This study reconceptualized partial nitrification from a microbial ecological perspective by elucidating the dynamic competition between AOB and NOB across the initiation， maintenance， and destabilization phases. Continuous selection pressure was proposed as the core determinant of process stability within a community-process coupled framework. The review indicates that the initiation depends on non-steady-state disturbances that amplify AOB growth advantages， whereas the maintenance phase is characterized by a metastable state with dynamic community structure but relatively stable function， where NOB persist at low abundance or under spatial constraint. When cumulative disturbances weaken AOB competitiveness， NOB can rapidly rebound， inducing a critical shift from partial to complete nitrification. Accordingly， operational strategies centered on resource supply， niche constraint， and community feedback are outlined， emphasizing window-period management to enhance system resilience. The alignment of time-resolved community data with key operational parameters is further discussed as a basis for identifying instability thresholds and early-warning signals to support predictive control and risk management in partial nitrification processes.

Nitrogenous pollutant discharges are rising with urbanization and industrialization， and their untreated release worsens aquatic nitrogen pollution. Currently， nitrogen removal from municipal and industrial wastewater is transitioning from an energy-intensive model to strategies emphasizing pollution reduction， carbon mitigation， and synergistic efficiency. Green and sustainable nitrogen removal technologies represent a key research frontier in water pollution control. This review systematically examined nitrogen pollution in China's wastewater， characterized nitrogen-laden industrial effluents， and highlighted challenges such as wide concentration ranges， complex compositions， and treatment recalcitrance. Based on this analysis， this paper comprehensively reviewed the principles and applications of advanced nitrogen removal technologies， including physicochemical， biological， electrochemical/bioelectrochemical， and advanced oxidation processes. Their treatment efficiency， advantages， and limitations were analyzed， with special emphasis on the application of advanced oxidation processes for refractory nitrogenous pollutants. Future efforts should prioritize adopting low-energy， low-chemical-consumption biological nitrogen removal processes， integrate electrochemical and advanced oxidation processes with conventional methods， enhance overall treatment efficiency， and reduce costs. These advancements are pivotal for achieving China's Dual Carbon Goals and advancing sustainable development.

Ozonation is an effective advanced treatment technology for textile dyeing and finishing wastewater； however， its large-scale application is primarily constrained by its intrinsically low ozone mass transfer efficiency. Membrane contactor reactors （MCRs） can significantly enhance ozone mass transfer by constructing microscale gas-liquid interfaces， offering advantages such as high mass transfer efficiency and the absence of secondary pollution. Nevertheless， issues including membrane fouling， high material costs， and poor operational stability still limit their engineering-scale implementation. This study systematically reviewed recent advances in the mechanisms of ozone mass transfer enhancement in MCRs. The principles of gas-liquid interfacial mass transfer and the design characteristics of hollow fiber membrane contactor configurations were introduced. The regulatory effects of membrane material properties （e.g.， the selection of hydrophobic PTFE/PVDF）， operating parameters （gas-liquid flow rates， transmembrane pressure， and pH）， and mass transfer models on the volumetric ozone mass transfer coefficient were critically analyzed. Furthermore， the application efficiency of MCRs in textile dyeing and finishing wastewater treatment was evaluated， with particular emphasis on efficient dye removal， organic matter mineralization， and decolorization. Research demonstrated that optimized MCR systems could increase the volumetric ozone mass transfer coefficient by 5~10 times compared with conventional bubble column processes， thereby substantially enhancing the kinetics of pollutant degradation. However， challenges such as membrane fouling-induced flux decline， bromate by-product formation， and cost-benefit optimization remained to be addressed. Finally， future research directions were proposed， focusing on the rational design of multifunctional composite membranes integrating antifouling properties， corrosion resistance， and low cost； the elucidation of interfacial reaction mechanisms through coupling with intensified fields such as high-gravity and electrocatalytic processes； the development of intelligent parameter regulation systems based on process modeling； and comprehensive techno-economic and environmental risk assessments at the pilot scale. These efforts will provide theoretical support and technical guidance for the engineering application of MCR-ozone processes.

Denitrification is a critical process for advanced nitrogen removal in wastewater treatment， fundamentally governed by microbially driven electron transfer and electron allocation. As research has shifted from macroscopic treatment metrics toward microscopic regulation， elucidating denitrification mechanisms from an electron-flow perspective has emerged as a major research frontier. This review systematically summarized the theoretical framework of electron flow in denitrification systems， compared intracellular electron transport pathways and energy allocation characteristics between heterotrophic and autotrophic denitrifiers， and highlighted the central role of the quinone pool in electron collection and redistribution. Furthermore， from the perspective of interspecies microbial interactions， recent advances in indirect interspecies electron transfer （IIET） and direct interspecies electron transfer （DIET） were summarized， and competitive as well as cooperative interactions among microorganisms in mixed systems during electron donor and electron acceptor utilization were analyzed. Building on this framework， the impacts of carbon source characteristics， pH， oxidation-reduction potential （ORP）， and coexisting contaminants on electron transport chains and electron allocation pathways were further discussed. Finally， in light of current limitations in the in situ quantification of electron fluxes， future research directions were proposed， including the development of multi-scale in situ characterization techniques， novel electron-conductive materials， and intelligent electron-flow regulation models.

