SINGLE-STAGE REMEDIATION OF CONTAMINATED SOIL-SLUDGE

Contaminated soil containing 3 wt. % hydrocarbons rich in polycyclic a romatic hydrocarbons (PAHs) has been cleaned to environmentally accept able levels by the use of the supercritical water oxidation system. Su percritical water oxidation is an emerging technology that exploits th e supercritical properties of water as a reaction medium. A combustion reaction takes place unhindered in the homogeneous supercritical wate r phase using oxygen or air as an oxidant. Since most organics dissolv e readily in supercritical water, the oxidation reaction can proceed a t very high kinetic rates. These kinetic rates allow for very short re actor residence times. The accelerated reaction makes supercritical wa ter oxidation an ideal form of treatment for site remediation of hydro carbon contaminated soil. Experiments conducted on the soil show a two fold beneficiation process, where hazardous material is extracted from the soil and completely destroyed by an oxidation reaction. The resul ting bottoms produce a clean soil with a residual hydrocarbon contamin ation of less than 200 ppm and a top gas stream rich in carbon dioxide and water thus establishing ''near-zero discharge condition'' of haza rdous substances. Preliminary results prove that the process can be ve ry effectively employed as an ultracleaning, ex situ, remediation tech nology that can readily be implemented on a mobile unit.