Restoration of contaminated sediments involves either mechanical removal of the sediment followed by treatment or in-situ treatment of the contaminants. Even after mechanical removal, considerable residues of the polluted material usually remain which require some form of in-situ treatment for eventual restoration. For in-situ treatment, conditions that appear to be rate determining are: (1) availability of oxygen; (2) availability of nutrients; and (3) nature of contaminants and sediment properties. There are significant variations in the redox potential of sediments as a function of depth. Aerobic bacterial biodegradation of PAHs is widely known and has been well studied. PAHs exhibit high octanol/water partition coefficient (KOW), which results in the accumulation of these compounds in fatty tissues with subsequent biomagnification in the food chain.

In this paper, a novel method of controlling the redox potential in contaminated sediments using semi-permeable synthetic membranes will be presented. The method allows in-situ biodegradation of PAHs in contaminated sediments while preventing the membranes from fouling. Experimental data will be presented on biodegradation rates of 18 PAHs ( 2 ring to 6 ring compounds) as a function of redox potential. The rate of biodegradation decreased with increasing ring size and decreasing oxidation potential. Experimental testing of the synthetic membranes showed that in-situ PAH degradation could be increased several fold by utilizing the membranes to increase the sediment oxidation potential. The membrane technology is widely applicable for in-situ biotreatment of contaminated freshwater and marine sediments. A detailed simulation model to estimate the required membrane area and treatment time will also be presented.