INFLUENCE OF BACTERIA ASSOCIATED WITH CORROSION OF METALS

The physicochemical characteristics of the soil beneath and adjacent to corroded petrol tanks were examined. The result revealed that the moisture content of the soil beneath the tanks was higher (3.2%) than the adjacent soil (0.4%). There was no significant difference in the temperature of the soil beneath and the adjacent one. The pH of the soil beneath the tanks was acidic (5.9). The organic matter of the adjacent soil was higher (1.8%) than the soil beneath the tanks. Nitrate and sulphate contents of the adjacent soil were higher (1.36 and 153.5mg/kg) than soil beneath the tanks which was 0.7 and 87.2mg/kg respectively. The bacteria isolated from scrapings of the tanks included Desulfovibrio vulgaris, Desulfotomaculum nigrificans, Desulfovibrio desulfuricans, Thiobacillus thiooxidans, Pseudomonas aeruginosa, Listeria monocytogenes, Bacillus cereus, Clostridium perfringes, Bacillus firmus, Staphylococcus cohnii, Bacillus laterosporus and Micrcococcus sedentarius. P. aeruginosa was the most frequently observed (12.5%), while the least was B. laterosporus (4.5%). The corroding ability of bacteria isolated was also examined and the result revealed that bacteria isolated have showed the corroding ability on metal strips and the average percentage weight loss of metal strips was 3.8%, thus indicating that these bacteria have contributed in the deterioration of the petrol tanks studied. The corrosion of storage petrol tanks could lead to seepages of petroleum products in the area, contaminating soil surface and ground water sources which could result in destruction of crops and aquaculture which consequently affect the ecosystem. The use of metals/plastic that can resist corrosion especially alloys to construct storage fuel tanks should be encouraged.