Naslov
Visualization of bacterial biofilms in porous media using X-Ray and neutron microtomography

Autori
Ivankovic, Tomislav ; Rolland du Roscoat, Sabine ; Geindreau, Christian ; Martins, Jean M.F

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, prošireni sažetak, znanstveni

Skup
5th International conference on Tomography of Materials & Structures (ICTMS 2022)

Mjesto i datum
Grenoble, Francuska, 27.06.2022. - 01.07.2022

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Neutron tomography: X-ray tomography: biofilm: 3D porous media

Sažetak
1. Introduction A biofilm is a community of microorganisms encapsulated within a self-developed polymeric matrix (EPS) and adherent to a living or inert surface. It can be used to purify wastewater, either in activated sludge systems or by biofiltration. Problem arises when biofilm growth in porous media (gravel, sand or synthetic beads) and clogs the biofilter reducing its filtration rate and compromising water purification. To prevent such problems, there is a need of a reliable numerical model of biofilm growth in porous media, based on experimental data. Recently, X-Ray Microtomography (XT) was suggested as a tool for 3D visualization of biofilms inside a porous media, but reliable data are difficult to obtain due to experimental drawbacks mainly arising from the usage of contrast agents needed for biofilm detection. We aimed to overcome the difficulties by using a novel contrast agent, 1-chloronaphtalen, for XT and using advantages of Neutron Tomography to image biofilms without the contrast agent. 2. Materials and Methods Over few years we grew biofilms (3 different bacteria strain) in mini biofilter constituted of glass or PTFE filled with glass beads (1, 2 and 4 mm Ø), plastic beads (1, 5 mm), clay beads (4 mm) or grains of natural mineral zeolite (1 – 1.25 mm size fraction). The mini biofilter were imaged using either synchrotron (ESRF) or lab X-ray or Neutron tomography (ILL) at a pixel size of 10μm after the desired time of growth (1 to 12 days) with various nutrient flow rates. A contrast agent (1-chloronaphtalen) was injected in the columns prior to X-Ray imaging whereas no contrast agent was used for neutron imaging. Microstructural descriptors such as volume fraction and specific surface area were quantified using Geodict© software on 3D data set binarised with Fiji. The datasets were also used volume to evaluate numerically (Geodict©) time evolution of the effective diffusion and permeability tensors arising in macroscopic models. 3. Results and Conclusion The visual comparison of the biofilm localization obtained with both imaging techniques show comparable biofilm spatial distributions, showing that the use of 1-chloronaphtalene does not significantly disrupt the biofilm. The obtained neutron images remain too noisy to allow quantitative measurements whereas X-ray microtomography (coupled with the introduction of suitable contrast agents) exhibit high quality images allowing segmentation and therefore microstructural quantification. Moreover, the statistical of microstructural descriptors obtained on X-ray images for various growth time showed a statistically reliability provided the beads/grains are smaller than 2 mm. We will present the evolution of the microstructural descriptors and the physical properties as a function of time and link them. These results constitute one of the key elements to build reliable models of biofilm growth in porous media.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

POVEZANOST RADA