Bioremediation of an aged hydrocarbon-contaminated soil by a combined system of biostimulation–bioaugmentation with filamentous fungi

This paper presents a study of the effect of a combined biostimulation–bioaugmentation treatment applied to a silty-loam soil polluted with 60,600 mg kg−1 of a complex mixture of total petroleum hydrocarbons (TPH), which comprises 40% aliphatic hydrocarbons (AH) and 21% polycyclic aromatic hydrocarbons (PAH). The bioaugmentation was performed with Rhizopus sp., Penicillium funiculosum and Aspergillus sydowii strains isolated from two aged soils contaminated with 60,600 and 500,000 mg of TPH per kilogram of dried soil. The native fungi were able to grow in a complex solid mixture of hydrocarbons of high molecular weight, after previous acclimatization in liquid culture. The three fungi mentioned above were able to remove, respectively, 36%, 30% and 17% more PAH in comparison with biostimulation alone. In the bioaugmented systems with Rhizopus sp. and A. sydowii, a positive correlation of respirometric activity (CO2 production) with hydrocarbon removal was obtained (R2=0.75; p(F)=0.001 and R2=0.78; p(F)=0.001, respectively); in contrast, P. funiculosum did not show any correlation. An interesting finding from this work is that two of these species of fungi had not previously been reported as being PAH-degrading.