ADVANCED SEWAGE TREATMENT METHOD AND SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide an advanced sewage treatment method and system by which nitrogen can be removed from sewage at a high removal ratio without expanding a sewage treatment facility on a large scale.

SOLUTION: The advanced sewage treatment method comprises the steps of: subjecting sewage 10 to anaerobically biological treatment in a first anaerobic treatment tank 1; subjecting the anaerobically-treated solution to aerobically biological treatment in an aerobic treatment tank 3; and withdrawing a part of the aerobically-treated solution from the aerobic treatment tank 3 and circulating the withdrawn aerobically-treated solution to the first anaerobic treatment tank 1. In the concrete, the ratio of a flow rate of the circulated aerobically-treated solution 11 to that of sewage to the first anaerobic treatment tank 1 ((a circulation flow rate)/(a sewage flow rate)) is kept ≥5. The aerobically-treated solution discharged from the aerobic treatment tank 3 is introduced into a second anaerobic treatment tank 5 and subjected to anaerobically biological treatment. The anaerobically-treated solution discharged from the second anaerobic treatment tank 5 is introduced into a membrane separation tank 7 having an immersion membrane 9 therein and aerated to separate sludge by the immersion membrane. At least a part of the separated sludge 13 is returned to the first anaerobic treatment tank as return sludge 15.

COPYRIGHT: (C)2007,JPO&INPIT