The co-occurrence of organohalides and heavy metals constitutes a pervasive environmental challenge in anthropogenically impacted settings such as industrial complexes, electroplating facilities, and e-waste recycling sites. Owing to their persistence, toxicity, and chemical recalcitrance, these co-contaminants pose substantial ecological and human health risks while markedly increasing the complexity of remediation. Conventional physicochemical treatments are frequently insufficient to address their combined presence, especially given the synergistic inhibitory interactions that undermine removal efficiencies. As a result, microbially mediated synergistic bioremediation has garnered considerable attention as a sustainable alternative capable of achieving concurrent detoxification. Within these systems, organohalide-respiring bacteria (OHRB) play a key role by transforming organohalides into non-halogenated products that are more readily subjected to biotoxicity reduction. In parallel, sulfate-reducing bacteria (SRB) facilitate heavy metal immobilization through sulfide-mediated precipitation while simultaneously supplying electron donors (e.g., acetate, hydrogen) that sustain OHRB metabolism. These intertwined carbon–sulfur metabolic networks support the formation of stable, functionally complementary microbial consortia, enhance dehalogenation kinetics, and alleviate heavy metal toxicity. This review integrates current advances in understanding the occurrence, ecological impacts, and microbial mechanisms governing the co-remediation of organohalide–heavy metal contamination. Special emphasis is placed on characterizing the functional roles, metabolic coordination, and syntrophic interactions among key microbial guilds. Collectively, these insights provide a mechanistic foundation for the rational design of targeted, efficient, and ecologically robust synergistic bioremediation strategies for complex co-contaminated environments.

Mariculture wastewater often contains emerging contaminants and elevated chloride concentrations, posing significant treatment challenges. This study developed and assessed a novel process that integrates hydrodynamic cavitation with calcium peroxide for the removal of the antibiotic tetracycline. The hydrodynamic cavitation/calcium peroxide system exhibited superior tetracycline degradation across a wider pH range compared to the homogeneous Fenton-like system, achieving over 92% removal at pH 3 with a synergistic coefficient of 9.40, while maintaining 61% efficiency under neutral conditions. Additionally, it achieved a chemical oxygen demand removal rate of 50.73% from actual mariculture wastewater, surpassing the performance of the homogeneous Fenton-like system. This approach also significantly reduced the formation of toxic disinfection by-products. The concentrations of trihalomethanes (0.29 μg/L), dichloroacetic acid (1.38 μg/L), and trichloroacetic acid (0.41 μg/L) were lower than those produced by the homogeneous Fenton-like system, resulting in an effluent with a markedly reduced toxicity-weighted concentration. Liquid chromatography-mass spectrometry analysis did not identify any stable large-molecule chlorine-containing intermediate products. Coupled with experiments on the hydrodynamic cavitation degradation of dichloroacetic acid, these findings suggest that the extreme conditions generated by hydrodynamic cavitation can effectively disrupt the C–Cl bond, thereby preventing the accumulation of chlorine-containing by-products. This study establishes the hydrodynamic cavitation/calcium peroxide system as an efficient and environmentally safe technology for the treatment of antibiotic-contaminated high-salinity wastewater.

Eutrophication leads to massive algal proliferation. During algal blooms, cyanobacteria often serve as the dominant species, while green algae are frequently the subdominant species. Algal organic matter can become a potential source for the formation of halonitromethanes (HNMs). During ultraviolet/chlorine treatment, bromide ions (Br⁻) promote the formation of brominated halonitromethanes (Br-HNMs), which exhibit greater toxicity compared to chlorinated halonitromethanes (Cl-HNMs). While the formation of Br-HNMs from cyanobacteria has been documented, research on how green algae contribute during UV/chlorine disinfection in the presence of Br^- remains limited. Therefore, Chlorella vulgaris, a widely distributed green alga, was selected as a model precursor to investigate the formation patterns and toxicity of Br-HNMs derived from its intracellular organic matter (IOM) during UV/chlorine disinfection. Bromonitromethane (BNM) and bromodichloronitromethane (BDCNM) were observed to form from the IOM of Chlorella vulgaris, with their concentrations rising initially and then falling as Br⁻ concentration and reaction time increased. Additionally, higher free chlorine concentration, UV intensity, and IOM concentration promoted Br-HNMs formation (i.e., BNM and BDCNM), whereas an increase in pH inhibited their formation. Potential pathways for the formation of Br-HNMs were deduced based on the experimental results. Moreover, Br-HNMs formation patterns from the IOM of Chlorella vulgaris in actual water samples closely resemble the results in simulated waters. This study elucidates the risks associated with Br-HNMs formation from the IOM of Chlorella vulgaris during UV/chlorine disinfection. These findings provide theoretical and technical support for optimizing water treatment processes and controlling Br-HNMs formation at water treatment facilities.

