Patent ID: 7704385

Claim:
A water treatment system comprising: an anaerobic treatment tank which subjects supplied sewage to anaerobic treatment by causing the sewage to upflow by a pump; and an aerobic treatment tank which subjects anaerobically treated water, which is supplied to an upper part of the aerobic treatment tank from the anaerobic treatment tank, to aerobic treatment by letting the anaerobically treated water to downflow by natural downflow, wherein the aerobic treatment tank includes an aerobic filter bed section in which carriers to which aerobic microorganisms are adhered are arranged, the aerobic filter bed section subjecting the anaerobically treated water to decomposition treatment by putting the anaerobic treatment water in contact with the aerobic microorganisms adhered to surfaces of the carriers, the aerobic filter bed section being provided with an air supply section which takes in air into under normal pressure, thereby activating the aerobic microorganisms.