Nitrogen removal efficiency of UMBR/Oxic Process was evaluated on various conditions and with numerical analysis methods. The effect of COD/N ratio was observed to confirm the nitrogen removal ability at low COD/N ratio. And in order to find the optimal operating condition, internal recycle ratio and stirring speed in UMBR were varying. As numerical methods, COD and nitrogen mass balance, and process simulation were used.
It was confirmed that UMBR/Oxic Process could remove high nitrogen at low COD/N ratio. The nitrogen removal efficiency was 59.1%, 72.5%, and 75.9% at COD/N ratio of 3, 5, and 7, respectively. The reason is that denitrification occurs quickly by high concentration of microorganism in UMBR. As internal recycle ratio increasing from 100% to 400%, nitrogen removal efficiency also increased from 69.5% to 82.9%, and if a main purpose is nitrogen removal, the optimal internal recycle ratio is 300%. However the effect of stirring speed was not observed. and COD and nitrogen mass balance did not show any tendency as varying conditions.
In this study, in order to simulate SS concentration distribution in UMBR, secondary settling tank model was applied. Consequently the simulation results showed good agreement with the experimental results. And UMBR model that was applying ASM3, could simulate well.