In　low-temperature　environments,　low　nutrients　such　as　inorganic　salts　limiting　microbial　proliferation　further　extended　the　start-up　period　of　biofilters　for　drinking　water　treatment.　This　study　explored　the　ammonia　and　manganese　(Mn)　removal　performance　and　the　relevant　mechanisms　under　single　and　combined　PO43-　at　30　mu　g/L　and　Cu2+　at　10　mu　g/L.　The　start-up　periods　of　R0　(control),　R1　(Cu2+　single),　R2　(PO43-　single)　and　R3　(combined　Cu2+　and　PO43-　)　were　98,　82,　32　and　24　days,　respectively.　PO43-　increased　the　concentration　of　extracellular　polymeric　substances　(EPS)　by　stimulating　cellular　metabolism,　which　promoted　the　formation　of　biofilm.　Additionally,　the　combined　Cu2+　and　PO43-　significantly　promoted　the　ammonia　monooxygenase　(AMO)　and　nitrite　oxidoreductase　(NXR)　activities,　which　further　facilitated　the　removal　of　ammonia.　The　combined　Cu2+　and　PO43-　accelerated　the　conversion　of　NH4+-N　to　NO2-　-N　and　NO2-　-N　to　NO3-　-N　processes　thereby　reducing　the　inhibition　of　Mn　removal　by　NH4+-N　and　NO2-　-N,　and　the　kinetics　of　biological　manganese　oxidation　showed　that　the　combined　Cu2+　and　PO43-　increased　the　rate　of　Mn　removal,　which　both　promoted　the　Mn　removal　in　the　biofilters.　Furthermore,　the　combined　Cu2+　and　PO43-　supported　the　proliferation　of　functional　microorganisms.　In　summary,　the　synergistic　effect　of　Cu2+　and　PO43-　enhanced　the　Mn　and　ammonia　removal　performance　and　achieved　rapid　start-up　of　the　biofilter　at　low　temperatures.