Novel insights into Feammox for nitrogen removal: research advances, mechanisms, and applications

Abstract

Microbial anaerobic ammonium oxidation coupled with iron reduction (Feammox) represents a novel pathway for nitrogen removal. The pivotal role of Feammox in the biogeochemical nitrogen cycle has attracted increasing scientific interest. However, its specific metabolic mechanisms and potential practical applications remain insufficiently elucidated and lack comprehensive interpretation. To advance the understanding of Feammox, research progress in this field is systematically reviewed and synthesized. Additionally, a bibliometric analysis is conducted to identify research hotspots and outline future research directions. Moreover, putative Feammox microorganisms and their associated electron transfer pathways are summarized to elucidate key metabolic mechanisms. The review also examines the influence of abiotic and biotic factors on Feammox activity. Remarkably, potential future applications of Feammoxin in mainstream, sidestream, and tailwater treatment are proposed, with particular emphasis on innovative strategies that sustain iron redox cycling while enhancing the removal of emerging contaminants. Finally, key challenges requiring further investigation are highlighted. This review aims to identify knowledge gaps and ongoing controversies in Feammox research, clarify priority research directions, and provide insights for advancing both mechanistic and engineering applications.

Graphical abstract

Keywords

Feammox / Wastewater treatment / Nitrogen removal / Iron cycle / Electron transfer / Emerging contaminants

Highlight

	● The key research progress, hotspots, and prospects in Feammox are summarized.
	● Microbial diversity and metabolic mechanism in Feammox are thoroughly reviewed.
	● The critical abiotic and biotic factors influencing Feammox are discussed.
	● The application prospects of Feammox in future wastewater treatment are explored.
	● Feammox has the potential for coremoval of N, P, and emerging contaminants.

References

[1] Anderson C R , Cook G M . (2004). Isolation and characterization of arsenate-reducing bacteria from arsenic-contaminated sites in New Zealand. Current Microbiology, 48(5): 341–347

[2] Bao P , Li G X . (2017). Sulfur-driven iron reduction coupled to anaerobic ammonium oxidation. Environmental Science & Technology, 51(12): 6691–6698

[3] Bi Y C , Liu F X , Fu Z S , Qiao H X , Wang J L . (2024). Enhancing total nitrogen removal in constructed wetlands: a comparative study of iron ore and biochar amendments. Journal of Environmental Management, 367: 121873

[4] Bonneville S , Behrends T , Cappellen P V , Hyacinthe C , Röling W F M . (2006). Reduction of Fe(III) colloids by Shewanella putrefaciens: a kinetic model. Geochimica et Cosmochimica Acta, 70(23): 5842–5854

[5] Butler J E , Young N D , Lovley D R . (2010). Evolution of electron transfer out of the cell: comparative genomics of six Geobacter genomes. BMC Genomics, 11(1): 40

[6] Cao J , Li N , Jiang J , Xu Y B , Zhang B P , Luo X N , Hu Y B . (2022). Activated carbon as an insoluble electron shuttle to enhance the anaerobic ammonium oxidation coupled with Fe(III) reduction process. Environmental Research, 204: 111972

[7] Cen X T , Hu Z T , Huang X , Yuan Z G , Zheng M . (2025). Integrated urban wastewater management through on-site generation and application of ferrous carbonate. Water Research, 268: 122732

[8] Chen H , Yu J J , Jia X Y , Jin R C . (2014). Enhancement of anammox performance by Cu(II), Ni(II) and Fe(III) supplementation. Chemosphere, 117: 610–616

[9] Chen Z , Zhang S H , Li Y Z , Wang Y T . (2023). Characteristics of denitrification activity, functional genes, and denitrifying community composition in the composting process of kitchen and garden waste. Bioresource Technology, 381: 129137

[10] Cheng L , Liang H , Yang W B , Yang T F , Chen T , Gao D W . (2023). The biochar/Fe-modified biocarrier driven simultaneous NDFO and Feammox to remove nitrogen from eutrophic water. Water Research, 243: 120280

[11] Cheng X H , Hu L L , Liu T , Cheng X , Li J Y , Xu K N , Zheng M . (2025). High-level nitrogen removal achieved by Feammox-based autotrophic nitrogen conversion. Water Research X, 27: 100292

[12] Clément J C , Shrestha J , Ehrenfeld J G , Jaffé P R . (2005). Ammonium oxidation coupled to dissimilatory reduction of iron under anaerobic conditions in wetland soils. Soil Biology and Biochemistry, 37(12): 2323–2328

