Modeling Tools for Environmental Engineers and Scientists

CC = in –(t t 0 )k C t in0 k– C 0 t 0 (t e –kt (5.6)t 0 )where t 0 = V 0 /Q and C 0 is the concentration remaining in the reactor at t = 0.While the final result is difficult to interpret in the above form, a plot of C vs.t can provide more insight into the dynamics of the process. An Excel ® modelof the process is presented in Figure 5.1. A complete model for a biologicalSBR with Michaelis-Menten type reaction kinetics is detailed in Chapter 8,where the profiles of COD, dissolved oxygen, and biomass are developedemploying three coupled differential equations.5.3.3 COMPLETELY MIXED FLOW REACTORSCompletely mixed flow reactors (CMFRs) are completely mixed withcontinuous inflow and outflow. CMFRs are, by far, the most common environmentalreactors and are often operated under steady state conditions,i.e., d( )/dt = 0. Under such conditions, the inflow should equal the outflow, whilethe active reactor volume, V, remains constant. A key characteristic of CMFRs isthat the effluent concentration is the same as that inside the reactor. CMFRs canFigure 5.1 Concentration profile in an SBR during the fill phase.© 2002 by CRC Press LLC