[Research on cultivation of aerobic granular sludge and its characteristics in sequencing fed batch reactor]

Aerobic granular sludge was cultivated in the sequencing fed batch reactor, and granules' characteristic and reactor's performance to the pollutants were studied. The SFBR was operated under the conditions as: inoculated with activated sludge former self-cultivated, fed with simulated wastewater, and continuous feed/intermittent discharge and alternately anaerobic/aerobic operation mode. The results showed that through gradually decreasing the settling time, aerobic granular sludge was successfully cultivated in 28 days, which was yellow, irregular shape, and small particle size (the average particle size was 0.56 mm). Under normal circumstances, the SVI stayed under 70 mLg-1. EPS (as MLVSS) reached the maximum 373.24 mg.g-1 on the 59 d, which increased about 2.5 times over the inoculums. However, EPS decreased sharply during the later period due to the disintegration of aerobic granular sludge. MLSS was always below 3 000 mg L -1 during the middle and later periods in the reactor. During the 63 days' operation, the removal rate of COD by the reactor maintained at about 90% except the abnormal circumstances, and the effluent COD was less than 100 mg.L-1. TIN and ammonia nitrogen's removal efficiency by the reactor fluctuated greatly, and the removal rates were 44.45% -94. 72% and 43. 87% -93. 13% respectively. The removal rate of TP was between 44. 50% -97. 40% , which could remain above 60% under normal circumstances. Limited to the automatic control level, AGS was disadvantage in the competition with filamentous bacteria that overgrew easily during the long time aerobic starvation period at night, which eventually led to the collapse of AGS.