Aerobic granulation for organic carbon and nitrogen removal in alternating aerobic–anaerobic sequencing batch reactor

Microbial granules with excellent settleability were successfully developed at different ammonium–N loadings in four sequencing batch reactors run under alternating aerobic–anaerobic conditions. Results showed that heterotrophic, nitrifying and denitrifying populations could co-exist in the microbial granules. The activity of denitrifying bacteria was highly determined by the availability of external carbon source in the anaerobic phase. Complete denitrification was achieved with supply of external carbon source, whereas only partial denitrification occurred with no addition of external carbon source. This study shows that microbial granules cultivated under the alternating aerobic–anaerobic condition could efficiently remove organic carbon and completely convert ammonia to nitrogen gas. A new generation of microbial granules-based bioreactor for organics and nitrogen removal can be envisaged.