Anaerobic　ammonia　oxidation　(Anammox)　is　an　efficient　nitrogen　removal　technology　for　wastewater,　and　has　been　successfully　applied　in　practical　wastewater　treatment.　The　preservation　and　rapid　reactivation　of　anammox　bacteria　(AnAOB)　play　an　important　role　in　the　anammox　application.　Biochar　has　been　widely　used　in　the　water　treatment　industry　due　to　its　stable　structure,　economic　and　environmental　protection　characteristics.　Hence,　this　study　used　biochar　to　accelerate　anammox　granular　sludge　(AnGS)　performance　recovery　after　60　d　preservation　under　low-temperature　frozen　(−20　°C).　The　time　of　AnGS　recovery　in　the　group　with　biochar　addition　was　shortened　by　15　d　than　the　natural　recovery　group.　Meanwhile,　biochar　addition　improved　the　shock　loading　resistance　of　the　anammox　system.　EPS　secretion,　and　the　types　and　quantities　of　functional　groups　in　EPS　increased　under　biochar　stimulation,　especially　tighter　PN.　The　functional　groups　in　biochar　can　act　as　electron　shuttles　during　anammox　process,　accelerating　the　electron　transfer　rate.　Biochar　addition　enhanced　the　relative　abundance　of　AnAOB,　especially　Candidatus　Brocadia.　PICRUSt　analysis　indicated　that　biochar　promoted　key　gene　related　to　anammox　process　and　accelerated　the　recovery　of　frozen　sludge.　In　addition,　the　changes　in　effluent　nitrogen　removal　efficiency　were　successfully　predicted　by　artificial　neural　network　modeling　with　R　=　0.9895　and　MSE　=　0.0048.　This　result　may　provide　a　new　technological　idea　for　the　rapid　recovery　of　AnGS　under　long　time　frozen　conditions.　©　2024　Elsevier　Ltd