Abstract:Although orbal oxidation ditch has been widely employed in our country, it removal efficiency of nitrogen was very low. Based on monitoring and analyzing operation data of orbal oxidation ditch, it was found that highly dissolved oxygen concentration, which inhibited the denitrification process as the main cause for the low nitrogen removal efficiency of the process. Therefore, reducing the number of aeration disc is the most flexible approach for effectively lowering the dissolved oxygen concentration in the orbal oxidation ditch system and improving the nitrogen removal efficiency. By reducing the number of aeration disc, the average concentration of dissolve oxygen in ditch reduced to 0.20mg/L from 0.51mg/L, and the nitrogen removal efficiency was increased to 70%, compared with 40% nitrogen removal efficiency last year.