Abstract: Domestic sewage water treatment apparatus, comprising an outer tank and an inner tank installed within the outer tank, the bottom of the inner tank being distant from the bottom of the outer tank. A space is formed between the vertical wall of the outer tank and the vertical wall of the inner tank. Means provided at the bottom of the inner tank prevent light particles from ascending into the clarification tank. Means provided at the top of the inner tank create a sufficient upwards suction thus providing the homogenization, aeration and recirculation of the bath and of the activated sludge contained in the aeration tank. Floating means are provided at the top of the inner tank for acting as a protection rampart against the turmoil created by the aeration, homogenization and recirculation means.