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.
With phenanthrene and pyreneas as test pollutants,four control factors(inoculation amount,water soil ratio, air flux and temperature) were selected to study the microbiology degradation control of PAHs in bio slurry reactor.Results indicated that at the test concetration the optimum parameters for obtaining the maximum degradation rates for phenanthrene and pyrenene are 5%～10% in incubation amount,2∶1 for water/soil ratio,0 06～0 1m 3·h -1 for air,and 30℃ in temperature,degradation rate was the highest in this condition with the values 98 9% and 84 2% phenanthrene and pyrnene respectively on the 15th day.These parameters provide useful basis for large scale engineering to treat soil PAHs by means of bio slurry reactor.
Bio remidiation possibility of soil contaminated by oil mud,and the optimization of the technological conditions for the bioremediation were studied using bio slurry reactor in pilot scale.A group of micro orgamism which are addicted to oil and rich in both amount and species in oil contaminated soil was discovered. Fusarium sp.was screeded for its high crude oil degradation rate.Oil mud with high concentration of crude oil was mixed with clean soil in the ratio of 1∶1,and 10% complex organic fertilizer and inorganic nutrients in proper proportion were added before treatment. Particularly,microbiological agent of indigenous superior strains for crude oil degradation was applied. Other operative conditions of the reactor included 25℃ for temperature and intermittent venting. After 75 days operation,the contents of total petroleum hydrocarbon (TPH) in oil mud was decreased from 43.39 to 0.72g·kg -1 .The degradation rate of TPH reached 98.3% under optimal conditions.
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.
