REDUCED PERMEABILITY IN GROUNDWATER REMEDIATION SYSTEMS - ROLE OF MOBILIZED COLLOIDS AND INJECTED CHEMICALS

The success of pump-and-treat or in situ remediation of contaminated a quifers depends in part on the ability to maintain the permeability of the aquifer, withdrawal wells, and delivery systems at a reasonable c ost while moving significant quantities of water. We have considered o ne case in which a previous bioremediation effort at Eglin Air Force B ase in Florida was halted due to delivery system failure attributed to iron precipitation. Laboratory solutions and groundwaters from the Eg lin site were passed through packed columns of aquifer material also o btained from the site. We investigated the effects of iron oxidation s tate and concentration, the presence of colloidal materials, and the e ffects of nutrient solutions and hydrogen peroxide in the feedwater on the permeability of the aquifer material. Our experiments show that r educed permeability of the aquifer near delivery systems was likely ca used by the re-deposition of colloids mobilized in the aquifer and by gas binding due to bacteriologically catalyzed hydrogen peroxide decom position rather than to iron precipitation.