| 摘要 |
PROBLEM TO BE SOLVED: To remarkably prolong an interval of regenerating work of a filtration pond by regenerating cleaning function of sand by a method except the washing method such as surface washing, back washing. SOLUTION: In this method, a prescribed quantity of filter sand 5 is sucked from a rapid filter bad 1 by a pump 2 at the time of back washing the rapid filter bed 1 for performing purification of water by the filter sand. The sucked filter sand 5 is supplied to a sand washing device 3 to remove dirt of the filter sand by the sand washing device 3. The filter sand 6 removed in the dirt is stocked in a washed sand stock vessel 4. The stocked filter sand 7 is returned to the rapid filter bed 1 at the time of the back washing the rapid filter bed 1. The filter sand in the rapid filter bed 1 is automatically washed by repeating the sucking, washing and returning work in this way.
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