effect of anaerobic phase duration on the formation of aerobic granular sludge in a sequencing batch reactor

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#