Abstract
Effects of an external magnetic field on sedimentation enhancement were investigated using three kinds of practical activated sludge. An indoor experiment was setup (3.5l aeration vessel) equipped with a broth circulation system and 800 G of external magnetic field. The application of an external magnetic field to the activated sludge enhanced the sedimentation irrespective of the nature of the activated sludge. At the same time, the flock size of the sludge was enlarged by the external magnetic field. However, the surface zeta potentials of the sludge were not changed by the external magnetic field. Addition of FeCl3 to the sludge enhanced the effects of the external magnetic field. Based on these results, the following mechanism for the enhancement of sedimentation by the external magnetic field is suggested: activated sludge containing iron was magnetized during entry to the magnetic field and coagulated with the magnetic force. As a consequence, the flock size was enlarged. Almost the same sedimentation enhancement by external magnetization was confirmed by a pilot scale magnetization system (2.0 m3 of aeration vessel) when the airlift type of mild broth circulation system was equipped with a 5000 G magnetic field.
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Hattori, S., Watanabe, M., Osono, H. et al. Effects of an external magnetic field on the flock size and sedimentation of activated sludge. World Journal of Microbiology and Biotechnology 17, 833–838 (2001). https://doi.org/10.1023/A:1013811114017
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DOI: https://doi.org/10.1023/A:1013811114017