[13] Dang H Z , Ma J , Wu X B , Yan Y , Zeng T X , Liu H , Chen Y Z . (2023a). Quinone electron shuttle enhanced ammonium removal performance in anaerobic ammonium oxidation coupled with Fe(III) reduction. Biochemical Engineering Journal, 195: 108912

[14] Dang H Z , Tang C X , Zeng T X , Yan Y , Wu X B , Ma J , Chen Y Z . (2023b). Use of soluble iron salt as an electron acceptor to provide Fe(III) for Feammox process: ammonium removal performance and mechanism. Journal of Water Process Engineering, 56: 104436

[15] Daugherty E E , Gilbert B , Nico P S , Borch T . (2017). Complexation and redox buffering of iron(II) by dissolved organic matter. Environmental Science & Technology, 51(19): 11096–11104

[16] Deng J Y , Wu Z S , Li Y Y , Liu J Y . (2023). Energy-neutral municipal wastewater treatment based on partial denitrification-anammox driven by side-stream sulphide. Science of the Total Environment, 884: 163790

[17] Ding B JLi Z KQin Y B (2017). Nitrogen loss from anaerobic ammonium oxidation coupled to Iron(III) reduction in a riparian zone. Environmental Pollution, 231(Pt 1): 379–386

[18] Ding B J , Luo W Q , Qin Y B , Li Z K . (2020a). Effects of the addition of nitrogen and phosphorus on anaerobic ammonium oxidation coupled with iron reduction (Feammox) in the farmland soils. Science of the Total Environment, 737: 139849

[19] Ding B J , Qin Y B , Luo W Q , Li Z K . (2020b). Spatial and seasonal distributions of Feammox from ecosystem habitats in the Wanshan region of the Taihu watershed, China. Chemosphere, 239: 124742

[20] Ding L J , An X L , Li S , Zhang G L , Zhu Y G . (2014). Nitrogen loss through anaerobic ammonium oxidation coupled to iron reduction from paddy soils in a chronosequence. Environmental Science & Technology, 48(18): 10641–10647

[21] Dou Q H , Zhang L , Lan S , Hao S W , Guo W , Sun Q X , Wang Y P , Peng Y Z , Wang X Y , Yang J C . (2022). Metagenomics illuminated the mechanism of enhanced nitrogen removal and vivianite recovery induced by zero-valent iron in partial-denitrification/anammox process. Bioresource Technology, 356: 127317

[22] Fan Y Y , Sun S S , He S B . (2023). Iron plaque formation and its effect on key elements cycling in constructed wetlands: functions and outlooks. Water Research, 235: 119837

[23] Feng C Y , Zhang X W , Gao G C , Ren K R , Li Z C , Xu Z H , Wei D , Zhang J . (2025). A new insight on simultaneous water purification and greenhouse gas reduction by constructing sulfur-siderite driven autotrophic denitrification pathways in constructed wetlands. Water Research, 274: 123130

[24] Fu X Z , Li Y Y , Huang W W , Wang D X , Yang C P , Han H J . (2025). Unveiling environmental adaptability of magnetite-mediated Feammox system: multiple pathways identification, metabolic responses and engineering potential analysis. Chemical Engineering Journal, 511: 161921

[25] Ge J Y , Huang S , Han I , Jaffé P R . (2019). Degradation of tetra- and trichloroethylene under iron reducing conditions by Acidimicrobiaceae. A6. Environmental Pollution, 247: 248–255

[26] González M , Cerda Á , Rodríguez C , Serrano J , Leiva E . (2024). Coupling of the Feammox-Anammox pathways by using a sequential discontinuous bioreactor. Bioresource Technology, 395: 130334

[27] Gu Y Q , Guberman-Pfeffer M J , Srikanth V , Shen C , Giska F , Gupta K , Londer Y , Samatey F A , Batista V S , Malvankar N S . (2023). Structure of Geobacter cytochrome OmcZ identifies mechanism of nanowire assembly and conductivity. Nature Microbiology, 8(2): 284–298

[28] Guan Q S , Cao W Z , Wang M , Wu G J , Wang F F , Jiang C , Tao Y R , Gao Y . (2018). Nitrogen loss through anaerobic ammonium oxidation coupled with iron reduction in a mangrove wetland. European Journal of Soil Science, 69(4): 732–741

