Water Environment Research最新文献

This study used density functional theory to study the reaction pathways and intermediates associated with the oxidation of salicylic acid (SA). The analysis was carried out for each of the three SA charge states (i.e., 0, -1, -2) that are observed in aqueous solution. SA can be oxidized to the three primary byproducts, 2,3 DHBA, 2,5 DHBA, and catechol, via cyclohexadienyl radical intermediate formation. A second mechanism consists of an initial H• radical abstraction, which produces organic radicals that react with hydroxyl radicals, but this pathway does not form a catechol. Activation energy calculations confirmed that 2,3 DHBA is the most thermodynamically favored byproduct, followed by 2,5 DHBA and catechol. Formation of uncommon byproducts was also investigated. The operational implications for water treatment processes are discussed. To the author's knowledge, this is the first study to use the electronic properties of SA to elucidate the oxidation pathways across the full range of pH values found in water.

Microplastics have garnered global attention due to their widespread presence in the environment, significant ecological impacts, and potential human health risks. This study was conducted in the Gulf of Bejaia (Algeria), focusing on three representative beaches: Sidi Ali Labher, Aokas, and Oueddas. Sampling was carried out between April and May 2024 across 100 m² transects at each site, subdivided into 50 cm × 50 cm quadrats, yielding 20 replicates under calm weather conditions. Microplastics (MPs) were separated using NaCl flotation and vacuum filtration on gridded cellulose ester filters. Quantitative analyses included MPs density (items/m²), ANOVA for abundance and size differences, and visualizations via Python libraries. Three indices were computed: the Microplastics Pollution Index (MPPI), the Pellets Pollution Index (PPI), and the Fibers Ingestion Potential Index (FIPI). The distribution of MP types showed that fragments were the most prevalent, followed by fibers, foams, films, and pellets. The MPPI indices revealed high abundance at Aokas (MPPI total = 17.18), moderate abundance at Sidi Ali Lebhar (MPPI total = 9.28), and low abundance at Oueddas (MPPI total = 4.22). The FIPI values for Aokas, Sidi Ali Labher, and Oueddas were 0.09, 0.10, and 0.11, respectively, indicating minimal to low potential for fiber pollution from beaches. This study highlights the significant variation in microplastic distribution across the studied beaches and suggests that fibers ingested by biota in these regions are not predominantly from beach pollution.

Groundwater is essential for drinking and irrigation, but its quality is impacted by human activities and rapid urbanization. This study presents a unique assessment of groundwater quality in agroecosystems situated at the rural-urban interface of Bengaluru, an area undergoing rapid land-use change and intensive agricultural practices. Unlike earlier studies that examine only rural or urban zones, this study integrates physicochemical analysis, hydrochemical facies (Piper plot), water quality index (WQI), and principal component analysis (PCA) to provide a comprehensive understanding of seasonal variations in groundwater quality. A total of 60 borewell water samples were collected from the study site and analyzed for various water quality parameters. Results show that groundwater remains within permissible limits set by the Bureau of Indian Standards (BIS). The Piper plot indicates that most samples are of mixed type, with alkaline earths exceeding alkalis, and strong acids surpassing weak acids. Water chemistry is affected by the dominance of evaporation and precipitation. The WQI showed that 50% of the samples were classified as excellent during the post-monsoon period, increasing to 76% in the pre-monsoon period. PCA explains 96.30% and 84.80% of the variance in post- and pre-monsoon conditions, with principal component (PC1) accounting for 49.40% and 48.60%, respectively. Most groundwater is suitable for human use and irrigation. However, the government should monitor contamination sources to enable more comprehensive future assessments of groundwater quality.

Population growth has intensified domestic effluent generation, created environmental risks when inadequately treated. The microalga Chlorella vulgaris shows strong potential for wastewater remediation. This study combined bibliometric analysis and experimental validation to assess its application in synthetic domestic effluent treatment. Two strains, SL2C (mangrove origin) and BMAK D1 (freshwater origin), were cultivated in synthetic effluent at concentrations of 25%-100% (diluted in WC medium) for 14 days. Optimal growth occurred at 50% for SL2C, which achieved the highest specific growth rate (0.353 ± 0.003 d^-1), and for BMAK D1, optimal growth occurred at 75% (0.262 ± 0.005 d^-1). Effluent remediation was evaluated by monitoring ammoniacal nitrogen, phosphate, and chemical oxygen demand (COD). Nitrogen removal exceeded 80% across treatments, phosphate removal averaged ≈65%, and SL2C demonstrated greater COD reduction (66.9%) than BMAK D1 (54.9%). These results demonstrate the biotechnological value of C. vulgaris for wastewater treatment and its relevance to circular bioeconomy strategies, contributing to Sustainable Development Goal 6 (Clean Water and Sanitation).

