Microbial-driven nitrogen conversion directly affects the soil nutrient supply and plant growth, playing a vital role in the ecological restoration of tailings ponds. Feammox, as a novel microbial nitrogen cycle pathway, might be more active in a tailings pond environment. Four distinct soil types adjacent to an acidic mine drainage (AMD) lake in a sulfur-rich pyrite tailings area were examined: tailings dam soil, shrubland soil, agricultural soil, and pond sediment. Environmental characteristics and microbial functional responses of these soils were systematically analyzed. The high-throughput sequencing results revealed significant differences in soil microbial communities from different environments. Agricultural management and high moisture content may significantly improve soil properties and promote a positive succession of microbial communities. The qPCR analysis revealed inhibited nitrogen transformation capacity in tailings dam and shrub soils. In contrast, agricultural soil showed the highest Feammox activity. The 15N isotope tracing experiment results revealed that the Feammox rate in agricultural soil was the highest, reaching 705 μg/kg N·d. The statistical analysis results show that bioavailable Fe, TN, NH4+-N, TOC, etc., significantly affect the process of soil microbial nitrogen transformation. Among them, bioavailable Fe is the most critical factor affecting Feammox. This study provides a case for studying soil microorganisms in tailings areas, which is of great significance for studying Feammox and carrying out in situ remediation in the soil of tailings areas. Soils in tailings pond vary in environmental indicators and microbial communities Agricultural soil and pond sediment excel in Feammox, driven by Bio-Fe, TN, NH4+-N Agricultural soil has highest Feammox rate, boosted by management and moisture

The treatment of coking wastewater is challenged by the inhibition of microbial nitrification due to refractory organics, limiting the efficiency of single-stage biological aerated filters (BAF). While iron-based materials are known to enhance electron transfer, the role of a carrier's balanced electron-accepting and donating capacity (EAC/EDC) in enabling simultaneous organics degradation and nitrogen removal remains unclear. In this study, a high-quality iron-ceramsite (HQ) with balanced electron transfer capacity (EAC/EDC approximate to 1) was developed which replaced the electron-accepting-biased conventional clay ceramsite (CK). When it was applied in a single-stage BAF, the HQ ceramsite substantially enhanced COD removal by 28-36 % and total nitrogen removal by 24-32 %, compared to the control. Integrated metagenomic and electrochemical analyses revealed that the balanced electron capacity alleviated inhibition on nitrifying bacteria, increasing the abundance of amo gene clusters by 78-fold. Concurrently, it enriched denitrifying genera (e.g., Thauera) and stimulated the secretion of electroactive extracellular polymeric substances, which exhibited a 136 % higher direct electron transfer capacity. This study demonstrates that engineering the electron transfer balance of biofilm carriers can organize microbial metabolism to achieve synergistic removal of refractory pollutants and nitrogen in toxic industrial wastewater.

In this study, the potential mechanism of goethite and hematite on the anaerobic digestion system with sodium acetate as substrate was investigated combined with the DNA-SIP and metagenomics. Results show that goethite and hematite significantly improved the efficiency of methane production. Microbial community showed that Clostridium was greatly enriched in the Hem-0.02 and its relative abundance increased from 11.3 % to 31.2 %. Hydrogenation experiments showed that hematite could mediate the direct electron transfer from Clostridium to Methanothrix for methane production, forming a DIET (Direct interspecies electron transfer) pathway between Clostridium and Methanothrix for methane production. Metagenomics demonstrated that goethite and hematite promoted the expression of functional genes, and enzymes for electron transfer. The abundance of flagellar genes in group of hematite was higher than that in group of goethite. The relative abundances of pilE, pilV, pilT, and pilR are higher, reaching 3.1 x 10(-5), 2.9 x 10(-5), 2.2 x 10(-5) and 2.3 x 10(-5) respectively. Moreover, goethite improves the gene expression abundance of key enzymes in the hydrogen-type methanogenesis pathway and the acetic acid cleavage-type methanogenesis pathway.

