Bioavailability of Xenobiotic Organic Compounds to Remediate Soil Containing Clay Fractions

Abstract

The bioavailability of xenobiotic organic compounds (XOC) is related to their partition among the solid, liquid and gaseous phases of soil components. Sorption/desorption, volatilization, diffusion and dispersion phenomena control the partitioning of XOC. Engineering experience showed that the presence of significant clay fraction in contaminated soils warrants specific considerations during the bioremediation process, due to the characteristics of the clay materials, their high specific surface area and surface charge. It was demonstrated that sorption of trichloroethylene (TCE) increased with the amount of clay and organic matter fractions. The highest TCE removal rate was observed in the presence of sorptive materials (clay and organic matter) where mixed methanotrophic cultures were added to the slurry reactor. It was concluded that clay as well as organic and inorganic amorphous materials associated with clay, can play positive role and may allow the initiation of biodegradation in cases where organic compounds were found at levels exceeding the toxic levels. It was also demonstrated that clay mineral content affects all principal biomass growth factors in soil, i.e. water content, temperature effects, pH, nutrients’ and electron acceptors distribution. Clay minerals also influence the production and activity of several enzymes. The formation of clay aggregates presents the uniform distribution of nutrients, water and electron acceptor. The aggregation decreases the access of microorganisms to substrate.