METHOD FOR TREATING DRAINAGE OF ELECTRODEPOSITION COATING

摘要

PROBLEM TO BE SOLVED: To improve phosphorus-removing efficiency, to decrease amt. of generation of sludge and to avoid decrease in activity in an activated sludge treating process by a method wherein a low phosphorus concn.-contg. drainage and a high phosphorus concn.-contg. drainage are separated and the high phosphorus concn.-contg. drainage is reacted with a phosphorus removing agent in a coagulating sedimentation tank to remove phosphorus. SOLUTION: A high phosphorus concn.-contg. drainage contg. zinc phosphate, etc., generated from a rinsing tank 3a is directly forwarded into a coagulating sedimentation tank 5a through a drainage control tank 4a. In addition, low phosphorus concn.-contg. drainages generated from rinsing tanks 2a and 1a are joined into a drainage adjusting tank 4b and are forwarded into a coagulating sedimentation tank 5b. Drainages from the coagulating sedimentation tanks 5a and 5b are finally treated in an activated sludge tank 6. The high phosphorus concn.-contg. drainage collected in the coagulating sedimentation tank 5a is reacted with a phosphorus removing agent and the treated water from the coagulating sedimentation tank 5a is joined with the treated water from the coagulating sedimentation tank 5b and are forwarded to the activated sludge tank 6.