Immobilized with PVA,sodium alginate and activated carbon,both Zoogloea sp. and Fusarium sp.strains could degrade phenanthrene and pyrene efficiently.The optimal carrier was made of 100ρ·g -1 L PVA,5 sodium alginateρ·g -1 L and 50 activated carbon ρ·g -1 L.The degradation rates of phenanthrene and pyrene in 10 days were 87.48% and 75.34% by the immobilized bacterium,37.04% and 20.85% higher than those by the free bacterium,and the rates in 15 days were 84.36% and 74.87% by the immobilized fungus,5.35% and 11.23% higher than those by the free fungus.
The biodegradation of most PAHs with high molecular weight is carried out by means of cometabolism. The development of the theory about cometabolic degradation is reviewed in this paper, and the achievements on the cometabolic degradations of PAHs are also summarized. It is demonstrated that glucose, biphenyl, organic acids and mineral oil could be used as cometabolic substrate to enhance the degradation rate of PAHs, and there are complex interactions in the microbiological degradation process among different PAHs. Some low molecular PAHs could serve as cometabolic substrate, which could also be used to enhance the transformation rate of high molecular weight recalcitrant PAHs. To achieve the cometabolic degradation of the PAHs in the soils, the following problems must be solved: the screening out of efficient degradative strains, the selection of the appropriate cometabolic substrate, the addition of surfactant if necessary and the optimization of operational parameters with the contaminated soils. These problems are the important parts of the project for the cometabolic degradation of PAHs in the soils.
