Inoculation of contaminated subsurface soils with enriched indigenous microbes to enhance bioremediation rates

Abstract

The inoculation of subsurface soils with enriched indigenous microbes to enhance bioremediation is described. The technique, designed to rapidly increase subsurface populations of specific microorganisms, is tested in laboratory soil columns using benzene, toluene and xylene as organic target compounds and a natural aquifer sand as a subsurface medium. A short biologically active carbon adsorber is demonstrated to be an efficient reactor system for the growth, acclimation and enrichment of indigeous microorganisms for re-inoculation purposes. Empty-bed reactor contact times of approx. 40 s are shown to be sufficient for continuous production of effluent streams of enriched indigenous microbes for re-inoculation. The ability of the technique to rapidly increase populations of such microbes to levels above 105 cells g-1 of dry solids in the previously uncontaminated aquifer sand studied is shown to result in enhanced rates of in situ degradation of the target hydrocarbons over a broad range of concentrations, from 25 to 9000 [mu]g l-1.