A CFD simulation and experimental study: The impact of aerator design on the bubble flow pattern, foulant removal and scouring capability of flat sheet membrane bioreactor (FSMBR)

Abstract

Membrane fouling is a main drawback of membrane bioreactor systems. Moreover, optimization of influential parameters via practical analyses is tedious and time-consuming. Therefore, the CFD-RSM approach accompanied by experimental results was employed to propose the optimal aerator design. In comparison with the linear nozzles, simulation results proposed that at equal air flow rate, the angular nozzle aerators with 30° toward the surface of the membrane could provide higher amounts of surface tension, air scouring capabilities as well as air volume fraction at a similar air flow. Simulation findings were experimentally validated using a bench-scale MBR system. Obtained results showed that the irreversible fouling ratio to the total fouling ratio for neat membrane was decreased from 62.99 % to 43.97 % for linear and angular nozzles, respectively. This improvement in the nozzle performance was more pronounced for nanocomposite membranes, in which the abovementioned ratio was decreased from 43.44 % to 24.57 %. It is confirmed that the impact of nozzle design on the nanocomposite membrane was 30.48 % higher than that of the neat membrane. Specific aeration demand (SADm) value was decreased from 0.77 to the 0.49 [Nm3/(m2h)] at an equal amount of shear stress and lower inlet velocity, when linear nozzles were replaced by the angular nozzles. The lower SADm and better foulant capability leads to the optimal operation condition and lower energy as well as operating costs.