| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent the deterioration of the quality of discharge water due to backward washing by preventing the inflow of SS peeled from a carrier by the backward washing of a fixed filter tank to a treated water tank in a septic tank equipped with a biological filter tank. SOLUTION: The septic tank has a carrier fluidizing tank housing and holding a carrier flowable by water streams in a freely floating state, the biological filter tank comprising the fixed filter tank filled with the carrier in a sedimented and deposited state and the treated water tank provided to the rear stage thereof. A water gathering chamber is provided under the fixed filter tank and allowed to communicate with not only the fixed filter tank by a large number of through-holes smaller than the carrier bored in the bottom surface of the fixed filter tank but also the treated water tank by small area openings bored in the lower end part of a partition wall partitioning the water gathering chamber and the treated water tank, and a backward washing air diffuser is arranged to the water gathering chamber and the suction part of a backward washing SS returning air pump is arranged to the treated water tank at the position approaching the openings.</p> |
