| 摘要 |
<p>PURPOSE: To sufficiently develop the capacity of submerged filteration by using a floating filter material having a compression ratio of a specific value when the filter bed in a filter apparatus is compressed by the differential pressure accompanied by the elapse of filtering treatment. CONSTITUTION: A floating filter material has compression properties such that pressure loss is generated with the elapse of a treatment time when the filter material is arranged in water or treated water and the height of the filter material bed is compressed within a range of 5/100-100/1000per the differential pressure rise of the filter material bed of 1m water column. As the floating filter material, a porous substance obtained by foaming polystyrene, polyethylene or polypropylene having specific gravity less than that of water is usually used because the surface area of the filter material is increased. Since the filter material is compressed properly by the rise of differential pressure with the elapse of a filtering time, a hardly filterable suspended substance can be collected without passing through the gaps of the filter material and the collection rate of the suspended substance per the unit volume of the filter material is kept high for a long time and the number of times of the washing of the filter material per a unit time is reduced and the drain amt. of washing water is reduced.</p> |
