Biofilters
h is the transfer coefficient for the hydraulic film diffusion. The solution of the
equations is:
(5.28)
where A. is a dimensionless quantity which expresses the ratio between hydraulic
film diffusion and biofilm diffusion corresponding to:
The result is shown in Fig 5.6. Hence there is a soft transition between the pure
hydraulic film diffusion, which corresponds to a first order reaction, and the half
order reaction for the biofilm.
For the first order reaction in the biofilm, a corresponding condition for the flux
through the area can be set up:
(5.29)
but the order of reaction will in any case be a reaction of first order, only reduced by
the diffusional limitation. In this case it may thus be difficult to distinguish between
the two kinds of diffusional limitation.
Fig5.6
~=)1+ 1
{I_
k112AS 112
4A. 2
2A.
1.0.------,,---,-----,
10" 1
10 1
hydraulic film I half order
diffusion
reaction
1.0
2.0
A.=.....!Ls,/2
k112a
3.0
The transition between dominant hydraulic film diffusion and dominant half order
heterogeneous biofilm reaction.
155