[29] Hao X J , Zeng W , Li J M , Zhan M J , Miao H H , Gong Q T . (2024). High-efficient nitrogen removal with low demand of Fe source and mechanism analysis driven by Fe(II)/Fe(III) cycle. Chemical Engineering Journal, 481: 148702

[30] He Y Y , Li Y M , Li X C , Liu Y R , Wang Y F , Guo H X , Hou J Q , Zhu T T , Liu Y W . (2023). Net-zero greenhouse gas emission from wastewater treatment: mechanisms, opportunities and perspectives. Renewable and Sustainable Energy Reviews, 184: 113547

[31] Hu X J , Xie J X , Xie H J , Huo J Y , Wu H M , Hu Z , Xue K , Song M Y , Liang S , Zhang J . (2023a). Towards a better and more complete understanding of microbial nitrogen transformation processes in the rhizosphere of subsurface flow constructed wetlands: effect of plant root activities. Chemical Engineering Journal, 463: 142455

[32] Hu Y D , Wang Y H , Han X , Shan Y W , Li F , Shi L . (2021). Biofilm biology and engineering of Geobacter and Shewanella spp. for energy applications. Frontiers in Bioengineering and Biotechnology, 9: 786416

[33] Hu Z T , Hu S H , Ye L , Duan H R , Wu Z P , Hong P Y , Yuan Z G , Zheng M . (2023b). Novel use of a ferric salt to enhance mainstream nitrogen removal from anaerobically pretreated wastewater. Environmental Science & Technology, 57(16): 6712–6722

[34] Huang J Z , Jones A , Waite T D , Chen Y L , Huang X P , Rosso K M , Kappler A , Mansor M , Tratnyek P G , Zhang H C . (2021). Fe(II) redox chemistry in the environment. Chemical Reviews, 121(13): 8161–8233

[35] Huang S , Chen C , Peng X C , Jaffé P R . (2016). Environmental factors affecting the presence of Acidimicrobiaceae and ammonium removal under iron-reducing conditions in soil environments. Soil Biology and Biochemistry, 98: 148–158

[36] Huang S , Jaffé P R . (2018). Isolation and characterization of an ammonium-oxidizing iron reducer: Acidimicrobiaceae sp. A6. PLoS One, 13(4): e0194007

[37] Huang S , Jaffé P R . (2019). Defluorination of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) by Acidimicrobium sp. strain A6. Environmental Science & Technology, 53(19): 11410–11419

[38] Huang S , Pilloni G , Key T A , Jaffé P R . (2024a). Defluorination of various perfluoro alkyl acids and selected PFOA and PFOS monomers by Acidimicrobium sp. Strain A6 enrichment cultures. Journal of Hazardous Materials, 480: 136426

[39] Huang S , Sima M , Long Y , Messenger C , Jaffé P R . (2022). Anaerobic degradation of perfluorooctanoic acid (PFOA) in biosolids by Acidimicrobium sp. strain A6. Journal of Hazardous Materials, 424: 127699

[40] Huang S , Smorada C , Schaefer C E , Jaffé P R . (2024b). Stimulating Acidimicrobium sp. Strain A6 in iron-rich, acidic sediments from AFFF-impacted sites for PFAS defluorination. Science of the Total Environment, 955: 176801

[41] Ji L M , Zhang X N , Zhu X R , Gao B , Zhao R , Wu P . (2024). Novel insights into Feammox coupled with the NDFO: a critical review. Science of the Total Environment, 951: 175721

[42] Ji M D , Wang J , Khanal S K , Wang S Q , Zhang J , Liang S , Xie H J , Wu H M , Hu Z . (2023). Water-energy-greenhouse gas nexus of a novel high-rate activated sludge-two-stage vertical up-flow constructed wetland system for low-carbon wastewater treatment. Water Research, 229: 119491

[43] Jones M E , Fennessey C M , Dichristina T J , Taillefert M . (2010). Shewanella oneidensis MR-1 mutants selected for their inability to produce soluble organic-Fe(III) complexes are unable to respire Fe(III) as anaerobic electron acceptor. Environmental Microbiology, 12(4): 938–950

[44] Kappler A , Bryce C , Mansor M , Lueder U , Byrne J M , Swanner E D . (2021). An evolving view on biogeochemical cycling of iron. Nature Reviews Microbiology, 19(6): 360–374

[45] Kügler S , Cooper R E , Wegner C E , Mohr J F , Wichard T , Küsel K . (2019). Iron-organic matter complexes accelerate microbial iron cycling in an iron-rich fen. Science of the Total Environment, 646: 972–988

