The　membrane　electrochemical　reactor　(MER),　integrating　oxidation,　softening,　and　acidification　within　a　single　system,　has　demonstrated　significant　potential　in　mitigating　membrane　fouling　during　leachate　treatment.　However,　the　specific　contributions　of　oxidation,　softening,　and　acidification　in　the　MER,　along　with　their　synergistic　effects　on　membrane　fouling　control,　remain　inadequately　understood.　In　this　study,　leachate　was　regulated　with　different　MER-related　strategies　before　membrane　distillation　treatment,　and　Differential　log-transformed　absorbance　spectra,　electrochemical　impedance　spectroscopy,　Derjaguin-Landau-Verwey-Overbeek　theory　were　employed　to　investigate　the　membrane　fouling　mechanism.　The　results　indicates　that　oxidation　effectively　removed　the　organic　matter,　thereby　mitigating　the　hydrophobic　interactions　between　the　membrane　and　foulant.　However,　it　also　promoted　the　deprotonation　of　carboxyl　groups　in　organic　matter,　such　as　polysaccharides　and　proteins,　enhancing　the　complexation　of　multivalent　cations.　Acidification　and　softening　reduced　organic–inorganic　complexation　fouling　by　inhibiting　carboxylate　deprotonation　and　reducing　Ca2+　and　Mg2+　concentrations,　respectively.　These　processes　counteracted　the　adverse　effects　of　oxidation　while　further　mitigating　organic　fouling　and　inorganic　scaling.　Additionally,　the　synergistic　effects　of　oxidation,　softening,　and　acidification　effectively　prevented　foulants　from　entering　membrane　pores　and　enhanced　wetting　resistance.　Overall,　this　study　demonstrated　the　potential　of　combining　oxidation,　softening,　and　acidification　while　elucidating　their　mechanisms　in　mitigating　membrane　fouling.　©　2025　Elsevier　B.V.