Non-point source pollution has become a critical factor in water pollution in China with the improvement of point-source pollution control technologies and strengthening of supervision. This study introduced non-point-source-polluted rivers in industrial parks into a constructed wetland (CW) with advanced treatment units to effectively treat the polluted rivers. Although the pollutant load of the CW initially increased, after 100 days of adaptation, the removal rates of total nitrogen and organic carbon in the CW were greater than 96.99% and 84.74%, respectively. The effluent water complied with the China Environmental Quality Standards for Surface Water Standards (GB 3838-2002) Class IV. Introducing non-point-source-polluted river water increased the richness, diversity, and complex functional potential of the microbial community in CW, which improved system stability. The reduction in industrial pollutant stress and improvement of the nutritional environment are the main driving factors for the reorganization of microbial communities in CWs. The community composition shifted from being dominated by industrial pollutant-tolerant microorganisms such as Cyanobacteria and Actinobacteria to a more diverse array of microorganisms, including Bacteroidetes, Chloroflexi, and Firmicutes. Before the CW reconstruction, nitrification and acetyl-CoA conversion may be the main rate-limiting steps in carbon and nitrogen conversion in industrial wastewater CWs. These processes may have been limited because of oligotrophic conditions and industrial pollutant stress. The introduction of rivers polluted by non-point sources alleviates these constraints, thus increasing the treatment potential of the CW system. This paper provides a case study for the collaborative treatment of point and non-point source pollution in industrial parks. This study provides valuable guidance for effectively managing and reconstructing CWs in industrial environments.

Saline azo dye wastewater is challenging traditional biological treatment processes. In this study, an electroactive granular sludge (E-AGS) was prepared by using a Shewanella Biologically Augmented saline SBR reactor, and its ability to treat saline azo dye wastewater was verified. The simulated wastewater contained 3 % NaCl, 50 mg/L NH4+-N, and 500 mg/L COD. After adding Shewanella, the removal rate of COD and TN increased by about 20 %, and the operational stability of the system in response to seasonal temperature changes was improved. After running for 350 days, larger particle size and higher electron transfer activity granular sludge were formed relatively quickly, with a relative increase of 150 % in MLVSS. In the SBR reactor, the nitrogen transformation function genes represented by AmoC were significantly up-regulated, and the abundance of Shewanella was also significantly increased. Furthermore, the treatment capacity of E-AGS for two types of azo dye wastewater, amaranth and reactive black 5, was tested at 50 mg/L initial dye concentration. Compared to the control group, E-AGS exhibited about four times higher decolourization efficiency, better pollution treatment performance, and electron transfer activity. The EEM and 2D-COS results show that E-AGS exhibits higher structural stability and environmental responsiveness in wastewater treatment through EPS. This study reveals the feasibility of using Shewanella bacteria to enhance the activated sludge process and form electroactive granular sludge. It provides a new perspective for developing and transforming activated sludge processes.

Thiocyanate (SCN-), a non-volatile inorganic pollutant, is commonly found in various types of industrial wastewater, which is resistant to hydrolysis and has the potential to be toxic to organisms. Premagnetized iron-copper-carbon ternary micro-electrolytic filler (pre-Fe/Cu/C) was prepared to degrade SCN-. Pre-Fe/Cu/C exhibited the most significant enhancement effect on SCN- removal when magnetized for 5 min with an intensity of 100 mT, and the SCN- removal rate was the highest at an initial pH of 3.0 and an aeration rate of 1.6 L/min. The electrochemical corrosion and electron transfer in the pre-Fe/Cu/C system were confirmed through SEM, XPS, FTIR, XRD, and electrochemical tests. This resulted in the formation of more corrosion products and multiple cycles of Fe2+/Fe3+ and Cu0/Cu+/Cu2+. Additionally, density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) were utilized to illustrate the oxygen adsorption properties of the materials and the participation of reactive oxygen species (1O2, ·O2-, and ·OH) in SCN- removal. The degradation products of SCN- were identified as SO42-, HCO3-, NH4+, and N2. This study introduced the use of permanent magnets for the first time to enhance Fe/Cu/C ternary micro-electrolytic fillers, offering a cost-effective, versatile, and stable approach that effectively effectively enhanced the degradation of SCN-.

