Development of an aerobic granular sludge bioreactor for simulated wastewater treatment and system reactivation after prolonged shutdown

ABSTRACT This study aimed to produce aerobic granular sludge in a non-tubular sequencing batch reactor, which is an unusual geometry in these systems. This reactor was inoculated with activated sludge from a municipal wastewater treatment plant. The reactor was operated in cycles of six hours, with five hours of fully aerobic reaction. The simulated wastewater contained a starch derivative used in the textile industry. Granulation was induced by gradually reducing the settling time; therefore, this is a critical parameter of the system. After stabilization, with a sedimentation time of 3 minutes, a Sludge Volume Index after 30 minutes of settling of 25 mL.gSST-1, a biomass concentration of 7 gTSS.L-1 and a Chemical Oxygen Demand removal of 88% were obtained. The granules were stored wet for 7 months at 4 and 25ºC, yielding exceptional results in the re-start of the reactor, with rapid recovery of their sedimentation characteristics, growth rate, and granular structure and integrity.