutions. L-Cysteine, for example, has been widely used to help maintain anaerobic conditions by reducing dissolved oxygen, yet its direct impact on corrosion behavior remains largely unexamined. This study investigates the effects of L-cysteine on MIC of carbon steel by sulfate-reducing bacteria (SRB). Anaerobic immersion tests were conducted to compare corrosion rates, pit depths, and bacterial activity in biotic and abiotic systems with and without L-cysteine. It was found that L-cysteine addition led to markedly higher SRB growth and corrosion rates, even though dissolved oxygen concentrations in solutions tested with and without L-cysteine remained within the same range over time. These results suggest that L-cysteine may enhance MIC through metabolic pathways unrelated to oxygen scavenging, such as increased sulfur availability for sulfide production and/or alterations to the biofilm microenvironment. This work challenges the conventional view of L-cysteine as a simple oxygen scavenger and underscores the need for standardized MIC testing protocols that account for its multifaceted biological and chemical effects.

Per- and polyfluoroalkyl substances (PFAS) are a class of persistent organic pollutants characterized by their exceptional chemical stability, environmental mobility, and adverse health effects. Their widespread presence in water resources and resistance to conventional treatment methods necessitate the development of effective destructive technologies. Sonochemical degradation, an advanced oxidation process (AOP) driven by acoustic cavitation, has emerged as a promising technology for the complete mineralization of PFAS. While previous reviews have provided foundational overviews, this work critically synthesizes the latest mechanistic insights, quantitative kinetic models, and emerging byproduct considerations (e.g. volatile organic fluorine (VOF) compounds) that distinguish the current state-of-the-art from earlier understanding. We systematically examine the effects of frequency, power density, solution chemistry (pH, temperature, matrix components), and PFAS molecular structure on degradation rates, with a new emphasis on Langmuir–Hinshelwood and Michaelis–Menten kinetic frameworks. The review uniquely integrates data from complex environmental matrices (groundwater, soils, AFFF source zones, ion exchange regeneration brines) and evaluates the energy efficiency of synergistic systems (sono-persulfate, sono-electrochemical, sono-piezocatalytic) using standardized electrical energy per order (EE/O) metrics. This review identifies critical knowledge gaps, including the fate of VOF byproducts, the scalability of hybrid reactors, and the treatment of short-chain PFAS. By addressing these areas, the work provides a forward-looking perspective on the research and engineering required to advance sonochemistry to field-scale remediation.

Groundwater quality in coastal aquifers is increasingly threatened by salinization and anthropogenic pressures, necessitating integrated assessment approaches. This study evaluates the hydrogeochemical characteristics and groundwater suitability in the Cuddalore district, Tamil Nadu, India, using a multi-index process-based framework. The study region is geologically, geomorphologically, and hydro-geologically more interesting; a total of 69 groundwater samples were collected and analysed for major hydrochemical parameters. Water quality index (WQI) classifies the groundwater samples into five categories, and around 58% of samples are in the excellent to good category, 26% of samples are in the poor to very poor category, and 16% of samples are unsuitable for drinking. Hydrochemical facies results indicate that Na–Cl and mixed Ca–Mg–Cl are predominant water types, and this reflects the influence of the reverse ion exchange, mineral weathering, and saline conditions. Moreover, cation–anion relation and electrical conductivity ranges in the coastal regions authorize the presence of a saline nature. Irrigation suitability assessments demonstrate that 54% of the samples belong to the C3S1 class, indicating moderate suitability, while approximately 10% of the samples are under high salinity hazard classifications. Elevated sodium and salinity levels in localised areas may adversely affect soil permeability and crop productivity. Ultimately, the results demonstrate that groundwater chemistry in this region is governed by the combined effects of rock–water interaction in the hard rock region, agricultural inputs, and coastal salinization. The integrated approach adopted in this study provides a reliable framework for groundwater quality assessment and management in coastal aquifers, offering applicability to similar hydrogeological settings worldwide.

