To test how the addition of rbCOD would affect staging, the treatment train created from the design methodology had 50 mg rbCOD/L added to its influent. Because of the increase in oxygen demand, each reactor in the treatment train with 50 mg rbCOD/L had its membrane air increased by 0.5 g O₂/g COD. This design was simulated, and its results are compared to the design without exogenous COD in Table 3. In the first stage, the addition of COD and the increased air loading rate decreased the total ammonia concentration by 1.13 mg N/L and total nitrogen effluent concentration by 2.62 mg N/L. At an influent C:N ratio of 1.0, the nitrate that was previously produced by NOB and AMX was completely reduced to nitrogen gas by heterotrophic denitrifying organisms, reinforcing the results observed in Figure 4, and the increased air loading to the membrane enabled increased nitrification of total ammonia. The first stage also accounted for 73% of the rbCOD removal in the treatment train. The second stage had a slightly higher C:N ratio of 1.13, as the total ammonia removal rate was larger than the rbCOD removal rate in the previous stage. The removal rates of total ammonia and rbCOD were lower in this stage due to having smaller effluent concentrations, and the net improvements in the total nitrogen and total ammonia concentrations between the two trains slightly decreased by 0.95 and 0.73 mg N/L, respectively. Finally, the third stage had the lowest rbCOD and total ammonia removal, resulting in a combined improvement of 0.55 and 0.17 mg N/L for the total nitrogen and total ammonia concentrations. 98% of the rbCOD was also removed from the influent. In summary, adding COD to a staged PNA MABR treatment train increased the total nitrogen and total ammonia removal, since the C:N ratio was below 2.0 in every reactor. Most of the benefits resulted from the first stage which had the largest AMX specific growth rate, and heterotrophic denitrification was able to reduce the produced nitrate from NOB and AMX to nitrogen gas.