Membrane Fouling Behavior Research And Optimum Control Of MBR

In recent years, membrane bioreactors (MBRs) have been widely used in wastewater treatment to achieve higher effluent quality, which is often difficult to be effectively met by conventional activated sludge process. The space occupied by MBR systems is greatly reduced due to the absence of settling tanks and the reduction in bioreactor volume made possible by the higher biomass concentration. Higher solid-liquid separation efficiency can be reached by using membrane model. However, the higher energy consumption and operation fee restricted the large scale application. A great deal study shows that membrane fouling is the main obstacle. Flux decline and extra membrane cleaning should be carried out as a result of membrane fouling.In this paper, the hydrophobic polythene hollow fiber membrane was adopted to investigate membrane fouling behavior. A mathematic model was put forward to predict membrane fouling resistance. The main research conclusions are summarized as follows:(1) The active sludge supernatant contains lots of colloidal particles and soluble substance. Protein and polysaccharide are the main components of the membrane surface pollutants. Fouling resistance increased with the supernatant turbidity increasing and that cause more serious membrane fouling, however, the specific resistance of the cake layer decreased.(2) Higher TMP results more rapid flux decline rate and form a more compact cake layer. The calculation of the pollutants on the membrane surface was controlled by back transport velocity. Brownian diffusion is dominant for small particles and low crossflow velocities while shear-induced diffusion and inertial lift seem to be most important as the crossflow velocity increased.(3) Multiple regression analysis was used to examine the influence of supernatant turbidity, transmembrane pressure and crossflow velocity on the fouling resistance values. This relationship devoted was as follow:R_f = 3.956 ×10^-2 Turbidity + 1.145TMP - 9.716CFV - 7.260 ×^-2(4) Membrane fouling resistance was increased exponentially with an increase of MLSS concentration. The relationship between MLSS concentration and viscosity was asη = 0.909e^0.0861MLSS ; MLSS concentration and sludge viscosity are two important factors affect membrane fouling. The Pearson relation coefficient between membrane fouling...