2005 Volume 6 Issue 2 Pages 151-160
In a packed rice cake niariufacturing plant, about 5 m3 fresh water to one Lori of raw rice is used in each process of the rice washing and soaking process. The amount of water used ini both processes accounted for about 60% of that in the whole plarit regardless of season. The purpose of this study is to clarify the rice washing drainage by inernbrane separation techriictue and to reuse the clarified water in the rice washing and soaking processes in order to decrease the costs of fresh water and wastewater treatirient without spoiling product quality. especially storage stability related to rrucroorganisins. Because the results of the preliminary experiments suggested that UF membrane is suitable fur clarification of rice washing drainage, three types of hollow fiber UF riiembrane modules were tested nominal molecular weight cut off. 30kDa, 100kDa. and 150kDa. The analysis of drainage from the rice washing and soaking processes revealed that the first and second rice washing drainage contained a lame quantity of solutes and suspended substances. and permeation flux were very low. Therefore, we decided that the first and second drainage should be treated by active sludge method. and the other drainage should be clarified by UF membrane for recycling. A mixture of third to fifth rice washing drainage and rice soaking drainage was used for clarification and recycling experiments. The membrane modules far clarification of rice washing drainage was evaluated from the viewpoint of peririeation tiux, rejection rate of solutes. which were protein as high molecular weight substance and fatty acid as low molecular weight substance, and tiux recovery by riiembrane washing. It was concluded the meiribraiie module of 150 k was the most suitable for the clarification and recycling of rice washing drainage.
