drbitboy DMD. What about the dead time? You graphs do not show any dead time.
Umm, I don't know what you are talking about. Maybe you are confused about the system: there is no dead time - or at least there is an immediate effect - in the system response to either changes in aeration or changes in flowrate; the dead time comes in mainly with the response to influent DO levels.
We can debate about how accurately my models represent the real system, because I chose to ignore several effects, but actually, no, there is no doubt that my graphs do show deadtime:
The first image below from the PDF I attached a dozen posts ago; the dead time in the effluent DO (top magenta line, bottom [Cell DO] figure in the top image) response to a change in the influent DO (bottom blue line, bottom figure) is obvious in the green-highlighted area.
The second image below, from the floating-point control simulations, shows a response to simultaneous changes to both influent DO (bottom blue line in bottom [Cell DO] figure in the bottom image) and influent flowrate (top figure). The modeled effluent DO (top magenta line, bottom figure) starts dropping immediately (at Time = 25600s), though slowly, from the increase in flowrate, to which the control starts responding, and then at about 26600s, i.e. one dead time later, there is a second sharper drop as the decrease in influent DO reaches the effluent cell.