Effects of aeration intensity on characteristics of aerobic granules in sequencing batch airlift reactor (SBAR)

This study investigated the physical performances of mature aerobic granules in SBAR,including granular shape and structure,mean size and granular relative strength,and cell metabolic activities to excrete extracellular polymeric substances(EPS),and nitrification and microbial activity,which performed visible differences at superficial upflow velocity of 1.8(cm·s~(-1)) and 0.9(cm·s~(-1)) respectively.Results show that granular surface was more irregular at the low aeration intensity than that at the high aeration intensity and granular interstice performed increasing with it.In 55 days,comparing with high aeration intensity,the sludge productivity and the mean size of aerobic granules at the low aeration intensity were increased by 33% and 25%,respectively,while the granular relative strength and EPS were reduced by 6% and 12%,respectively.The sludge volume index in two reactors were about between 10(mL·g~(-1)) and 15(mL·g~(-1)), which implied that granules at both aerations behaved well settling ability.The two reactors still performed well nitrification characteristic and ability to remove COD.The activity of nitrifying bacteria in aerobic granules at the low aeration intensity was lower than that at the high aeration intensity,while heterotrophs performed higher activity at the low aeration intensity.