Bioremediation of Crude Oil Polluted Soil by Cyanobacteria and Bacterial Consortium in Izombe Community of Imo State, Nigeria

The bioremediation of Crude Oil Polluted Soil by Cyanobacteria and bacteria consortium was done using random sampling method. Two sets of soil samples were collected (Sample A and B). Sample A, 1.0 kg each of the oil polluted soil was collected from ten points at a depth of 15cm to give a total of 10kg of soil sample; while sample B, 2.0 kg each of the unpolluted soil was also collected from ten points on the site at a depth of 15cm to give a total of 20kg of soil sample for the biodegradation. The samples were homogenized, collected in a sack bag and immediately transported to the Laboratory for analysis. Cyanobacteria and Indigenous bacteria were isolated and identified using standard methods to molecular level. Synechoccocus elongates and Microcystis holsatica were identified as Cyanobacteria; while Pseudomonas, Bacillus, Aeromonas, Enterobacter and Corynebacterium identified as bacteria. Physicochemical parameters, heavy metals of the bacteria isolates were also determined. Inoculum development and biodegradation experiment was carried out in standard laboratory condition. The soil sample was autoclaved, divided into four parts of 5kg each and was poured into sterile transparent bucket labeled X, Y, Z and C. To prevent any fungal, bacterial and cyanobacterial activity, 0.25 g/kg each of nystatin, streptomycin, CuSO4 was added to the respective buckets. Bacterial growth of each set of samples was measured by viable counts on nutrient agar; pH, temperature and moisture content were also measured. The depletion on the total hydrocarbon was monitored using gas chromatography, while heavy metals were monitored using Atomic Absorption Spectroscopy. The data generated were analyzed using analysis of variance (ANOVA) and Duncan alpha test at p≤ 0.05. The result shows that the pH level after the experiment decreased from 6.17 to 5.85, 6.17 to 6.04 and 6.17 to 5.92 for set up X, Y and Z respectively, thus showing a level of acidity. The moisture content increased progressively rom6.20 to 14.10,6.20 to 11.0 and 6.20 to 13.8 for the three set up respectively, the temperature recorded 31oC to 32oC for all the set ups, which shows that the isolates were mesophiles. Heavy metals concentrations were drastically reduced after three months; for instance, Arsenic showed a highest reduction from 5.10ppm – 0.10ppm for set up Y. Silicon shows the highest reduction of 10.81ppm – 0,10ppm for set up Z. Zinc in set up X decreased from 19.36ppm – 0.15ppm, Lead in set up Y decreased from 3.11ppm – 0.39ppm. Mercury and Nitrate showed a reduction of 0.06ppm – 0.04ppm, and 2.85mg/kg – 4.07mg/kg for set up Y respectively. Phosphate recorded an increase of 2.1mg/kg – 44.03mg/kg. The findings of this study obviously established the ability of Cyanobacteria and bacteria consortia in the different set ups to degrade crude hydrocarbon. The setup Y performed best in the heavy metals’ concentration reduction followed by Setup X then finally Setup Z which was the lowest in performance. This shows that the combination of Cyanobacteria and bacteria can be used in cleanup of heavy metal and total petroleum hydrocarbon in a polluted area, which has been the most severe environmental problems facing Nigeria.