Biological reactors are widely used to treat dissolved organic pollution in wastewater. In fact, this type of process offers very attractive Chemical Oxygen Demand (COD) abatement at low investment and operating costs.

Among the reactors commonly used in water treatment, biofilm reactors offer some interesting advantages over the classic "activated sludge" process (free bacteria in a perfectly stirred aerated reactor). Firstly, the biomass is highly concentrated in the reactor, with no impact on effluent viscosity (liquid phase), thanks to biofilm growth on a porous support with a high specific surface area. Secondly, the residence time of the biomass in the reactor (or sludge age) is long, even infinite. This offers the advantage of speciation and acclimatization of the biomass to the effluent. Finally, the biofilm structure of the biomass makes it more resistant to pollution shocks.

All these advantages lead to higher degradation yields in a smaller footprint.

The hydrodynamic behavior of this type of reactor has a major effect on biofilm growth and material transfer between the liquid, gas and solid phases. It therefore sets the framework for the biological kinetics implemented in the reactor.

For this reason, the team studies and develops these reactors using an approach that combines hydrodynamics and kinetics, in order to optimize the system and propose a global model for prediction and scale-up.

In these studies, the effluent is considered as much as possible as a secondary resource, and the concern to reduce the energy expenditure of the treatment is permanent.

To meet these objectives, the team is proposing new treatment methods:

-   water and waste recovery: biogas production (H2, CH4)

- implementing coupling between innovative processes: advanced biological-oxidation coupling 

- offering maximum degradation yields for carbonaceous and nitrogenous organic matter: simultaneous C-N treatment