Completely　autotrophic　nitrogen-removal　over　nitrite　(CANON)　has　been　considered　as　a　promising　nitrogen-removal　technology　in　treating　high　ammonia　and　high　temperature　wastewater.　In　this　study,　the　exact　effect　of　different　temperatures　on　process　performance　and　microbial　features　based　on　two　lab-scale　CANON　reactors　was　investigated.　Results　showed　extraordinary　nitrogen　removal　performance　with　mean　total　nitrogen　(TN)　removal　efficiency　of　80.01%　and　66.90%　under　high　TN　removal　loading　of　2.09　kg　m(-3)　d(-1)　and　1.02　kg　m(-3)　d(-1)　at　30　degrees　C　and　ambient　temperature　(16-23　degrees　C)　respectively.　Biodiversity　analysis　indicated　Nitrosomonas-related　aerobic　ammonia　oxidizing　bacteria　(AerAOB)　and　Candidatus　Brocadia-like　anaerobic　ammonia　oxidizing　bacteria　(AnAOB)　were　predominant　functional　microorganisms　that　coexisted　without　distinguishable　niche　on　the　volcanic　carriers　in　both　two　CANON　reactors.　Temperature　could　noticeably　impact　functional　bacterial　population:　the　population　of　AerAOB　and　AnAOB　decreased　to　one　to　two　orders　of　magnitude　whereas　Nitrospira　and　Nitrobacter　increased　at　ambient　temperature.　Based　on　the　bacterial　experimental　results,　some　feasible　strategies　have　been　discussed　to　improve　the　bioactivity　and　increase　the　function　bacterial　population,　aiming　at　enhancing　nitrogen-removal　capacity　at　ambient　temperature.　(C)　2015　Elsevier　B.V.　All　rights　reserved.