Environmental Research最新文献

Anammox is an energy-efficient process for biological wastewater treatment, yet its performance is often limited by the environmental sensitivity of anammox bacteria. Sludge aggregation has been shown to enhance biomass retention by promoting sludge settleability. This study proposes that the dissolution of iron-bearing minerals (i.e., pyrite) promotes sludge aggregation and bacterial retention, and the anammox sludge in turn continuously stimulates further pyrite dissolution, creating a positive feedback loop that amplifies the enhancement effect. Experimental results demonstrated that supplementation with pyrite increased the nitrogen removal rate by 37.3%, with its dissolution accounting for 56.8% of this enhancement. To elucidate the interactions between anammox sludge and pyrite, comprehensive analyses were conducted on microorganisms, minerals, and extracellular polymeric substances (EPS). The findings revealed that anammox sludge continuously stimulated pyrite dissolution, as indicated by a decrease in pyrite's self-corrosion potential from 0.127 V to -0.076 V, along with an increase in its surface roughness from 2.02 nm to 5.54 nm after contact with sludge. Quartz crystal microbalance with dissipation (QCM-D) analysis further showed that pyrite dissolution facilitated sludge aggregation by enhancing EPS adhesion, evidenced by an increase in the ΔD/ΔF ratio from -0.2095 to -0.0897. These results highlight a synergistic dissolution-aggregation mechanism that offers a theoretical foundation for enhancing the stability and resilience of anammox systems treating wastewater through the application of iron-containing minerals.

Alkali-activated cementitious materials are recognized as promising low-carbon materials. Preparing all-solid-waste cementitious materials circumvents energy-intensive commercial alkali activators, thereby reducing carbon footprint and energy consumption. The property of all-solid-waste materials is significantly influenced by reactivity of components. Current reactivity evaluation for solid waste relies on empirical mechanical and chemical tests, lacking quantitative activity models based on microscopic features. This study aims to establish quantitative mapping between reactivity micro-characteristics and performance for solid waste. Reactivity parameters of 15 solid wastes, classified by silicate tetrahedron polymerization degree, ionic bond content, and oxygen valence, were acquired via XRF, FTIR, XPS, and TG characterization, then dimensionally reduced into four principal factors. High-precision fitting of compressive strength and principal factors was achieved through support vector regression (SVR) modeling. Subsequently, a multi-solid-waste cementitious material was developed. Results indicates that reactivity parameters of different solid waste types intuitively reflect their roles in all-solid-waste system. Discrepancy in the strength formation mechanism across curing periods stem from phase-dependent hydration kinetics and time-sensitive contributions of constituents. The proposed reactivity evaluation method is applicable to small-sample, nonlinear material property prediction, providing quantitative support for performance regulation.

Polyhydroxyalkanoates (PHAs) from mixed cultures offer a sustainable alternative to plastics, and high salinity presents a promising selective pressure for PHA producers. However, the osmotic stress imposed by high salinity perturbs carbon and energy metabolism, yet how different volatile fatty acid (VFA) substrates influence PHA synthesis efficiency under sustained saline conditions remains poorly understood, particularly regarding carbon flux partitioning and energy trade-offs. This study investigated the effects of single VFA (acetate, propionate, butyrate, and valerate) on the enrichment, PHA accumulation, and metabolic flux of PHA-producing mixed cultures under 1.8% salinity. Butyrate and valerate-fed systems achieved superior PHA accumulation (0.636 ± 0.015 and 0.698 ± 0.005 g PHA/g VSS, respectively) compared to acetate (0.541 ± 0.006 g PHA/g VSS) and propionate (0.382 ± 0.021 g PHA/g VSS). This was due to more direct precursor supply and lower energy demands. Carbon flux analysis confirmed butyrate and valerate directed over 85% of utilized carbon to PHA, whereas propionate diverted more to cell maintenance. Metagenomics revealed that Paracoccus was a versatile salt-tolerant PHA producer across all substrates. Cultures fed with butyrate and valerate also exhibited enhanced respiratory chain activity and higher ATP/NAD(P)H, enabling better salt stress while maximizing PHA synthesis. These findings highlight the critical interplay between VFA type, salt stress, and metabolic trade-offs, providing crucial insights for optimizing high-salinity waste to PHA bioprocesses.

