In order to explore the optimal conditions of nitrifying sludge granulation

test was carried out in a sequencing batch reactor (SBR) at operation conditions: temperature 28℃

aeration 0.2 m3·h-1

dissolved oxygen(DO)>2.0 mg·L-1

sludge age (SRT) 15d

leading to settling time shorten to 2min. The granulation of nitrifying floccular activated sludge was achieved successfully after 80 stable cycles (19d) by parameter control of ammonia oxidation process

by optimization of aerobic time and against over-aeration

and average diameter of sludge granular obtained was between 1.5—2.0 mm. The efficiency of COD and ammonia removal was 80% and 95%

respectively. The nitrite accumulation rate (NO-2-N/NO-x-N) was over 95%.The quantitative results from fluorescence in situ hybridization (FISH) analysis for molecular biology show that the dominant micro-organism was still AOB

about 17.8% of total bacteria，while NOB only 0.6%. The main factors for stable performance of nitrification were FA inhibition and real-time control.