The　partial-denitrification/anammox　(PDA)　process　is　a　promising　method　to　achieve　mainstream　anammox　in　wastewater　treatment　plants　(WWTPs).　To　investigate　the　feasibility　of　developing　a　granule-based　process　for　effective　nitrogen　removal　via　PDA,　an　upflow　anaerobic　sludge　bed　reactor　was　used　as　a　PDA　reactor　treating　low　C/N　sewage　for　over　200　days.　Granules　were　formed　with　an　average　particle　size　of　1.92　mm.　Metagenomic　analysis　revealed　that　the　two　most　abundant　genera　in　granules　were　Thauera　(17.46%)　and　Candidatus　Brocadia　(6.24%)　which　played　important　roles　in　achieving　partial-denitrification　and　anammox,　respectively.　Effective　nitrogen　removal　was　achieved　with　an　average　effluent　TN　concentration　of　8.74　mg/L　when　influent　TN　concentration　and　COD/TN　ratio　were　42.56　mg/L　and　1.52,　respectively.　Nitrogen　removal　via　anammox　accounted　for　90%　of　dinitrogen　production　in　the　PDA　reactor.　Finally,　a　granule-based　combined　process　of　PDA　with　nitrification　was　proposed　for　achieving　anammox　in　mainstream　WWTPs.