This　study　aimed　at　investigating　the　removal　performance　of　the　gravity-driven　membrane　(GDM)　system　in　treating　the　heavy　metals-containing　secondary　effluent,　as　well　as　evaluating　the　respective　roles　of　Fe　and　Mn　addition　on　the　removal　of　heavy　metals.　GDM　process　with　the　formation　of　biocake　layer　exerted　effective　removals　of　Cr,　Pb　and　Cd,　with　an　average　removal　efficiency　of　98%,　95%　and　40%,　respectively,　however,　after　removing　the　biocake　layer,　the　removal　efficiencies　of　Cr,　Pb　and　Cd　reduced　to　59%,　85%　and　19%,　respectively,　indicating　that　the　biocake　layer　played　a　fundamental　role　in　removing　heavy　metals.　With　the　assistance　of　Fe,　the　removal　efficiency　of　heavy　metals　increased,　and　exhibited　a　positive　response　to　the　Fe　dosage,　due　to　the　adsorption　by　the　freshly　generated　iron　oxides.　On　the　contrary,　the　Mn　involvement　would　result　in　the　reduction　of　Cd　removal　due　to　the　competitive　adsorption　of　residual　dissolved　Mn2+　and　Cd.　Furthermore,　the　addition　of　a　high　dosage　of　Fe　increased　the　diversity　of　eukaryotic　communities　and　facilitated　the　elimination　of　heavy　metals,　however,　the　involvement　of　Mn　would　lead　to　a　reduction　in　microbial　diversity,　resulting　in　a　decrease　of　heavy　metal　removal　efficiency.　These　findings　are　expected　to　develop　new　tactics　to　enhance　heavy　metal　removal　and　promote　widespread　application　of　GDM　technology　in　the　fields　of　deep　treatment　of　heavy　metals-containing　wastewater　and　reclamation　of　secondary　effluent.　©　2023