Modelling of membrane fouling in a submerged membrane bioreactor

A mathematical model was developed to model membrane fouling in a submerged membrane bioreactor (SMBR) used for wastewater treatment and reclamation. The sectional technique was employed to account for the uneven distribution of the aeration turbulent shear intensity and the fouling material coverage on the membrane surface. The dynamics of the biomass attachment to and detachment from the membrane in relation to the filtration and aeration turbulence were considered in the model formation. The fouling components of pore clogging, sludge cake growth, and temporal sludge film coverage were included in the calculation of the total membrane fouling resistance. With this new model, membrane fouling under different SMBR operational conditions can be successfully simulated, and the influences of a number of process variables on fouling development can be well quantified. The simulation results demonstrate that filtration flux is the most significant factor that causes sludge cake deposition and fouling problems, followed by sludge stickiness and sludge concentration, and that aeration is important for fouling control. Membrane fouling due to sludge cake accumulation can be minimized in an SMBR by using a lower sludge concentration, enhancing the aeration rate, and reducing the filtration flux. The results of the numerical simulations compare fairly well with the experimental results that were obtained with a laboratory-scale SMBR in this study, which validates the applicability of the new fouling model.