Soil Washing for Remediation of Non Volatile Hydrocarbon Polluted Soils

This paper illustrates the possibilities of applying what is essentially a physical soil-washing technique for treatment of soil contaminated by semi-volatile hydrocarbons in order to reduce the level of pollution to that permitted by Italian regulations. The ground around a factory producing lubricating-oil additives consists of silty-sandy soils, which have long been contaminated by heavy hydrocarbons, especially branched alkyl benzenes and naphthalene derivatives. Pollution is particularly marked in some zones (hot-spots) where Total Petroleum Hydrocarbon (TPH) values are as high as 7000ppm. The hydrogeological characterization showed the presence of a gravely soil in a sandy/silty matrix, with big stones making preferential paths to the water circulation. The permeability is 10m/s and the water-table occurs at about 3m below ground level. After laboratory and pilot-scale studies on representative samples of in-situ soils with TPH between 2700 and 7000ppm a flowsheet is proposed for reducing TPH values below the acceptable limits in Italy, namely 700ppm for hydrocarbons with more than 12 carbon atoms and less than 250ppm for those with fewer. Recovery of remediated soil to be returned to the site is around 90%. © 2002 SDU. All rights reserved.