This study enhanced low-temperature (13 +/- 0.5 degrees C) Anammox performance under high NLRs using immobilized cold-acclimated granules (M2). As the NLR increased stepwise from 1.5 to 5.5 kg-TN/(m3 center dot d), M2 maintained high nitrogen removal efficiency (93 %-82 %), demonstrated superior performance at higher NLR, while the cold-acclimated granules without immobilization (M1) declined sharply to 25 %. M2 exhibited over a threefold increase in biomass retention and approximately 1.9 times higher activity than M1 under NLRs of 3.5-5.5 kg-TN/ (m3 center dot d). The gel matrix in M2 provided abundant attachment sites, promoting microbial retention, and controlling the excessive release of tightly bound extracellular polymeric substances (TB-EPS). Specifically, M2 had significantly lower TB-EPS protein (TB-PN) content. Crucially, the TB-PN in M2 had a lower relative abundance of alpha-helix and a lower alpha-helix/(beta-sheet + random coil) ratio compared to M1. This indicated a looser secondary protein conformation, favoring better sludge aggregation. Furthermore, microbial analysis revealed that Candidatus Brocadia abundance increased significantly in M2 under higher NLRs, replacing Candidatus Kuenenia as the dominant genus (reaching 20 %). Concurrently, M2 granules possessed markedly higher abundances of the key functional genes (hzo, hzsB and hdh) and enhanced clusters of orthologous groups of proteins (COG) function annotation (inorganic ion transport and metabolism, and amino acid transport and metabolism, etc) compared to M1. The combined effects of improved biomass retention via immobilization, the favorable loose TB-PN structure promoting aggregation, the shift to Candidatus Brocadia, elevated functional gene expression and enhanced COG function enabled M2 granules to achieve higher nitrogen removal activity under challenging low-temperature and high-NLR conditions.

Aiming at the technical bottlenecks of insufficient carbon source and poor synergistic efficiency of nitrogen and phosphorus removal in the conventional biological treatment of wastewater with a low carbon-to-nitrogen (C/N) ratio, this study developed an enhanced sequencing batch reactor‑anaerobic/oxic/anoxic (SBR-A/O/A) process synergistically strengthened by elemental sulfur (S0) and zero-valent iron (Fe0). A static magnetic field (MF) (10 mT) was introduced to mitigate Fe0 passivation. The performance and mechanisms of the system for nitrogen and phosphorus removal from low C/N (C/N = 4) wastewater were investigated. The results demonstrated that after adding S0 and Fe0 carriers, the total nitrogen (TN) removal efficiency increased from 69.63% to 78.03%. With MF application, sustained iron ion release further improved average TN and total phosphorus (TP) removals to 82.26% and 81.56%, respectively, while effluent sulfate remained below 250 mg/L. Microbial community analysis revealed that autotrophic functional bacteria, such as sulfur oxidizing bacteria (SOB) (Thiobacillus) and nitrate-dependent ferrous oxidizing (NDFO) bacteria (Gallionellaceae and Thermomonas), were enriched inside the carriers, forming a synergistic metabolic network with glycogen‑accumulating organisms (Candidatus_Competibacter and Defluviicoccus) and denitrifying phosphorus‑accumulating organisms (Paracoccus, Dechloromonas, and Acinetobacter) in the suspended sludge. Additionally, Fe0 achieved chemical phosphorus removal by releasing iron ions to form Fe-P precipitates. The phosphorus content in the system sludge increased significantly (19.5 wt%), indicating considerable potential for phosphorus resource recovery. The proposed S0-Fe0 synergistically enhanced A/O/A process offers the dual benefits of sludge reduction and phosphorus resource recovery, providing a promising solution for efficient nitrogen and phosphorus removal from low C/N wastewater.

Anaerobic ammonium oxidation (Anammox) biofilm process is often limited by insufficient microbial attachment to traditional carriers. This study assessed the impact of a pyrite modified polyethylene (MPE) carrier on biofilm formation and nitrogen removal by comparing R1 (polyethylene, PE) and R2 (MPE) reactors over 60 days. Results showed that MPE exhibited higher surface roughness, hydrophilicity and positive charge, promoting microbial attachment. MPE also increased extracellular polymeric substance (EPS) secretion and the protein/ polysaccharide (PN/PS) ratio, resulting in a 66.83 f 6.67% higher biofilm growth rate than PE. Additionally, the slow-release iron and sulfur from MPE markedly enhanced the electron transfer system activity (ETSA) in R2, yielding higher specific Anammox activity (SAA) and total nitrogen removal efficiency (TNRE) in R2 (94.33 f 0.35%) compared to R1 (83.30 f 0.68%). Microbial community analysis indicated that MPE promoted the growth of EPS-producing bacteria and strengthened the interaction network between anaerobic ammoniumoxidizing bacteria (AnAOB) and iron/sulfur autotrophic denitrifying bacteria. Metagenomic analysis further revealed that MPE enhanced key metabolic pathways, including oxidative phosphorylation and the WoodLjungdahl cycle, promoting metabolic substrate exchange and bacterial cooperation, thus improving nitrogen removal. This study supports the high-value reuse of waste minerals and the development of carbon-neutral wastewater treatment.