With the acceleration of global industrialization, antimony (Sb) pollution poses an increasing threat to ecosystems and human health, and the issue of Sb contamination is gaining attention. In this study, the impact of earthworm activity on Sb bioavailability in various agricultural soils and the influencing factors were evaluated. Soil samples were collected from diverse regions in China and assessed for Sb bioavailability through chemical extractions and earthworm avoidance and growth tests. The primary objectives were to determine how earthworm activity affects Sb bioavailability and to understand the intrinsic influence of soil properties on earthworm behavior and growth. The results revealed that earthworm activity significantly reduced the pH in acidic and neutral soils, increasing Sb bioavailability, whereas alkaline and calcareous soils exhibited minimal changes in pH, leading to reduced or variable Sb mobility. Soil properties-particularly pH and organic matter-critically influenced earthworm behavior (e.g., avoidance responses) and growth inhibition. A clear interspecific difference in sensitivity to Sb contamination was detected, with the epigeic Eisenia fetida being more sensitive than the anecic Pheretima guillemi. These findings underscore the role of earthworms as "bioengineers" in modulating Sb environmental behavior through pH-driven processes. This study highlights the necessity of integrating soil-specific properties (e.g., pH and organic matter) and ecological differences among earthworm species to increase the accuracy of Sb risk assessments in contaminated agricultural environments.

Anaerobic fermentation coupled with thermophilic bacteria (TB) pretreatment represents a viable and eco-friendly approach for waste treatment and resource recovery. However, the high salinity and structural complexity of mariculture solid wastes (MSW) hinder overall solubilization and acidogenesis efficiency. This study investigated the feasibility and underlying mechanisms of adding magnetic granular activated carbon (MAC) to TB-based pretreatment to trigger MSW solubilization and short-chain fatty acids (SCFAs) accumulation. The results showed that the maximal SCFAs yield increased from 419.7 to 1180.2 mg/L with the addition of 1 g/L MAC, compared to the control group. TB + MAC pretreatment enhanced disruption of the substrate matrix, increased the biodegradability of organic matter. Flow cytometer and enzymatic analysis revealed that the proportion of alive TB cells increased to 34.4%, and the activities of protease and α-glucosidase were improved by 22.0% and 61.0% with addition of 1 g/L MAC. Electrochemical analysis further verified that TB + MAC pretreatment efficiently released electron shuttles and accelerated intracellular and extracellular electron transfer. Microbial community analysis indicated that TB + MAC pretreatment selectively enriched acidogenic bacteria associated with SCFAs biosynthesis. This study proposes a strategy to alleviate hydrolysis and acidogenesis constraints in MSW processing.

Marine biofilms quickly colonize submerged surfaces, causing drag, reduced efficiency, and corrosion in vessels and marine infrastructure. Thus, the development of coatings that can resist bacterial adhesion and biofilm growth is essential. This study investigated two nanostructured surfaces - black silicon (bSi) and diamond-coated black silicon (black diamond, bD) - designed to physically disrupt bacterial cells using nanoscale spikes. Hydrogen- and fluorine-terminated versions of these surfaces were evaluated against 7-week-old Cobetia marina biofilms under controlled hydrodynamic conditions using flat silicon (Flat-Si) and flat diamond as controls. Nanostructured surfaces were less wettable than Flat-Si, with the contact angle of the fluorinated black diamond (bD-F) reaching 132°. Scanning Electron Microscopy confirmed that bSi and bD maintained their high-aspect-ratio nanoneedles, resisted protein adsorption, and had reduced biofilm coverage compared to flat controls. Optical Coherence Tomography revealed ∼50% thinner and less porous biofilms on the bD-F surface. Confocal Laser Scanning Microscopy analysis showed a 75% reduction in biofilm biovolume on bD-F compared to Flat-Si, with only 45% cell viability. Non-viable cells were predominantly located in inner biofilm layers, indicating a bactericidal effect. Flow cytometry supported these results, showing altered bacterial membrane potential and metabolic activity in bacteria exposed to bD surfaces. Experiments using real seawater and field immersion assays confirmed that bD surfaces maintain structural integrity and strongly reduce biofilm formation under realistic marine conditions. These findings demonstrate the antifouling and antimicrobial effects of nanostructured diamond-coated surfaces, particularly fluorine-terminated ones, for durable marine applications.

