Bioremediation off loamy sandy soil contaminated with different crude oil levels by exogenous and indigenous oil degrading microorganisms

Abstract EN

Bioremediation of loamy sandy soil contaminated with different concentrations (10, 15 and, 25 g kg-1) of crude oil was studied in vitro.

The soil was seed with a mixed culture of oil degraders and associated with indigenous microorganisms.

Favorable conditions for microbial growth were available.

The growth of microorganisms was generally low in soil contaminated with high crude oil concentration (25 g kg-1) (1.

3 x 107 cfu g-1-bacteria and 7.

2 x 106 cfu g-1-fungi after 28 days of biodegradation).

However, a significant microbial growth was observed in soil contaminated with low crude oil concentrations (10 and 15 g kg-1).

After 28 days of process, 9.

x cfu g-1 and 7.

0 x 109 cfu g-1, and 7.

0 x 1011 cfu g-1 and 4.

8 x 108 cfu g-1 fold increase in oil degrading bacteria and fungi respectively compared with 7 days of biodegradation was recorded.

The oil degradation percentage in soil contaminated with crude oil concentrations of 10 and 15 g kg-1 was approximately the same (90 and 87 % after 28 days).

Whereas it was very low in soil contaminated with crude oil concentration of 25 g kg-1 (68 % after 28 days).

Generally, the high molecular weight n-alkanes and aromatic hydrocarbons were less biodegraded than low molecular weight ones.

Pristane and phytane compounds were more resistant to microbial attack than n-alkanes.

The biodegradation rate of aromatic compounds was lower than n-alkanes and isoalkanes.

After 28 days of process time, the degradation percentage of n-alkanes, aromatics, pristane and phytane in soil contaminated with concentrations of 10, 15 and 25 g kg-1 reached to 83, 78 and 35 % ; 47, 42 and 19 % ; 37, 32 and 16 % ; and 41, 37 and 17 % respectively.

The crude oil weight loss percentage by abiotic and biotic processes was found to be 60 % (10 g kg-1), 56% (15 g kg-1), and 30% (25 g kg-1) after 28 days of process.