In this study, the effect of hydrothermal carbonation (HTC) on the pyrolysis behavior and the distribution of nutrients and metal species of waste-activated sludge (WAS) was investigated. Results showed that the pyrolysis activation energy range of WAS decreased from 11 to 57 kJ/mol to 10-36 kJ/mol when the hydrothermal carbonization was at 160 degrees C. As indicated by thermodynamic parameters, the hydrothermal carbonization process reduces the pyrolysis reaction activity of the hydrochar. The results of the chemical analysis indicate that hydrothermal carbonization significantly enhances the release of phosphorus and nitrogen, with maximum recovery at a temperature of 200 degrees C. The standard measurement and testing protocol revealed that hydrothermal carbonization increased the content of non-apatite inorganic P fraction in hydrochar and enhanced the availability of P. Heavy metal analysis shows that hydrothermal carbonization can strengthen the stability of heavy metals in WAS.

Acid mine drainage (AMD), a common environmental problem around the world, is characterized by low pH, high concentrations of heavy metals and sulfate. AMD treatment technology based on stimulating in-situ microorganisms has received widespread attention, but lack of organic matter is a limiting factor that restricts the remediation by heterotrophic microorganisms such as sulfate-reducing bacteria (SRB). In this study, a pilot scale reactor was set up next to an acid reservoir to evaluate the effect of livestock wastes on the in-situ bioremediation of AMD, focusing on performance assessment, heavy metal removal efficacy, and the evolution of the microbial community. Results indicated that the pH of AMD rises rapidly from 3.23 to 4.11, and metals (e.g., Fe, Cu, and Zn) rapidly got removed in Stage I. However, AMD experienced significant stratification in Stage II (biogas slurry supplemented). The pH of surface layer (0.5 m below the surface) gradually dropped to 3.67, and the bottom layer (2.3 m below the surface) remained around 4.1, and the metal removal efficiencies further improved. Microbial communities were dominated by Fe-OB and Fe-RB in surface layer, while SRB dominated in bottom layer. The addition of biogas slurry significantly increased the relative abundance of functional microbe in bioremediation. The growth of SRB in the bottom of the reactor made an important contribution to heavy metal removal. Heavy metals were mainly removed through the formation of insoluble hydroxide and sulfide precipitation and co-precipitation. This study innovatively integrates low-cost, locally sourced livestock waste as nutrient supplements into AMD bioremediation processes, and demonstrated the potential for integrating AMD treatment with livestock waste management, addressing both the nutrient needs for AMD processing and the challenge of livestock waste disposal. The findings contribute to the development of cost-effective and ecofriendly strategies for AMD management while advancing the understanding of microbial mechanisms of insitu bioremediation.

This study aims to thoroughly investigate the impact mode of salinity carried by industrial wastewater on the anaerobic-anoxic-oxic (A2O) sludge in wastewater treatment plants (WWTPs). Through comprehensive investigation of the A2O stage activated sludge (AS) from 19 industrial WWTPs in the downstream area of the Yangtze River, China, A total of 38 samples of anaerobic sludge and oxic sludge were collected and analyzed. We found that salinity stress significantly inhibits the growth of the AS community, particularly evident in the anaerobic sludge community. Furthermore, the high-saline environment induces changes in the structure and functional patterns of the AS community, leading to intensive interactions and resource exchanges among microorganisms. Halophilic microorganisms may play a crucial role in this process, significantly impacting the overall community structure, especially in the oxic sludge community. Additionally, salinity stress not only suppresses the nitrogen transformation potential of the AS but also leads to the accumulation of nitrite, thereby increasing the emission potential of both NO and N2O, exacerbating the greenhouse effect of the A2O process in industrial WWTPs. The findings of this study provide necessary theoretical support for maintaining the long-term stable operation of the A2O sludge system in industrial WWTPs, reducing carbon footprint, and improving nitrogen removal efficiency.

Acidic pit lakes (APLs) emerge as reservoirs of acid mine drainage in flooded open-pit mines, representing extreme ecosystems and environmental challenges worldwide. The bioremediation of these oligotrophic waters necessitates the addition of organic matter, but the biogeochemical response of APLs to exogenous organic matter remains inadequately comprehended. This study delves into the biogeochemical impacts and remediation effects of digestate-derived organic matter within an APL, employing a multi-omics approach encompassing geochemical analyses, amplicon and metagenome sequencing, and ultra-high resolution mass spectrometry. The results indicated that digestate addition first stimulated fungal proliferation, particularly Ascomycetes and Basidiomycetes, which generated organic acids through lignocellulosic hydrolysis and fermentation. These simple compounds further supported heterotrophic growth, including Acidiphilium, Acidithrix, and Clostridium, thereby facilitating nitrate, iron, and sulfate reduction linked with acidity consumption. Nutrients derived from digestate also promoted the macroscopic development of acidophilic algae. Notably, the increased sulfate reduction-related genes primarily originated from assimilatory metabolism, thus connecting sulfate decrease to organosulfur increase. Assimilatory and dissimilatory sulfate reduction collectively contributed to sulfate removal and metal fixation. These findings yield multi-omics insights into APL biogeochemical responses to organic matter addition, enhancing the understanding of carbon-centered biogeochemical cycling in extreme ecosystems and guiding organic amendment-based bioremediation in oligotrophic polluted environments.