In this study, a fully aromatic thin-film composite (TFC) polyamide layer was prepared on a porous polyethersulfone substrate via interfacial polymerization and subsequently coated with a glutaraldehyde (GA)-cross-linked polyvinyl alcohol (PVA) hydrogel to form a TFC PVA composite. Compared with two commercial nanofiltration (NF) membranes (NF270 and TS80), the hydrogel coating increased transport resistance and modified ion separation behavior. Consequently, the seawater permeate flux of the TFC PVA membrane decreased (2.2 L m⁻² h⁻¹ at 4 bar) following hydrogel coating, while rejection of major ions increased (Na⁺ and K⁺: 40–46%; Ca²⁺ and Mg²⁺: 67–74%). Moderate boron rejection (45%) was also observed at natural seawater pH without chemical adjustment, while commercial NF membranes NF270 and TS80 showed negligible boron rejection. Although membrane permeability decreased following hydrogel coating, stable operation was maintained over 38 h of continuous filtration relative to the uncoated TFC membrane. These combined mechanisms confer unique separation characteristics, highlighting the TFC PVA membrane's potential for use in targeted ion-removal tasks in resource recovery and removal of ions in pretreatment of high salinity water.

Pharmaceuticals and metabolites excreted by humans are a threat to aquatic ecosystems globally. Gaps exist in environmental data sets which can be filled by predicting concentrations using prescribing data available at suitable spatial (e.g., wastewater treatment plant [WWTP] catchment area) and temporal scale (e.g., monthly). The aim was to improve the accuracy of predicted pharmaceutical concentrations in untreated influent wastewater. A conventional prediction approach of applying human excretion information to prescribing data found three of 12 analytes (metformin, desmethylvenlafaxine and clarithromycin) had acceptable predictions (within ±50% of their measured concentration) at three WWTPs of varying size. Several analytes had systematic underestimated predictions across WWTPs related to low analyte excretion rates. Laboratory-scale gravity sewer experiments revealed an important contributor was glucuronide metabolite deconjugation back to their parent pharmaceutical which could not be accounted for using excretion information. Therefore, numerical correction factors were derived (0.027–0.86) from prescribing and wastewater data to establish the fraction of prescribed pharmaceuticals found in wastewater. These account for changes between prescription of a pharmaceutical and its presence in wastewater (e.g., human metabolism and in-sewer transformation) without the need to quantify and correct for them individually. This enabled acceptable predictions for another six analytes (carbamazepine, propranolol, venlafaxine, fluoxetine, norfluoxetine and desmethylclarithromycin). Therefore, incorporating this approach in prediction models for treated effluents and river water can improve their accuracy for improved risk assessment. This is key to identify where subsequent technological or ‘upstream’ intervention is needed to target pharmaceutical environmental impacts.

Microplastics (MPs) are ubiquitous in wastewater treatment plants (WWTPs), but there is still much to learn about their role in WWTPs. In this study, polypropylene (PP) and polylactic acid (PLA) were added to a sequencing batch reactor (SBR), and the single and combined effects of MPs and copper ions on the wastewater treatment process were evaluated. The study revealed that single copper ions had a significant negative effect on SBR operational performance, inhibiting the removal efficiency of chemical oxygen demand (COD) and nitrogenous compounds. The removal efficiencies of COD and NH₄⁺-N decreased to 70.61% and 16.42%, respectively, at the end of the SBR. Single MPs had no effects on SBR performance. However, when MPs coexisted with copper ions, the MPs partially mitigated the toxicity of copper ions through adsorption. In addition, the coexistence of MPs with copper ions significantly promoted the secretion of extracellular polymers (EPS). Copper ions significantly affected the abundance of copper resistance genes (CRGs), while MPs in combination with copper ions could promote the abundance of CRGs. The combination of MPs and copper ions increased the abundance of antibiotics resistance genes (ARGs) and integrons (intl1), and PLA presented a more severe risk of transmission compared to PP. Furthermore, single copper ions significantly suppressed the abundance and diversity of microbial communities, while MPs and copper ions combined to relieve the inhibitory effect of single copper ions on microbial communities. Dechloromonas, OLB12, Saccharimonadales, and Blastocatellaceae were the dominant genera in SBR. pcoA, copA, and cusA were the primary CRGs influencing the copper resistance of Dechloromonas, while sul1, sul2, tetQ, and tetM were the main ARGs affecting Dechloromonas and Saccharimonadales. This study provides new insights into understanding the effects of heavy metal and MPs contamination on the performance of SBR.

