The　cultivation　of　nitritation　granules　in　sequencing　batch　reactor　(SBR)　by　seeding　conventional　floccular　activated　sludge　was　investigated　using　ethanol-based　synthetic　wastewater.　Reducing　settling　time　offers　selection　pressure　for　aerobic　granulation,　and　stepwise　increase　of　influent　N/C　ratio　can　help　to　selectively　enrich　ammonia　oxidizing　bacteria　(AOB)　in　aerobic　granules.　The　spherical　shaped　granules　were　observed　with　the　mean　diameter　of　1.25　mm,　average　settling　velocity　of　1.9　cm　s(-1)　and　the　sludge　volume　index　(SVI)　of　18.5-31.4　ml　g(-1).　After　25　days　of　operation,　the　nitrogen　loading　rate　reached　0.0455　kg　NH4+-N　(kg　MLSS.d)(-1),　which　was　4.55　times　higher　than　that　of　the　start-up　period.　The　mature　granules　showed　high　nitrification　ability.　Ammonia　removal　efficiency　was　above　95%　and　nitrite　accumulation　ratio　was　in　the　range　of　80-95%.　The　nitrifying　bacteria　were　quantified　by　fluorescence　in　situ　hybridization　analysis,　which　indicated　that　AOB　was　14.9　+/-　0.5%　of　the　total　bacteria　and　nitrite　oxidizing　bacteria　(NOB)　was　0.89　+/-　0.1%　of　the　total　bacteria.　Therefore,　AOB　was　the　dominant　nitrifying　bacteria.　It　was　concluded　that　the　associated　inhibition　of　free　ammonia　at　the　start　of　each　cycle　and　free　nitrous　acid　during　the　later　phase　of　aeration　may　be　the　key　factors　to　start　up　and　maintain　the　stable　nitritation.