E-Andrew Sindt Creative Component S11.pdf

Percent removala linear trend from anaerobic/oxic periods of 40-110 minutes with a more gradual slope from 120-140minutes. These results indicate that the modifications to the simulator parameter default values resultin a significant increase in the impacts of anaerobic period length on effluent phosphorus concentration.The differences in TP removal are probably due to the adjustment made to the aerobic P/PHA uptakeratio for the calibrated settings. The aerobic P/PHA uptake ratio was decreased by 19% meaning theamount of P stored per unit PHA oxidized under aerobic conditions was reduced. In other words, morePHA is required per unit P stored by PAOs. PHA is produced by PAOs during the anaerobic phase. Thedecrease to aerobic P/PHA uptake appears to have increased the importance of PAOs production of PHAduring the anaerobic phase since TP removal decreases as anaerobic period decreases.100959085807570656055500 50 100 150Anaerobic period length (min)Default TNDefault TPCal. TNCal. TPFigure 4.20 - Percent removal plot for BNR-S1 mode for oxic-anaerobic period length variations. Dashedline signifies default period length (90min). Oxic period length (min)= 180 (min) - anaerobic periodlength (min)Total nitrogen removal decreases with decreasing anaerobic phase length from 120- 40 minutes for bothsettings. This indicates that part of the anaerobic period is actually an anoxic period in whichdenitrification limits TN removal. This is probably related to the system’s ability to denitrify duringanaerobic conditions. A reduced amount of NO 3 - is converted to N 2 gas given a shorter anaerobic phase.From 120 minutes to 140 minutes, calibrated and default settings TN removals diverge. Calibrated TNremoval decreases when the anaerobic period is greater than 120 minutes. This is most likely due toincomplete nitrification during the oxic phase. Calibrated settings reduced the system’s ability to nitrifythrough reductions to AOB and NOB maximum specific growth rates.4.6.2 Anoxic-Oxic Phase VariationA plot of the results for combinations of anoxic-oxic period durations is given in Figure 4.21. Similar tothe anaerobic –oxic combinations, TN removal trends the same for calibrated and default settings whileTP does not. Increased TP removal for increasing anoxic period duration was observed for the calibrated66