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[Display omitted] • An iron-rich encrustation layer (IEL) on anammox granular surface has been created. • IEL forms by the aggregation of gel networks and binding of iron species with EPS. • IEL leads to superior settling ability, heme content, and metabolic gene abundance. • IEL AnGS shows excellent nitrogen removal performance under high load stress. • IEL reduces shear force, enhancing the AnGS's resistance to high load stress. Anaerobic ammonia oxidation (anammox) is a cost-effective technology but its performance can be seriously inhibited by high load stress. This study has created an innovative iron-rich encrustation layer (IEL) on the surface of anammox granules (AnGS) through the addition of a certain amount of nano zero-valent iron. The IEL was formed through the aggregation of a gel network and the binding of iron species with extracellular polymeric substances (EPS), resulting in a significant increase in settling ability, EPS secretion, and heme content. Metagenomic analysis indicated a notable rise in the functional genes associated with nitrogen andiron metabolism in IEL AnGS. Under high load stress, the ammonia removal performance of AnGS without IEL severely declined. In contrast, IEL AnGS exhibited excellent ammonia removal efficiency of over 90%. The IEL served as a protective barrier for AnGS, effectively mitigating the strong shear forces, thereby enhancing their resistance to high load stress. [ABSTRACT FROM AUTHOR]

[Display omitted] • Addition of nZVI promoted efficiently the aerobic denitrification. • nZVI relieved the toxicity of harsh factors to aerobic denitrification. • nZVI enhanced the denitrification enzyme activities. • nZVI accelerated the electron transfer and the respiration of the bacteria. • nZVI improved the express of genes related to denitrification and Fe regulation. Aerobic denitrification and its mechanism by P. stutzeri was investigated in the presence of nanoscale zero-valent iron (nZVI). The removal of nitrate and ammonia was accelerated and the nitrite nitrogen accumulation was reduced by nZVI. The particle size and dosage of nZVI were key factors for enhancing aerobic denitrification. nZVI reduced the negative effects of low carbon/nitrogen, heavy metals, surfactants and salts to aerobic denitrification. nZVI and its dissolved irons were adsorbed into the bacteria cells, enhancing the transfer of electrons from nicotinamide adenine dinucleotide (NADH) to nitrate reductase. Moreover, the activities of NADH-ubiquinone reductase involved in the respiratory system, and the denitrifying enzymes were increased. The expression of denitrifying enzyme genes napA and nirS , as well as the iron metabolism gene fur , were promoted in the presence of nZVI. This work provides a strategy for enhancing the biological denitrification of wastewater using the bio-stimulation of nanomaterials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Methanogenesis was hindered divergently under long-term increasing NZVI stress. • Fatty acid evolution of cell membrane was pivotal in resisting chronic NZVI toxicity. • 1000 mg/L NZVI induced inhibition of methanogenesis after 80 days. • 5000 mg/L NZVI hindered the transcription of CoM and mcrA. • Abundance of amino-utilizing bacteria was decreased in NZVI groups. Nano zero-valent iron (NZVI) is commonly used in industrial wastewater treatment. However, its long-term impact mechanisms of metabolization in anaerobic systems are not well understood. This study investigated the effects of long-term and continuous addition of NZVI on methanogenic activity, microbial community, and transcription activity. The results demonstrated that low levels of NZVI (1000 mg/L) induced inhibition of methanogenesis after 80 days, while high levels of NZVI (5000 mg/L) immediately led to a sharp decrease of cumulative methane production and chemical oxygen demand removal, which arrived at a steady state (14.4 % of control and 17 %) after 30 days. NZVI adversely affected cell viability, adenosine triphosphate production, and fatty acid evolution of cell membranes played a crucial role in resisting chronic NZVI toxicity. Moreover, high NZVI levels hindered the transcription of key enzymes CoM and mcrA , while low NZVI levels maintained its high CoM and mcrA activity, but down-regulated the transcription of cdh and hdr. Besides, amino-utilizing bacteria was reduced under the high NZVI concentration, while low NZVI changed dominant genus with potential protein hydrolysis function from Candidatus Cloacamonas to Sedimentibacter. These results provide a guideline for proper NZVI utilization in wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • nZVI was adopted for the first time to remove ARGs at the maturation stage of composting. • The addition of nZVI reduced iARGs and eARGs in composting by 51–99%. • The removal of iARGs was due to the decreased abundance of host bacteria and intI 1. • The addition of nZVI improved the quality of the compost. Applying compost to soil may lead to the spread of antibiotic resistance genes (ARGs) in the environment. Therefore, removing ARGs from compost is critical. In this study, for the first time, nano zero-valent iron (nZVI) was added to compost during the maturation stage to remove ARGs. After adding 1 g/kg of nZVI, the abundance of total intracellular and total extracellular ARGs was decreased by 97.62% and 99.60%, and that of total intracellular and total extracellular mobile genetic elements (MGEs) was decreased by 92.39% and 99.31%, respectively. A Mantel test and network analysis indicated that the reduction in potential host bacteria and intI 1 after nZVI treatment promoted the removal of intracellular and extracellular ARGs. The addition of nZVI during composting reduced the horizontal transfer of ARGs and improve the total nitrogen and germination index of compost, allowing it to meet the requirements for organic fertilizers. [ABSTRACT FROM AUTHOR]