Against the backdrop of increasingly severe global sustainability challenges， Bipolar Membrane Electrodialysis （BMED） technology is emerging as a pivotal solution driving transformation in the chemical， environmental， and resource management sectors. This technology not only demonstrates remarkable efficiency and economic benefits in critical areas such as resource extraction， pollution control， and CO₂ capture but also exhibits substantial potential for large-scale commercial implementation. This review systematically outlines the working principles and fabrication methods of bipolar membranes， along with their applications across various industrial fields， highlighting their significant capacity to advance greener and more efficient industrial processes. Representative case studies in resource recovery， pollution mitigation， and CO₂ capture are presented to illustrate the promising industrial prospects of BMED and validate its practical value in enabling sustainable resource utilization and environmental protection.

Iron-dependent autotrophic denitrification （IDAD） is a promising biological technology for nitrogen removal from wastewater with a low C/N ratio. While significant differences in community structure among IDAD consortia from different studies have been reported， the underlying reasons remain unclear. Hypothesizing that the anion type of ferrous salts could be a key contributing factor， this study enriched two IDAD consortia （R1 and R2） using FeCl₂ and FeSO₄ as respective electron donors under identical inoculum sludge conditions. Their nitrogen removal performance， extracellular polymeric substance （EPS） composition， iron oxidation product properties， microbial community structure， and functional gene distribution characteristics during long-term operation were systematically compared. The results showed that R1 exhibited higher denitrification efficiency and Fe（Ⅱ） oxidation activity. Key iron-oxidizing bacterial genera such as Gallionella showed a significantly higher relative abundance in R1 than in R2， and R1 also maintained higher community diversity. Metagenomic analysis further revealed a higher abundance of functional genes related to iron oxidation and denitrification in R1. In contrast， R2 was enriched with more genera associated with sulfate metabolism and complex organic matter degradation. Distinct differences were also observed in EPS composition and iron mineral surface properties between the two consortia. This study confirms that the type of ferrous salt significantly regulates the structural assembly and metabolic functions of IDAD consortia， providing a theoretical basis for optimizing their application in practical wastewater treatment.

This study took a large municipal wastewater treatment plant （WWTP） in northern China as the research object， and systematically investigated the influence characteristics and response mechanism of abnormal influent shock load on the structure of activated sludge microbial community. The results showed that influent shock caused drastic changes in the structure of activated sludge microbial community： the abundances of core functional flora such as Proteobacteria and Bacteroidetes decreased significantly by 55.30% and 44.35%， respectively； the community diversity was reduced， the nitrification function was weakened， and the concentration of effluent ammonia nitrogen increased. Meanwhile， shock-resistant flora such as the genus SJA-28 within Chlorobi proliferated rapidly， showing a 5.68‑fold increase in relative abundance compared to the normal period， which helped sustain the pollutant removal capacity of the system to some extent. These findings confirmed that the activated sludge system has strong shock resistance and self-recovery capacity. The implementation of regulatory measures such as shortening sludge retention time （SRT） and increasing the dosage of sodium acetate and phosphorus removal chemicals was shown to be conducive to the rapid recovery of functional flora. Based on these findings， it is suggested that in practical operation， SRT adjustment strategies should be flexibly adjusted according to influent quality characteristics and temperature conditions， so as to improve the stability and resilience of the wastewater treatment system in responding to shock loading.

