This　study　evaluated　a　long-term　impact　of　biological　activated　carbon　(BAC)　filter　that　was　employed　in　a　fullscale　drinking　water　treatment　plant　to　enhance　the　removal　of　contaminants　by　the　ultrafiltration　(UF)　process.　The　results　showed　that　BAC　enhanced　UF　performance　by　increasing　the　flux　by　18.5%　and　extending　the　filtration　run　by　45%.　The　presence　of　BAC　improved　the　removal　of　primary　contaminants,　including　dissolved　organic　carbon　(4-40%),　UV254　(10-57.7%),　geosmin　and　2-methylisoborneol　(80%).　BAC　was　also　effective　in　decreasing　the　concentration　of　biopolymers,　humic　substances,　(semi-)volatile　organics,　chlorite　and　halonitromethanes,　thereby　lowering　contaminant　load　on　the　UF　unit.　The　changes　in　primary　water　quality　parameters　in　the　combined　process　showed　that　the　humic　substances　in　dissolved　organic　nitrogen,　low　molecular　weight　substances　in　UV254,　and　fluorescence　protein-like　substances　could　be　useful　indicators　for　DBPs　as　these　organic　fractions　had　strong　correlation　with　DBPs.　Obvious　spatio-temporal　characteristics　of　GAC　grain　and　microbial　communities　in　BAC　filter　were　observed　with　operation　time　and　filter　depth.　The　bacterial　community　in　BAC　filter　was　highly　diverse　and　was　less　influenced　by　influent　quality　with　an　increase　in　filter　depth,　while　the　communities　in　UF　cake　layer　correlated　with　organic　removal　in　the　UF　system.