| 摘要 |
PURPOSE:To attain the conservation of fuel cost, by sending sludge sedimented in the first sedimentation basin of a sewage treatment process to a flocculation reaction tank while pumping up the same and adding a flocculant to said sludge to form flocs before performing solid-liquid separation. CONSTITUTION:A flocculation reaction tank 19 and a screen apparatus 20 are arranged in parallel to a sludge concn. tank 17. A part of sludge is withdrawn from a first sedimentation basin 12 to be sent to the flocculation reaction tank 19 through a pump 21 and suspended particles in sludge are flocculated by a polymer flocculant 22 and concn. and separated in the screen apparatus 20. Conc. sludge and return water 23 extremely reduced in BOD and SS are obtained and the load of the sludge concn. tank 17 is reduced by a method for transferring the obtained ones to the next process and, at the same time, hardly sedimenting particles are positively treated. The sedimentation speed of sludge is increased and the treatment of sewage is reduced.
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