Clogging of a limestone fracture by stimulating groundwater microbes

Biological clogging is promoted in aquifers either to contain or to remedia te groundwater. In this study. an apparatus able to detect small changes in hydraulic conductivity (K) was developed to measure the clogging of a sing le fracture in limestone, following microbial stimulation. The fracture had a 2.5 mm(2) section and was 50cm long. Prior to the inoculation of the lim estone, the sequencing ol representative clones from 16S rRNA gents isolate d from groundwater, showed significant affiliation with Cytophaga spp., Arc obacter spp. and Rhizobium spp. These bacteria are known to secrete extrace llular polymeric substances and form biofilms. When nutrients were added to the inoculated limestone, a decrease in K occurred after 8 days, reaching 0.8% L of its initial value after 22 days (K-n = 330 cm min(-1)) This study should that a stimulation of Indigenous microbes from groundwater effectiv ely clogged a macrofracture ill limestone. suggesting the potential applica tion of biobarriers in Fractured rock aquifers. (C) 2001 Elsevier Science L td, All rights reserved.