Comparison of fouling behaviors between activated sludge suspension in MBR and EPS model solutions: A new combined model

How to precisely describe the fouling behavior of activated sludge suspension in constant flux cross-flow filtration is a challenge. In this paper, a three-mechanism (standard pore blocking, complete pore blocking and cake filtration) model was established based on the classic blocking law to describe the fouling behavior of activated sludge suspension in the constant flux cross-flow filtration. The results showed that the predictions of the proposed model showed good agreements with experimental data not only for activated sludge suspension (R²≥0.994), but also for bovine serum albumin protein (BSA) (R² ≥ 0.966), humic acid (HA) (R² ≥ 0.940), sodium alginate (SA) (R² ≥ 0.801) and kaolin (R² ≥ 0.961). Meanwhile, for activated sludge suspension, the variation rate of the cake resistance increased with the filtration flux, and the steady available membrane area ratio (A_steady/A₀) was independent on the filtration flux while it decreased with the increase of MLSS concentration. In addition, the available membrane area ratio (A(t)/A₀) decreased slower for activated sludge suspension than that for single model solution (BSA, HA and SA) in the fouling process.