In　order　to　evaluate　the　feasibility　of　the　free　nitrite　(FNA)　lateral　flow　treatment　of　flocculent　sludge　by　initializing　the　autotrophic　nitrogen　removal　(CANON)　processing,　this　study　was　conducted　to　investigate　effects　of　the　FNA　treatment　on　ammonia　oxidizing　bacteria　(AOB)　and　nitrite　oxidizing　bacteria　(NOB)　activities　and　the　operation　efficiency　of　hydraulically　screened　flocculent　sludge　treatment　in　the　granular-flocculation　sludge　SBR　reactor.　The　results　show　that　after　0.6mg/L　FNA　treatment　of　R1　for　30days,　the　removal　rate　of　NH4+-N　returned　to　the　level　before　the　treatment　and　the　short-range　nitrification　was　stable.　The　average　total　effluent　nitrogen　of　the　system　was　13.84mg/L;　and　the　∆NO3--N/∆NH4+-N　ratio　was　close　to　the　theoretical　one　of　the　CANON　reaction　equation　of　0.11,　indicating　successful　start　of　the　CANON　process.　However,　R2,　treated　with　0mg/L　FNA　failed　to　start　due　to　the　massive　proliferation　of　NOB.　The　batch　test　results　confirm　that　after　the　treatment　of　0.6mg/L　FNA,　the　NOB　activity　was　only　16.39%　of　the　control　group　(FNA=0mg/L),　and　the　recovery　of　NOB　activity　was　not　found　in　subsequent　operation　thus　NOB　was　effectively　inhibited.　Additionally,　the　activity　of　AOB　was　affected　because　the　removal　rate　of　NH4+-N　in　the　reactor　was　only　69.69%　of　that　of　before　treatment　and　the　activity　of　AOB　recovered　by　only　68.06%　after　6h.　©　2022　Chinese　Society　for　Environmental　Sciences.　All　rights　reserved.