TREATMENT OF ORGANIC SEWAGE

PURPOSE:To enhance P-removal efficiency while reducing installation cost, by introducing org. sewage sufficiently denitrified in a denitrification tank into an anaerobic tank. CONSTITUTION:P-component discharge reaction is performed under an anaerobic condition in an anaerobic tank 1 and a part of high P-concn. sewage is introduced into a sedimentation basin 11 to be separated into sedimented sludge S3 and a supernatant solution L5 while the sedimented sludge S3 is returned to a denitrification tank 2. The supernatant solution L5 is introduced into a chemicals injection and suspension tank 12 to be mixed with a flocculant under stirring and subsequently introduced into a flocculative sedimentation tank 13 to be separated into flocculatated sedimented sludge S4 and a supernatant solution L6 while the supernatant solution L6 is returned to a digestion tank 3 to receive the excessive intake reaction of a P-component under an aerobic condition along with the remainder of the high P-concn. sewage introduced from the anaerobic tank 1 and the concn. of the P-component in the aqueous phase part is reduced.