| 摘要 |
<p>PURPOSE: To reduce a washing frequency and to prolong a filter operating time per one time by executing a biological filtration while utilizing an all of a filter material constituting a packed layer. CONSTITUTION: In a downward stream filter type biological filter in which a packed layer 10 is constituted by the filter material to which a biological membrane is stuck, the packed layer 10 of the filter material is formed in the inside of a closed filter vessel 11, an air discharge valve 14 capable of controlling an opening degree is attached on the upper wall 12 of the filter vessel, a pressure loss detecting means 15 for detecting a pressure loss of a raw water supplied from upward to the packed layer is installed in the inside of the filter vessel to control the opening degree of the air discharge valve by the pressure loss detecting means.</p> |
