A　three-dimensional　biofilm-electrode　reactor　(3D-BER)　was　applied　for　nitrate　removal　from　simulated　municipal　wastewater　treatment　plant　(WWTP)　effluent.　It　was　found　that　when　the　influent　C/N　ratio　ranged　from　1.0　to　2.0,　both　heterotrophic　and　autotrophic　denitrifying　microorganisms　played　important　roles　in　nitrate　removal.　The　extension　of　hydraulic　retention　time　(HRT)　could　enhance　nitrate　removal,　but　too　long　HRT　was　not　necessary.　A　phylogenetic　tree　of　gene　sequences　in　biofilm　was　established,　and　the　biofilm　was　abundant　with　Thauera-like　and　Enterobacter-like　bacteria.　The　results　illustrated　that　3D-BER　is　a　feasible　and　effective　technology　for　the　denitrification　of　WWTP　effluent　with　poor　organic　carbon　source.　A　nitrate　removal　of　98.3%　was　obtained　with　C/N　ratio　of　3.0　and　HRT　of　7　h.　About　85.0-90.0%　of　nitrate　removal　was　found　at　a　C/N　ratio　of　1.5　and　HRT　of　10　h　due　to　cooperative　heterotrophic　and　autotrophic　denitrification.　(C)　2013　Elsevier　Ltd.　All　rights　reserved.