This study evaluated the short-term, acute impacts of elevated Cu(II) and Cr(VI) concentrations on the nitrogen-removal efficiency, microbial community composition, and predicted metabolic responses of anammox granular sludge. Results showed that 12mg/L Cu(II) induced a temporary inhibition of anammox activity. In contrast, 8mg/L Cr(VI) caused a near-complete cessation of nitrogen removal. High concentrations of Cu(II) and Cr(VI) decreased the relative abundance of Candidatus Kuenenia by 4.86% and 2.88%, respectively, indicating that heavy metals likely impair anammox performance by directly inhibiting key anammox bacteria. Functional-prediction analysis (PICRUSt2) suggested that, under Cu(II) and Cr(VI) stress, the anammox community upregulated pathways associated with cell motility, energy metabolism, chemotaxis, signal transduction, and xenobiotic biodegradation—presumably as adaptive responses to mitigate toxicity.

To explore the influence of trace elements and change in environmental conditions at low temperature on the nitrification performance of biofilm reactor, a simulated wastewater containing NH₄⁺-N was treated. The effects of trace elements, low temperature, aeration rate and flow rate on nitrification performance of the biofilm reactor were studied. The microbial community structure was analyzed by 16S rRNA high-throughput sequencing technique. The results showed that trace elements significantly affected the nitrification performance (P<0.0001). After adding trace elements to the influent, the removal load of NH₄⁺-N increased from 0.93kg/(m³·d) to 1.63kg/(m³·d) and the generation load of NO₃^--N increased from 0.23kg/(m³·d) to 1.21kg/(m³·d). Low temperature can affect nitrifying bacteria. Nitrite oxidizing bacteria (NOB) are sensitive to low temperature shock, while ammonia oxidizing bacteria (AOB) are resistant to it. The decrease in aeration rate led to a lack of dissolved oxygen (DO) in the reactor, which further affected the nitrification performance. The change in flow rate had no significant effect on the nitrification performance. Analysis of the microbial community structure at low temperatures showed that the nitrobacteria of Nitrosomonas and Nitrospira were enriched during operation, which ensured that the reactor can still have stable nitrification performance. The research provides experimental evidence and theoretical guidance for improving the nitrification performance and enhancing the low-temperature resistance of biofilm reactor in wastewater nitrification treatment practice.

An anaerobic sequencing batch biofilm reactor was used to explore the combined effect mechanism of anammox under the co-existence conditions of quinoline (50~200mg/L) and microplastics (PET-MPs) (20~100mg/L). With the increase of the concentrations of quinoline and PET-MPs, the performance of Anammox first decreases and then gradually recovers, and recovery time of reversible inhibition was positively correlated with the concentration of combined pollutants. The specific anammox activity (SAA) decreased from 22.8mg N/(g VSS·h) in stage C1 to 16.2mg N/(g VSS·h) in stage C3, while the corresponding reactive oxygen species (ROS) production increased by 55.7%, indicating that the inhibition of Anammox was enhanced under combined pollution. Extracellular polymer (EPS) analysis revealed that an increase in the concentrations of quinoline and PET-MPs would lead to a rapid decrease in the EPS content of the biofilm from 75.3mg/g VSS to 39.2mg/g VSS. The significant reduction in protein (PN) secretion, which in turn led to a significant decrease in PN/PS, indicates a decline in the structural stability of the Anammox biofilm. High-throughput sequencing revealed that the concentration of quinoline /PET-MPs increased, while the microbial community diversity and richness indices decreased. The relative abundance of Candidatus_Brocadia decreased from 1.73% to 1.24%, while the relative abundance of Denitratisoma changed little. However, the relative abundance of anaerobic heterocyclic degrading bacteria increased significantly.

