Drying and re-cultivation of aerobic granules

Abstract

Aerobic granules stored in liquid medium can lose structural integrity during storage. This study demonstrated that the aerobic granules cultivated by seeding activated sludge into column-type sequential batch reactors and fed with synthetic wastewater at organic loading rate of 1.5kg/m3-d can be dried by acetone gradient method to moisture content less than 1%. Then, the dried granules can be reactivated through a re-cultivation process to recover their organic degradation capacity in 12h, or their appearance in 5d. During the drying and recovery, the granules experienced volume and weight losses by >80% and >85%, respectively, with minimal loss in structural integrity. The microbial communities of the dried and re-cultivated granules were probed using polymerase chain reaction-denaturing gradient gel electrophoresis technique. The family Xanthomonadaceae and the family Comamonas can survive in dried granules and could contribute to maintain structural integrity in re-cultivation stage. ? 2013 Elsevier Ltd.