Journal of Food, Agriculture and Environment

Vol 7, Issue 2,2009
Online ISSN: 1459-0263
Print ISSN: 1459-0255

Bioaugmentation and composting of oil-field drill-cuttings containing polycyclic aromatic hydrocarbons (PAHs)


Josiah M. Ayotamuno 1, Reuben N. Okparanma 2*, Peremelade P. Araka 1

Recieved Date: 2008-12-12, Accepted Date: 2009-04-15


The potentials of bioaugmentation and composting as bioremediation technologies for the removal of polycyclic aromatic hydrocarbons (PAHs) from oil-field drill-cuttings have been compared. From a mud-pit close to a just-completed crude-oil well in the Niger Delta region of Nigeria, 4000 g of drill cuttings was obtained and homogenized with 667 g of top-soil (to serve as microbes carrier) in three separate reactors (A, B and C). The bioaugmentation of indigenous bacteria in the mix was done by adding to reactors A and B a 20-ml working solution (containing 7.6×1011 cfu/ml) of pure culture of Bacillus and Pseudomonas respectively while a 20-ml working solution (containing 1.5×1012 cfu/ml) of the mixed culture of Bacillus and Pseudomonas was added to reactor C. The bio-preparation was added to each reactor (excluding the control) every two weeks for six weeks. The composting experiment was conducted in a sufficiently well lagged, very low thermal conductivity, 10-litre reactor in which 4000 g of drill cuttings, 920 g of top-soil and 154 g of farmyard manure and poultry droppings were homogenized. Mixing and watering of the set-ups was done at 3 days interval under ambient temperature over a period of six weeks. Results showed that the initial individual PAHs concentrations of the drill cuttings ranged from 1.67 to 70.7 mg/kg dry weight, with a predominance of the combustion-specific 3-ring PAHs (representing 90% of a total initial PAHs concentration of 223.52 mg/kg). This indicates that anthropogenic sources of the PAHs were more of pyrogenic than petrogenic. There were far more PAHs reductions at the end of the experiment with the bioaugmentation method than with the composting method particularly at the initial and final stages of the experiment, which indicates that the performance of the bioaugmentation method was better than the composting method. Maximum composting temperature observed was 54oC. Considering the impact of the environmental bacterial isolates (i.e. Bacillus and Pseudomonas) used to degrade the PAHs of the drill cuttings, the Pseudomonas degraded the 3-ring and 4-ring PAHs relatively better than did the Bacillus. However, the Bacillus degraded the 5-ring PAHs relatively better than the Pseudomonas only in the first two weeks of treatment. It was also observed that the cometabolism of the 3- or 4-ring PAHs could not have a synergetic effect on the 5-ring PAHs when the mixed culture was tested. Instead, this resulted in the limited degradation of the 5-ring PAHs particularly in the fourth week of the experiment.


Polycyclic aromatic hydrocarbons, oil-field drill-cuttings, petroleum waste, bioremediation, bioaugmentation, composting, PAHs-degraders, Niger-Delta

Journal: Journal of Food, Agriculture and Environment
Year: 2009
Volume: 7
Issue: 2
Category: Environment
Pages: 658-664

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