Recently, the newly discovered anaerobic ammonium oxidation coupled with iron reduction (i.e., Feammox) has been proven to be a widespread nitrogen (N) loss pathway in ecosystems and has an essential contribution to gaseous N loss in paddy soil. However, the mechanism of iron-nitrogen coupling transformation and the role of iron-reducing bacteria (IRB) in Feammox were poorly understood. This study investigated the Feammox and iron reduction changes and microbial community evolution in a long-term anaerobic incubation by 15N isotope labeling combined with molecular biological techniques. The average rates of Feammox and iron reduction during the whole incubation were 0.25 ± 0.04 μg N g-1 d-1 and 40.58 ± 3.28 μg Fe g-1 d-1, respectively. High iron oxide content increased the Feammox rate, but decreased the proportion of Feammox-N2 in three Feammox pathways. RBG-13-54-9, Brevundimonas, and Pelomonas played a vital role in the evolution of microbial communities. The characteristics of asynchronous changes between Feammox and iron reduction were found through long-term incubation. IRB might not be the key species directly driving Feammox, and it is necessary to reevaluate the role of IRB in Feammox process.

For the hydrothermal liquefaction (HTL) process as the final method for waste activated sludge, the liquid byproduct of the process, i.e., the HTL aqueous solution, poses the greatest bottleneck due to its large volume and contaminant levels. In this study, the effects of hydrothermal liquefaction pretreatment (HTL) on the performance of anaerobic digestion and energy balance of the waste-activated sludge (WAS) aqueous phase were investigated. The results showed that HTL could greatly increase the hydrolysis of WAS and enhance the protein, polysaccharide and volatile fatty acid contents in the aqueous phase. The anaerobic digestion showed that the optimal gas and methane production efficiency was achieved at 160 degrees C. Positive net energy gain was obtained in each process (Delta E) and the optimal HTL heat recovery rate was obtained at 160 degrees C. HTL was found to improve the hydrolyzing bacterial community in anaerobic digestion but had little effect on the archaeal community.

The long-term salinity stress may affect the nitrogen transformation processes and microbial community assembly patterns in constructed wetlands treating tailwater, influencing their operational effectiveness. In this study, we employ 16S rRNA gene sequencing, combined with multivariate ecological and statistical methods, to investigate interactions between bacterial community diversity and nitrogen transformation genes in constructed tailwater wetlands under salinity stress. The results revealed that long-term salinity stress led to reduced microbial diversity and increased community heterogeneity. Additionally, salinity stress led to decreased functionality of microbial community, intensified competition, and elevated expression of functional genes. Furthermore, as predicted by PICRUSt2, long-term salinity stress resulted in overall inhibition of community nitrogen conversion functions, while short-cut nitrification-denitrification processes played a bigger part in nitrogen conversion. Moreover, the symbiotic nitrogen fixation process was promoted, while the competing dissimilatory nitrate reduction process was inhibited. Salinity can greatly explain the apparent differences in microbial communities and nitrogen transformation potential in saline constructed wetland systems compared to common wetlands. These findings provide novel insights into the mechanisms underlying nitrogen transformation processes in constructed tailwater wetlands under long-term salinity stress and important implications for redesign and renovations of constructed wetlands.