[46] Lai A X , Fan S M , Xue J Y , Wang H W , Xie K , Li H B , Xu H , Li B , Wu Q L . (2025). Ammonium removal through anaerobic ammonium oxidation coupled to iron(III) reduction along the Yangtze river-estuary continuum. Journal of Environmental Sciences, 152: 178–187

[47] Le C P , Nguyen H T , Nguyen T D , Nguyen Q H M , Pham H T , Dinh H T . (2021). Ammonium and organic carbon co-removal under feammox-coupled-with-heterotrophy condition as an efficient approach for nitrogen treatment. Scientific Reports, 11(1): 784

[48] Li H , Su J Q , Yang X R , Zhou G W , Lassen S B , Zhu Y G . (2019). RNA stable isotope probing of potential Feammox population in paddy soil. Environmental Science & Technology, 53(9): 4841–4849

[49] Li J M , Zeng W , Liu H , Zhan M J , Miao H H . (2022). Achieving deep autotrophic nitrogen removal in aerated biofilter driven by sponge iron: performance and mechanism. Environmental Research, 213: 113653

[50] Li J M , Zeng W , Liu H , Zhan M J , Miao H H , Hao X J . (2023). Achieving deep autotrophic nitrogen removal from low strength ammonia nitrogen wastewater in aeration sponge iron biofilter: simultaneous nitrification, Feammox, NDFO and Anammox. Chemical Engineering Journal, 460: 141755

[51] Li J M , Zeng W , Zhan M J , Miao H H , Hao X J . (2024). Performances and mechanisms of anaerobic nitrogen removal through Fe(III)/Fe(II) cycle with sponge iron biofilm without external iron addition. Journal of Water Process Engineering, 66: 105913

[52] Li X , Huang Y , Liu H W , Wu C , Bi W , Yuan Y , Liu X . (2018). Simultaneous Fe(III) reduction and ammonia oxidation process in Anammox sludge. Journal of Environmental Sciences, 64: 42–50

[53] Li X F , Hou L J , Liu M , Zheng Y L , Yin G Y , Lin X B , Cheng L , Li Y , Hu X T . (2015). Evidence of nitrogen loss from anaerobic ammonium oxidation coupled with ferric iron reduction in an intertidal wetland. Environmental Science & Technology, 49(19): 11560–11568

[54] Li Z , Xu H , Zhang L , Zhou Y . (2025). Genome-resolved metagenomic and metatranscriptomics reveal Feammox meta-bolism of anaerobic ammonia oxidation bacteria in microaerobic granular sludge. Environmental Science & Technology, 59(14): 7145–7155

[55] Liamleam W , Annachhatre A P . (2007). Electron donors for biological sulfate reduction. Biotechnology Advances, 25(5): 452–463

[56] Liang E L , Xu L , Su J F , Yang Y Z , Liu Y . (2023). Nano iron tetroxide-modified rice husk biochar promoted Feammox performance of Klebsiella sp. FC61 and synergistically removed Ni²⁺ and ciprofloxacin. Bioresource Technology, 382: 129183

[57] Liang Z X , Shi J , Yang W , Dai L L , Dai X H . (2022). Coupling anammox and feammox via polymeric ferric sulfate: an efficient and aeration-saving way for nitrogen removal. Journal of Cleaner Production, 355: 131788

[58] Lim E T , Jeong G T , Bhang S H , Park S H , Park D H . (2009). Evaluation of pilot-scale modified A₂O processes for the removal of nitrogen compounds from sewage. Bioresource Technology, 100(24): 6149–6154

[59] Liu Y , Dong J C , Cheng X H , Cen X T , Dang Y , Xu K N , Zheng M . (2025). Dual role of organic matter in Feammox-driven nitrogen and phosphate removal. Water Research X, 27: 100312

[60] Liu Y K , Ying L X , Li H , Awasthi M K , Tian D , He J S , Zou J M , Lei Y J , Shen F . (2024). Allophane improves anaerobic digestion of chicken manure by alleviating ammonia inhibition and intensifying direct interspecies electron transfer. Bioresource Technology, 400: 130692

[61] Liu Y W , Ni B J . (2015). Appropriate Fe (II) addition significantly enhances anaerobic ammonium oxidation (Anammox) activity through improving the bacterial growth rate. Scientific Reports, 5(1): 8204

