The　imperative　for　sustainable　urban　development　necessitates　the　proper　treatment　of　landfill　leachate　(LFL),　driven　by　its　high　level　of　contaminants.　Although　membrane　distillation　(MD)　effectively　captures　non-volatile　contaminants,　impediments　persist　in　practical　implementation　in　LFL,　notably　membrane　fouling　and　scaling　induced　by　organic　and　inorganic　substances.　These　challenges　are　particularly　salient　in　treating　LFL　with　varying　contaminant　concentrations　contingent　upon　its　age.　This　study　comprehensively　investigated　the　treatment　efficiency　of　direct　contact　membrane　distillation　(DCMD)　for　both　young　landfill　leachate　(YLFL)　and　aged　landfill　leachate　(ALFL),　along　with　an　examination　of　the　associated　membrane　fouling　and　scaling　conditions　over　a　15-d　period.　The　results　demonstrated　that　chemical　oxygen　demand　(COD)　and　metal　ions　in　both　YLFL　and　ALFL　were　effectively　retained　by　DCMD,　with　rejection　rates　exceeding　99　%.　Nevertheless,　escalating　membrane　fouling　led　to　diminished　distillate　fluxes,　with　reductions　of　26　%–32　%　for　YLFL　and　63　%–86　%　for　ALFL.　The　fouling　mechanisms　differed　between　YLFL　and　ALFL　treatments.　YLFL　primarily　induced　organic　fouling　through　biopolymers　and　humic　acid　(HA),　while　ALFL　introduced　inorganic　salt　ions　(e.g.,　Ca2+　and　Mg2+)　and　organics,　resulting　in　scaling　and　hybrid　organic-inorganic　fouling.　Acid　cleaning　proved　more　efficacious　than　alkali　cleaning　for　ALFL　treatment,　as　it　dissolved　ions　and　disrupting　the　crystal-organic　cross-linked　fouling　layer.　This　study　sheds　new　light　on　membrane　fouling　control　during　DCMD-based　treatment　of　LFL　at　varying　ages.　©　2024