Aerobic granular sludge cultivation in a sequencing batch reactor (SBR) using activated sludge as inoculum

Granular sludge technology represents a novel alternative to the conventional activated sludge wastewater treatment plants. Granules were cultured under aerobic conditions in a laboratory scale sequencing batch reactor (SBR). In order to enhance the growth of granular sludge, the SBR was operated with very short sedimentation and draw phases resulting in the washout of slow settling biomass and development of high density sludge granules (anaerobic feeding - 45 min, aerobic reaction - 11 h, settling - 5 min and effluent withdrawal - 10 min). The reactor was inoculated with conventional activated sludge, sampled from a wastewater treatment plant, and fed with dairy industry wastewater with high organic and nutrient load. Treatment performances increased along with the growth of granules size. Microscopic investigations were performed to assess the diversity and dynamics of the aerobic granular sludge biocenosis community and granules formation.