PURPOSE: To make sanitary reduction treatment of the excess sanitary sewage in a privy tank by carrying the evaporated moisture in a heated sanitary sewage chamber to a low temp. liquefying chamber by a gas circulating along a circulation system between a heated filth chamber and the low temp. liquefying chamber and condensing and liquefying said moisture in the low temp. liquefying chamber.

CONSTITUTION: An inflow port 2 for the sanitary sewage stored in the privy tank B is provided in the heated sanitary sewage chamber 1 and a discharge port 5 is disposed to a treated water storage part 4 in the low temp. liquefying chamber 3. The heated sanitary sewage chamber 1 and the low temp. liquefying chamber 3 are communicated with a forward ventilation path 11 from the chamber 1 to the chamber 3 and a backward ventilation path 12 from the chamber 3 to the chamber 1 in the circulation system 6 for the gas. As a result, the excess sanitary sewage in the privy tank is sanitarily and mechanically reduced in the volume at the generation source thereof and the absolute treatment amt. on the treatment side is exceedingly decreased, by which the burden of sewer facilities is reduced to a greater extent and a favorable influence is exerted in terms of environment such as maintenance of water quality.