Response of an aerobic granular and conventional flocculated reactors against changing feed composition from simple...

This research evaluated the effect of changing feed composition on the performances of a conventional activated sludge (CAS) and an aerobic granular sludge (AGS) reactor operated simultaneously. Both reactors were initially fed with 100% synthetic feed. In a stepwise manner, the feed composition was slowly changed to real primary effluent collected from a local wastewater treatment plant. After an initial stabilization period, both reactors could achieve more than 90% NH₄⁺-N removal. However, PO₄^3--P removal eventually reached to a maximum of 92% in the AGS and 88% in the CAS. COD removal in both reactors was least affected, with the lowest percent removal of 81 ± 3% achieved in AGS and 62 ± 4% in CAS respectively when fed with 100% real wastewater. Despite granule breakage the AGS reactor was able to remove the pollutants (COD, N, P). The abundance of Candidatus Accumulibacter, a polyphosphate accumulating organism, in the AGS system increased over the operational phases: II (6.2%), III (10.32%), and IV (11.9%). While in CAS, it increased from phase I to phase II (12.6%), but decreased in phase III to 9.9%. Genus-based classification revealed a successive increase in the relative abundance of Nitrospira to 11.05% during Phase III and 10.3% during Phase IV in the AGS. In contrast with its presence in the CAS, which was, 3.4% during Phase III and 9.5% during Phase IV.