| 摘要 |
<p>PURPOSE:To omit the use of a sedimentation tank in a combined purifying tank and to make the purifying tank compact as a whole. CONSTITUTION:In a circulating type anaerobic and aerobic activated sludge treatment method wherein an anaerobic activated sludge tank and an aerobic activated sludge tank being a next stage treatment tank are mounted and sewage is subjected to purifying treatment while a liquid mixture of treated sewage is returned to the anaerobic activated sludge tank from the aerobic activated sludge tank, in such a state that the inflow of sewage to the anaerobic activated sludge tank is stopped, the transfer of the sewage from the anaerobic activated sludge tank to the aerobic activated sludge tank and the return of said sewage in the reverse course are stopped and the diffusion of air to the aerobic activated sludge tank is also stopped to set a stationary state in the aerobic activated sludge tank to settle the sludge in said tank. Subsequently, only the aforementioned return flow is generated to return the settled sludge to the anaerobic activated sludge tank and the sludge interface level in the aerobic activated sludge tank is lowered and, thereafter, the supernatant liquid in the aerobic activated sludge tank is discharged to the outside of the aerobic activated sludge tank to lower the water surface position of the sewage and, at the point of time when the sewage lowers to a definite water level, the treatment of sewage is again reopened.</p> |
