Mecaflu team

Reagent transfer, rheology and environmental processes

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Research conducted under the theme Reagent Transfer, rheology and environmental processes includes three items:

  • The dynamics of hydro-systems;
  • Environmental process engineering;
  • The rheology of complex fluids.

Modeling of the mechanisms of action of contaminants in hydro-systems

Modeling of the action mechanisms of contaminants within hydro-systems is a response to Directive 2000/60 / EC, or "Water Framework Directive" defining a community water management and protection policy. Its Article 16 specifies that actions must be taken "against the water pollution by certain pollutants or groups of pollutants presenting a significant risk to or via the aquatic environment, in particular the risks to which the waters are used as drinking water ".

In this context, one of our objectives is to optimize the processes of depollution of urban effluents (domestic and rainfed). The decontamination structures we are studying range from the so-called conventional systems to alternative techniques consisting essentially on rustic processes.

The technical and scientific locks are, on the one hand, the phenomenological understanding of the biotic and abiotic processes within the hydro-systems and on the other hand, the understanding of the nature of the contaminants. The fate of heavy metals and polycyclic aromatic hydrocarbons resulting from urban discharges in rainy weather is one of the focal points of research carried out at the Ostwaldergraben field experimental site. Similarly, we are interested in the identification and quantification of pharmaceutical residues whose induced stresses on fauna and flora are still poorly known.

480px|center|thumb|Lagoon and massif filtering

Modeling the operation of secondary clarifiers

The optimization of the operating models of secondary decanters used in sewage treatment plants requires an accurate experimental characterization of the sedimentation of the activated sludge. Our research focuses initially on the decantation of sludge by means of a non-invasive ultrasound experimental method for the measurement of velocity and concentration fields. In a second step, the experimental datasets thus acquired allow the development of dynamic models taking into account the rheology of the sludge as well as the different sedimentation regimes.


Rheology of complex fluids

The study of the rheology of complex fluids is mainly based on two axes. The first concerns the characterization of the rheological properties of complex (threshold and thixotropic) fluids. The influence of different additives on the rheological behavior of colloidal suspensions such as bentonite suspensions and polymer solutions is studied. The effect of temperature on the variation of viscous, elastic, viscoelastic, thixotropic, physicochemical properties is studied.

The second axis focuses on methanation. The technology chosen is dry anaerobic biodigestion. Through this study, the aim is to optimize the production of biogas by controlling the composition of the substrate by the nature of the medium, the size of the solid particles, the moisture content, the rheological (in particular the viscosity) and physico-chemical properties, the variation of the temperature, which are all factors conditioning the production of biogas and its composition.


To answer these questions, we have:

  • Developed numerical models of flow and reactive transfer within biological treatment channels, with fixed (porous medium variably saturated) or free (biological reactor, clarifier, etc.) cultures;
  • Designed laboratory pilots dedicated to the study of hydro-systems;
  • Conducts in-situ tracing experiments to characterize the operation of treatment facilities;
  • Developed sampling strategies adapted to intensive and extensive in situ treatment channels;
  • Developed a method for estimating plant evapotranspiration incorporating measurements from meteorological stations and an IRGA system.

Furthermore, work has recently been started with colleagues of Strasbourg on the engineering of polymerization processes to improve the modeling and simulation of radical polymerization in continuous and discontinuous reactors. We have thus developed an exact analytical model of radical polymerization taking into account the effects of frost and temperature in closed reactor. This analytical solution was then coupled to CFD simulations and we were able to test this model in different configurations.

480px|center|thumb|Tracing on a valley

Experimental means

  • PACELeS (Liquid and Solid Sample Analysis and Packaging Platform)
  • Rheological loop
  • Ultrasonic transducers
  • Laser Diffraction Granulometer
  • Rheometers
  • Field fluorimeters
  • Field physico-chemical sensors
  • Portable automatic chilled or non-refrigerated samplers
  • Double-ring infiltrometer
  • Auger