I think bioligical reactors ...

I think bioligical reactors – like wastewater teatment basins – mostly are designed trough empirical arguments. The mentoined F/M relation, or the age of sludge are parameters for characterising the biological processes. It can be true, but I learned from the bankfiltering radically different views:

1. The biological cleaning happens in biofilms. The biofilm is the living space of bacterias and is adhered on solid biofilmhoder surface (sand by bankfiltration, flocks by wastewatertreatment).
2. The cleaning process can be divide in two subpocesses.
   1. First we have to transport the substrate to and into the biofilm. This is a „logistic” function described by physical (hidrodinamics and diffusion) parameters.

The nondimensional Pe-number and the also nondimensional L/d geometric relation are the main parameters for this subprocess, and trough these parameters can be designed (determined the geometry) biological reaktors.

The substattransport is a requisite, but it’s not enough. We need also great surface for our bacterias inside the reactor. Small Peclet-number (Pe~10) would be satisfied this two needs.

The biodegration depends from Pe-number by inversely way (1/Pe).

1. After that the biodedration happens in the biofilm, wich has a bio-chemical character. The Michaelis-Menten enzyme- and the Monod qrowth-kinetics describes this process. pH, Ne (Nernst-factor, the nondimensional redox potential) are the main „climatic” parameters here.

I think to influence the bio-chemical process – for increasing the efficiency of cleaning – it can be only setting trough the climatic parameters, because the pattern of the substrate and bacteria(enzyme) must be the same.