Script > Ch 4
Physical, chemical and biological transformation
In the previous chapters, concentrations change in response to
transport processes, such as diffusion, advection, and
dispersion, and we have considered these processes in mass conserving systems.
Now, we would like to look at systems where the mass of a given species of interest is not conserving.
Processes that remove mass can be physical, chemical or biological in nature.
Since the total mass of the system must be conserved, these processes
generally change the species of interest into another species; thus, we will
call these processes transformation.
This chapter begins by describing the common types of
transformation reactions. Since we are interested in concentration changes, we review reaction
kinetics and derive rate laws for first- and second-order systems.
The methods are then generalized to higher-order reactions. Transformation is
then added to our transport equation for two types of reactions. In the first case, the reaction becomes a
source or sink term in the governing differential equation; in the second case, the
reaction occurs at the boundary and becomes a boundary constraint on the governing
transport equation. The chapter closes with an engineering application to bacteria die-off downstream of a wastewater