Environmental Research最新文献

Excessive sludge production and unstable suppression of nitrite-oxidizing bacteria (NOB) are key obstacles to sustainable mainstream partial nitrification (PN) in conventional activated sludge systems. This study demonstrates how a mainstream PN reactor equipped with encapsulated biofillers, operated under carbon-nitrogen decoupling, can achieve stable nitritation with minimal sludge production for low C/N domestic wastewater. Hydrolysis-acidification and denitrification (HA-DN) was used as a front-end carbon management module, redirecting readily biodegradable organics to denitrification, removing 72.9% of influent SCOD and producing an extremely carbon-limited influent (C/N ≈ 0.8-1.2) for the PN stage. Within the PN reactor, the encapsulated biofiller created a high-density, long-SRT autotrophic niche whose internal oxygen gradient selectively enriched ammonia-oxidizing bacteria (AOB), completely washed out NOB, and maintained a nitrite accumulation rate >98% even under increased ammonium loading. Under this combined high-DO and carbon-starved regime, residual heterotrophic bacteria (HB) were confined to a low-abundance, maintenance-oriented guild and shifted toward endogenous respiration rather than net growth. Consequently, the observed sludge yield in the PN stage was as low as 0.013 kgMLSS/kgCOD, representing a >93% reduction compared with typical CAS operation. Thus, carbon-nitrogen decoupling, realized through an encapsulated, carbon-starved PN niche, provides a generalizable strategy to achieve stable mainstream partial nitrification with minimal sludge production in low C/N domestic wastewater treatment.

Valorizing hazardous Electric Arc Furnace Dust (EAFD) remains a critical challenge in the circular economy. Herein, we report a facile H₂O₂-mediated surface reconstruction strategy to upcycle EAFD into a high-performance electrocatalyst for the two-electron oxygen reduction reaction (2e^- ORR). Mechanistically, this oxidative treatment induces the in-situ formation of a ZnO/ZnO₂ heterostructure interface. This unique architecture modulates the local electronic distribution to optimize reaction pathways while simultaneously transforming the surface from hydrophobic to hydrophilic (contact angle decreases from ∼93° to ∼28°), thereby accelerating interfacial mass transport. Consequently, the engineered catalyst delivers an exceptional H₂O₂ yield of 2082 mmol·g^-1·h^-1 at 0 V (vs. RHE) with >80% selectivity over a broad potential window (0-0.68 V) and robust stability. Furthermore, an integrated system coupling on-site H₂O₂ electrosynthesis with pollutant degradation was established. This work demonstrates a sustainable "waste-treats-waste" paradigm, transforming industrial environmental liabilities into strategic assets for decentralized water purification.

Constructed wetlands (CWs) are an effective wastewater treatment system and an important sink for microplastics (MPs). However, MPs impacts on nitrogen removal performance of CWs remain unclear. Here, we collected 1903 datasets from 34 studies for a meta-analysis to explore MPs effects on nitrogen removal performance of CWs from characteristics and experimental parameters of MPs. The results showed that dosage frequency and exposure duration of MPs were the main influencing factors, and there was a positive interaction between them. MPs affected nitrogen removal performance of CWs by altering metabolic activities of microorganisms and plants. MPs reduced the relative abundance of Chloroflexi and Bacteroidetes in nitrification or denitrification processes. MPs affected the denitrification process by reducing NIR and NAR activities, and narG abundance, while influencing the nitrification process by reducing HAO activity. Furthermore, MPs trigger oxidative stress and reduce chlorophyll content and plant biomass, hindering nitrogen absorption and thus decreasing nitrogen removal performance of CWs. Meanwhile, operational parameters of CWs, such as influent C/N, CWs type, plant type and hydraulic retention time (HRT), also affected nitrogen removal performance of CWs. The horizontal subsurface flow CWs with a mixed planting mode, which regulates the appropriate HRT and influent C/N, may effectively reduce the impact of MPs on the nitrogen removal performance of CWs. This research will enhance the understanding of the impact of MPs pollution on nitrogen removal performance of CWs, providing scientific and reliable reference opinions for stable operation management of CWs under complex pollution loads in the future.