Pit lakes are artificial hydrological features created by mining operations that typically suffer from acid mine drainage (AMD), which not only endangers water quality but also exacerbates carbon loss. However, the impacts of AMD on the fate and role of dissolved organic matter (DOM) in pit lakes remain unclear. This study employed negative electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with biogeochemical analysis to examine DOM molecular variations and environmental controls across the AMD-induced acidic and metal-liferous gradients in five pit lakes. The results demonstrated distinct DOM pools in pit lakes characterized by the prev-alence of smaller aliphatic compounds compared to other waterbodies. AMD-induced geochemical gradients promoted DOM heterogeneity among pit lakes, with acidic pit lakes containing more lipid-like compounds. Acidity and metals enhanced DOM photodegradation, reducing the content, chemo-diversity and aromaticity. Organic sulfur was detected in high abundance, potentially from sulfate photo-esterification and mineral flotation agent. Further-more, microbial involvements in carbon cycling were revealed by DOM-microbe correlation network, but microbial contributions to the DOM pools decreased under acidic and metal stresses. These findings highlight abnormal carbon dynamics caused by AMD pollution and integrate DOM fate into pit lake biogeochemistry, thereby contributing to management and remediation.

Acidic pit lakes represent hydrological features resulting from the accumulation of acid mine drainage in mining operations. Long-term monitoring is essential for these extreme and contaminated environments, yet tracking investigations integrating microbial geochemical dynamics in acidic pit lakes have been lacking thus far. This study integrated historical data with field sampling to track decadal biogeochemical changes in an acidic pit lake. With limited artificial disturbance, significant and sustained biogeochemical changes were observed over the past decade. Surface water pH slowly increased from 2.8 to a maximum of 3.6, with a corresponding increase in bottom water pH to around 3.9, despite the accumulation of externally imported sulfate and metals. Elevated nutrient levels stimulated the macroscopic growth of Chlorophyta, resulting in a shift from reddish-brown to green water with floating algal bodies. Furthermore, microalgae-fixed organic carbon promoted the transition from the initial chemolithotrophy-based population dominated by Acidiphilium and Ferrovum to a heterotrophic community. The increase in heterotrophic iron- and sulfate-reducers may cause an elevation in ferrous levels and a decline in copper concentrations. However, most metals were not removed from the water column, potentially due to insufficient biosulfidogenesis or sulfide reoxidation. These findings offer novel insights into microbial succession in extreme ecosystem evolution and contribute to the management and remediation of acidic pit lakes.

随着对水生态保护和再生水回用的日益重视,污水处理厂外排尾水水质要求进一步提高.利用人工湿地深度处理尾水已被广泛推广,明晰人工湿地各单元中污染物去除过程和机制对出水水质提升和湿地稳定运营具有重要意义.研究结合三维荧光分析和高通量测序技术,对湿地各单元尾水中主要污染物的降解和微生物群落结构进行监测.结果表明,湿地系统对尾水中主要污染物具有良好的处理效果,CODCr、TN、NO-3-N、TP去除率分别约为 93.5％、87.1％、85.4％、100％.组合湿地系统中污染物的降解主要集中在曝气好氧塘单元,而预处理塘单元对污染物降解能力较弱.分析结果表明,水体DOM中主要为外源性组分,进入湿地后内源性组分逐渐升高,湿地系统对类腐殖质组分降解效果显著.湿地中水体和表面沉积物的微生物群落结构具有显著的差异性,其中假单胞菌(Pseudomonas)、丛毛单胞菌(Comamonas)、拟无枝酸菌(Amycolatopsis)和马赛菌(Massilia)等具有氮、磷转化功能的微生物在曝气好氧塘单元水体和生物膜中富集.RDA分析显示,水体中的营养组分主导了变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)、蓝藻门(Cyanobacteria)和放线菌门(Actinobacteria)分布的主要原因.研究结果为组合型人工湿地系统工艺调整和水质提升提供科学依据.

文章通过厌氧培养和乙炔抑制技术对水稻土进行模拟培养,证明水稻土中存在厌氧氨氧化耦合Fe(Ⅲ)还原,即铁氨氧化(Feammox)过程,并研究外加不同浓度水铁矿对Feammox过程产N2速率及途径的影响.结果表明:水稻土中Feammox过程产N2速率(以N计,下同)为(0.85±0.14)mg/(kg·d),在添加10、50 mmol/L水铁矿后,其产N2速率分别为(0.86±0.15)mg/(kg·d)、(1.09±0.20)mg/(kg·d);水铁矿的加入能够促进氨氮直接通过Feammox过程氧化为N2,随着水铁矿浓度从10 mmol/L增加到50 mmol/L,Feammox过程直接产N2途径占总产N2的比例从49.41％ 增加到62.82％;Fe(Ⅲ)的还原速率与N2的产率具有很强的相关性(R2=0.901,p<0.01).微生物群落分析结果表明,uncultured Acidimicro-biaceae、Anaeromyxobacter和Clostridium 3种菌的相对丰度随Feammox过程产N2速率的增加而显著增加,3种菌可能参与Feammox过程.该文研究表明,水铁矿的加入促进Feammox过程中N H4+向N2的直接转化,加速水稻土中氮元素的流失.

