E-Andrew Sindt Creative Component S11.pdf

Percent deviation (predicted-observerved)100500-50TNNO2-NNO3-NNH3-N-100-150-80 -60 -40 -20 0 20 40 60 80Percent adjustment of AOB maximum specific growth rateFigure 4.7 - AOB maximum specific growth rate percent error plot for regular mode. NH 3 valuescorresponding to -50% and -60% simulator parameter values are 850% and 1400%, respectively. (0%represents default AOB maximum specific growth rate value in simulator)4.2.1.4 Nitrite Oxidizing Bacteria (NOB) Maximum Specific Growth RateNitrite oxidizing biomass (NOB) maximum specific growth rate results are presented in Figure 4.8. Fordecreasing values of NOB maximum specific growth rate, a sharp increase in NO 2 - -N concentrations anda significant decrease in TP concentrations were observed in the effluent. The increase in nitriteconcentrations is expected because if the growth rate of the bacteria responsible for converting nitriteto nitrate is significantly reduced, fewer of those bacteria will be present to carry out the reactions and agreater concentration of nitrite will result. This is similar to the critical SRT concept discussed in theprevious section (4.2.1.3) for AOB maximum specific growth rate. A proportional decrease in NO 3 - -Nconcentration is observed as the NO 2 - -N concentration increases. A proportional decrease in TPconcentration is also observed for an increasing NO 2 - -N concentration. The cause of this relationshipbetween TP concentration and NOB maximum specific growth rate is not known.No significant changes were observed in the effluent parameters as NOB maximum specific growth rateis increased beyond the default value. Similar to AOB maximum specific growth rate, this indicates thatthe simulator is achieving the maximum possible nitrification process efficiency by the AOBs at defaultsettings and at the 13 day SRT process operating point. No further improvements in effluent quality canbe made by increasing AOB maximum specific growth rate.48