AERATION TANK FOR PURIFYING TREATMENT OF SEWAGE

PROBLEM TO BE SOLVED: To provide an aeration tank capable of performing effective purifying treatment to a degree capable of reutilizing treated watder as washing water within a short time when sewage such as waste washing water is purified using bacteria (lactic acid bacteria, yeast, actinomyces, photosynthetic bacteria or filamentous fungi). SOLUTION: Almost semispherical projections with a height of 10-30mm are formed to the vertical inner wall surfaces 6, 7 of a container housing mixed sewage of sewage to be treated and bacteria at random and an air diffusing pipe 2 is arranged to the bottom part of the container and vertical revolving streams 5 are generated in the mixed sewage in the container by air bubbles diffused from the air diffusing pipe to bring mixed sewage revolving streams into contact with the projections on the vertical inner wall surfaces of the container. In order to effectively generate revolving streams, the bottom part of the container is formed so as to have a circular arc bottom surface 9 and a cylindrical guide means 10 is horizontally arranged to the center of the container.