The biodegradation of polycyclic aromatic hydrocarbons (PAHs) (8.15mg PAHs kg−1 soil) in aged contaminated
soil by isolated microbial consortium (five fungi and three bacteria) during the incubation of 64 d is
reported. The applied treatmentswere: (1) biodegradation by adding microbial consortium in sterile soils
(BM); (2) biodegradation by adding microbial consortium in non-sterile soils (BMN); and (3) biodegradation
by in situ “natural” microbes in non-sterile soils (BNN). The fungi in BM and BMN soils grew rapidly
0–4 d during the incubation and then reached a relative equilibrium. In contrast the fungi in BNN soil
remained at a constant level for the entire time. Comparison with the fungi, the bacteria in BNN soils
grew rapidly during the incubation 0–2 d and then reached a relative equilibrium, and those in BM and
BMN soils grew slowly during the incubation of 64 d. After 64 d of incubation, the PAH biodegradations
were 35%, 40.7% and 41.3% in BNN,BMNand BM, respectively. The significant release of sequestrated PAHs
in aged contaminated soilwas observed in this experiment, especially in the BM soil. Therefore, although
bioaugmentation of introduced microbial consortium increased significantly the biodegradation of PAHs
in aged contaminated soil with low PAH concentration, the creation of optimum of the environmental
situation might be the best way to use bioremediation successfully in the field.