The study used humic acid (HA) to drive the potassium permanganate/persulfate (PM/PMS+HA) system to investigate the removal of small molecule organic pollutants and the effectiveness of membrane fouling control. The experimental results showed that the PM/PMS+HA system exhibited excellent removal performance for different small molecule organic compounds, including Atrazine (ATZ), Phenol (Phenol), Diclofenac Sodium (DCF), Carbamazepine (CBZ), Ibuprofen (IBP) and Sulfamethoxazole (SMX). The first-order kinetic constants of the PM/PMS+HA system were all higher than 18×10^-2min^-1, far higher than the PM/PMS system, PM system, and ultrafiltration system alone. At the same time, the PM/PMS system has a good membrane fouling alleviation effect. When HA was used as the pollutant, the effluent specific flux of the PM/PMS system only decreased to 0.919 within 15 minutes, much higher than the 0.393 obtained by HA filtration alone. Meanwhile, when using the PM/PMS system for membrane cleaning, the membrane flux recovery rate reached 98.51%. The mechanism of the PM/PMS+HA system was explored through capture experiments and measurements using a UV spectrophotometer. The experimental results indicate that during the filtration process of PM/PMS+HA, it is mainly the rich electronic HA in the system that triggers the decomposition of the composite oxidant (PM-PMS). The decompositionof composite oxidants produces reactive oxygen species (^•OH、SO₄^•-、¹O₂) and reactive manganese(Mn(V)and Mn(VI)). The generated reactive oxygen species and reactive manganese oxidize pollutants, leading to the removal of new pollutants and a decrease in the molecular weight of membrane pollutants, thereby achieving the removal of new pollutants and the control of membrane pollution. The PM/PMS system driven by pollutants has achieved the coupling of ultrafiltration membranes with advanced oxidation technology, providing new ideas for the removal of small molecule organic compounds and membrane fouling control in ultrafiltration technology.

This study investigated the effects of raw water turbidity variation on the stable flux, pollutants removal, and bio-cake layer of gravity flow ultrafiltration (GDM) system. The results showed that the increase of raw water turbidity led to a significant decrease in the flux of GDM system, but a new stable flux can be achieved in 17~30 days. Compared to control GDM with low influent turbidity (1.8~3.7NTU), the increase of raw water turbidity to 10, 50 and 100 NTU reduced the stable flux of GDM system by 15%, 36% and 61%, respectively. The macromolecular organic matter carried by particles was degraded by microorganisms in the bio-cake layer to low molecular weight organic matter, which passed through the membrane and resulted in increase of dissolved organic matter in the effluent with the increase of raw water turbidity. The ammonia removal rate of GDM system reached more than 80% after 9days of start-up, and the temporary decrease in ammonia nitrogen removal capacity occurred due to the increase of raw water turbidity. However, it recovered after 7~11days of adaptation period. With the increase of raw water turbidity, the thickness of bio-cake layer increased by 1.8 to 7.9 times and the microbial extracellular polymeric substances increased by 37 to 98%. Meanwhile, the microbial community structure underwent certain changes. This study shows that GDM system has certain adaptability to increase of raw water turbidity.

A novel catalytic membrane (AC-MgO@PVDF) was fabricated by loading activated carbon (AC) and MgO onto a poly (vinylidene fluoride) (PVDF) membrane using a vacuum filtration method. The as-prepared catalytic membrane (AC-MgO@PVDF) was employed to activate persulfate (PS) for the oxidation of ammonia nitrogen (NH₄⁺-N) in aqueous solution. The structure and elemental composition of the catalytic membrane were characterized by SEM, Raman and XPS. The efficiency and mechanism of NH₄⁺-N oxidation by the AC-MgO@PVDF/PS system were investigated. The results showed that under the conditions of a flow rate of 1mL/min, a PS dosage of 8g/L and an AC loading of 4.8mg/cm², the removal rate of 30mg N/L NH₄⁺-N and the nitrogen gas (N₂) selectivity of the NH₄⁺-N oxidation products reached 100% and 91.7%, respectively, after 25min of operation. The system exhibited a broad pH tolerance range (3~12) and was barely affected by common anions and natural organic matters in water body. Even after 240min of continuous operation, the system could still achieve a removal rate of over 60% for NH₄⁺-N. Quenching experiments, EPR measurements, and electrochemical tests revealed that f NH₄⁺-N was primarily oxidized through a non-radical pathway, with direct electron transfer being the main mechanism for its oxidation to N₂.

This study implemented an integrated precipitation-air stripping-electrochemical oxidation process to treat limestone wet desulfurization wastewater, systematically investigating the effects of operational parameters on chloride removal, nitrogen elimination, and organic pollutant degradation. The removal mechanisms of multiple contaminants were comprehensively elucidated. Through response surface methodology (RSM) optimization, the salt precipitation achieved 66.9% chloride ion removal efficiency under optimal conditions (Ca/Al/Cl molar ratio of 6.8:1.9:1, operational temperature 37.5℃). Air stripping was conducted under alkaline condition, which attained 76.5% ammonia nitrogen removal efficiency. Finally, after 180min electrochemical oxidation, the effluent ammonia nitrogen and COD concentrations were significantly reduced to 7mg/Land 165mg/L, respectively. Mechanistic analysis revealed that the introduction of calcium-aluminum salts facilitated the transformation of tetrahedral Al(OH)₄^- into Ca-O-Al octahedral under high Ca/Al ratios and appropriate thermal conditions. Cl^- were immobilized through adsorption or ion exchange by calcium-aluminum bimetallic layered hydroxide, then the Ca₄Al₂(OH)₁₂Cl₂•10H₂O was formed and precipitated from the water. After precipitation-air stripping process, the residual Cl^- concentration in the effluent was high, enabling its participation in electrochemical activation, and generating reactive species such as •Cl, •OH and ¹O₂, Thus those pollutants such as ammonia nitrogen and organic matters in the effluent was efficiently purified by direct anodic oxidation and indirect oxidation of active substances.

