BIOLOGICAL TREATMENT OF ORGANIC SEWAGE

摘要

PURPOSE:To reduce the cost of a chemical agent in the adjustment of pH by treating org. sewage in a high pH biological treatment process and subsequently treating the same in a neutral pH biological treatment process in which acidic waste water is injected. CONSTITUTION:Alkaline org. waste water 1 flows in the aeration tank 6 of a high pH(alkaline) treatment process along with return sludge 2. The aeration tank 6 is held to pH 8.5 or more and BOD in raw water is oxidized herein by the action of BOD oxidizing bacteria and the waste water is subjected to solid-liquid separation in a sedimentation basin 7. The overflow water containing the residual BOD component from the sedimentation basin 7 flows in the aeration tank 9 of a neutral pH treatment process 8 along with acidic waste water 1' and return sludge 3 and the BOD component is perfectly removed herein and the waste water is subjected to solid-liquid separation in a sedimentation basin 10 to be discharged as discharge water 17. The sludge discharged from the high pH treatment process is excellent in dehydration and sedimentation properties and the generation amount of sludge is also reduced by 20-40% as compared with conventional biological treatment within a neutral pH region.