Selection of ultrafiltration (UF) menbrane modules for clarification of rice washing drainage from packed rice cake manufacturing plant
2005
Rahaman, A.(Niigata Univ. (Japan)) | Jyou, T. | Itou, A. | Kataoka, T. | Oonishi, M. | Watanabe, A.
In a packed rice cake manufacturing plant about 5 m(3) fresh water to one ton of raw rice is used in each process of the rice washing and soaking process. The amount of water used in both processes accounted for about 60% of that in the whole plant regardless of season. The purpose of this study is to clarify the rice washing drainage by membrane separation technique and to reuse the clarified water in the rice washing and soaking processes in order to decrease the costs of fresh water and wastewater treatment without spoiling product quality, especially storage stability related to microorganisms. Because the results of the preliminary experiments suggested that UF membrane is suitable for clarification of rice washing drainage, three types of hollow fiber UF membrane 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 large 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 for clarification of rice washing drainage was evaluated from the viewpoint of permeation flux, rejection rate of solutes, which were protein as high molecular weight substance and fatty acid as low molecular weight substance, and flux recovery by membrane washing. It was concluded the membrane module of 150 k was the most suitable for the clarification and recycling of rice washing drainage.
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