Oxygen transfer in moving bed biofilm reactor and integrated fixed film activated sludge processes

A demonstrated approach to design the, so-called, medium-bubble air diffusion oxygen transfer system for moving bed biofilm reactor (MBBR) and integrated fixed film activated sludge (IFAS) processes is described. Operational full-scale biological water resource recovery systems treating municipal sewage, designed using this methodology, provide reliable service. Further improvement is possible, however, as knowledge gaps are filled and results in more rationally-based system designs. Pilot-scale testing demonstrates significant enhancement of oxygen transfer capacity from the presence of media. Establishment of the relationship in full-scale systems between diffuser submergence, aeration rate, and biofilm carrier fill fraction will enhance MBBR and IFAS aerobic process design, cost, and performance. Limited testing of full-scale systems prevents computation of alpha values and can be addressed by further full-scale testing under actual operating conditions. Control of MBBR and IFAS aerobic zone oxygen transfer systems can be optimized by recognizing that varying residual dissolved oxygen concentrations are needed, depending on operating conditions. Further application of oxygen transfer control approaches used in activated sludge systems, such as ammonia-based oxygen transfer system control, further improves MBBR and IFAS system energy efficiency.