Wastewater treatment facility explores treatment potential ammonia in its facilities. The aeration basin of this installation is a reservoir with baffles which can be modeled as an ideal PFR. The inlet flow of the installation wastewater treatment is 445,000 m3 /d with assumed ammonia concentration of 27 mg of NH3-N/L. The baffle tank has a volume of 27,000 m3 and a kinetics of constant ammonia elimination reaction of 8.7 L/(mg·d). Note that the reaction ammonia removal rate depends on both the ammonia concentration and the dissolved oxygen concentration, r = kCNH3CO2. Wastewater treatment plant plans to provide a constant dissolved oxygen concentration of 4 mg O2/L or 8 mg O2/L in the aeration basin to achieve an effluent ammonia target of 1.25 mg NH3-N/L. Apply a pseudo-first order THR equation for the baffle tank to determine the effluent ammonia concentrations at 4 and 8 mg O2/L. What O2 level is required to meet effluent ammonia requirements?