Monitoring of biofilm growth inside the porous media in real-time by using neutron tomography

Short term visitor's project

Biofilters are more and more used for the treatment of industrial or urban waste effluents. They consist in a fixed bed made of a granular porous matrix through which the liquid effluent flows, supplying nutrients to a population of bacteria which forms a water-purifying biofilm on the surface of the solid matrix.

The main goal of this project is to characterise and quantify the evolution of the 3D microstructure of this bacterial biofilm growing in a porous media. To overcome the lack of 3D measurements and to improve 3D modelling of biofilm growth, there exists only a few experimental study using Synchrotron or laboratory X-Ray Microtomography. However, these studies can neither give access to the temporal evolution of the biofilm’s growth on a single experiment due to radiation damage induced by X-ray, nor to the spatial repartition of the biofilm in the height of the biofilter due to several limitations coming from the contrast agent required when using X-ray.

The aim of the present study, based on the use of neutron tomography which can overcome the previous limitations, is twofold:

1. the characterisation of the interface of the biofilm (bacteria + exopolymeric matrix) with its neighbourhood (fluid and bead). This will give us access to the shape, the spatial distribution and sizes of the biofilm at the pore scale inside the whole biofilter.

2. the study of the evolution of the aforementioned biofilm characteristics at different stages of its development (days of growth) and according to the operating conditions (flow rate, nutrient conditions) on a single biofilter and in real-time.