[62] Lovley D R . (1991). Dissimilatory Fe(III) and Mn(IV) reduction. Microbiological Reviews, 55(2): 259–287

[63] Luo M , Liu Y X , Huang J F , Xiao L L , Zhu W F , Duan X , Tong C . (2018). Rhizosphere processes induce changes in dissimilatory iron reduction in a tidal marsh soil: a rhizobox study. Plant and Soil, 433(1−2): 83–100

[64] Ma B , Wang S Y , Cao S B , Miao Y Y , Jia F X , Du R , Peng Y Z . (2016). Biological nitrogen removal from sewage via anammox: recent advances. Bioresource Technology, 200: 981–990

[65] Ma DWang JFang J TJiang Y FYue Z B (2024). Asynchronous characteristics of Feammox and iron reduction from paddy soils in southern China. Environmental Research, 252(Pt 1): 118843

[66] Ma D , Wang J , Li H , Che J , Yue Z B . (2022). Simultaneous removal of COD and NH₄⁺-N from domestic sewage by a single-stage up-flow anaerobic biological filter based on Feammox. Environmental Pollution, 314: 120213

[67] Melton E D , Swanner E D , Behrens S , Schmidt C , Kappler A . (2014). The interplay of microbially mediated and abiotic reactions in the biogeochemical Fe cycle. Nature Reviews Microbiology, 12(12): 797–808

[68] Miao Y Y , Peng Y Z , Zhang L , Li B K , Li X Y , Wu L , Wang S M . (2018). Partial nitrification-anammox (PNA) treating sewage with intermittent aeration mode: effect of influent C/N ratios. Chemical Engineering Journal, 334: 664–672

[69] Nguyen H T , Nguyen L D , Le C P , Hoang N D , Dinh H T . (2023). Nitrogen and carbon removal from anaerobic digester effluents with low carbon to nitrogen ratios under feammox conditions. Bioresource Technology, 371: 128585

[70] Oshiki M , Ishii S , Yoshida K , Fujii N , Ishiguro M , Satoh H , Okabe S . (2013). Nitrate-dependent ferrous iron oxidation by anaerobic ammonium oxidation (Anammox) bacteria. Applied and Environmental Microbiology, 79(13): 4087–4093

[71] Park W , Nam Y K , Lee M J , Kim T H . (2009). Anaerobic ammonia-oxidation coupled with Fe³⁺ reduction by an anaerobic culture from a piggery wastewater acclimated to NH₄⁺/Fe³⁺ medium. Biotechnology and Bioprocess Engineering, 14(5): 680–685

[72] Qi S Z , Xu L , Su J F , Li T M , Wei H , Li X . (2024). Fe³⁺/Fe²⁺ cycling drove novel ammonia oxidation and simultaneously removed lead, cadmium, and copper. Journal of Hazardous Materials, 480: 136124

[73] Qin H , Nie W B , Yi D , Yang D X , Chen M L , Liu T , Chen Y . (2024). Hematite-facilitated microbial ammoxidation for enhanced nitrogen removal in constructed wetlands. Frontiers of Environmental Science & Engineering, 18(7): 82

[74] Qin Y B , Ding B J , Li Z K , Chen S . (2019). Variation of Feammox following ammonium fertilizer migration in a wheat-rice rotation area, Taihu Lake, China. Environmental Pollution, 252: 119–127

[75] Reguera G , McCarthy K D , Mehta T , Nicoll J S , Tuominen M T , Lovley D R . (2005). Extracellular electron transfer via microbial nanowires. Nature, 435(7045): 1098–1101

[76] Reguera G , Nevin K P , Nicoll J S , Covalla S F , Woodard T L , Lovley D R . (2006). Biofilm and nanowire production leads to increased current in Geobacter sulfurreducens fuel cells. Applied and Environmental Microbiology, 72(11): 7345–7348

[77] Rios-Del Toro E E , Valenzuela E I , López-Lozano N E , Cortés-Martínez M G , Sánchez-Rodríguez M A , Calvario-Martínez O , Sánchez-Carrillo S , Cervantes F J . (2018). Anaerobic ammonium oxidation linked to sulfate and ferric iron reduction fuels nitrogen loss in marine sediments. Biodegradation, 29(5): 429–442

[78] Rodríguez C , Cisternas J , Serrano J , Leiva E . (2021). Nitrogen removal by an anaerobic iron-dependent ammonium oxidation (Feammox) enrichment: potential for wastewater treatment. Water, 13(23): 3462

