Influence of temperature on the characteristics of aerobic granulation in sequencing batch airlift reactors

Aerobic granular sludge was cultivated in sequencing batch airlift reactors (SBAR) at 25, 30, and 35 degrees C, respectively. The effect of temperature on the granules characteristics was analyzed and the microbial community structures of the granules were probed using scanning electron microscope (SEM) and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The results showed that 30 degrees C is optimum for matured granule cultivation, where the granules had a more compact structure, better settling ability and higher bioactivity, the oxygen utilization rate (OUR) reached 1.14 mg O2/(g MLVSS x min) with COD removal rate of 97% and TP removal rate of 75%. The removal efficiency of NH3-N increased from 68.5% to 87.5% along with the temperature increment from 25 to 35 degrees C. The DGGE profiles revealed that the microbial community structure at 25 degrees C showed the least similarity with those at other temperatures. The sequencing results indicated that the majority of dominant microbes belonged to Actinobacteria and Proteobacterium. Thermomonas sp., Ottowia sp. and Curtobacterium ammoniigenes might play important roles at different temperatures, respectively.