Modeling the distribution of dissolved oxygen concentration in bioreactors of a leachate treatment plant

A necessary condition for proper functioning of the economically optimal biological reactor is the correlation between the flow rates of introduced oxygen with the consumed in the metabolic degradation of organic materials. Modeling of physical, chemical and biological processes of aeration tanks in leachate treatment plants is difficult because they are very complex. In the aerobic biological reactor, the oxygen consumption varies over time and space due to the unevenness of the influent load of biodegradable organic substances or
change the kinetic relationship between the growth rates of biomass and
elimination rates of the substrate.
Biological reactors for the treatment of leachate considered, provided
with two types of air dispersion devices placed at the bottom of the
basin(perforated pipe in the first bioreactor and porous diffusers in second
bioreactor), was created using Flex PDE, two models.
Modeling the dissolved oxygen concentration in the leachate, was aimed
to optimize the process of mass transfer of oxygen from air into water, having
an important role in minimizing the operating costs of facilities, energetic
optimization of aeration systems and an improving on performances for
leachate treatment.
The models were designed for a two-dimensional domain, and to
appreciate the distribution of oxygen concentration for both bioreactors
equipped with different lenses (perforated pipes and porous diffusers).
Numerical integration of the dispersion equation for the analyzed case was
adapted by running a program written by the user using Flex PDE software
package. The phenomenon of mass transfer at the interface was found by a
continuous flow conditions required in the surface pores through which
compressed air is blown.
The results shows that the use of air insufflation made from porous
diffusers is more efficient, compared to the system made from perforated pipes,
the required value of the concentration of dissolved oxygen reached in a time
period much lower, similar to that encountered in practice.