The　transformations　of　carbon,　nitrogen,　and　iron　are　closely　interrelated　within　the　elemental　biogeochemical　cycles,　influenced　by　numerous　factors.　The　key　roles　of　Shewanella　in　the　three　cycles,　which　drives　Biological　Fenton　(Bio-Fenton)　and　improves　biological　nitrogen　removal,　have　not　been　clarified.　In　this　study,　by　coupling　Anammox　with　Bio-Fenton　in　the　cathodic　chamber　of　a　microbial　electrochemical　system　(MES),　we　explored　the　ability　of　Shewanella　to　force　C,　N,　and　Fe　transformation,　and　excavated　the　interactions　among　the　complex　reactions.　In　the　coupling　systems,　nitrogen　removal　efficiency　was　enhanced　by　22.69%,　and　Shewanella-mediated　Fe　(III)　reduction　improved　hydroxyl　radical　([rad]OH)　production　to　decompose　1,4-dioxane.　Fe　(II)　was　generated　with　electrons　from　the　cathode　and　then　chemically　oxidized,　and　one-electron　transfer　pathway　was　prioritized　in　[rad]OH　production.　Functional　gene　abundance　reflected　that　the　antioxidant　systems　of　microorganisms　were　highly　developed　to　resist　the　oxidative　stress.　The　robustness　of　the　coupling　systems　was　demonstrated　during　long-term　operation.　This　study　provides　valuable　insights　into　the　importance　of　Shewanella　in　redox　zones　and　presents　novel　technological　advancements　for　wastewater　treatment.　©　2024　Elsevier　B.V.