[Display omitted] • The caproate concentration can be improved by 100% when 5 g/L NZVI was added. • NZVI addition can increase ethanol utilization, reduce butyrate and butanol. • NZVI can provide extra electron donor and prevent pH to fall below 5.4. • Oscillibacter Marseille-P3260 was found to be the key chain elongator with NZVI. Chain elongation produce medium chain carboxylates, which are important precursors to many pharmaceuticals, antimicrobials and biofuels. Results in the presented investigations show that the supply of nano zero-valent iron (NZVI) can enhance caproate production. The highest caproate concentration achieved amounted to 27.2 mmol/L when 5 g/L NZVI were added, which was about 100% higher than the control. The study also showed increase of ethanol oxidation and decrease of butyrate and butanol with NZVI addition. Mechanism study showed NZVI can stimulate caproate production by preventing pH to fall below 5.4 through displacement reaction. Electron balance analysis displayed that NZVI provides extra electron by promoting ethanol oxidation and its dissolution. H 2 was the potential electron shuttle between NZVI and chain elongators; High throughput sequencing showed function of NZVI on reshaping of microbial communities, especially enriching Oscillibacter Marseille-P3260 , a kind of chain elongator and Corynebacterium which possesses fatty acid biosynthesis and iron utilization. [ABSTRACT FROM AUTHOR]

• nZVI@BC enhanced the reductive defluorination and inhibited the infiltration of TA. • TA bio-dehalogenation was accompanied by side-chain rupture, oxidation, and ring opening. • Defluorination accounted for 42.2% of biodegradation in the nZVI@BC system. • TA removal was positively correlated with bacterial diversity and activity. • Functional microbes with iron oxidation and reductive dehalogenation contributed to TA removal. The main aim of this study was to investigate the effect of a nano zero-valent iron-modified biochar-amended composite riverbed (nZVI@BC-R) on inhibited infiltration and enhanced biodegradation of fluoroglucocorticoids (FGCs) in a river receiving reclaimed water. The results demonstrated that the removal efficiency of triamcinolone acetonide (TA), a representative FGC, increased from 38.40% and 77.91% to 91.60% in the nZVI@BC-R compared with that of a natural soil riverbed (S-R) and biochar-amended soil riverbed (BC-R). The main removal mechanism was attributed to adsorption and biodegradation, of which the contribution rates were 32.2% and 59.4% in nZVI@BC-R, 18.9% and 19.5% in S-R, and 24.4% and 53.5% in BC-R, respectively. The removal process could be described by a two-compartment, first-order dynamic model with decay rate constants for adsorption and biodegradation of 4.02700, 22.44400, and 29.07300 d−1 and 0.00286, 0.01562, and 0.03484 d−1 in the S-R, BC-R and nZVI@BC-R, respectively. The mechanism of defluorination accounted for 42.2% of biodegradation in the nZVI@BC-R, which was accompanied by side-chain rupture, oxidation, and ring opening. Functional microbes with iron oxidizing ability and reductive dehalogenating genera, namely Pseudoxanthomonas , Pedobacter , and Bosea , contributed to the high removal rate of TA, particularly in the nZVI@BC-R. Overall, the nZVI@BC-R provided an effective method to inhibit glucocorticoids infiltration into groundwater. [ABSTRACT FROM AUTHOR]