BIOLOGICAL FILTERING METHOD

摘要

PROBLEM TO BE SOLVED: To reduce the operation cost of an equipment concerning oxygen supply and to improve the water quality of treated water by efficiently supplying oxygen required for the oxidation reaction of nitrogen and an organic substance in a biological filtering method in which nitrogen and the organic substance in raw water is removed by passing the raw water upward through a biological filter layer formed by packing a floatable filter material. SOLUTION: In the biological filtering method in which the raw water is passed in upward through the biological filter layer 5 formed by packing the floatable filter material and a part of the treated water discharged from the upper part of the biological filter layer 5 is introduced to the lower part of the biological filter layer 5, pure oxygen or oxygen-enriched air is dissolved in a part of the raw water, and the water is introduced from an intermediate part in the height direction of the biological filter layer 5, and the other part of the raw water is introduced from a lower part of the biological filter layer 5.