In view of the typically unsatisfactory antibiotics removal performances that were observed in the traditional 'three ponds and two dams' combination process, a new composite packing filter dam was developed. Through the synergetic combination of composite packing balls with a specially designed filter dam structure, highly efficient and broad-spectrum removal of antibiotics was achieved. Results showed that the removal rates of antibiotics (in terms of total mass concentrations) in perch, eel, raw fish and shrimp culture pond water were maintained at more than 80% by the composite packing filter dam. Quinolones, sulphonamides, tetracyclines and chloramphenicol were removed to different extents, among which the best removal effects were observed for quinolones and sulphonamides. The composite filler consisting of iron filings, ceramsites and polybutylene succinate (PBS) was found to significantly improve the removal of quinolones and sulfonamides. Ceramsites were demonstrated to play an adsorption role through which quinolone and sulfonamide antibiotics were removed via pore filling and π-π electron donor-acceptor interactions, which was identified as the main antibiotic removal pathway. Iron filings were shown to remove tetracycline and chloramphenicol through adsorption and reduction processes, and were suggested to have accelerated the direct electron transfer process that promoted antibiotic degradation. PBS was involved in the removal of antibiotics through co-metabolic denitrification. Both iron filings and PBS were proven to enhance the metabolic activity of functional microorganisms, thereby accelerating antibiotic removal. The synergistic effect between these components was confirmed to help achieve efficient and broad-spectrum antibiotic removal.

The reed biochar was chemically modified using hydrochloric acid, dicyandiamide, and magnesium chloride as activators. This study investigated the effects of varying pH values, addition amounts, and initial solution concentrations on the nitrate nitrogen adsorption capacity of four types of biochar. Additionally, the adsorption kinetics and thermodynamic characteristics of the biochars for nitrate nitrogen removal were analyzed. When reed straw is pre-carbonized at 500℃ for 2hours and subsequently activated with modified materials at 700℃ for 2hours, the resultant dicyandiamide-modified biochar (DBC) exhibits the best adsorption performance, achieving a removal efficiency of 75.5%. Compared to unmodified biochar (BC), the surface morphology of the modified biochars becomes more concave, with denser pores, increased functional groups, and a specific surface area enhanced by 7 to 10 times. When the potassium nitrate concentration is 500mg/L, the optimal dosages are 1g for BC, DBC, and magnesium chloride-modified biochar (MBC), and 0.8g for hydrochloric acid-modified biochar (HBC). The nitrate nitrogen adsorption performance of DBC is favorable in a slightly alkaline environment, with the highest adsorption capacity observed at a pH of 9. The nitrate nitrogen adsorption behavior of all four biochars aligns well with the pseudo-second-order kinetic model, and their isothermal adsorption curves fit the Langmuir equation, suggesting predominantly monomolecular layer adsorption. Overall, DBC demonstrates excellent nitrate nitrogen adsorption performance and offers a promising solution for mitigating nitrate pollution in aquatic environments.

In this study, a method for control of humic acid-cadmium composite pollution using MXene/PMS process in the presence of trace Fe(III) was proposed. The results showed that the removal efficiency of Cd²⁺ by MXene material in the presence of humic acid decreased from 70% to 48%, and addition of 0.5µmol/L Fe(III) and 50µmol/L peroxymonosulfate increased the removal efficiency of Cd²⁺ to above 60%. too much or less PMS inhibited the removal of Cd²⁺. Reducing Fe(III) from 1.0µmol/L to 0.3µmol/L promoted the removal of Cd²⁺. The strong reducing property of MXene material and its strong interaction with metal ions triggered the Fe(III)/Fe(II) cycle and inhibited the hydrolysis of iron ions, realizing the efficient removal of humic acid-cadmium composite pollution under neutral conditions. The reactive species generated in the reaction system were mainly hydroxyl radicals and sulfate radicals. Under the background condition of Xijiang river, this technique maintained good removal effect.