Abstract
The purpose of the study is to clarify the conditions of the factors of denitrification which are necessary for an improvement of nitrogen removal efficiency in the circulated anxic-aerobic submerged bed process. The denitrification proceeds in the first anoxic reactor as well as in inner parts of the attached materials in the second aerobic reactor. 17 series of experiments were performed treating an artificial organic wastewater in the bench-scale pilot plants. The conditions of DO, ORP, and the C/N ratio which have been known to influence the denitrification efficiency were investigated. A little quantity of DO which is transported from the settling tank with the recirculation of nitrified effluent influences the denitrification in the first reactor. The optimum range of DO in the second reactor was below about 4mg·l-1. The TOC/NOx-N ratio was needed above 2 for the progress of denitrification in the first and second reactors. On the basis of those conditions, the appropriate conditions of design factors such as the recirculation ratio, the TOC loading rate and the HRT for the progress of denitrification were clarified.