In recent years, Feammox has made it possible to remove NH4+-N under anaerobic conditions; however, its application in practical wastewater treatment processes has not been extensively reported. In this study, an up -flow anaerobic biological filter based on limonite (Lim-UAF) was developed to facilitate long-term and stable treatment of domestic sewage. Lim-UAF achieved the highest removal efficiency of chemical oxygen demand (COD) and NH4+-N at a hydraulic retention time (HRT) of 24 h (Stage II). Specifically, the COD and NH4+-N content decreased from 240.8 and 30.0 mg/L to about 7.5 and 0.35 mg/L, respectively. To analyze the potential nitrogen removal mechanism, the Lim-UAF was divided into three layers according to the height of the reactor. The results showed that COD and NH4+-N removal had remarkable characteristics in Lim-UAF. More than 55.0% of influent COD was removed in the lower layer (0-30 cm) of Lim-UAF, while 60.2% of NH4+-N was removed in the middle layer (30-60 cm). Microbial community analysis showed that the community structure in the middle and upper layers (60-90 cm) was relatively similar, but quite different from that of the lower layer. Hetero-trophic bacteria were dominant in the lower layer, whereas iron-reducing and iron-oxidizing bacteria were enriched in the upper and middle layers. The formation of secondary minerals (siderite and Fe(OH)3) indicated that the Fe(III)/Fe(II) redox cycle occurred in Lim-UAF, which was triggered by the Feammox and NDFO pro-cesses. In summary, limonite was used to develop a single-stage wastewater treatment process for simultaneously removing organic matter and NH4+-N, which has excellent application prospects in domestic sewage treatment.

Although conductive materials (CM) gained increasing attention over the last decades to facilitate methane production, its influence on the whole process of anaerobic digestion was not clear yet, especially for the acidogenesis. The purpose of this study was to investigate the role of goethite on methane production and its effects on the volatile fatty acids (VFAs) in acidogenesis under different pH conditions. Results showed that the methane production and chemical oxygen demand (COD) removal efficiency in continuous stirring tank reactors (CSTRs) were increased with the addition of goethite. The promotion effects of goethite were particularly significant under acidic conditions. Microbial community analysis indicated that Clostridium and Syntrophic bacteria were enriched in goethite-dosed reactors, while methanogens community was mainly affected by pH. Goethite inhibited the generation of acetate and increased the butyrate production, which may benefit to keep the pH of the reactors stable. The results revealed the underlying mechanism of goethite to promote performances of anaerobic digestion and confirmed goethite was a potential additive under different pH conditions.

The application of N fertilizer is one of the most critical soil acidification factors in China, and soil acidification significantly alters biogeochemical processes such as N loss. Anaerobic ammonium oxidation coupled with iron reduction (Feammox) is an important biological process for N loss in natural environments, with the end-products of N2, NO2− and NO3−. However, the response of Feammox pathways to soil pH fluctuation has not been thoroughly studied. In the current study, Feammox pathways and microbial communities were explored through a slurry culture experiment with an artificially adjusted pH combined with a 15N isotope tracing technique and molecular biotechnology. Results showed significant differences in the gaseous N loss through Feammox (0.42–0.97 mg N kg−1 d−1) under different pH conditions. The gaseous N loss pathways were significantly affected by the pH, and Feammox to N2 was the predominant pathway in low-pH incubations. The proportion of N loss caused by Feammox coupled with denitrification increased as the soil pH increased. The gaseous N loss through Feammox increased by 43.9% when the soil pH decreased from 6.5 to 5.0. Fe-reducing bacteria, such as Ochrobactrum, Sphingomonas, and Clostridium increased significantly in lower pH incubations. Overall, this study demonstrated the effects of soil pH on Feammox pathways and extended the understanding of the N biogeochemical cycle in acidic soil.