Low　water　temperatures　and　ammonium　concentrations　pose　challenges　for　anammox　applications　in　the　treatment　of　low　C/N　municipal　wastewater.　In　this　study,　a　10　L-water　bath　sequencing　batch　reactor　combing　biofilm　and　suspended　sludge　was　designed　for　low　C/N　municipal　wastewater　treatment.　The　nitrogen　removal　performance　via　partial　nitrification　anammox-(endogenous)　denitrification　anammox　process　was　investigated　with　anaerobic-aerobic-anoxic　mode　at　low　temperatures　and　dissolved　oxygen　(DO).　The　results　showed　that　with　the　decrease　of　temperature　from　30　to　15℃,　the　influent　and　effluent　nitrogen　concentrations　and　nitrogen　removal　efficiencies　were　73.7　±　6.5　mg/L,　7.8　±　2.8　mg/L,　and　89.4　%,　respectively,　with　aerobic　hydraulic　retention　time　of　only　6　h　and　DO　concentration　of　0.2–0.5　mg/L.　Among　that,　the　stable　anammox　process　compensated　for　the　inhibitory　effects　of　the　low　temperatures　on　the　nitrification　and　denitrification　processes.　Notably,　from　30　to　15℃,　the　anammox　activity　and　relative　abundance　of　the　dominant　Brocadia　genus　were　increased　from　39.7　to　45.5　mgN/gVSS/d　and　7.3　to　12.0　%,　respectively;　the　single　gene　expression　level　of　the　biofilm　increased　9.0　times.　The　anammox　bacteria　showed　a　good　adaptation　to　temperatures　reduction.　However,　nitrogen　removal　by　anammox　was　not　improved　by　increasing　DO　(≥　4　mg/L)　at　8–4℃.　Overall,　the　results　of　this　study　demonstrate　the　feasibility　of　the　mainstream　anammox　process　at　low　temperatures.　©　2024