Abstract: Waste water containing organic materials is introduced into an aeration tank, and is subjected to aeration treatment in the presence of activated sludge, while supplying oxygen to the aeration tank. The tank provided with an air diffusion pipe at the bottom of the tank, an air dispersion device above the air diffusion pipe and a plurality of inside cylinders above the air dispersion device. An overall circulating stream and partial circulating streams are generated in the aeration tank.

Abstract: A filtration method employs a water tank, a filtration tank within the water tank and provided with a filter material for straining solids from sewage supplied to the water tank, to produce filtered water within the filtration tank, a shield or guide plate encompassing the filtration tank adjacent the filter material to provide a liquid flow passage therebetween, and a bubble generator having a plurality of openings for generating bubbles within the flow zone, so that the bubbles pass along the filter material. Sewage water that is supplied to the water tank is conducted to the flow zone where part of the water passes through the filter material and solids suspended therein are strained out and attached to the outer surface of the filter material.

Abstract: Method of and apparatus for separation of solids from a liquid employs an elastic sheet filter which has pores of diameter larger than an average diameter of the solid and smaller than the maximum diameter thereof. The liquid is filtered under pressure by a filtered residue layer developed on the sheet filter. Then liquid is rapidly introduced to the sheet filter portion from the reverse direction to liquid flow occured during the filtration of the liquid so that the sheet filter and filtered residue layer pressed during the filtration is rapidly pressed in the reverse direction, whereby the filtered residue layer is flaked out in the liquid and separated therefrom.