[79] Rothwell K A , Thomasarrigo L K , Kaegi R , Kretzschmar R . (2025). Low molecular weight organic acids stabilise siderite against oxidation and influence the composition of iron (oxyhydr)oxide oxidation products. Environmental Science: Processes & Impacts, 27(1): 133–145

[80] Ruiz G , Jeison D , Chamy R . (2003). Nitrification with high nitrite accumulation for the treatment of wastewater with high ammonia concentration. Water Research, 37(6): 1371–1377

[81] Ruiz-Urigüen M , Shuai W T , Jaffé P R . (2018). Electrode colonization by the Feammox bacterium Acidimicrobiaceae sp. strain A6. Applied and Environmental Microbiology, 84(24): e02029–18

[82] Ruiz-Urigüen M , Steingart D , Jaffé P R . (2019). Oxidation of ammonium by Feammox Acidimicrobiaceae sp. A6 in anaerobic microbial electrolysis cells. Environmental Science: Water Research & Technology, 5(9): 1582–1592

[83] Sancho I , Lopez-Palau S , Arespacochaga N , Cortina J L . (2019). New concepts on carbon redirection in wastewater treatment plants: a review. Science of the Total Environment, 647: 1373–1384

[84] Sawayama S . (2006). Possibility of anoxic ferric ammonium oxidation. Journal of Bioscience and Bioengineering, 101(1): 70–72

[85] She Y CQi XXin X DHe Y QWang WLi Z K (2023). Non-rhizosphere reinforces the contributions of Feammox and anammox to nitrogen loss than rhizosphere in riparian zones. Environmental Research, 239(Pt 1): 117317

[86] Sheng A X , Li X X , Arai Y , Ding Y F , Rosso K M , Liu J . (2020). Citrate controls Fe(II)-catalyzed transformation of ferrihydrite by complexation of the labile Fe(III) intermediate. Environmental Science & Technology, 54(12): 7309–7319

[87] Shi L , Dong H L , Reguera G , Beyenal H , Lu A H , Liu J , Yu H Q , Fredrickson J K . (2016). Extracellular electron transfer mechanisms between microorganisms and minerals. Nature Reviews Microbiology, 14(10): 651–662

[88] Shi L , Richardson D J , Wang Z M , Kerisit S N , Rosso K M , Zachara J M , Fredrickson J K . (2009). The roles of outer membrane cytochromes of Shewanella and Geobacter in extracellular electron transfer. Environmental Microbiology Reports, 1(4): 220–227

[89] Shrestha J , Rich J J , Ehrenfeld J G , Jaffe P R . (2009). Oxidation of ammonium to nitrite under iron-reducing conditions in wetland soils: laboratory, field demonstrations, and push-pull rate determination. Soil Science, 174(3): 156–164

[90] Shuai W T , Jaffé P R . (2019). Anaerobic ammonium oxidation coupled to iron reduction in constructed wetland mesocosms. Science of the Total Environment, 648: 984–992

[91] Sima M W , Huang S , Jaffé P R . (2023). Modeling the kinetics of perfluorooctanoic and perfluorooctane sulfonic acid biodegradation by Acidimicrobium sp. Strain A6 during the feammox process. Journal of Hazardous Materials, 448: 130903

[92] Swathi D , Sabumon P C , Maliyekkal S M . (2020). Anoxic ammonia removal using granulated nanostructured Fe oxyhydroxides and the effect of pH, temperature and potential inhibitors on the process. Journal of Water Process Engineering, 33: 101066

[93] Tan X , Xie G J , Nie W B , Xing D F , Liu B F , Ding J , Ren N Q . (2022). Fe(III)-mediated anaerobic ammonium oxidation: a novel microbial nitrogen cycle pathway and potential applications. Critical Reviews in Environmental Science and Technology, 52(16): 2962–2994

[94] Wang G , Li B , Zhang Y F . (2023a). Ammonia-mediated iron cycle for oxidizing agent activation in advanced oxidation process. Water Research, 242: 120295

[95] Wang P , He D , Xiao Z X , Zhao J S , Jin Q H , Ma X M , Ma J X , Zheng M . (2025a). Dual sludge system driven NDFO-Feammox coupling: optimization of the iron cycling network for sustainable and efficient nitrogen removal. Water Research, 286: 124186

