Enhancement of start-up of pilot-scale granular SBR fed with real wastewater

A novel operational strategy with a combination of short settling time and high food/microorganism (F/M) ratio was developed to start up a pilot-scale granular sequencing batch reactor fed with real wastewater on site. It was found that only 17 days were needed to form granule-dominant sludge in the reactor, which was much shorter than 400 days reported previously. After 50-day operation, COD and NH4+-N removal efficiencies could reach above 80% and 90%, respectively. Simultaneous nitrification and denitrification was observed in the reactor and up to 86% total inorganic nitrogen (TIN) removal was achieved occasionally. But TIN removal was not stable during the long-term operation, which indicated that TIN removal could not singly rely on anaerobic zone in aerobic granule without DO control or other control of operational condition. In addition, the 9-month reactor operation demonstrated that rapidly formed aerobic granules by the novel strategy could maintain the long-term stability.

► A novel strategy for start-up of pilot-scale reactor was developed.
► Start-up period for granulation could be shortened to 17 days.
► The granule sludge formed –nwith the novel strategy maintained long-term stability.
► The total nitrogen removal efficiency is above 50% in this granular sludge system.