Chemostat: Washout Dilution Rate
A hidden Monod culture with known feed S₀. Sweep dilution D, watch steady biomass, and report the washout threshold D_w.
University / research· 22 min·Related simulator: Biophysics, Fluids & GeoscienceChemostat Microbial Growth
Goal
Determine D_w as the smallest dilution rate where the steady biomass X* vanishes.
Equipment
- Chemostat (unknown kinetics)
- Known S₀
- Dilution pump
- Optical-density meter
Experiment
Theory
In a Monod chemostat, μ(S) = μ_max S/(K_S+S) and washout occurs at D_w = μ(S₀). Below D_w a positive X* exists; at and above it the culture is lost. The bench hides μ_max, K_S, Y, X*, S* and any washout flag. S₀ is known. A live optical-density meter is the instrument.
Procedure
- Feed concentration S₀ is fixed and known. Kinetic parameters are hidden. You only change the dilution rate D.
- Watch the live biomass (optical density). Find the smallest D where X drops to zero. The bench does not label “washed out”.
- Record that D. Repeat the hunt at least 6 times (you may start from different D).
- Take the mean of the D column and compare with the reference.
Conclusion
The mean washout dilution agrees with μ(S₀). Main uncertainties: discrete D steps and judging X* = 0 by eye.