Bioclogging in Porous Media: Effect of the Presence of Clay

International audienceIn this work, the interest was focused on the study of clogging and durability of soils clogged using the Biosealing® process. During this process, bacteria initially present in the soil are fed with an appropriate nutritive solution. The aim is to provoke phenomena resulting in a sharp permeability drop. The durability tests objective was to measure the effect of a progressive increase in hydraulic gradient values on the permeability of totally clogged samples. The grain size of the materials varies from 0.1 to 10 mm (permeability values between 1.1 10−2 and 10−5 m/s). The results showed that clogging occurs regardless of grain size distribution. However, longer time was needed to obtain total clogging for coarse materials. For the durability tests, the behavior is depending on the grain size. For coarse materials a drastic increase in the permeability was obtained when the hydraulic gradient was increased; however, no changes were observed for the fine materials in spite of the imposed high hydraulic gradient values. These results are due to the higher specific surface area accessible to the bacteria in the case of fine materials, whereas this area is lower for the coarse materials. In order to improve the clogging durability of the coarse materials, the nutrition solution and a clay suspension were injected alternatively. The clay presence reduces the treatment duration and improves the durability of coarse materials, especially for them presenting higher uniformity coefficient values. Analytical parameters monitoring like pH, electrical conductivity, redox potential and dissolved oxygen concentration were carried out to follow the bacteria activity