This study， conducted at the Haikou Jiangdong Water Plant， applied a direct ultrafiltration process to treat the Nandu River water for potable use. Pilot-scale experiments were performed to optimize key operational parameters， including filtration cycle， backwash regime， and chemical-enhanced backwash （CEB） dosing and frequency. Under the optimized condition， the study comprehensively evaluated treatment performance， membrane-fouling characteristics， and techno-economic outcomes. The results showed that with a filtration cycle of 90 min and a high-intensity， short-duration backwash regime （170 L/（m²·h） flux， 150 s air scouring， 10 s combined air-water top backwash， 10 s combined air-water bottom backwash）， together with CEB using 500 mg/L sodium hypochlorite at a frequency of 7 days， the system exhibited robust adaptability and stable performance across varying raw-water qualities. The system maintained regulatory-compliant effluent even when raw-water COD_Mn reached 7.01 mg/L during high-turbidity periods （≥50 NTU）. However， when raw-water COD_Mn approached 3.6 mg/L during low-turbidity periods （<50 NTU）， there was a potential risk of the effluent COD_Mn exceeding the applicable drinking-water standard. Over 42 days of operation， the transmembrane pressure increased by a cumulative 8.48 kPa but stabilized following a short-term high-turbidity perturbation. Membrane-fouling analyses confirmed that the optimized operating conditions effectively limited fouling and identified siliceous-aluminous inorganic residues as the primary irreversible foulant fraction. A techno-economic assessment indicated water production costs of RMB 0.226/m³ （low-turbidity） and RMB 0.243/m³ （high-turbidity）， both lower than the RMB 0.261/m³ estimated for a conventional coagulation-sedimentation-filtration-disinfection process. The operational-parameter framework established in this study provides experimental evidence and technical support for applying direct ultrafiltration as a primary pretreatment unit in engineering practice.

In the context of global carbon neutrality goals and energy transformation，it is urgent to develop new technologies that efficiently convert CO₂ into renewable energy carriers such as CH₄. Microbial electrolysis cells （MECs）， which couple electrochemistry with microbial metabolism for CO₂ conversion， exhibit performance that is heavily dependent on the electron transfer capabilities and biocompatibility of the cathode.Therefore，Nafion was employed to load nanoscale Fe₃O₄ and carboxylated multi-walled carbon nanotubes onto nickel foam （NF）. The electrochemical performance of the modified NF was characterized using techniques such as electrochemical impedance spectroscopy （EIS），cyclic voltammetry （CV），and linear sweep voltammetry （LSV）. The results indicated that the modified NF exhibited lower internal resistance，a larger electrochemical active surface area，and enhanced hydrogen evolution capabilities.Ultimately，this modified cathode was employed in a constant current dual-chamber anaerobic methanogenic MECs for the electrochemical reduction of CO₂ to CH₄.The results demonstrated that under a constant current of -0.1 A，the CH₄ concentration of the nanoscale Fe₃O₄ and carboxylated multi-walled carbon nanotube-modified NF group could reach 90%，surpassing the 80% CH₄ concentration of the NF group. Moreover，the daily CH₄ production of the modified group was 295 mL，higher than the 260 mL daily methane production of the NF group，reflecting an increase of 13%. It was found that the modified NF exhibited higher hydrogen production and lower internal resistance， creating a more favorable environment for the growth and enrichment of hydrogenotrophic methanogens， thereby facilitating the electrochemical reduction of CO₂ to CH₄. Subsequent microbial community analysis also indicated that the relative abundance of the hydrogenotrophic methanogen Methanobacterium in the reactor with the modified NF was higher than that in the NF group，further facilitating the process of H₂ serving as an electron donor for CO₂ reduction to CH₄. This research provides new ideas and experimental evidence for the development of novel non-precious metal composite cathode materials in bioelectrochemical systems.

Per- and polyfluoroalkyl substances （PFASs） are frequently detected at elevated concentrations in water bodies of the lower Yangtze River， posing risks to drinking water safety and human health. This study investigated the occurrence of 23 typical PFASs in source water， treated water， and tap water from eight drinking water treatment plants （DWTPs） in the lower reaches of the Yangtze River. The removal efficiency of PFASs by the treatment processes and their priority for control were also assessed. The results revealed the presence of 19 PFASs across the eight DWTPs， with total concentrations ranging from 32.02 to 167.68 ng/L and an average of 85.86 ng/L. Among these， 14 long-chain and 5 short-chain PFASs were identified， contributing 35.7% and 64.3% to the total concentration， respectively， indicating that short-chain PFASs were the predominant pollutants. The major contaminant monomers were perfluorooctanoic acid （PFOA）， perfluorobutanoic acid （PFBA）， perfluorobutanesulfonic acid （PFBS）， and perfluorohexanoic acid （PFHxA）. The overall removal efficiency of PFASs by the drinking water treatment processes was 17.8%， with a removal efficiency of 22.2% for long-chain and 15.1% for short-chain congeners. Notably， concentrations of 14 PFASs increased during distribution from the treatment plant to the tap， resulting in an overall rebound rate of 39.6%. PFBA， PFOA， and PFBS were the primary contributors， accounting for over 92.8% of this concentration increase. Modeling assessment identified PFOA， perfluorononanoic acid （PFNA）， perfluorododecanoic acid （PFDoA）， and perfluorooctanesulfonic acid （PFOS） as priority PFASs requiring enhanced monitoring and control measures.