F-53B and OBS, two major alternatives to perfluorooctane sulfonate (PFOS), are frequently detected in wastewater treatment systems; however, their effects on aerobic granular sludge (AGS) formation and functional stability remain poorly understood. Therefore, this study investigated the impacts of long-term F-53B and OBS exposure on sludge performance and microbial community dynamics during AGS granulation. Compared with the control reactor, both F-53B and OBS significantly stimulated extracellular polymeric substance (EPS) secretion (R1: 103.09 ± 1.73 mg/g VSS; R2: 132.63 ± 4.05 mg/g VSS; R3: 115.23 ± 1.53 mg/g VSS), thereby accelerating granulation (R1: 48 d; R2: 42 d; R3: 46 d). However, the enhanced granulation rate came at the expense of treatment performance, as total nitrogen removal decreased from 74.86 ± 1.78% in R1-66.78 ± 2.28% and 67.69 ± 2.23% in R2 and R3, respectively. Further analyses revealed that F-53B and OBS increased intracellular reactive oxygen species (ROS) levels to 133.84 ± 0.46% and 121.67 ± 0.55% of the control, respectively, accompanied by increases of 20.0% and 12.8% in the proportion of membrane-damaged cells. Multi-omics analyses demonstrated that excessive ROS activated the RpoS/c-di-GMP signaling pathway and upregulated key genes involved in glycolysis and the tricarboxylic acid cycle, thereby promoting EPS-producing bacteria such as Candidatus_Competibacter (R1: 10.69 ± 0.68%; R2: 15.52 ± 1.67%; R3: 11.32 ± 0.91%) to synthesize more EPS as a protective barrier and accelerate granule aggregation. During this process, microbial carbon and energy allocation shifted from nutrient removal toward EPS production, resulting in competitive suppression of key functional microorganisms involved in nitrogen and phosphorus removal, such as Candidatus_Accumulibacter and Nitrosomonas, ultimately reducing treatment efficiency. Enzyme activity assays and molecular docking further confirmed that both compounds interfered with antioxidant enzymes and weakened ROS-scavenging capacity. Overall, F-53B and OBS induced a ROS-mediated metabolic trade-off in AGS, promoting rapid granulation through excessive EPS production while compromising the stability of nitrogen and phosphorus removal. These findings provide new insights into the ecological risks of PFOS alternatives and offer a scientific basis for improving the stability of AGS-based wastewater treatment processes.

Neodymium (Nd(III)) and sulfate (Na2SO4) are commonly present in neodymium mining wastewater. However, the effects of their coexistence on microorganisms responsible for removing nitrogen from wastewater have been poorly reported. In this study, the combined inhibition of Nd(III) and Na2SO4 on anaerobic ammonium oxidation (Anammox) and its recovery were investigated in terms of performance, kinetics, Nd(III) distribution characteristics and sludge morphology. The results shown that > 150 mg & BULL;L-1 Nd(III) or > 3 g & BULL;L-1 Na2SO4 decreased specific Anammox activity (SAA), and intracellular Nd(III) was identified as the primary factor for individual Nd (III) inhibition. Furthermore, the combined inhibition of Nd(III) and Na2SO4 on Anammox was stronger than individual inhibition, but low doses of hydroxylamine (NH2OH) could restore the Anammox. Notably, the combined effect of low doses of Na2SO4 (1 g & BULL;L-1) and Nd III (10 mg & BULL;L-1) on the long-term performance of Anammox reactor was not significant. However, when the dose of Nd(III) was kept constant and the dose of Na2SO4 was increased to 7 g & BULL;L-1, the total nitrogen removal efficiency (TNRE) decreased by 56.88%. Following the elimination of inhibitors and the addition of 5 mg & BULL;L-1 NH2OH, the TNRE of the Anammox reactor was increased from 20.83% to 29.78%. The Hill, modified Michaelis-Menten, and modified Boltzmann models were able to properly describe the inhibition effects of Nd(III) and Na2SO4 and recovery process of Anammox. In addition, scanning electron microscopy (SEM) and energy-dispersive X-ray (EDS) analysis revealed that the content of extracellular polymeric substances (EPS) and neodymium increased with increasing Na2SO4 concentration.

污废水的高效节能脱氮技术一直以来都是研究和应用的焦点。短程反硝化-厌氧氨氧化耦合工艺因具有能耗低、产泥少、温室气体减排和脱氮效果好等优点，已成为废水脱氮领域研究和应用的热点。其中，短程反硝化被认为是厌氧氨氧化菌获取底物（NO2--N）的重要途径之一，对其进行研究具有重要的科学和工程意义。基于此，综述了短程反硝化的工艺原理，总结了硫自养短程反硝化和异养短程反硝化微生物的富集方法，并探讨了短程反硝化-厌氧氨氧化耦合工艺处理城市污水、高浓度氨氮废水和硝酸盐废水的工程应用。最后对短程反硝化及其耦合厌氧氨氧化工艺的研究和应用方向进行了展望，以期为短程反硝化-厌氧氨氧化耦合工艺处理实际污水提供参考。

We present a preliminary design for a microbial-enhanced permeable reactive barrier technology for the treatment of nitrate contaminated groundwater.

