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CE5504 Surface Water Quality Modeling. Lab 1. Modeling 101. CE5504 – Surface Water Quality Modeling. Surface Water Quality Engineering. discovery. application. integration. fate and transport. decision support. Reactor Analogs. Plug Flow Reactor (rivers). Fox River, Wisconsin.
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CE5504 Surface Water Quality Modeling Lab 1. Modeling 101 CE5504 – Surface Water Quality Modeling
Surface Water Quality Engineering discovery application integration fate and transport decision support
Reactor Analogs Plug Flow Reactor (rivers) Fox River, Wisconsin Completely-Mixed Flow Reactor (lakes, bays, nearshore) Mille Lacs Lake, Minnesota CE5504 – Surface Water Quality Modeling
The Reactor Analog for Lakes Completely Mixed Flow Reactor CMFR CE5504 – Surface Water Quality Modeling
The Mass Balance • CMF Reactor Characteristics • completely mixed (Cout = C) • constant volume (Qin = Qout) CE5504 – Surface Water Quality Modeling
The Mass Balance • Control Volume • the system about which the mass balance will be computed. CE5504 – Surface Water Quality Modeling
The Mass Balance • Kinetics • growth • decay RXN RXN CE5504 – Surface Water Quality Modeling
The Mass Balance • Kinetics • 0 order reactions • rate is not a function of concentration Ct = C0 - k∙t k, mg·L-1·d-1 CE5504 – Surface Water Quality Modeling
The Mass Balance • Kinetics • 1st order reactions • rate is a function of concentration lnCt = -k∙t + lnC0 or Ct = C0·e-k·t k, d-1 CE5504 – Surface Water Quality Modeling
Writing the Mass Balance RXN 1st order decay CE5504 – Surface Water Quality Modeling
At Steady State 0 RXN 1st order decay At steady state, the source terms are equal to the sink terms and there is no net change in mass within the control volume. CE5504 – Surface Water Quality Modeling
Time Variable (analytical solution) flushing out building in CE5504 – Surface Water Quality Modeling
Time to Steady State Variable Noting that the hydraulic retention time, = V/Q and (Chapra, Sec. 3.3) or or, for 95% CE5504 – Surface Water Quality Modeling
Variability in and k CE5504 – Surface Water Quality Modeling
Review • Can you see any limitations to the analogs in Slide 3? • Can you identify 2 additional source terms for lakes in Slide 4? • Discuss the completely mixed and constant volume assumptions in Slide 5. • Develop an example of an inappropriately-defined control volume in Slide 6. • Provide some additional examples of growth and decay in Slide 7. • Show how a system acts to bring itself to steady state; see Slide 10. • In lab - • Determine half-lives of selected chemical species. • Compare response times of lake/chemical couplets. • Calculation of steady state concentrations. • Time variable solutions: kinetics and step function response. CE5504 – Surface Water Quality Modeling