Sewage purification system and purification method

The invention discloses a sewage purification system and a purification method, and relates to the field of sewage purification. The purification system provided by the invention mainly comprises an aeration tank and a membrane tank; an aeration pipe is arranged in the aeration tank, a solid-liquid separation membrane is arranged in the membrane tank, a reflux pump is arranged outside the membranetank, a water inlet of the reflux pump is connected with a water outlet of the membrane tank, and a water outlet of the reflux pump is connected with the aeration tank; and the aeration tank is filled with activated sludge. According to the system, clear water flowing out of the circulating membrane tank enters the aeration tank, so that the treatment load of the solid-liquid separation membranecan be effectively reduced, the cleaning period of the solid-liquid separation membrane is effectively shortened, the service life of the solid-liquid separation membrane is prolonged, and it is ensured that the effluent water quality is qualified and reaches the standard; and the method and system is suitable for domestic sewage with small water quantity and industrial sewage with similar water quality conditions and has a wide application range.