Phytoplankton communities are of vital importance to the functioning of freshwater ecosystems, but the role of the metabolic capacity of the community in regulating community dynamics under natural conditions has yet to be sufficiently considered. This study investigated 26 lakes situated along the eastern section of the Hu Line, combining field surveys with metagenome-assembled analyses to ascertain the factors responsible for the divergence in Chlorophyta and Bacillariophyta communities. The results demonstrated that the diversity of Chlorophyta was markedly higher than that of Bacillariophyta whereas the abundance was significantly lower. These discrepancies in community attributes were predominantly attributable to variations in the response of the two algal groups to nutrients. The abundance and diversity of diatom metabolic genes were significantly higher than those of green algae. The greater diversity and extent of metabolic genes in Bacillariophyta confer enhanced metabolic capacity and, consequently, greater adaptive capacity. Such differences in metabolic gene composition may be attributed to the disparate evolutionary pathways that these organisms have followed.

Bayannur City in northern China, which includes Urad Rear Banner, has a high concentration of non-ferrous metal mining activities and is a key region for the regulation of heavy-duty enterprises. There are 14 heavy-duty enterprises in Urad Rear Banner, involving a population of 48,000. The regulation of mining activities in this area necessitates effective ecological and human health risk assessments of the heavy metal(loid)s produced by the numerous lead-zinc ore and copper ore smelting operations. In this study, the pollution levels and pollution sources of toxic heavy metal(loid)s (Cr, As, Pb, Cd, and Hg) in topsoil and groundwater were analyzed using a self-organizing feature map (SOM) for the first time. So the pollution source impacts, site characteristics and geographic properties can be further evaluated. The results revealed significant Pb and Cd pollution, exceeding the standard established by China MEE, resulting from the high concentration of heavy industry in the study area. The distributions of toxic metals were linked to pollution source and site characteristics using the neural network-based SOM. Based on the optimal neurons, k-means clustering, and the Davies-Bouldin index (DBI), the SOM indicated five possible pollution sources: human factors, natural sources, natural settlement, wastewater leakage, and wind effect. Meanwhile, the ecological risk assessment showed that the ecological risk decreased in the order of Cd > Hg > As > Pb > Cr, which reflects the difference between ecotoxicological sensitivity and pollution level. That is, low-polluting metals may still have high toxicity. In the health risk assessment of heavy metal(loid)s in topsoil and groundwater, the hazard quotient (HQ) and hazard index (HI) were all below the safety limit of 1, while the carcinogenic risk (CR) and total carcinogenic risk (TCR) values were 10^-6 to 10^-4 (within the range of human tolerance). Among the heavy metal(loid)s evaluated, Pb and As had relatively high carcinogenic risks. Due to contributions from multiple sources, the southeastern part of the study area was heavily polluted. This study represents an innovative use of SOM in pollution source apportionment. This novel approach has the advantages of high precision, high efficiency, good visualization, and little human interference. SOM can be used to quantify sources while also comprehensively considering the hydrogeochemical characteristics, and it is especially suitable for case studies with large sample sizes. In this study, we applied SOM in an innovative way to evaluate the ecological and human health risks of heavy metal pollution in an area with numerous heavy industries and revealed the potential risk pathways. The findings provide a basis for the prevention, control, and remediation of pollution along with associated policymaking.