The microalgae-bacteria granular sludge (MBGS) system represents an environmentally friendly technology; however, its removal mechanism for trace emerging contaminants remain inadequately elucidated. This study investigated the removal and underlying mechanisms of 17α-ethinylestradiol (EE2) at an environmentally relevant concentration (2 μg/L) in MBGS systems under regulated light intensities. MBGS achieved 99.2% removal and 97.8% detoxification of EE2 under 360 μmol/(m²·s) illumination, with photodegradation identified as the dominant pathway, contributing 63.3% of total removal. This photodegradation was primarily driven by proteins within the extracellular polymeric substances (EPS) matrix, secreted through a synergistic partnership between Chlorella vulgaris and bacteria from the phyla Planctomycetota, Bacteroidota, and Acidobacteriota. Metaproteomic analysis identified five putative photosensitizer proteins capable of generating reactive oxygen species (ROS). Probe-based chemical experiments confirmed that EPS functioned as an effective photocatalyst by generating triplet excited state of EPS (³EPS*) at exceptionally high steady-state concentrations. The generated ³EPS*exhibited high photosensitivity and accounted for 95.2% of EE2 photodegradation. This work provides new insights into the photochemical mechanisms governing trace pollutant removal in MBGS systems and highlights the potential for optimizing performance through the targeted manipulation of light intensity or protein expression.

Perchlorate (ClO₄^-), a persistent oxyanion pollutant, poses significant threats to water systems. Despite the widespread use of granular activated carbon-supported nanoscale zero-valent iron (GAC-nZVI) for removing various contaminants (e.g., heavy metals, dyes, and antibiotics), its efficacy and mechanism for perchlorate removal remain unclear. In this study, GAC-nZVI composites with different GAC:nZVI mass ratios ([GAC/nZVI]_mass) were synthesized and their perchlorate removal performance were investigated. The results indicated that GAC-nZVI exhibited a significantly higher perchlorate removal efficiency (99.5%) than GAC (51.71%) or nZVI (63.92%). Through SEM, XRD, BET, XPS, and electrochemical analyses, it was demonstrated that GAC successfully dispersed nZVI, suppressed its agglomeration and passivation, and reduced charge-transfer resistance, thereby establishing an efficient and stable platform for oxyanion remediation in complex water matrices. The reaction pathway and key intermediates (ClO₃^-, ClO^- and Cl^-) were also identified. Furthermore, the removal performance was evaluated by varying the [GAC/nZVI]_mass, dosage, pH, temperature, dissolved oxygen, and coexisting anions. The optimized composite offers scalable potential for industrial and environmental applications.

The anaerobic/aerobic/anoxic-aerobic granular sludge (AOA-AGS) process possesses capacity for efficient external carbon usage and potential to enrich autotrophic anammox bacteria. However, how do these two distinct ways perform under low dissolved oxygen (DO) in treating low carbon to nitrogen (C/N) wastewater remains largely unknown. An AOA-AGS system was therefore configured treating wastewater with a C/N of 4.5 ± 0.5 and low DO of 0.5 ± 0.2 mg/L over a long period of 126 days. Results showed that admirable and stable TIN and TP removal efficiency up to 90.75% and 95.16% on average was maintained over operation. Two distinct microbial patterns were found, i.e., simultaneous nitrification, endogenous denitrification and phosphorus removal (SNEDPR) pattern via dominant Defluviicoccus (23.57%) and Candidatus Competibacter (10.17%) in transitional phase, and enhanced SNEDPR pattern coupled with anammox (SNAEDPR) via in-situ self-enriched Candidatus Brocadia (0.01%) in terminal phase. The dynamics of functional microbial communities optimized the allocation of limited carbon sources, with the proportion of COD utilized for denitrification and phosphorus removal in influents COD increasing from 27.98% and 42.02% to 40.30% and 49.48%, respectively. This study finally proposed a possible mechanism for AOA-AGS process treating low C/N wastewater with low DO via dynamic microbial interactions, providing theoretical and technical supports for the practical engineering application.

The strategic conversion of fermentation effluents from organic waste into microbial lipids for biofuel production has emerged as a key strategy for advancing sustainable development. However, inhibitory components in fermentation broths substantially impair the metabolism of oleaginous microbes, critically compromising bioconversion efficiency. Traditional pretreatment methods, such as chemical and enzymatic approaches, incur additional costs. Adaptive Laboratory Evolution (ALE) technology is based on the principle of directed evolution, precisely constructs biological stress environments and reshapes microbial metabolic networks to enhance strain tolerance and functionality. This enables the direct utilization of complex fermentation broths for lipid production. This paper first introduces the mechanism of selective pressure exerted by the ALE technique, and proposes strategies for nutrient supply and extreme environmental stress based on the physiological characteristics of strains. It then focuses on the technical principles of the ALE process, with a key discussion on the different evolutionary modes of ALE and their applicable scenarios. Building on this foundation, this review introduces novel integrative strategies bridging ALE and synthetic biology, employing precision metabolic engineering, genomic editing and machine learning to expand the application boundaries of ALE technology. Finally, the future development trends of ALE technology in the field of organic waste resource utilization are systematically explored in this review.