[96] Wang P , He D , Zhao J S , Xiao Z X , Tan J , Ma J X , Zheng M . (2025b). Transition from Anammox to Feammox metabolic modes: regulation strategies for nitrite in Anammox enrichment cultures. Bioresource Technology, 432: 132674

[97] Wang R G , Zhao X , Wang T C , Guo Z Z , Hu Z , Zhang J , Wu S B , Wu H M . (2022). Can we use mine waste as substrate in constructed wetlands to intensify nutrient removal? A critical assessment of key removal mechanisms and long-term environmental risks. Water Research, 210: 118009

[98] Wang T , Zhang J Y , Wang Z Y , Zhao Q , Wu Y , Li N , Jiang X L , Wang X . (2024). Bioelectrochemically enhanced autotrophic Feammox for ammonium removal via the Fe(II)/Fe(III) cycle. Environmental Science: Water Research & Technology, 10(6): 1355–1364

[99] Wang Z X , Wang X P , Sun Y , Yu Q L , Zhao Z Q , Zhang Y B . (2023b). Fe(OH)₃ induced the Anammox system to perform extracellular electron transfer for enhancement of NH₄⁺ removal. Chemical Engineering Journal, 460: 141768

[100] Weber K A , Achenbach L A , Coates J D . (2006). Microorganisms pumping iron: anaerobic microbial iron oxidation and reduction. Nature Reviews Microbiology, 4(10): 752–764

[101] Weralupitiya C , Wanigatunge R , Joseph S , Athapattu B C L , Lee T H , Kumar Biswas J , Ginige M P , Shiung Lam S , Senthil Kumar P , Vithanage M . (2021). Anammox bacteria in treating ammonium rich wastewater: recent perspective and appraisal. Bioresource Technology, 334: 125240

[102] Wu H M , Wang R G , Yan P H , Wu S B , Chen Z B , Zhao Y Q , Cheng C , Hu Z , Zhuang L L , Guo Z Z . et al. (2023). Constructed wetlands for pollution control. Nature Reviews Earth & Environment, 4(4): 218–234

[103] Wu S B , Vymazal J , Brix H . (2019). Critical review: biogeochemical networking of iron in constructed wetlands for wastewater treatment. Environmental Science & Technology, 53(14): 7930–7944

[104] Xia Q , Cheng J , Yang F , Yi X S , Huang W L , Lei Z F , Wang D X , Huang W W . (2025a). Activated carbon and anthraquinone-2,6-disulfonate as electron shuttles for enhancing carbon and nitrogen removal from simultaneous methanogenesis, Feammox and denitrification system. Bioresource Technology, 418: 131975

[105] Xia Q , Liu F , Sun S R , Huang W L , Zhao Z W , Yang F , Lei Z F , Huang W W , Yi X S . (2023). Coupling iron sludge addition and intermittent aeration for achieving simultaneous methanogenesis, Feammox, and denitrification in a single reactor treating fish sludge. Environmental Science & Technology, 57(40): 15065–15075

[106] Xia Q , Qiu Q Z , Cheng J , Huang W L , Yi X S , Yang F , Huang W W . (2025b). Microbially mediated iron redox processes for carbon and nitrogen removal from wastewater: recent advances. Bioresource Technology, 419: 132041

[107] Xiong Y J , Du Y , Deng Y M , Ma T , Wang Y X . (2022). Feammox in alluvial-lacustrine aquifer system: nitrogen/iron isotopic and biogeochemical evidences. Water Research, 222: 118867

[108] Xu L J , Li L , Liu J X , Wang X Z , Zhao Y P , Zhao J J , Gu L , He Q , Wang X Z , Zhang J H . (2024). Ferrihydrite optimizing Feammox inoculum to enhance ammonia removal from concentrate wastewater through continuous upflow anaerobic sludge blanket (UASB). Journal of Environmental Chemical Engineering, 12(6): 114469

[109] Yang L L , Li W X , Liu J , Zhu H J , Mu H , Hu K Y , Li J , Dong S Q . (2024). Nitrate-dependent ferrous oxidation: feasibility, mechanism, and application prospects for wastewater treatment. Journal of Water Process Engineering, 60: 105226

[110] Yang W H , Weber K A , Silver W L . (2012). Nitrogen loss from soil through anaerobic ammonium oxidation coupled to iron reduction. Nature Geoscience, 5(8): 538–541

[111] Yang X R , Li H , Su J Q , Zhou G W . (2021a). Anammox bacteria are potentially involved in anaerobic ammonium oxidation coupled to iron(III) reduction in the wastewater treatment system. Frontiers in Microbiology, 12: 717249

