Cross-flow microfiltration of submicron microbial suspension

The mechanism of cross-flow microfiltration of submicron microbes is studie d. Experiments are carried out using pseudomonas suspensions. The effects o f operating conditions on the filtration performance are discussed. The res ults show that the filtration rates increase with increasing the cross-flow velocity, while decrease with increasing the filtration pressure. The Brow nian dynamic simulation method is adopted for simulating the trajectories o f microbes in cross-flow micro filtration. The deposition flux of microbes on the membrane surface can then be estimated from the simulated trajectori es. Based on the continuity equation of cake compression and Kozeny equatio n, a dynamic analysis method is developed for simulating the distributions of local cake properties, such as porosity and specific filtration resistan ce in the filter cake. The deformation of microbes, the area contact betwee n microbes and the creeping effect of cake compression are taken into consi deration. The simulated values of average cake properties agree with the ex perimental data. It can be found that a skin layer controlled the filtratio n rate will form next to the membrane surface. Although the thickness of th e skin layer is only about 10% of the whole cake, it plays the major role o n the filtration resistance. Increasing the filtration pressure results in more compact skin layer; therefore, a lower filtration rate is obtained. Mo reover, a higher cross-flow velocity will results in a thinner but more com pact cake, a higher filtration rate can be given. (C) 2001 Elsevier Science B.V. All rights reserved.