UV-Vis Assessment of Petroleum Hydrocarbon Residues and Growth Response of Indigenous Bacteria from Contaminated Soil and Water

Road, sea, and river transport of petroleum products contributes to pollution of aquatic and terrestrial ecosystems, often leading to ecological disasters that are harmful to human health and the environment. Added to this is the dumping of waste oil from combustion engines directly into nearby aquatic and terrestrial ecosystems. In most developing countries, dealing with water and land pollution from petroleum products became a major concern. This study involved collecting and characterizing surface water and soil samples contaminated with petroleum products from Natitingou and Bohicon, in the Republic of Benin, and then evaluating the growth response of Pseudomonas aeruginosa and Escherichia coli in a hydrocarbon containing mineral medium supplemented with TotalEnergies Quartz 5000 mineral oil. Physico-chemical and microbiological characterization of the samples revealed concentrations of petroleum hydrocarbons (1298 ± 282.84 mg/L- 18338 ± 70.71 mg/L and 4918 ± 84.85 mg/L- 23358 ± 42.43 mg/L), dissolved oxygen (3.18 ± 0.07 mg/L- 6.39 ± 0.04 mg/L and 1.37 ± 0.06 mg/L – 3.61 ± 0.01 mg/L), Conductivity (212.73 ± 0.35 µs/cm – 1674.67 ± 0.58 µs/cm and 150.30 ± 0.65 µs/cm – 272.77 ± 0.06 µs/cm), TDS (142.60 ± 0.20 mg/L- 1121.67 ± 0.58 mg/L and 100.73 ± 0.38 mg/L- 182.73 ± 0.06 mg/L), Nitrates (0.71 ± 0.02 mg/L- 3.55 ± 0.01 mg/L and 0.90 ± 0.01 mg/L – 3.35 ± 0.04 mg/L), nitrites (0.13 ± 0.01 mg/L- 0.47 ± 0.01 mg/L and 0.14 ± 0.01 mg/L – 0.50 ± 0.01 mg/L), Ammonium (0.21 ± 0.01 mg/L- 0.25 ± 0.01 mg/L and 0.08 ± 0.01 mg/L – 0.49 ± 0.01 mg/L), Phosphates (0.058 ± 0.01 mg/L- 0.16 ± 0.01 mg/L and 0.06 ± 0.01 mg/L – 0.35 ± 0.01 mg/L) and TOC (0.44 ± 0.03% – 8.60 ± 0.15%) respectively in water and soil samples including bacteria such as total coliforms, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, and fungi such as Aspergillus sp., Penicillium sp., and Trichophyton sp. Growth tests conducted for 336 hrs in a hydrocarbon-containing mineral medium showed increases in OD600 from 0.312 to 0.988 for P. aeruginosa and from 0.010 to 1.099 for E. coli, with specific growth rates of 0.018 and 0.037 h-1, respectively. The study showed that Pseudomonas aeruginosa and Escherichia coli can grow in a hydrocarbon-containing mineral medium. Further studies are needed to assess their ability to utilize or transform specific petroleum hydrocarbons.