Abandoned mines represent a considerable risk to ecosystems surrounding former exploitation sites. In metal mining, the exposure of waste significantly increases the mobility and bioavailability of potentially toxic elements (PTEs), affecting adjacent soils and organisms. Assessing the toxicity of mining waste involves challenges related to selecting appropriate bioassays and those recommended by current environmental regulations. Considering the expected increase in metal and metalloid extraction to supply critical raw materials, improving our understanding of the advantages and limitations of specific bioassays is essential for accurate risk assessment. Three representative abandoned metal mining sites in the Iberian Peninsula were selected to apply and compare different bioassays for a robust ecotoxicological assessment of mining waste. Total and soluble PTEs concentrations at all sites significantly exceeded geochemical threshold values (GTVs) and water quality standards. Bioassays using Lepidium satuvium, Spirodela polyrhiza and Raphidocelis subcapitata revealed that acidic conditions combined with elevated PTEs concentration (e.g., Cd, Pb), are highly toxic to primary producers. Conversely, root growth measurements suggested that low soluble concentrations of metalloids (As, Sb) may stimulate root development. Overall, the results indicated that Sb was not a major contributor to observed toxicity in the bioassays under the studied conditions. The Zucconi test showed low sensitivity and reliability, limiting its suitability for risk assessment. Moreover, stimulation effects observed in the algal bioassay question its effectiveness for delineating contaminated areas, as they may lead to false negatives. Therefore, combined bioassay approaches are recommended to avoid underestimation of toxicity. Tailings and dumps from the three mines were classified at least as moderately toxic, particularly in areas affected by acid mine drainage (AMD), identified as the main factor increasing toxicity.

Efficient nitrogen removal from low carbon-to-nitrogen (C/N) municipal wastewater remains a major challenge. Although the endogenous denitrification (ED) in the anaerobic/aerobic/anoxic (A/O/A) process attracts increasing attention for saving carbon and energy, achieving reliable start-up and controllable enrichment techniques of key functional microorganisms in practice remains challenging. This study demonstrates the successful transition from exogenous to endogenous electron donor-driven denitrification in an A/O/A sequencing batch reactor (SBR) under low dissolved oxygen (DO) and extended anoxic conditions. After operational optimization, the system achieved a substantial enrichment of Candidatus Competibacter (relative abundance increasing from 0.96% to 35.42%), which played a crucial role in ED. Consequently, the nitrogen removal efficiency increased from 60.2% to 83.2%. Results indicated that the optimal Polyhydroxyalkanoates (PHA) accumulation occurred at 90 minutes in anaerobic stage. The low DO range (0.5-1.0 mg/L) was key to minimizing aerobic PHA consumption, ensuring its availability for subsequent denitrification. During the extended anoxic duration of 4 h, glycogen was identified as the primary electron donor, with secondary contributions from PHA, extracellular polymeric substances (EPS), and cellular metabolites. Microbial community analysis confirmed Candidatus Competibacter as the dominant organism, facilitating nitrate reduction using internally stored polymers. This enrichment was attributed to sufficient glycogen storage (37.3mmolC/L) and reduced competition with Denitrifying polyphosphate -accumulating organisms (DPAOs). Finally, the combined strategy and selective enrichment of Denitrifying glycogen-accumulating organisms (DGAOs) promoting internal carbon source utilization not only enables efficient nitrogen removal without external carbon addition but also reduces sludge production for treating low C/N wastewater.

As nanoplastics (NPs) gain recognition as "emerging global pollutants," characterizing their environmental risks has become an international priority. Ubiquitous in soil and aquatic systems, humic acid interacts with these particles-an interaction that illustrates how natural ecosystems respond to anthropogenic contaminants. Elucidating this dynamic refines traditional toxicity assessments (previously based solely on pure NPs), aligning them with complex real-world exposure conditions. This review synthesizes recent advances in understanding how humic acid governs the environmental behavior of NPs, encompassing aggregation kinetics, colloidal stability, pollutant adsorption, bioavailability, ecotoxicity, and environmental influences on their binding affinity. Such insights demonstrate that humic acid-NPs interfacial interactions fundamentally reshape the environmental fate of this pollutant.

The global accumulation of microplastics (MPs) in natural environments has raised significant ecological concerns, with wastewater treatment plants serving as major accumulation points. This study investigated the impact of polylactic acid (PLA) MPs on volatile fatty acid (VFA) production from waste activated sludge (WAS). Under different PLA MPs levels (0-200 particles/g-TS), the VFA production, extracellular polymeric substances (EPS) structure, and the microbial community responses were systematically examined. Results demonstrated a clear inhibition on acidogenic efficiency by PLA MPs, with VFA yields decreased by 5.14-18.18% compared to the control. Although PLA MPs enhanced sludge solubilization (increased by 2.3-11.91%), they significantly inhibited subsequent hydrolysis and acidification processes through: (1) inhibition of key enzymatic activities, (2) increase of oxidative stress (39.9% increase in lactate dehydrogenase (LDH) leakage), and (3) alteration of microbial community structure (reduced Bacteroidota and key functional genera). These findings provide novel insights into the complex interactions between biodegradable MPs and anaerobic fermentation processes, highlighting the need for mitigation strategies in WAS treatment systems confronted with increasing biodegradable microplastic contamination.

