Abstract
The aim in this paper is to clarify that the apparatus of rotating magnetic disk separation (apparatus of RMDS) is useful to remove filamentous bacteria from the activated sludge during the waste water treatment. The bulking sludge was mixed with ferromagnetic powder (Fe3O4) to prepare magnetic sludge (SVI: 430ml·g-1 VSS) containing 2 g·l-1 MLVSS and 2 g·l-1 Fe3O4. The apparatus of RMDS composed of the aeration tank knd the magnetic separation tank equipped rotating magnetic disk with scraper was compared with that of gravitational sedimentation (apparatus of GS) composed of the aeration tank and the sedimentation tank on the separation of magnetic sludge. Six days experiments were carried out with adding 200mg·l-1 CODCr as the influent at HRT=6h using both apparatuses of RMDS and GS. In case of GS method, the SVI kept constant at around 250ml·g-1 VSS after 70h. On the other hand, the SVI with RMDS method decreased to about 200ml·g-1 VSS after 30h, and about 100ml·g-1 VSS after 90h. It was found by microscopic observation that filamentous bacteria remained in the apparatus of GS, but almost not in that of RMDS after the 6 d experiments.
