Assessment of the Hydrocarbon Degrading Abilities of Three Bioaugmentation Agents for the Bioremediation of Crude Oil Tank Bottom Sludge Contaminated Libyan Soil

摘要

Bioremediation is a widely used environmental friendly treatment method for petrogenic hydrocarbon contaminated soils but its application to the treatment of crude oil tank bottom sludge (COTBS) contaminated soil is limited especially in Mediterranean countries such as Libya. Therefore in this study, the hydrocarbon degrading abilities of three bioaugmentation agents Pseudomonas sp (4M12), Pseudomonas xanthomarina (4M14) and Arthrobacter nitroguajacolicus (1B16A) (isolated from COTBS polluted soils) applied as part of a biostimulation-bioaugmentation (BS/BA) strategy were assessed in COTBS contaminated Libyan soils. Biostimulated (BS) and natural attenuation (NA) microcosms were also set up for comparative purposes. Gas chromatograph mass spectrometer (GC- MS) analysis revealed a total soil petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAHs) content of 30,703 mg kg-1 and 13,816 mg kg-1 respectively. Two carcinogenic fractions (naphthalene and benzenamine, 4, 4`methylenbis [2-methyl-]) and 4 mutagenic fractions (pyrene, phenanthrene, fluorene and anthracene) were detected. Substantial PAH degradation occurred in 4M14 and 4M12 samples within 15 days in contrast to up to 23 days in 1B16A, NA. However, substantial reduction in TPH (> 97%) was only observed in 4M12 and 4M14 inoculated microcosms within 15 days compared to 25-30 days in 1B16A inoculated, BS and NA microcosms. 4M14 inoculated microcosms were most efficient at complete removal (D100) of all carcinogenic and mutagenic fractions; 4M14 (9-10 days), 4M12 (9-15 days), 1B16A (15-23 days), BS (18-21 days) and NA (18-22 days). Pseudomonas xanthomarina was therefore shown as the best candidate for use in a BS/BA approach for treating COTBS contaminated Libyan soils. This study shows the importance of pre-screening bioaugmentation agents for the removal of carcinogenic and mutagenic fractions prior to use; in order to carry out safe, efficient and sustainable COTBS bioremediation in Libya.