| 摘要 |
PROBLEM TO BE SOLVED: To provide an inexpensive and eco-friendly method for filtration with a filter press by using the cake formed in a dehydration system as a precoat material and to provide an apparatus therefor. SOLUTION: A coagulant comprising polyaluminum chloride or aluminum sulfate is added to raw water to form flocks. The flocks are dehydrated under pressure and ground to a particle having diameter of about 0.1-0.8 mm. The ground cake is mixed with water, and the mixture is fed into a filtration chamber 7 of a filter press 1 to form a precoat layer comprising the ground cake on the surface of the filter medium, and the raw water is fed into the filter medium and is filtered and dehydrated. The use of particles larger than the diameter of an opening of the filter medium as the precoat layer eliminates the clogging of the medium and the penetration of cake into the medium. Therefore, the cake can be easily released. The dehydrated cake can be recycled as the precoat material, so that the amount of the cake to be disposed of can be reduced.
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