Water Environment Research最新文献

Macrophytes such as Pistia stratiotes and Pontederia crassipes can release allelopathic compounds and reduce cyanobacteria biomass. Cyanobacterial cells interact with heterotrophic bacteria, which contribute to nutrient uptake and antioxidative responses, among other functions. However, the role of microbial communities in allelopathic interactions between macrophytes and cyanobacteria remains unexplored. We investigated how the bacterial community associated with Microcystis aeruginosa influences the effects of aqueous macrophyte extracts. Both extracts inhibited cyanobacterial growth and photosynthetic activity (99% for P. stratiotes and 55% for P. crassipes) while increasing bacterial abundance (threefold). The composition of the bacterial communities stimulated by extracts shifted: whereas original cultures were rich in Methyloversatilis and Rhodobacter, the P. stratiotes extract promoted the growth of Shinella, Flavobacterium, and Comamonadaceae, and the P. crassipes extract favored Enterobacterales. When these stimulated communities were reintroduced into M. aeruginosa cultures, allelopathic inhibition was reduced (40% for P. stratiotes and 12% for P. crassipes). We concluded that the growth of the associated microbiota attenuated the allelopathic effects, partially preserving cyanobacterial cells. Bacterial groups favored by the treatments may participate in allelochemical degradation and antioxidant protection or activate other types of metabolism beneficial to cyanobacteria, mitigating the harmful effects of the extracts. These results highlight the importance of considering the role of microbial communities in cyanobacterial allelopathic interactions.

Mainstream anaerobic ammonium oxidation (ANAMMOX) offers a promising alternative to conventional nitrogen removal processes in municipal wastewater treatment. However, research has largely focused on its potential to reduce oxygen demand rather than external carbon requirements. This study compared the external carbon demand of mainstream ANAMMOX with that of anaerobic-anoxic-oxic (A2O) and partial denitrification/ANAMMOX (PD/A) processes. Stoichiometric ratios, validated in a laboratory-scale packed-bed biofilm reactor, were implemented in a simulation framework reflecting representative conditions in Korean wastewater treatment plants. A 5 × 5 × 3 × 3 simulation matrix evaluated external carbon demand and its sensitivity to sidestream ammonium concentration (SAC), mainstream ammonium concentration (MAC), mainstream total organic carbon concentration (MTC), and sidestream flow rate (SFR) through gradient-based analysis and regression modeling. Mainstream ANAMMOX reduced external carbon demand by up to ~10.8%-72.2% compared with A2O and ~3.7%-41.2% compared with PD/A, depending on influent loading conditions. SAC and MTC were identified as the dominant drivers of carbon reduction. Notably, higher MAC levels slightly diminished the relative carbon savings due to the increased external carbon requirement for polishing the stoichiometric nitrate byproduct. Three composite indices (sidestream effective nitrogen load index, total effective nitrogen load index, and sidestream contribution ratio [SCR]) were proposed, with SCR exhibiting the highest predictive accuracy. Although the absolute savings are site-specific, these findings suggest that mainstream ANAMMOX can substantially decrease reliance on external carbon sources, and the proposed indices provide practical tools for process evaluation and design optimization.

Groundwater serves as an indispensable freshwater source in arid high-altitude urban basins. This study investigates the western Xining city on northern Tibetan Plateau, to elucidate the hydrochemical characteristics, genetic mechanisms, and resource implications of its groundwater in arid urban basins. A comprehensive approach integrating hydrochemical and statistical analyses, the entropy-weighted water quality index, and irrigation suitability evaluation was employed. The results show groundwater in the present arid high-altitude urban basin is generally neutral to weakly alkaline, exhibiting marked spatial variability in total dissolved solids (TDS), with 47.83% exceeding drinking water standards. Along the groundwater flow path, the hydrochemical facies evolve from HCO₃-Ca type to mixed Cl-Mg·Ca type and ultimately to Cl-Ca type, reflecting a clear salinization trend. Groundwater chemistry is mainly governed by silicate weathering, with secondary contributions from carbonate and evaporite dissolution, accompanied by limited cation exchange. Anthropogenic influences, particularly agricultural fertilization, have caused extensive nitrate enrichment, affecting 96% of the samples. River water exhibits excellent quality and is suitable for direct consumption, whereas only 56.5% of the groundwater meets drinking water standards, with the remainder classified as medium to poor quality. Regarding irrigation suitability, river water is highly favorable, and most groundwater is also acceptable. However, certain localities show elevated salinity and sodium hazards, highlighting the need for enhanced management to ensure sustainable water resource utilization. This study elucidates the hydrochemical genesis of groundwater in fragile plateau urban environments and contribute to sustainable local water resource management.

Achieving ultra-low phosphorus levels (< 0.05 mg L^-1) in wastewater effluents is a critical engineering challenge for mitigating eutrophication. This study developed a coupled microflocculation and micro-nanobubble flotation process for enhancing phosphorus removal. Comprehensive screening determined that 50 mg L^-1 polyaluminum chloride coupled with 1.0 mg L^-1 cationic polyacrylamide provided optimal microflocculation performance. Orthogonal experiments confirmed that a hydraulic retention time of 15 min, aeration rate of 200 L h^-1, and dissolved air pressure of 0.60 MPa resulted in the highest TP removal efficiency. The process was able to reduce TP in actual secondary effluent from 0.86 to 0.036 mg L^-1, achieving an average removal efficiency of 95.8% over 30 days of continuous operation. Mechanistic analysis revealed that high dissolved air pressure (0.60 MPa) was critical for generating a dense, bimodal distribution of micro- and nanobubbles with extended residence times, dramatically increasing bubble-floc collision and electrostatic attachment efficiency. This study establishes a highly efficient technology for meeting increasingly stringent phosphorus discharge standards in municipal wastewater treatment.

The sustainability of sand is becoming more uncertain; therefore, a critical need exists to identify alternative materials for green infrastructure that meet desirable, site-specific functions. Technosol rain gardens (glass, shale, and shell) were tested for their ability to infiltrate and filter stormwater of chemical pollutants. Technosols had similar infiltration rates as sand, while large particle sizes of technogenic materials led to significantly higher saturated hydraulic conductivities (111-211 cm h^-1) compared to sand (37.3 cm h^-1). Technosols decreased all pollutant concentrations, except Zn, compared with the synthetic stormwater. Shale (0.0461 mg L^-1), shell (0.0544 mg L^-1), and sand (0.0306 mg L^-1) had comparable effluent NH₄-N. Compared with sand, shale removed 27.8% more Cu, while glass, shale, and shell removed 58.9%, 85.3%, and 57.7% more Pb, respectively. Glass and shell demonstrate potential for increasing long-term runoff capture under saturated conditions while removing > 50% of chemical pollutants like NH₄-N, P, Cu, and Pb.

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.