>Exercises on  start and control of a chemostat.

 Open the SIMSPEC-file chemostat_dyn and train on starting and controlling specific growth rate and biomass concentration in a chemostat.

1. Why was there a slight decrease in biomass concentration after start of the chemostat in the simulation with default values of chemostat-dyn? Can you adjust the initial parameters to get a faster steady state at the start?

2. Investigate the effect of recirculating some of the outlet biomass from the chemostat. The recirculation factor (delta) is defined so that the net outlet concentration of biomass is delta*X, where X is the concentration in the bioreactor.

Why do you think cell (sludge) re-cycling is used in waste-water activated sludge processes? Discuss advantages and disadvantages (limitations).

Cell recycling as also been applied in some processes for biopharma products. Discuss advantages/disadvantages.

3. Compare the sensitivity of the state variables to a change of F  with the steady-state simulations made with chemostat_ss (D=F/V).

 Task nr 2 can also be illustrated (perhaps better) if you run  steady-state simulations with chemostat-ss with cell recycling.