| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve treated water quality and also to enable a highly loaded operation by arranging a flocculating and separating device at the upstream side of an aeration tank. SOLUTION: The flocculating and separating device C consisting of a mixing tank C1 having an agitating means 1i and a liq. chemical feed means 1j, a similar flocculating tank C2 and a flocculating and settling tank C3 is disposed at the upstream side of a membrane separation type activated sludge treating device A having the aeration tank A1 . A settled sludge at the flocculating and settling tank C3 is returned to the mixing tank C1 with a piping P2 . An SS component in a raw water W1 is flocculated and removed, and an SS concn. is reduced till an order of about 20mg/L. An accumulation of the SS component at the post stage aeration tank A1 is prevented by attaining this residual SS concn. A floculant such as aluminum sulfate and a pH adjusting agent such as sodium hydroxide are used at the mixing tank C1 of the flocculating and separating device C. A high-molecular floculant such as nonionic floculant is used at the flocculating tank C2 . In this way, the SS concn. is reduced and BOD components are removed sufficiently.</p> |
