Synergistic bioremediation of crude oil contaminated soil: Role of bioreactor and pigeon droppings

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Aim: The aim of study was to assess the role of Bioreactor and Pigeon Droppings in the synergistic bioremediation of crude oil contaminated soil.Study Design: This study employs experimental designs, Randomized Block Design Treatment set up, Statistical analysis of data and Interpretation.Place and Duration of Study: The area used for this study is within the Rivers State University Demonstration Farmland in Nkpolu-Oroworukwo, Mile 3 Diobu area of Port Harcourt, Rivers State. The piece of land is situated at Longitude 4.80620oN and Latitude 6.97752oE measuring 5.4864 m x 5.1816 m with a total area of 28.4283 m2. This was cleared and sub-partitioned into 9 blocks of 100 cm x 50 cm x 20 cm giving 150kg soil in each plot using a digital standing scale (Fig 3.1), with each block 65 cm apart. Two of these plots were designated as pristine and crude oil soil to serve as negative and positive controls.Methodology: Crude oil used in this experiment was obtained from Nigerian Agip Flow Station Ebuocha. The stock culture was prepared by weighing out 4000 g (PCE analytical weighing balance PCE-6000 UK), and dissolving in 1.0 l of distilled water to give initial crude oil concentration of 2500 g/l. The soil was artificially contaminated by spiking the prepared crude oil concentration on the plots and allowed to stay for 21 days (To ensure volatilization and sorption of crude oil into the soil matrix) before application of various treatments.The plots were amended with 750 g of pigeon droppings, 375 ml of Pseudomonas and 375 ml of Bacillus broth, respectively. Plot one was uncontaminated and plot 2 was contaminated. These two plots served as controls. Other plots were amended with different concentrations of treatment. These were allowed for 7 days with the objective of assessing the microbial activities within week 1 of treatment (Bioremediation) sampling.Results: The microbiological (THB, F, HUB, HUF) analysis for uncontaminated and contaminated soil showed average counts of 4.77±0.47×106CFU/g and 2.40±2.80×107 CFU/g for THB, 4.33±0.96×104SFU/g and 5.10±1.11×105SFU/g for F, 2.43±0.10×103CFU/g and 3.69±0.59×103CFU/g for HUB, 1.85±0.59×103SFU/g and 4.00±0.53×103SFU/g for HUF, respectively. The physicochemical results revealed that the pH was acidic with value of 6.3±0.13 for uncontaminated soil and 6.9±0.02 for contaminated soil. The temperature was 27.47±0.35OC for uncontaminated while the contaminated was 27.80±0.10OC. Nitrogen was 15.67±0.03 for uncontaminated whereas the contaminated was 12.7±0.04 mg/kg, phosphorus revealed 0.75±0.04 mg/kg and 0.597±0.25 mg/kg for uncontaminated and contaminated. The potassium was 1.825±0.05mg/kg for uncontaminated and 1.813±0.15 mg/kg for contaminated. THC for uncontaminated was 44.0±2.01 mg/kg and contaminated revealed value of 5785±0.063 mg/kg. The bacterial genera isolated from crude oil contaminated soil were: Pseudomonas sp, Bacillus sp, Micrococcus sp, and Serratia sp while the fungal isolates were: Aspergillus sp, Penicillium sp Alternaria sp, Candida sp and Fusarium sp. Conclusion: The study showed that the bioreactor was effective in multiplying the microbial isolates used in the various treatment plots which in turn enhanced the degradation of the contaminated soil. The isolation and identification of microorganisms from the soil samples indicated an abundance of hydrocarbon utilizing microorganisms, thus, indicating that the isolates possess the functional ability for hydrocarbon degradation. From this study, the synergistic bioremediation of crude oil contaminated soil using Pseudomonas aeruginosa, Bacillus safensi and pigeon droppings with 51.17% hydrocarbon reduction offers a potential option for crude oil remediation. This is cost-effective and a tool for the preservation of the agricultural ecosystem.

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