Sewage purification system

The invention relates to the field of sewage treatment and in particular relates to a sewage purification system. The sewage purification system comprises a first dosing device, a second dosing device, a third dosing device, a coagulation tank, a flocculation tank, a filter device and a liquid storage tank, wherein the first and second dosing devices are communicated with the coagulation tank via pipelines; the third dosing device is communicated with the flocculation tank via a pipeline; the coagulation tank is communicated with the flocculation tank via a pipeline; the filter device comprises a motor, a rotating shaft, adsorption discs, positioning discs, scrapers, sewage tanks, sub-sewage tanks and clear water tanks sleeved outside the sewage tanks; the rotating shaft is arranged on the sewage tanks; a plurality of adsorption discs are arranged on the rotating shaft; each adsorption disc is matched with a scraper; the sub-sewage tanks are fixedly arranged in the sewage tanks; the clear water tanks are comm