E-Andrew Sindt Creative Component S11.pdf

Percent deviaton in value (model-observerved)However, NO 3 -N concentration is negatively affected by decreasing the AOB maximum specific growthrate.40200-20-40-60-80NO2-NTPNO3-N-100-120-80 -60 -40 -20 0 20 40 60 80Percent adjustment of NOB maximum specific growth rateFigure 4.10 - NOB maximum specific growth rate percent error plot for regular mode (0% representsdefault NOB maximum specific growth rate value in simulator)4.2.1.5 Maximum Vesilind Settling Velocity DiscussionThe BioWin process simulation model includes three types of settling models: point, ideal, and fluxbased models. Point separation models require the user to specify the percent of solids captured on amass basis. The incoming solids are separated into two streams (thickened stream, and clarified stream)by a simple mass balance according to the user specified solids capture efficiency (BioWin user manual).The ideal model for separation is similar to the point model with one major exception; the ideal modeltakes volume into account whereas the point model does not.BioWin contains two flux-based separation models: Modified Vesilind and Double Exponential. Allmodeling for this report used the Modified Vesilind model. More information on the DoubleExponential model is included in the BioWin user manual. The Modified Vesilind flux-based separationmodel applies mass balances in a layered approach, focusing only on the vertical movement of solids.Figure 4.11 shows a representation of how BioWin implements a layered approach in the ModifiedVesilind settler model. There are essentially three different zones in the settling tank: the zone abovethe feed zone, the feed layer, and the zone below the feed layer. Influent flow will disperse to zonesabove and below the influent feed layer. Gravitational settling pulls solids down across all layers. Thesettling velocity in a given layer is calculated using equation 7.50