Effect of Srt and Bio-Carriers on Performance of a Full Scale Mbr Plant

Abstract

Membrane bioreactors (MBRs) are considered as a most viable wastewater treatment process in view of its superior effluent quality, small footprint, and reduced sludge production. In this study, in 1st phase, optimum combination of solids retention time (SRT) and flux for newly commissioned full scale MBR plant was found within MLSS range of 8-10g/L which gives excellent treatment performance with good sludge characteristics and minimum membrane fouling. Overall, more than 90% carbon removal was achieved in all combinations of steady state SRT and flux combination. Sludge characteristics varied significantly at different SRT and flux combinations but in case of treatment performance, there was no significant difference in performance. Moreover membrane fouling in terms of EPS generation was much severe in 15 days SRT and 15 LMH. An SRT of 20 days with 20 LMH was selected as most optimum combination because of excellent treatment performance with good sludge characteristics and moderate membrane fouling. Capillary suction time (CST), sludge volume index (SVI) and particle size were less in case of shorter SRT and vice versa. In 2nd phase of the study, 20L vacant beads i.e., 0.65% of M-tank volume of MBR Plant were added in order to further optimize the plant by mitigating membrane fouling. Results showed vacant beads not only reduced the membrane fouling, but also played a crucial role in reduction of EPS due to absorption of AHLs. Vacant beads deteriorated sludge characteristics like CST and TTF along with increase in SVI by breaking the flocs by collision. Mean size of sludge particle was also reduced. Moreover the introduction of vacant beads did not have any notable effect on carbon and nutrients removal of MBR plant.