Impact of carrier filling ratio on oxygen uptake & transfer rate, volumetric oxygen transfer coefficient and energy saving potential in a lab-scale MBBR

This study investigates the effect of bio-carriers on the oxygen uptake rate (OUR) in the effluent of the reactor with an aim to provide optimized filling ratio for the practical operation of a moving bed biofilm reactor. The experimental work was carried out in seven different phases with respect to the filling ratio. In each phase, oxygen transfer efficiency and volumetric oxygen mass transfer coefficient (kla) were measured by varying the carrier filling ratio (10–70%). The effect of filling ratios, mixing intensity, hydraulic retention time and kla on OUR were observed. The value of OUR increased 2–3 times with the augmentation of carrier filling ratio but it decreased when more carriers were added inside the reactor. Secondly, efforts were also made to find ways to reduce aeration energy. Savings of energy consumption (up to 35%) were noted by providing intermittent aeration at an average oxygen transfer rate of 6 mg-O2L−1 h−1. Still, further scope exists to conserve more energy if the oxygen transfer rate is maintained at 4 mg-O2L−1 h−1.