To　improve　the　quality　of　the　tailings　water　from　a　wastewater　treatment　plant　(WWTP),　a　denitrification　biofilter　(DNBF)　with　a　composite　filler　composed　of　a　new　slow-release　organic-carbon　source　(SOC-F),　sponge　iron,　and　activated　carbon　was　tested.　Studies　were　conducted　in　the　combined　process　of　DNBF-O3-GAC　to　explore　the　efficiency　of　the　advanced　removal　of　nitrogen,　phosphorus,　and　microbial　metabolite　by　using　synthetic　effluent　made　from　running　water　and　chemicals.　Corresponding　comparative　studies　were　conducted　by　using　the　secondary　effluent　from　the　WWTP.　The　microbial　population　structure　in　the　biofilm　of　the　denitrification　biofilter　was　analyzed　by　adopting　MiSeq　high-throughput　sequencing　technologies.　The　results　indicated　that　the　combination　process　achieved　high　efficiency　removal　of　nitrogen,　phosphorus,　and　microbial　metabolite.　The　average　removal　rate　of　NO3--N　in　the　simulated　and　actual　water　period　reached　88.87%　and　79.99%,　respectively;　the　average　removal　rate　of　TP　reached　87.67%　and　65.51%,　respectively;　and　the　average　removal　rate　of　UV254reached　45.51%　and　49.23%,　respectively.　Each　processing　unit　had　different　functions.　The　changes　in　NO3--N,　TN,　TP,　and　TFe　mainly　occurred　in　the　denitrification　biofilter,　and　the　removal　of　UV254　and　the　change　in　the　three-dimensional　fluorescence　intensity　mainly　occurred　in　the　ozone-activated　carbon　reactor.　The　cluster　analysis　at　the　genus　level　indicated　that　the　denitrification　system　had　sulfur　autotrophic　denitrifying　bacteria　and　heterotrophic　denitrifying　bacteria.　Sulfur　autotrophic　denitrification　increased　obviously　in　the　actual　water　period　when　relatively　lack　of　carbon　sources,　and　the　proportion　of　Thiobacillus　increased　from　7.44%　to　29.62%.　The　complementary　effect　of　sulfur　autotrophic　denitrification　and　heterotrophic　denitrification　had　extended　the　use　of　the　new　slow-release　carbon　source.　©　2018,　Science　Press.　All　right　reserved.