Abstract
Ozone-added activated sludge process is one of the modified processes for reduction of excess sludge production. Although ozone-added activated sludge system was originally developed in order to reduce excess sludge production, it is expected that its direct ozonation to activated sludge can also remove some biorefractory compounds by chemical oxidation, and the treatment efficiency and stability can be increased as results. In this study, phenol was used as a biorefractory compound in wastewaters and behaviors of EDCs at sludge ozonation were also investigated in order to evaluate several functions of ozone-added activated sludge process. The treatment characteristics were investigated with lab scale experimental setups. It is made clear that direct ozonation to activated sludge within a range of 15 mgO3/gSS does not inhibit biological activities and biorefractory compound(phenol) is promptly removed chemically. On the other hand, the experimental case without ozonation can not remove phenol quickly and biological activity is inhibited by existence of phenol. These results suggest that the system can treat wastewaters which contain biorefractory compounds effectively and stably besides both bulking control and low excess sludge production.