Nanoplastics (NPs), as emerging contaminants in aquatic environments, critically influence the environmental fate and ecological risks of antibiotics via adsorption. Continuous environmental aging markedly alters NP surface properties, including functional groups and surface charge, leading to increasingly complex interactions with antibiotics. In this study, batch adsorption experiments combined with density functional theory (DFT) calculations were employed to systematically elucidate how aging-induced oxygen-containing functional groups-including carbonyl (C=O), hydroxyl (-OH), phenolic hydroxyl (-OHm), and carboxyl (-COOH)-govern the adsorption of ciprofloxacin (CIP) onto polystyrene nanoplastics (PSNPs). The characterization results revealed that UV-induced aging enhanced adsorption performance by introducing additional adsorption sites. Adsorption kinetics followed a pseudo-second-order model (R² > 0.973), while isotherms were well described by the Freundlich model (R² > 0.986), confirming heterogeneous multilayer adsorption. Compared with pristine PSNPs (49.42 mg/g), the maximum adsorption capacity of aged PSNPs increased to 86.38 mg/g, accompanied by an increase in Freundlich constant k_F from 25.94 to 35.06 L/mg. DFT calculations further showed that aging-induced functional groups stabilized PS-CIP complexes, with binding energies of -13.46 to -18.08 kJ/mol, higher than pristine PSNPs (-13.31 kJ/mol). Electrostatic potential mapping and IGMH analysis revealed that van der Waals interactions dominant in pristine PSNPs were weakened after aging, whereas hydrogen bonding and electrostatic contributions were strengthened. The synergistic interplay of these interactions explains the enhanced adsorption capacity of aged PSNPs. This study provides mechanistic insights into how aging-induced surface functionalization controls antibiotic adsorption on NPs and highlights its implications for environmental risk assessment of aged NPs.

Algal-bacterial granular sludge (ABGS) has unique advantages and broad application prospects in the treatment of mariculture wastewater. However, the rapid granulation process and performance evolution of ABGS under high salt stress have not been clearly defined. Compared with AGS, the influence of algal intervention on the structural integrity and metabolic activity of particles under the same salinity gradient is also unknown. Therefore, in this study, a parallel ABGS and AGS system was established. The results showed that intertwined algal filaments provided a structural skeleton for particle formation and led to complete granulation of ABGS within 20 days. Compared with conventional AGS, ABGS formed under high-salinity conditions exhibited a larger average particle size (1.07 mm), higher biomass (7.59 g/L) and higher extracellular polymeric substance (EPS) secretion (258.56 mg/g VSS). Additionally, chemical oxygen demand (COD) and total inorganic nitrogen (TIN) removal efficiencies exceeded 99% and 66%, respectively. Metagenomic analysis revealed that Thauera, Fragilaria and Nitzschia were dominant taxa associated with granule formation and stabilization. ABGS also showed an elevated abundance of functional genes associated with nitrogen metabolism (nxrA, nasA, and nasD) and polysaccharide metabolism (glmM, glmU, and pmm-pgm), which were in accordance with the enhanced nitrogen removal and granulation capability. Increased abundance of tricarboxylic acid cycle genes further indicated the superior granulation performance of ABGS. Overall, this study clarifies the morphological evolution and microbial functional mechanisms underlying rapid ABGS formation in mariculture wastewater, offering valuable insights for engineering optimisation and application of this technology in saline wastewater treatment.

Atrazine (ATZ) may co-occur with elevated particulate pollution during application seasons, yet how PM₁₀ modifies its atmospheric behavior and toxicological outcomes remains unclear. Here, we combined greenhouse-based atmospheric simulation with a 21-day mouse inhalation exposure model to evaluate PM₁₀-ATZ co-pollution and hepatotoxicity. Under haze conditions, the mean atmospheric ATZ concentration was higher (301.33 ng/m³), and its apparent half-life was 1.31 d higher than non-haze periods. In mice, co-exposure to PM₁₀ and ATZ induced more pronounced liver injury than single exposure, characterized by aggravated histopathological lesions and increased hepatocyte apoptosis. The average TUNEL-positive cell percentage increased from 0.4% (ATZ) to 1.1% (PM₁₀+ATZ), and the density of TUNEL-positive cells reached 0.07, significantly higher than ATZ alone (P < 0.01). Overall, PM₁₀ promoted the atmospheric persistence of atrazine and amplified its hepatotoxic effects under combined inhalation exposure, highlighting the importance of considering particulate pollution when evaluating atrazine-related exposure scenarios.