Precise and timely chemical oxygen demand (COD) prediction is key to regulatory compliance and process control in a full-scale wastewater treatment, but laboratory assays and sluggish online measurements hinder responsiveness. Thus, a deployment-conceived hybrid pipeline for near-term COD predictions is proposed in this study. This method introduces a deployment-oriented hybrid framework that integrates complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), gated recurrent units (GRU), and a multi-objective observer-teacher-learner-based optimizer (MOOTLBO) for near-term COD forecasting. Daily measurements from the Gebze municipal wastewater treatment plant (Türkiye) between 2019 and 2023 were collected from regularly available measured data together with total suspended solids, total nitrogen, total phosphorus, and pH with statistically enlightened lags to encode process memory. Intrinsic mode functions were obtained from the COD series with the application of CEEMDAN, and the intrinsic mode functions were concatenated with exogenous features and forwarded to recurrent learners. Long short-term memory (LSTM) and gated recurrent units (GRU) were studied as two potential configurations in the study. Hyperparameters were optimized with a multi-objective observer-teacher-learner optimizer (MOOTLBO) in order to balance fidelity, parsimony, and training cost. Evaluation occurred on a held-out test set (80/20 partition) with RMSE, MAE, R², MAPE, MBE, and KGE metrics. Across alternatives, decomposition-then-learn decreased error compared with non-decomposed baselines. A CEEMDAN–GRU variant turned out to be the most accurate configuration, which reached good performance with RMSE = 2.84 mg L⁻¹, MAE = 2.28 mg L⁻¹, R² = 0.9999, MAPE = 0.46%, MBE = 1.47 mg L⁻¹, and KGE = 0.9974. In an optimized CEEMDAN–GRU–MOOTLBO configuration, similarly strong accuracy (RMSE = 4.19 mg L⁻¹, MAE = 2.66 mg L⁻¹, R² = 0.9999, MAPE = 0.52%, MBE = 0.16 mg L⁻¹, KGE = 0.9997) was obtained with excellent bias control. In view of accuracy, stability, and runtime, the CEEMDAN–GRU family represents the most suitable choice for real-time soft sensing of COD, facilitating proactive control and early warning with the presence of changing influent conditions in challenging plant practice.

Anaerobic digestion (AD) of household food waste (HFW) can be promoted greatly using a high-rate reactor like expanded granular sludge bed (EGSB), but the low hydrolysis efficiency of the solid organics limits its practical applications. In this study, protein hydrolysis was identified as the limiting factor for achieving high-rate AD in the EGSB reactor, and then, EGSB effluent recirculation was implemented to enhance its pre-hydrolysis. An EGSB reactor treating HFW was operated with an increasing organic loading rate from 2.0 to 9.0 g COD/L/d to identify the key hydrolysis-limiting solid organic component (carbohydrate or protein) of HFW. The results showed that the protein removal efficiency was 54–64%, much lower than that of carbohydrate (89–99%). Protein hydrolysis was implied as the bottleneck restricting high-rate AD performance for treating HFW in the EGSB reactor. On this basis, effluent recirculation from the EGSB to a pre-hydrolysis reactor at a ratio of 0.5 was applied to enhance the hydrolysis of HFW. It was found that the carbohydrate hydrolysis efficiency increased from 86% to 93%, while the hydrolysis efficiency of protein increased by a factor of two (from 27% to 53%) at pH 6.5. The enrichment of Proteiniphilum (from 0.3% to 39.0%) enhanced protein hydrolysis in the recirculated pre-hydrolysis reactor. These findings suggest that EGSB effluent recirculation is an effective and practical way to enhance the protein pre-hydrolysis of HFW, thereby enabling the high-rate AD of HFW using the EGSB reactor.

Disinfection by-products (DBPs) are formed during the chlorination of drinking water and present a risk to human health, with brominated DBPs identified as more toxic than their chlorinated analogues. The most widely regulated DBPs are trihalomethanes (THMs), but increasingly focus is on haloacetic acids (HAAs), including consideration of all nine brominated and chlorinated HAAs for regulation (HAA9). Recently, aliphatic carbonyl compounds have been recognised as important DBP precursors and to favour bromine incorporation. This research specifically focuses on smaller aliphatic carbonyl precursors, enabling identification of the molecular-level features that are most significant for increasing the risk of forming the more toxic brominated DBPs and for reducing compliance with potential HAA9 regulations. This showed that β-keto acids present a particular problem due to their high propensity for bromination and Br-HAA formation. However, in the context of HAA9 standards, the neutral ester compounds were equally significant due to formation of the mixed chlorinated and brominated bromochloroacetic acid, which is within the currently unregulated HAAs. The enhanced understanding of Br-DBP formation from such hydrophilic organic precursors is important as such compounds are poorly removed by standard coagulation water treatment and are formed during oxidative treatment processes. Consequently, source waters containing these compounds and bromide are at significant risk of forming unacceptable levels of HAA9, a problem which becomes increasingly urgent as pressure on resources forces reliance on poorer quality drinking water sources containing higher levels of bromide. Further, the work shows that current monitoring approaches are inadequate when we need to consider HAA9.