The global shortage of potable water and the rising environmental burden from industrial waste highlight the need for sustainable and low-cost desalination technologies. This study presents an enhanced passive solar still (PSS) that integrates recycled aluminum thin films and polypropylene insulation to improve thermal performance, freshwater productivity, and overall system sustainability. Material characterization confirms that waste-derived recycled aluminum plates possess high solar absorptivity and excellent thermal conductivity, enabling rapid heat absorption and extended thermal storage. Experimental evaluation under real climatic conditions shows that the PSS achieves a 35.5% increase in daily yield compared to the conventional solar still (CSS), supported by higher basin temperatures, improved evaporation-condensation dynamics, and reduced heat losses. Thermodynamic analysis reveals significant improvements in energy efficiency, exergy efficiency, gain output ratio, and productivity ratio, whereas economic assessment indicates a reduction in cost per liter and a shortened payback period. A machine-learning framework using RNN, XGBoost, Random Forest, and RVFL models accurately predicts hourly yield, and NSGA-II optimization identifies an optimal configuration of 18 recycled aluminum plates with 2 × 5 cm spacing. Environmental metrics confirm substantial reductions in material cost, energy consumption, and CO₂ emissions. The proposed system demonstrates a practical, scalable, and circular-economy-driven approach for decentralized freshwater production.

The growing global concern over oily wastewater pollution necessitates the development of advanced and efficient separation technologies. In this study, polyimide (PI) based mixed matrix membranes were fabricated by incorporating SiO₂, TiO₂, and metal organic frameworks (MOFs) into a polyethersulfone (PES) matrix to enhance oily wastewater treatment performance. The successful integration of these nanomaterials was confirmed through FTIR and XRD analysis. The modified membranes showed enhanced thermal stability (Tg PES/PI/MOF: 80.63°C) and increased surface hydrophilicity. Among the fabricated membranes, MOF incorporated exhibited the highest pure water flux of 50 L m^-2 h^-1. The PES/PI/MOF membrane achieved superior performance in separating different oil water emulsions, including DCM/SLS and PE/CTAB systems, with flux of 73.23 ± 0.82 L m^-2 h^-1 and 64.78 ± 0.59 L m^-2 h^-1, respectively. It also displayed a high flux recovery ratio (82.34%), demonstrating excellent antifouling behavior, and achieved an oil rejection efficiency of 83.02% for the DCM/SLS emulsion. Overall, this study highlights the synergistic effect of nanomaterial incorporation in enhancing membrane permeability, selectivity, and fouling resistance, showing PES/PI based mixed matrix membrane as promising candidates for sustainable oily wastewater treatment applications.

Inorganic nitrogen and organic pollutants are commonly coexisted in various wastewaters. Bacteria capable of removing multiple pollutants simultaneously possess unique advantages in wastewater treatment. In this study, the heterotrophic nitrification-aerobic denitrification (HNAD) bacterium Pseudomonas sp. A2 simultaneously possessed the ability to degrade benzoic acid. Experimental data demonstrated that strain A2 exhibits outstanding nitrogen removal performance, with the maximum removal rates of 13.87 and 12.69 mg/L/h for ammonium and nitrate, respectively. Approximately 99.42% of ammonium and 100% of nitrate were efficiently removed under optimal conditions: sodium succinate as carbon source, C/N ratio 14, 30°C, pH 7.0, and shaking speed of 160 rpm. Batching test and genome analysis suggested that A2 achieved heterotrophic nitrification with hydroxylamine as an intermediate and reduced nitrate to N₂ under aerobic condition. Additionally, strain A2 could utilize benzoic acid as an electron donor for nitrogen removal, though the nitrogen removal efficiency decreased significantly. Genomic analysis indicated that strain A2 may degrade benzoic acid via both the ortho pathway and the protocatechuate pathway. Bioaugmentation with strain A2 improved both nitrogen removal performance and stability of sequencing batch reactor (SBR), suggesting its potential in application. The discovery of strain A2 enriches the understanding of the nitrogen removal mechanism of HNAD bacteria and provides novel insights into the simultaneous removal of nitrogen and benzoic acid from wastewater.

Contaminated groundwater must be treated to protect drinking water supplies. This study investigated the degradation of MTBE and TBA with UV/persulfate (PS) and UV/hydrogen peroxide (H₂O₂) advanced oxidation processes. Experiments were conducted at initial concentrations of MTBE and TBA of 7.4 and 6.2 mg/L respectively over a range of conditions and computational analysis was carried out to elucidate reaction mechanisms and pathways. Pseudo first-order rate constants were retrieved from temporal degradation profiles. MTBE degradation was faster than that of TBA, and UV/PS-driven oxidation of both chemicals was faster than that of UV/H₂O₂. Relative absorptivity measurements showed that PS absorbed a higher proportion of light than H₂O₂ did, which in turn created greater potential to generate radicals. Density Functional Theory (DFT) results provided additional new insights. UV/PS is a promising groundwater remediation technology for the removal of MTBE and TBA.