Optimal Operating Strategies of a Submerged Membrane Bioreactor for Wastewater Treatment

Submerged membrane bioreactors (SMBR) are hybrid systems that couple a biological reactor, where the biodegradable substrates are consumed by the active biomass, and a membrane module, which prevents the solids to pass into the effluent, replacing the classical separation and recirculation unit. An improved version of an available mathematical model describing a SMBR was used to search for the optimum operating strategies of a semi-continuous system for wastewater treatment. The model takes into account two simultaneous processes: biological chemical oxygen demand (COD) removal and the cake layer formation/removal onto the membrane surface. Based upon this model, an optimization was done, searching for the operating parameters which maximize the final global conversion of ammonia plus ammonium nitrogen. These optimal values were then used to study the behavior of the system for two operating strategies: discontinuous and continuous permeate recycling. The results showed that the former strategy is the most effective.