Harmful algal blooms represent a significant global challenge. In this study, we integrated allelochemicals with a flow-through copper ionization cell to inhibit Microcystis aeruginosa. Our findings revealed that the combined treatment achieved maximum inhibition rates of 84.39% and 79.55% for toxic and non-toxic M. aeruginosa, respectively, after seven days. These results demonstrated significantly stronger inhibition compared to individual treatments, including L-lysine (38.62% and 27.73%), electric field treatment (64.45% and 56.67%), and copper ionization cell (less than 20%) applications. The combined treatment induced more substantial reductions in chlorophyll a, carotenoids, and phycobiliproteins, causing greater damage to the photosynthetic system. Notably, phycocyanin content exhibited the most pronounced decline, suggesting its potential as a critical target for intervention. Furthermore, the combined stress triggered the highest levels of oxidative stress and disruption of antioxidant enzymes in algal cells, ultimately leading to programmed cell death-like responses. These findings provide valuable insights into a promising strategy for cyanobacteria control.

River confluences are characterized by complex hydrodynamics, which can significantly influence mass transport and microbial community, and further make a difference to biogeochemical processes. However, mechanistic links between confluence hydrodynamics, microbial community processes, and nitrogen transformation remain poorly understood. Here, a self-circulating confluence flume was employed to analyse how hydrodynamic characteristic influence microbial community assembly, coalescence, and nitrogen transformation processes. Results revealed that the microbial community succession was primarily governed by deterministic processes, especially homogeneous selection, with its contributions were higher than 50%, causing the similarity of community composition at the earlier stage. With time going by, influence of ecological drift increased, which contributed to the divergence in community composition at the later stage. Community coalescence, assessed by SourceTracker and ASV overlap, was proved to exist in the confluence area, and significantly enhanced in low-velocity zones due to increased hydraulic retention time (p < 0.01). Partial least squares path modelling identified that low flow velocity directly promoted ammonia accumulation, which in turn stimulated ammonia oxidation and ultimately enhanced nitrogen removal. Conversely, strong homogenizing selection and community coalescence in low velocity zones suppressed nitrogen removal by reducing niche diversity. This suggests an optimal design of flow velocity to balance the redox environment and microbial community dynamics is necessary for the maximization of the nitrogen removal capacity. Our study provided mechanistic insights into how hydrodynamic heterogeneity at river confluences regulated nitrogen transformation through mediating microbial community assembly and coalescence, highlighting the critical role of confluence morphology in river network nutrient management.

Municipal sludge (MS) threatens ecological security and human health, requiring efficient, low-carbon treatment technologies for environmental protection. The sustainable use of MS in brick and tile kilns to manufacture building materials with lower environmental impacts is a promising approach for sludge disposal and resource/energy recovery. This study investigated the kinetics, gas emissions, and synergistic effects of the co-disposal of MS, coal gangue (CG), and shale (SH). Results showed that MS significantly enhanced the combustibility of CG-SH blends, with 5% MS increasing the comprehensive combustion index S by 502%. Kinetic analysis revealed that the combustion of MS-blended systems was best described by a first-order model. At the conversion rate of 0.5, MS combustion processed transition from Power law P6 to Avrami–Erofeev A2.7, reflecting a shift from surface-diffusion-controlled volatilization to nucleation-controlled char oxidation. Gas emissions, especially emissions of reducing species, varied with atmospheric conditions. This affected the release of NO_x through in-situ denitrification, which was critical for air pollution control. The 5% MS blend showed synergistic combustion enhancement, while 20% MS induced the strongest inhibition near 560 °C due to ash-mediated solid-solid reactions. Under inert conditions, the highest suppression was found at 880–1000 °C in the 10% MS blend. This work provides insights and theoretical guidance for optimizing MS co-disposal in brick and tile kilns, facilitating efficient waste treatment, emission control and energy recovery.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are persistent pollutants that threaten ecosystems and human health. This review examines the adsorption performance and mechanisms of biochar in PFAS-contaminated soils, emphasizing the effects of different modification strategies. Unmodified biochar typically exhibits equilibrium adsorption capacities of 10–200 mg/g for perfluorooctanoic acid (pH 6–8, adsorbent dosage 1 g/L), substantially lower than commercial activated carbon (> 800 mg/g). Acid–base treatments and metal or mineral loading generally enhance adsorption by 2–8 fold. Mechanistically, long-chain PFAS (C₈–C₁₂) are predominantly captured via hydrophobic partitioning and hydrogen bonding, whereas short-chain PFAS (C₄–C₆) rely on electrostatic attraction and surface complexation. Biochar modifications adjust surface area, functional groups, and charge distribution, enabling selective adsorption. Mineral- or metal-loaded biochars promote electrostatic interactions and regeneration, while oxidant or acid treatments reinforce hydrophobic and hydrogen-bonding effects. Collectively, this review elucidates the multi-mechanistic and synergistic pathways governing PFAS adsorption by modified biochars and provides a framework for evaluating trade-offs among modification strategies and designing high-efficiency materials for environmental remediation.

