| 摘要 |
PURPOSE:To decrease BOD components and to decrease the load in a secondary treatment stage by subjecting night soil to an anaerobic digesting treatment, discharging the liquid in a digesting tank under full agitation, adding a flocculating agent thereto to form a floc and dehydrating solids. CONSTITUTION:Night soil is subjected to a pretreatment such as settling of grit in a pretreating device 1. If necessary, an iron salt is added thereto in a mixing tank 2, then the night soil is introduced into a digesting tank 3. After the night soil is subjected to an anaerobic digesting treatment in the tank 3, the night soil is discharged in the form of the liquid mixture consisting of digested sludge and reparated liquid under full agitation. The discharged liquid mixture is transferred into a mixing tank 4, where a flocculating agent is added to the mixture; thereafter the mixture is fed to a dehydrator 5 such as centrifugal dehydrator, whereby the same is dehydrated. The dehydrated cake formed by the dehydration is incinerated. The separated liquid is fed to a secondary treating device 6 having an aerating means of an activated sludge method or the like and a settling means. Here, the liquid is subjected to a secondary treatment consisting mainly of BOD removal, and the treated water is discharged to the outside of the system. |
