Abstract: In treating organic-containing wastewater by a biological treatment in a stage prior to a advanced treatment such as membrane separation or the like, the amount of the biological metabolites produced in the biological treatment step is reduced to reduce the amount of the organic substances flowing into the advanced treatment step in a latter stage, thereby making the advanced treatment stable and efficient and efficiently recovering treated water of high quality. Water anaerobically biologically treated in an anaerobic reaction tank 11 including an acid production tank 11A and a UASB reaction tank 11B is subjected to a coagulation treatment and then to solid-liquid separation in a No. 1 sedimentation tank 14. The resultant separated water is aerobically biologically treated water is subjected to a coagulation treatment and then to solid-liquid separation in a No. 2 sedimentation tank 24.

Abstract: In treating organic-containing wastewater by a biological treatment in a stage prior to a advanced treatment such as membrane separation or the like, the amount of the biological metabolites produced in the biological treatment step is reduced to reduce the amount of the organic substances flowing into the advanced treatment step in a latter stage, thereby making the advanced treatment stable and efficient and efficiently recovering treated water of high quality. Water anaerobically biologically treated in an anaerobic reaction tank 11 including an acid production tank 11A and a UASB reaction tank 11B is subjected to a coagulation treatment and then to solid-liquid separation in a No. 1 sedimentation tank 14. The resultant separated water is aerobically biologically treated in an aeration tank 21, and aerobically biologically treated water is subjected to a coagulation treatment and then to solid-liquid separation in a No. 2 sedimentation tank 24.