The effect of the heavy rare earth element erbium [Er（Ⅲ）] on the short-term and long-term nitrogen removal efficiency of the short-cut nitrification process was studied, and the related kinetic analysis was carried out. Short-term experiments showed that Er（Ⅲ） at the concentration of 0—10mg/L promoted the activity of AOB bacteria, 20—60mg/L Er（Ⅲ） slightly inhibited the activity of AOB bacteria,and 80—120mg/L Er（Ⅲ） showed severe inhibition on the activity of AOB bacteria. AOB bacteria would adsorb a large amount of Er（Ⅲ）, and the Er（Ⅲ） removal rate was greater than 90% when the influent Er（Ⅲ） concentration was lower than 60mg/L. However,the Er（Ⅲ） removal rate gradually decreased when the influent Er（Ⅲ） concentration was higher than 60mg/L. The results of ICP-MS and EDS analysis showed that Er（Ⅲ） could be adsorbed extracellularly and uptaked intracellularly by AOB bacteria, and the extracellular adsorption was the main one. The experimental results were fitted by Vadivelu model,Hellinga model, Michaelis-Menten model and Hill model, respectively. The results showed that the inhibition kinetics process of Er（Ⅲ） on AOB bacteria can be better described by subsection fitting（0—60mg/L and 60—120mg/L） using Hill model, the R2 obtained by fitting are 0.9909 and 0.9999,respectively, and the maximum matrix removal rate qmax（ΔSNPR） was 2.59mg/（g·h） and 7.15mg/（g·h）,respectively. Long-term experiments showed that the performance of the short-cut nitrification system will gradually disappear with the addition of 10mg/L Er（Ⅲ）, and the performance of the reaction system could not recover after the addition of Er（Ⅲ） was stopped.

During the mining of rare earth minerals, the application of neodymium-containing manures, and the treatment of spent neodymium iron boron magnet, the generation of ammonia wastewater containing neodymium is increasing. Thus, the effects of neodymium (Nd(III)) on anaerobic ammonium oxidation (Anammox) were investigated from the aspects of performance, kinetics, statistics, microbial community and sludge morphology, and the recovery strategy of EDTA-2Na wash was discussed. The nitrogen removal efficiency of the Anammox reactor decreased significantly and eventually collapsed at the Nd(III) dosing levels of 20 and 40 mg L-1, respectively. And the toxicity of Nd(III) to AnAOB was determined by the amount internalized into the cells. The EDTA-2Na wash successfully increased the total nitrogen removal rate (TNRR) of Nd(III)-inhibited Anammox to 41.60% of its initial value within 30 days, and the modified Boltzmann model accurately simulated this recovery process. The transient and extended effects of Nd(III), self-recovery, and EDTA-2Na wash on Anammox were effectively assessed using a one-sample t-test. 16S rRNA gene sequencing indicated that Nd(III) remarkably decreased the relative abundance of Planctomycetes and Candidatus Brocadia. The scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) revealed crystal-like neodymium particles on the surface of Anammox sludge. The above-mentioned results demonstrate that the concentration of Nd(III) should be below the toxicity threshold (20 mg L-1) when treating ammonia wastewater containing neodymium by Anammox, and also emphasize the importance of an appropriate recovery strategy.

The effects of two typical heavy metal ions[Cu(Ⅱ) and Ni(Ⅱ)] and humic acid on ANAMMOX nitrogen removal (SAA) were studied through batch experiments, and the kinetic model was analyzed. At the same time, the effects of humic acid-heavy metal on ANAMMOX nitrogen removal were discussed. The results showed that ANAMMOX was promoted when ρ[Cu(Ⅱ)] and ρ[Ni(Ⅱ)] were 3 mg·L-1, and SAA was increased by 8.64% and 7.78%, respectively; ANAMMOX was inhibited when the ρ[Cu(Ⅱ)] and ρ[Ni(Ⅱ)] were 20 mg·L-1 and 5 mg·L-1, respectively, and the inhibition effect was more significant with the increase in heavy metal ion concentration. The index fitting showed that the IC50 of Cu(Ⅱ) and Ni(Ⅱ) on ANAMMOX were 29.67 mg·L-1 and 28.75 mg·L-1, respectively. SAA was increased by 7.37% when the ρ(humic acid) was 1 mg·L-1, and the inhibition rate reached 36.80% when the humic acid concentration was 40 mg·L-1. The linear fitting showed that the IC50 of humic acid on ANAMMOX was 58.36 mg·L-1. The modified Michaelis-Menten model could better describe the inhibitory kinetic behavior of heavy metals and humic acid on ANAMMOX. The model fitting showed that the complete inhibition concentrations (I*) of Cu(Ⅱ), Ni(Ⅱ), and humic acid on ANAMMOX were 49.59, 74.46, and 84.27 mg·L-1, respectively. An appropriate amount of humic acid was beneficial to improve the inhibition of heavy metals on ANAMMOX bacteria activity, and excessive humic acid would cause inhibition on ANAMMOX bacteria again.