REMEDIATION OF PERSISTENT ORGANIC POLLUTANTS USING A NOVEL TWO-PHASE SOIL WASHING BIOSORPTION PROCESS ALBERT L. JUHASZ ∗ , EUAN SMITH, JULIE SMITH and RAVENDRA NAIDU CSIRO Land and Water, PMB2 Glen Osmond, S.A., 5064 Australia ( ∗ author for correspondence, e-mail: Albert.Juhasz@csiro.au, fax: +618 8303 8572) (Received 14 December 2001; accepted 7 May 2002) Abstract. A two-phase soil washing biosorption process was developed for the remediation of p,p ′ - DDT-contaminated soil. The process involved desorption of contaminants from soil using dilute primary alcohols (40% 1-propanol) followed by contaminant removal from cosolvent solutions using fungal biosorption. Bench scale remediation studies were preformed to simulate ex situ (recycling ex- periment) or in situ (soil column study) treatment strategies. Both systems were effective at cleaning the soil to below Australian regulatory p,p ′ -DDT levels. After 50–80 hours of soil washing, over 93% of p, p ′ -DDT was removed from the soil (990 mg kg −1 to <65 mg kg −1 ) using either of these methods. p, p ′ -DDT was removed from the cosolvent phase by sorption onto the fungal biomass. This resulted in only low levels of p,p ′ -DDT remaining in the cosolvent solution (<1.5 mg l −1 ). The application of both treatment strategies resulted in the rapid clean up of p, p ′ -DDT-contaminated soil and the potential to recycle cosolvent solutions. The ability to recycle cosolvent solutions provides a mechanism for cost reductions of the remediation strategy. Keywords: biosorption, cosolvent, DDT, 1-propanol, remediation, soil washing 1. Introduction Over the past 10–15 years, bioremediation has gained acceptance as a viable technology for the clean up of a number of organically contaminated matrices. The main advantage of utilising the metabolic capabilities of microorganisms for the clean up of contaminated soil or water is the economics of the process. Bioremediation is considered an economic clean up strategy if clean up time is not a limiting factor. Although petroleum hydrocarbons, BTEX, low molecu- lar weight PAHs etc. are amenable to bioremediation (Cerniglia, 1992; Atlas and Atlas, 1991), some chlorinated pesticides, such as 1,1,1-trichloro-2,2-bis-(p- chlorophenyl)ethane (DDT), are highly resistant to microbial attack (Aislabie et al., 1997). Bioremediation of p,p ′ -DDT-contaminated soils has generally been un- successful due to the recalcitrant properties of the compound i.e., low aqueous sol- ubility, high hydrophobicity, high degree of chlorination. When degradation does occur, however, p,p ′ -DDT degradation rates are extremely slow and the resultant The CSIRO’s right to retain a non-exclusive royalty free licence in and to any copyright is acknowledged. Water, Air, and Soil Pollution: Focus 3: 233–242, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands.