Durability of bioclogging treatment of soils

Abstract : A study of the clogging of two soils, a sand with grains ranging from 0.4 to 4 mm, and a gravel with grains ranging from 1 to 10 mm, was carried out by feeding the bacteria initially present in the soils. The focus of this research is to study the durability of bioclogging. The results showed that clogging occurred quickly after the injection of nutrients. The soils were subjected to gradient increases and a critical hydraulic gradient i(crit) (corresponding to the gradient for which unclogging occurred and an increase in the flow of water was observed) was determined. It is equal to 0.8 for the sand and to 0.06 for the gravel. The durability of bioclogged soils was also studied by performing 10 to 30 hydraulic gradient cycles between the initial value and i(crit)/2. For the sand, the permeability increase after the cycles was very low. In contrast, in the gravel, unclogging occurred very quickly, highlighting the influence of grain size and materials grading. (C) 2016 American Society of Civil Engineers.