The anammox process is considered as a revolutionary new denitrification technology. In this study, the anammox process was started in a single-stage moving bed biofilm reactor (MBBR) and the mechanism of excess removal of ammonia nitrogen was studied. At stage I (day 0–51), anammox bacteria (AnAOB) was enriched by feeding synthetic sewage without adding organic carbon. The removal rate of ammonia nitrogen was maintained at about 54% and the removal rate of total inorganic nitrogen was maintained at about 62%. At stage II (day 52–91), internal circulation was added into the MBBR. After adding internal circulation, the ammonium removal efficiency reached about 96% (at day 56) and the total nitrogen removal efficiency reached about 86%. At day 90, the biofilm sample was drowned out for high-throughput sequencing. The results showed that the relative abundance of AnAOB was 23.23%. The dominant anammox genus was Candidatus Brocadia. The relative abundance of Nitrosomonas (ammonia oxidizing bacteria, AOB) was 0.63%. The excess ammonia nitrogen was removed by AOB and AnAOB through the partial nitrification and anammox (PNA) process.

Electrochemical oxidation of ammonia is an attractive process for wastewater treatment, hydrogen production, and ammonia fuel cells. However, the sluggish kinetics of the anode reaction has limited its applications, leading to a high demand for novel electrocatalysts. Herein, the electrode with the in situ growth of NiCu(OH)₂ was partially transformed into the NiCuOOH phase by a pre-treatment using highly oxidative solutions. As revealed by SEM, XPS, and electrochemical analysis, such a strategy maintained the 3D structure, while inducing more active sites before the in situ generation of oxyhydroxide sites during the electrochemical reaction. The optimized NiCuOOH-1 sample exhibited the current density of 6.06 mA cm⁻² at 0.5 V, which is 1.67 times higher than that of NiCu(OH)₂ (3.63 mA cm⁻²). Moreover, the sample with a higher crystalline degree of the NiCuOOH phase exhibited lower performance, demonstrating the importance of a moderate treatment condition. In addition, the NiCuOOH-1 sample presented low selectivity (<20%) towards NO₂⁻ and stable activity during the long-term operation. The findings of this study would provide valuable insights into the development of transition metal electrocatalysts for ammonia oxidation.

In recent years, the simultaneous partial nitrification, anammox, and denitrification (SNAD) process has attracted considerable attention due to its advantages such as low energy consumption and low sludge production. This study investigated the long-term performance and microbial mechanisms of a single-stage moving bed biofilm reactor (MBBR) employing the SNAD process for treating real domestic sewage at room temperature. A pre-carbon adsorption unit (reactor A) reduced the influent C/N ratio from 5.68:1 to 3.13:1, enabling efficient nitrogen removal in reactor B. Results demonstrated that dissolved oxygen (DO) and C/N ratio critically influenced system performance. At DO ~0.3 mg/L, stable SNAD operation achieved 65% total nitrogen (TN) removal, with synergistic contributions from partial nitrification, anammox, and heterotrophic denitrification. Elevated C/N ratios (4.71:1) reduced TN removal by ~30%, linked to decreased abundances of anammox bacteria. Microbial analysis revealed Candidatus Brocadia as key anammox bacteria, Nitrospirae as dominant ammonia-oxidizing bacteria and Denitratisoma as main denitrifying bacteria to drive nitrogen conversion. This study confirms the feasibility of SNAD-MBBR for real domestic sewage under ambient conditions, highlighting optimal DO and C/N control for microbial synergy and process stability.

Magnesium-ion batteries have attracted extensive attention due to their abundance, high safety, and superior volumetric energy density. However, their development remains constrained by the sluggish diffusion of Mg²⁺ ions and the limited magnesium storage capacity of electrode materials. In this work, we systematically investigate the Mg storage performance and underlying mechanisms of monolayer MoS₂ anodes substitutionally doped with Cu, Ag, and Au at a concentration of 4% on the Mo sublattice. The results reveal that all three dopants maintain the structural integrity of the two-dimensional MoS₂ framework after optimization while introducing localized electronic states near the Fermi level, thereby enhancing Mg adsorption. Compared with intrinsic MoS₂, the doped systems exhibit markedly improved Mg binding. Sequential adsorption calculations indicate that, at the investigated 4% substitution concentration, Cu-MoS₂, Ag-MoS₂, and Au-MoS₂ can stably accommodate up to five Mg atoms, elevating the theoretical specific capacity to ~67 mAh/g while maintaining low open-circuit voltages during magnesium intercalation. Diffusion kinetics analysis further shows that Cu-MoS₂ possesses the lowest Mg migration barrier (0.25 eV), surpassing Ag-MoS₂ (0.38 eV) and Au-MoS₂ (0.61 eV). Considering both thermodynamic stability and ion transport kinetics, Cu-MoS₂ achieves an optimal balance among storage capacity, operating voltage, and diffusion performance, highlighting its promise as a high-performance anode material for magnesium-ion batteries.