Effects of animal wastes treatments of diesel polluted soils on hydrocarbon-utilizing microbial counts and oil degradation
The effect of different organic nutrient supplements on the total hydrocarbon-utilizing microbial counts and oil degradation in diesel-polluted soil was investigated. Heavily and moderately polluted soil samples were amended with different grades (200, 400 and 600 g) of organic nutrient supplements (poultry waste, pig waste and cow dung) and inorganic fertilizer. Soil samples obtained were also polluted with different percentage of diesel oil. Viable aerobic diesel oil-utilizing microorganisms were enumerated at two weeks interval using the vapor phase transfer method. The residual oil and grease contents of the samples were determined at the beginning and at the end of the study. The microbial counts increased with corresponding increase in the quantity of supplements added. Poultry waste-amended samples had higher counts, followed by pig waste, cow dung and inorganic fertilizer-amended samples. In the sample polluted with different percentage of diesel oil, the microbial counts decreased with increase in the percentage of diesel oil pollution. The quantity of residual oil and grease increased with decrease in the quantity of supplements. More diesel oil degradation was achieved in poultry waste-amended samples followed by the pig waste-amended, cow dung-amended and lastly, inorganic fertilizer-amended samples. This showed that in the soil, the rate of degradation of diesel oil can be increased by the addition of organic wastes. Poultry waste proved the best organic waste for the remediation process.
Keywords: Diesel oil, organic wastes, hydrocarbon-utilizing count, bioremediation, pollution