CIRCULATION TYPE NITRIFICATION DENITRIFICATION APPARATUS AND ITS METHOD

摘要

PROBLEM TO BE SOLVED: To decrease load of a final sedimentation basin or to omit the final sedimentation basin itself and to improve quality of treated water by combining an improved filter device in a circulation type nitrification/denitrification process. SOLUTION: In a circulation type nitrification/denitrification process wherein a reactor with an oxygen-free region on the inlet side of water to be treated and an aerobic region on the outlet side of treated water is used and a part of nitrification mixture in the aerobic region is circulated to the oxygen-free region to remove nitrogen in the water to be treated, a hollow filter body 5 wherein at least a part of the surrounding wall comprises a water-permeable supporting material with a mesh opening of particle diameter of at least 20μm and a thickness of at most 2mm is arranged by submerging it in at least one of the aerobic region or the succeeding final sedimentation basin 3 and a filter membrane consisting of nitrification sludge and turbid substance is formed on the supporting material and the treated water is made to flow into the filter body through the filter membrane by water head difference between it and the succeeding tank and the treated water is extracted from the filter body.