PURPOSE: To efficiently clarify the raw night soil, by agitating and frothing the raw night soil through adding slaked lime in excess and separating solid from liquid by means of floatation method.

CONSTITUTION: Night soil, after being separated from foreign matters contained in them, are fed to an agitator 1 and added with slaked lime of more than three times of chemically equivalent quantity. The raw excreta in agitator are emulsified and frothed while being agitated by a blade 6 and added with the air from a pump 7. The night soil after being treated in agitator 1 are sent to a floatation apparatus 2 via a conduit pipe 8 and separated there to a frothed part and a liquid part. The frothed is taken out of a overflow port 10 connected to the upper part of a cylindrical tower 11 and sent to a bubble dryer 3 and the solid matters are finally obtained by means of a cyclone 4. On the other hand, the liquid part is flown to a receiver tank 9 and the top clear part of the liquid is discharged from outlet port 12. The excessive and unreacted slaked lime is settled in the receiver tank 9 and taken out of the tank bottom by means of a circulation pipe 13 and sent to the agitator 1 for use again. In order to raise the efficiency of deodorizing effect, some ferrous compounds are added to slaked lime and some frothing agents are also added to promote the frothing.