METHOD FOR BIOLOGICALLY REMOVING PHOSPHOROUS IN OXIDATION DITCH

摘要

PROBLEM TO BE SOLVED: To provide a method for biologically removing phosphorous which can obtain a high removal rate of phosphorous (for example, 85% or larger) by arranging a phosphorus-releasing tank at a prior stage to an oxidation ditch tank and by letting the solutions flowing in the two tanks and the functions of the tanks cooperate with each other and simplify the processes as a whole. SOLUTION: The phosphorous-releasing tank (2) is arranged at a prior stage to the oxidation ditch (7). Sewage (a) is put into the phosphorous-releasing tank (2), and sludge (b) returned from a settling pond (9) and process water (c) in the oxidation ditch (7) containing organic substances are introduced. The water in the phosphorous-releasing tank (2) is homogeneously mixed and circulated with a submersion-type stirrer (3) while keeping the anaerobic atmosphere, and then the phosphorous is released into the water from anaerobic microorganisms. The phosphorous-dissolved water (d) in the phosphorous- releasing tank (2) where the phosphorous is released into the water is introduced into the oxidation ditch (7) and refluxed, and then the phosphorous is biologically removed.