Effect of Pore Size on the Filtration Characteristics of Ceramic Membrane for Membrane Bioreactors

For the purpose of selecting or developing appropriate inorganic membranes for methane-fermentation membrane bioreactors, the relationship between the pore size of a membrane and the filtration characteristics for methanogenic waste was studied. Tubular alumina membranes having pore size of 0.01μm1.6μm were used for the experiments. Filtation tests showed that an optimum pore size giving maximum permeation flux through the membrane existed. The permeation flux was restricted by the hydraulic resistance of the particle layer formed on the membrane surface through filtation. It was also affected by the resistance of a plugging layer formed in the membrane interior when pore size was over 0.4 μm and by the resistance of the membrane when pore size was under 0.1 μm. Therefore, the alumina membrane of 0.1 μm pore size gave the highest J value. It was also shown that plugging occurred in the starting period of the filtration when the membrane pore size was bigger than particle size. This was confirmed by measurement of particle rejection.