Temperature fluctuation is a major constraint on the stability of anammox systems, yet the cellular and community-level mechanisms underlying cold inhibition remain poorly understood. In this study, a 159-d continuous-flow anammox reactor was operated under sequential temperature shifts (35 °C \to 25 °C \to 15 °C) to elucidate the responses of microbial metabolism, enzyme conformation, and community interactions. Low temperature (15 °C) markedly suppressed nitrogen removal performance, with effluent NH₄⁺-N and NO₂⁻-N concentrations increasing threefold. Intracellular cofactors (NAD⁺/NADH, NADP⁺/NADPH) and heme c content declined sharply, while extracellular polymeric substances accumulated, indicating energy reallocation from metabolism to structure maintenance. Molecular dynamics simulations revealed that hydroxylamine oxidoreductase exhibited reduced conformational flexibility and distorted redox centers at 15 °C, explaining the enzymatic activity loss. Metagenomic and qPCR analyses showed that the abundance of hdh and other anammox functional genes decreased by over 80%, accompanied by a community shift from Candidatus Kuenenia to psychrophilic Pseudomonadota and denitrifying Denitratisoma. Functional pathway analysis highlighted the downregulation of oxidative phosphorylation and quorum sensing, and the upregulation of stress-response and transport systems. Collectively, these results reveal a multi-level adaptation strategy and identify the molecular basis of cold inhibition in anammox consortia, providing theoretical guidance for improving nitrogen removal resilience in low-temperature environments.

Microbial anaerobic ammonium oxidation coupled with iron reduction (Feammox) represents a novel pathway for nitrogen removal. The pivotal role of Feammox in the biogeochemical nitrogen cycle has attracted increasing scientific interest. However, its specific metabolic mechanisms and potential practical applications remain insufficiently elucidated and lack comprehensive interpretation. To advance the understanding of Feammox, research progress in this field is systematically reviewed and synthesized. Additionally, a bibliometric analysis is conducted to identify research hotspots and outline future research directions. Moreover, putative Feammox microorganisms and their associated electron transfer pathways are summarized to elucidate key metabolic mechanisms. The review also examines the influence of abiotic and biotic factors on Feammox activity. Remarkably, potential future applications of Feammoxin in mainstream, sidestream, and tailwater treatment are proposed, with particular emphasis on innovative strategies that sustain iron redox cycling while enhancing the removal of emerging contaminants. Finally, key challenges requiring further investigation are highlighted. This review aims to identify knowledge gaps and ongoing controversies in Feammox research, clarify priority research directions, and provide insights for advancing both mechanistic and engineering applications.

The use of extracellular polymeric substances (EPS) stripped from sludge as a supplementary carbon source represents a novel method for enhancing nitrogen removal in low-carbon wastewater. This approach aims to leverage EPS while preserving the sludge metabolic activity. However, the effect of the EPS stripping degree on sludge metabolic activity remains poorly understood. In this study, EPS were progressively removed from activated sludge via ultrasonic centrifugation, and the resulting changes in sludge metabolic activity and settleability were systematically evaluated. The results demonstrate that key metabolic indicators, such as the specific oxygen uptake rate (SOUR), ammonia utilization rate (AUR), nitrogen utilization rate (NUR), and phosphorus release rate (PRR), initially increased and then decreased with increasing EPS removal. Optimal activity rates were observed at a 45% EPS stripping ratio, where SOUR, AUR, NUR, and PRR increased by 24%, 59%, 14%, and 9%, respectively, compared to the original sludge. Notably, the sensitivity to over-stripping varied: PRR inhibition commenced at 67% stripping, while NUR began to decline only after 86% stripping. In contrast, SOUR and AUR were enhanced across all tested stripping levels (up to 100%). This study is the first to establish a biological response relationship between the degree of EPS stripping and overall sludge metabolic activity, identifying 45% stripping as the optimum. It was also found that ultrasonic stripping reduced floc size and increased surface negative charge, thereby impairing sludge settleability. Consequently, practical application requires a balance between metabolic enhancement and sludge settleability.

The global energy transition’s reliance on lithium-ion batteries (LIBs) faces a critical sustainability trilemma, in which the simultaneous pursuit of rapid decarbonization, resource security, and economic viability generates inherent trade-offs. This perspective highlights that the trilemma is reinforced by three interconnected systemic dilemmas: a policy-action chasm (weak enforcement), a technology-market dislocation (scalability gaps), and a temporal disequilibrium (economic misalignment). Current fragmented approaches are insufficient to address these core challenges. We propose an integrated circularity framework that aligns interventions across policy, technology, and market domains. To bridge the policy-action chasm, we advocate for smart regulations, including multilateral certification reciprocity. To mitigate the technology-market dislocation, we recommend adaptable, modular recycling systems augmented with AI. To resolve the temporal disequilibrium, we suggest market restructuring through blockchain-tracked material certificates linked to tradable environmental, social, and governance tokens. This framework provides a coordinated pathway to decouple LIB growth from dependence on virgin resources, directly tackling the root causes of the sustainability trilemma.