Biodegradation of Crude Oil by Bacteria Isolated from Produced Formation Water of an Onshore Oil Field in Sudan

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Date
2015-06-15
Authors
Manal Elsayed, Abdel Rahman
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Publisher
University of Khartoum
Abstract
ABSTRACT The produced formation water stored in the processing facilities in oil fields of Muglad Basin is highly contaminated with crude oil. The aim was to isolate as many as possible of indigenous crude oil degrading bacteria and develop a consortium of bacteria with high biodegradation capabilities which can be offered for the treatment of the contaminated produced water before disposal. Indigenous hydrocarbon degrading bacterial strains adapted to tropical environment were isolated from uncontaminated soil and from crude oil contaminated samples collected from Higlig Central Processing Facility which is situated within Higlig oil fields in South Kordofan State. Using enrichment technique forty six bacterial strains were isolated from produced water and from the sediment of a pond storing produced water as well as from an uncontaminated soil far away from the facility. All strains including unidentified five rods and five cocci bacteria were aerobic and Gram positive. Molecular techniques confirmed that the isolates were Aerococcus sp., Arthrobacter sp., Bacillus subtilis subsp. subtilis, B. cereus, B. licheniformis, B. endophyticus, B. firmus, B. lentus, Kocuria flava, K. rosea, Paenibacillus cineris, Microbacterium aborescens, and Rhodococcus equi. Bacillus spp. were the most prevalent crude oil utilizers. The ability of all strains to degrade crude oil was assessed quantitatively and qualitatively by growing bacteria on broth mineral salts and oil agar media using Sudanese Nile Blend crude oil and the lighter Norwegian crude oil as sole source of carbon. Twelve isolates showed high degrading capability, 18 showed moderate and 14 showed low growth in Norwegian crude oil, while in Sudanese Nile Blend crude oil 11 were high growers, 21 moderate and 12 were low growers. Seven strains showed high growth in both crude oils, thus Bacillus subtilis subsp. subtilis strain 168 , B. lentus strain?, B. endophyticus strain CT7, B. firmus strain AU9, B. cereus strain 03BB102, Aerococcus sp. strain 4103 . and Kocuria flava strain CT9. The percentage loss of the two crude oils due to bacterial degradation was assessed quantitatively after 14-day incubation period using spectrophotometer instrument. The loss of Norwegian crude oil which varied between 2.5% and 62% was achieved by Bacillus cereus 03BB102 being greater than that achieved by B. Endophyticus strain CT7 > B. Subtilis subsp. subtilis strain 168 > B. lentus strain?> B. firmus strain AU9 > Aerococcus sp. strain 4103. The loss of the heavier Sudanese Nile Blend crude oil which varied between 1.0 and 51% was achieved by B. firmus strain AU9 > B. subtilis> Aerococcus sp. strain 4103 > B. cereus strain 03BB102 > B. lentus strain?. Gas chromatographic (GC) analysis was carried out as a qualitative assessment using degradation loss of individual crude oil constituents, mainly alkanes and some alkenes and alkynes. For the Norwegian crude oil the isolates with the highest degrading capacity were recorded in the following order: Bacillus subtilis subsp. subtilis strain 168 > B. endophyticus strain CT7 > B. lentus strain?> B. cereus strain 03BB102 > B. firmus strain AU9> Kocuria flava strain CT9> Aerococcus sp. strain 4103, while for Sudanese Nile Blend crude oil the order was B. subtilis subsp. subtilis strain 168 > B. lentus strain? > B. firmus strain AU9 > B. cereus strain 03BB102> Aerococcus sp. strain 4103 > K. flava strain CT9 > B. endophyticus strain CT7. GC alkanes fraction analyses obtained from the residual crude oil after 14 days, showed that alkanes level was significantly reduced by B. subtilis subsp. subtilis strain 168. GC proved B. subtilis subsp. subtilis strain 168 as the best degrader isolate for both crude oils. In Norwegian crude oil B. subtilis subsp. subtilis strain 168 degraded n-alkanes with chain lengths C7, C8 and C9 completely but only 31% of C10 n-alkanes. For Sudanese Nile Blend crude oil it completely degraded n-alkanes with chain lengths C13, C14, C15. Degradation of n-alkanes with chain lengths C16-C18 ranged between 50 and 75% and between 28 and 41% for n-alkanes with chain lengths C19-C21. The highest percentage loss of crude oil was at pH 7.0 for all strains except B. subtilis subsp. subtilis strain 168 which was slightly higher at pH 8.5. pH 5.5 did not favour high rates of oil degradation. B. firmus strain AU9 and Aerococcus sp.strain 4103 did not grow at all in any of the two crude oils at pH 5.5. No increase in loss of oil especially in Norwegian crude oil occurred when the C:N ratio was changed from 5:1, to 2.5:1 and to 1:1. Sudanese Nile Blend crude oil showed that some strains even exhibited a lower rate of biodegradation with increase in nitrogen. Increase in phosphorus seemed to inhibit biodegradation processes.
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140 Pages
Keywords
BiodegradationCrude ;Oil by Bacteria Isolated from Produced Formation ;Water of an Onshore Oil Field in Sudan;Hypothesis and research objective;Microscopic characteristics;Urease test;DNA extraction
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