Filtration performance of ceramic membrane for the recovery of volatile fatty acids from liquid organic sludge

This research focused on the filtration performance of a membrane-coupled fermenter system for dissolved organics recovery from liquid organic sludge. Over the range 0.1-5 μm, the magnitude of total membrane resistance (R1) is ranged as follows in the order: 0.1 μm>0.2 μm>0.5 μm>1 μm>2 μm>5 μm. The cake layer resistance (Rc) occupied about 68-88% of total resistance. The decline of permeation flux was mainly attributed to Rc, which was formed by a strong deposition from physicochemical interactions of solids on the membrane surface. Higher suspended solids concentration of suspension caused lower permeation flux. However, there was not a proportional relation beyond a certain SS concentration. The cross-flow velocity on the membrane surface was faster, which resulted in higher permeation flux and also more efficiency with low transmembrane pressure. The appropriate pH of suspension was in the range of 5.0 to 6.0 for dissolved organics recovery as well as permeation flux. It is possible for bacteria to be separated perfectly with 0.1 μm and 0.2 μm membrane pore sizes. Based on experimental results, optimal membrane pore size for the recovery is believed to be around 1 μm.