Effect of intermittent aeration cycles on EPS production and sludge characteristics in a field scale IFAS reactor

In the present study, an integrated fixed-film activated sludge (IFAS) bioreactor was subjected to dissimilar intermittent aeration (IA) cyclic operations, and its effects were investigated on extracellular polymeric substances (EPS) production, sludge characteristics, and specific power consumption. A total of three IA cycles (IA1, 150 min aeration on and 30 min off; IA2, 120 min aeration on and 60 min off; IA3, 90 min aeration on and 60 min off) were evaluated in the present IFAS reactor. Specific EPS production (mg/g of suspended solids) was found to be following the increasing trend with respect to the non-aeration to aeration time ratio, whereas, the sludge production followed the reverse trend. The amount of bound EPS was observed to be much higher (6-10 times) than soluble microbial product (SMP) in each intermittent aeration phase. During all the investigated IA cycles, the pilot was observed to be significantly affected in terms of biomass characteristics, which was also confirmed by increasing trends of sludge volume index (SVI) and filamentous index (FI) values. In-situ monitoring and measurement of reactor operation parameters such as pH, oxidation reduction potential (ORP), and dissolved oxygen (DO) was also done in all IA cycles. A maximum of 27.05% reduction in electrical energy was observed in highest non-aeration period cycle.