Microbial disposal of waste petroleum oils

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Micro -organisms, which are believed to metabolize, waste petroleum oils from soaked soils were isolated and characterized using available equipment and information into the appropriate genera. Further studies classed the isolates in the aerobic and micro-aerophilic category. Isolate metabolic activity of the various petroleum fractions gave the following percentage fractions for profuse growth; 0.1-1.0% (petrol), 0.1-3.8% (Kerosene), 0.1 -2.3% (Engine oil) and 0.1-3.8% (Diesel). Morphological characteristics of the isolates were identical with average dimension of colonies ranging between 3.0mm and 4.9mm, and cell size between 0.7μm and l.6μm. The isolates showed gram-negative reactions. Cultured for the same period and using equal amounts of suspension, petrol gave 4.213 x l05 cells, Engine oil 3.78lx 105 cells, Kerosene 2.641 x l05 cells, Diesel 1.499 x l05 cells per milliliter by the total microbial count technique. This means that the petrol metabolic organisms were the most efficient metabolizers in the study. The maximum growth period, which occurred at the end of the log phase, was 5 days for Petrol, Kerosene, Diesel isolates and 6 days for Engine oil isolates. Growth rates determination for the isolates showed that the isolates from Diesel gave the highest growth rate per day followed by Petrol, Engine oil and Kerosene isolates, with their cell mass concentration doubling times per hour in the decendind order of Kerosene, Engine oil, Petrol and Diesel isolates.The organisms are mesophilic. The variation of PH with time of the isolates was very small with optimum PH ranges between 6.2-7.5 for petrol, 7.1-8.4 for Kerosene, 6.0-7.4 for Diesel and 7.1-7.5 for Engine oil isolates. Metabolic products analysis showed that all the isolates converts waste petroleum oils into compounds with the following functional groups; hydroxyl, carbonyl and carboxylic groups. The isolates belong to members of the following families; Pseudomonadaceae, Azotobacteraceae, Rhizobium, Methylomonodaceae and Halobacteraceae.
A thesis submitted to the Department of Chemical Engineering for the degree of Master of Science in Chemical Engineering, 1999