Simultaneous Removal of Nitrogen and Phosphorus by Hybrid Anaerobic-aerobic Filter with Flotation.

ISHIKAWA Susumu, SUZUKI Tatsuhiko, NIKATA Toshiyuki, KAKII Kazuo, SHIRAKASHI Takashi

doi:10.5956/jriet.29.955

A simultaneous removal system of nitrogen and phosphorus for small-scale sewage treatment facilities was developed. The process flow includes anaerobic filter dissolved air flotation aerated filter. Nitrified liquid (aerated filter treated water) was circulated to the anaerobic filter. Packing the anaerobic filter with plastic medium having large specific surface area, a mixing device was installed in the anaerobic filter to prevent the filter bed from being clogged with biofilm and to achieve an efficient denitrification. The aerated filter comprises two filter beds: The upper bed was packed with plastic medium, and the lower bed was packed with anthracite. The upper plastic medium was fluidized by the process air. Further, to remove phosphorus, a metallic coagulant was added to the inlet pipe of flotation tank. Two kinds of the metal coagulants, poly-aluminum chloride and poly-ferric sulfate, were respectively added.<BR>A pilot-scale experiment was carried out (25m³/day) by using untreated sewage. Excellent simultaneous removal of nitrogen and phosphorus (90% or higher of nitrification ratio, 75% of T-N removal and 90% of T-P removal) was achieved in 6.5 hours entire retention time, even under a low water temperature period (11.5 to 18.5°C) . Moreover, the stability of treatment performance was confirmed with an experiment design for the variation of quantity of flow rates, in inflow sewage.

Simultaneous Removal of Nitrogen and Phosphorus by Hybrid Anaerobic-aerobic Filter with Flotation.

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