WASTEWATER TREATMENT METHOD

To provide a wastewater treatment method capable of obtaining an excellent coagulation treatment effect, improvement of treated water quality and improvement of solid-liquid separability in the solid-liquid separation step by using a coagulation auxiliary agent in the returned sludge, and capable of achieving compactness of sedimentation equipment, increase in the amount of treated water in the existing sedimentation equipment, and high performance of water quality improvement.SOLUTION: A wastewater treatment method including a biological treatment step, includes a solid-liquid separation step in a subsequent stage of the biological treatment step. The wastewater treatment method includes adding a coagulation auxiliary agent to sludge drawn from the solid-liquid separation step in a subsequent stage of the biological treatment step or concentrated sludge obtained by concentrating the sludge, and then returning the sludge or the concentrated sludge containing the coagulation auxiliary agent to the biological treatment step.SELECTED DRAWING: Figure 5 【課題】返送汚泥に凝集補助剤を使用することで、固液分離工程で優れた凝集処理効果、処理水水質の向上と、固液分離性の向上を得ることができ、沈殿装置のコンパクト化や既存沈殿装置における処理水量の増加や、水質向上の高性能化が達成できる排水処理方法を提供すること。【解決手段】生物処理工程を含む排水処理方法であって、前記排水処理方法は前記生物処理工程の後段に固液分離工程を含み、前記生物処理工程後段の固液分離工程から引き抜かれる汚泥又は当該汚泥を濃縮した濃縮汚泥に凝集補助剤を添加した後に、前記生物処理工程に、前記凝集補助剤を含む前記汚泥又は前記濃縮汚泥を返送することを含む排水処理方法。【選択図】図５