| 摘要 |
PURPOSE:To increase the amt. of SS collected per unit volume of a filter medium and to enhance the filtration capacity by forming a tank filter consisting of a floating filter medium having <=1 sp.gr., and supplying raw water from plural raw water supply ports. CONSTITUTION:The floating filter mediums are laminated in a vessel 7 provided with an intake 8 for treated water to form a filter bed 10, and plural raw water supply ports 13 are provided within >=60% of the thickness of the filter bed 10. The SS from raw water is widely dispersed in the filter bed and internally collected, the duration of filtration can be prolonged, and the frequency of back washing can be reduced. Although the increasing of the thickness of the filter bed to >=2m is not effective even in the pressure filtration of the conventional process, the thickness of the filter bed can be effectively increased to >=2m in this process, and the setting area necessary for the tank filter can be reduced.
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