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[Studies on aerobic granular sludge cultivated under selective pressure].

As inoculum sludge from a conventional COD removal activated sludge wastewater treatment plant was used, aerobic granular sludge was cultured in sequencing batch reactor (SBR) fed with glucose as carbon substrate. The SBR was operated with decreasing sedimentation time and increasing COD loading rate resulting in the selective pressure to enhance the formation of granular sludge. According to morphology change of sludge, the generation of granule could be divided into three stage. Granules started to appear after 67 days operation. After increasing COD loading rate to 4.8 kg/(m3.d), and superficial gas velocity to 0.0175 m/s, granules were the dominant sludge forms with diameter about 6-9 mm, the minimal settling velocity of 32.7 m/h, and the MLSS of 7800 mg/L. Aerobic granular sludge demonstrates high activity and ability to withstand high COD loading rate. The properties of aerobic granular sludges and the effect of different operational conditions on the formation of these aerobic granules were also analyzed preliminarily.