JPS555723A - Septic tank - Google Patents

Abstract

PURPOSE: The septic tank for efficiently execute the aerobic and anaerobic denitrification reaction, by introducing a part of treated water obtained from the household sewage being treated in the aeration chamber of the septic tank, for the purpose of preventing the clogging of the sewage entrance due to the filth included in the excrement being diluted with extremely small amount of the washing water.

CONSTITUTION: The sewage, being diluted with the washing water of about 1/10 or less amount of flush water for the general flush toilet, is introduced into the separating chamber 3; and the scum piled up in the upper zone of the chamber 3 is scattered and disintegrated by the treated water being returned 9 and injected 8; hereby, the sewage is diluted to a degree of BOD 1W2000 ppm. In this chamber 3, the separation of solid and liquid phases is executed, and at the same time, N of NO₂ and NO₃ of the treated water is denitrified owing to the aerobic and anaerobic denitrification reaction. Next, only the treated supernatant liquid is transferred 14 to the dilution chamber 10, and is diluted by the treated water 13 sent from the upper zone of the settling chamber 7 to BOD about 300ppm, and moreover, the denitrification treatment is executed by the aerobic and anaerobic denitrifying bacteria sticking on the packings 12. Then, the sewage, being denitrified and diluted to BOD concentration suitable for the biological treatment, is transferred to the aeration chamber 4, in which the aeration treatment is carried out by the injected air 17, and the sludge piled up in the lower zone of the chamber 7 is returned to the chamber 4. The top liquid of the chamber 7 is discharged through the disinfection chamber 19.

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