Bacterial Treatment of Drill Cuttings: Experimental Investigation

The presence of polycyclic aromatic hydrocarbons (PAH) from crude oil and gas condensate, ferrochrome lignosulphate, and lead compounds in drill cuttings and drilling mud additives is a cause of worry for the environment during exploration and development drilling operations. Environmental toxicants detected during drilling operations sparked this inquiry. In order to achieve the millennium goal of a sustainable environment, this study focused on applying scientific and technological solutions that are both efficient and cost-effective in lowering chemical toxicants in the environment to levels below the allowed limit. This was accomplished by employing microorganisms found in drill cuttings to induce PAH and TPH breakdown in the hydrocarbon. The physiochemical parameters that enhance the multiplication of bacteria that use hydrocarbons have been discovered. Microbial populations, total petroleum hydrocarbon (TPH), and PAH levels were assessed at regular intervals throughout the experiment. A sample of drill cutting (Dc) was taken from an oil well in the Usan field for bioremediation treatment. The five treatment options Dc, Dc+S, Dc+F, Dc+S+F+D, and Dc+D were established in triplicates in different cells using plastic bowls. A total of 15 plastic bowls, each measuring 35cm in diameter and 11cm in depth, were used. The setup was sampled at regular intervals for analysis throughout the study period. Biostimulated with soil (S), NPK fertiliser (F), or Gold Crew dispersant (D), with controls (DC) and heat-treated (HT) (hDC). 40g of treatment material was added to 2 kg (wet weight) of drill cutting for each treatment option. The bioremediation process was investigated during a 56-day period. On day 0, Dc had the highest heterotrophic bacterial count (4.5 x 105 cfu/g), while Dc+D had the lowest (3.0 x 103 cfu/g) on day 56.

According to the hydrocarbon using bacterial count, Dc+D had the maximum count (6.5x 103 cfu/g) on day 28 and the lowest level (2.6 x 102 cfu/g) on day 56. Total petroleum hydrocarbons (TPH) varied from 33.22 to 46.00 mg/kg on day 0, whereas polycyclic aromatic hydrocarbons (PAH) ranged from 3.51 to 6.4 mg/kg for all treatment options. TPH was 8.0mg/kg and PAH was 2.5mg/kg in all treatment options at day 56. Dc(71.82 percent ), Dc+S(77.09 percent ), Dc+F(83.58 percent ), Dc+S+F+D(79.95 percent ), Dc+D(81.58 percent ), Dc+S+F+D(79.95 percent ), Dc+D(81.58 percent ), Dc+D(81.58 percent ), Dc+D(81.58 percent ), Dc+D(81.58 percent (30.56 percent ). Dc (49.92%), Dc+S (52.35%), Dc+F (86.09%), Dc+S+F+D (64.74%), Dc+D (74.20%), and heat-treated PAH degradation rates were as follows: Dc (49.92%), Dc+S (52.35%), Dc+F (86.09%), Dc+F+D (64.74%), Dc+D (74.20%) (2.23 percent ). For both TPH and PAH, Dc+F yielded the highest percentage degradation. Using bacterial isolates, 52 hydrocarbons were generated. Bacillus spp. (26.92%), Proteus spp. (1.92%), Pseudomonas spp. (7.36%), Alcaligenes spp. (5.77%), Micrococcus spp. (7.55%), Acinetobacter sp. (1.92%), Aeromonas spp. (21.15%), and unidentified bacteria were among the bacteria isolated (28.85 percent ). According to a screen test for degradative potential, many of the bacterial isolates had hydrocarbon degradative capability. The drill cuttings studied could be remediated using microbiological agents, as shown in the heat-treated control, and ambient variables (abiotic factors) had a role in hydrocarbon alternation.

Author (S) Details

S. E. Ibekwe
Department of Microbiology, University of Port Harcourt, P.M.B 5323 Port Harcourt, Nigeria.

G. C. Okpokwasili
Department of Microbiology, University of Port Harcourt, P.M.B 5323 Port Harcourt, Nigeria.

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