Effect of anaerobic phase duration on the formation of aerobic granular sludge in a sequencing batch reactor
Volume Title: 1
Department of Chemical Engineering, Amirkabir University of Technology, Tehran, Iran
In the present study, the effect of anaerobic phase duration on the process of aerobic granule formation in a sequencing batch reactor (SBR) operated for a period of 126 days was examined. During the first 76 days of operation, SBR was operated under 6 h cycles with 2h anaerobic phase, whereas from day 76 till end of operation, a 1 h anaerobic phase was employed. The extent of aerobic granulation, quantified by determination of %GR0.5 and %GR0.3, decreased during latter half of operation at 2 h anaerobic phase. This was attributed to deflocculation of particles in the anaerobic phase. Decrease in the anaerobic phase length from day 76 to 1 h halted this decrease. The trend of change in the values of %GR0.3 and %GR0.5 during SBR operation was negatively correlated with the trend of change in the concentration of loosely bound extracellular polymeric substances (LB-EPS) and its protein to carbohydrate (P/C) ratio. On the other hand, tightly bound EPS (TB-EPS) and its P/C ratio were found to have a positive effect on aerobic granule formation. The percentage of particles with size bigger than 0.25mm at the end of SBR operation was 50.