[112] Yang Y F , Xiao C C , Lu J H , Zhang Y B . (2020). Fe(III)/Fe(II) forwarding a new anammox-like process to remove high-concentration ammonium using nitrate as terminal electron acceptor. Water Research, 172: 115528

[113] Yang Y F , Zhao Z Q , Zhang Y B . (2021b). Anaerobic ammonium removal pathway driven by the Fe(II)/Fe(III) cycle through intermittent aeration. Environmental Science & Technology, 55(11): 7615–7623

[114] Yao J Z , Qin S P , Liu T , Clough T J , Wrage-Mönnig N , Luo J F , Hu C S , Ge T D , Zhou S G . (2022). Rice root Fe plaque enhances oxidation of microbially available organic carbon via Fe(III) reduction-coupled microbial respiration. Soil Biology and Biochemistry, 167: 108568

[115] Yao Z B , Wang C H , Song N , Wang C L , Jiang H L . (2020). Oxidation of ammonium in aerobic wastewater by anoxic ferric iron-dependent ammonium oxidation (Feammox) in a biofilm reactor. Desalination and Water Treatment, 173: 197–206

[116] Yi B , Wang H H , Zhang Q C , Jin H , Abbas T , Li Y , Liu Y M , Di H J . (2019). Alteration of gaseous nitrogen losses via anaerobic ammonium oxidation coupled with ferric reduction from paddy soils in southern China. Science of the Total Environment, 652: 1139–1147

[117] Yong S N , Lim S , Ho C L , Chieng S , Kuan S H . (2022). Mechanisms of microbial-based iron reduction of clay minerals: current understanding and latest developments. Applied Clay Science, 228: 106653

[118] Yu C Q , Huang X , Chen H , Godfray H C J , Wright J S , Hall J W , Gong P , Ni S Q , Qiao S C , Huang G R . et al. (2019). Managing nitrogen to restore water quality in China. Nature, 567(7749): 516–520

[119] Zhang Y , Li P Y , Jiang Z , Ji C Y , Han X , Ren H T , Wang J . (2023a). Enhancement of N removal by electrification coupled by Feammox and Fe(II)/Fe(III) cycle in wastewater treatment. International Biodeterioration & Biodegradation, 177: 105535

[120] Zhang Y S , Ji S J , Xie P R , Liang Y T , Chen H , Chen L P , Wei C H , Yang Z P , Qiu G L . (2023b). Simultaneous partial nitrification, Anammox and nitrate-dependent Fe(II) oxidation (NDFO) for total nitrogen removal under limited dissolved oxygen and completely autotrophic conditions. Science of the Total Environment, 880: 163300

[121] Zheng X Y , Zhou C , Wu F , Xu H , Zhao Z L , Han Z S , Zhang H J , Yang S S . (2023). Enhanced removal of organic, nutrients, and PFCs in the iron-carbon micro-electrolysis constructed wetlands: mechanism and iron cycle. Chemical Engineering Journal, 457: 141174

[122] Zheng Y K , Wang J R , Niu X J , Su X T , He X Y , Hu Y X , Zhao D M , Chen D Y , Lin Y , Li K . (2025). Ferrihydrite enhance performance in anaerobic digestion of pig manure: methane production, Feammox and metabolic pathway. Journal of Water Process Engineering, 72: 107621

[123] Zhou G W , Yang X R , Li H , Marshall C W , Zheng B X , Yan Y , Su J Q , Zhu Y G . (2016). Electron shuttles enhance anaerobic ammonium oxidation coupled to iron(III) reduction. Environmental Science & Technology, 50(17): 9298–9307

[124] Zhu J X , Li T , Liao C M , Li N , Wang X . (2021a). A promising destiny for Feammox: from biogeochemical ammonium oxidation to wastewater treatment. Science of the Total Environment, 790: 148038

[125] Zhu T T , Lai W X , Zhang Y B , Liu Y W . (2022). Feammox process driven anaerobic ammonium removal of wastewater treatment under supplementing Fe(III) compounds. Science of the Total Environment, 804: 149965

[126] Zhu T T , Zhang Y B , Liu Y W , Zhao Z S . (2021b). Electrostimulation enhanced ammonium removal during Fe(III) reduction coupled with anaerobic ammonium oxidation (Feammox) process. Science of the Total Environment, 751: 141703

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