A Mathematical Model Incorporating the Influence of Biodegradation on the Fate of a Simulated Oil Spill in a Brackish Aquatic System

Abstract

Aims: To address the limitation in the Nigerian Oil Spill Model (NOSM) which models biodegradation using the first order decay process in which the rate of oil biodegraded is proportional to the initial mass and an empirical decay coefficient. It does not monitor the total biomass of the microorganisms involved in biodegradation. It is not a reflection of natural systems which is a combination of first, second and third order reactions. Study Design: Cross-sectional study. Place and Duration of Study: Eagle Island (Brackish water) behind the Rivers State University of Science and Technology, Port Harcourt, Rivers State, Nigeria between July and September, 2009. Methodology: Monod biodegradation kinetics is used. Crude oil serves as the substrate for microorganisms. Here, there is stimulation of the destruction of substrates, consumption of electron acceptors (oxygen, nitrate) and the growth of biomass. Substrate is biodegraded by microorganisms in the aqueous phase or by biomass present as micro colonies (Molz et al., 1986). In order to simulate this model, MATHLAB/SIMULINK was used. This powerful software package offers an array of numerical methods that can be used for modeling simulation of non-linear differential equations PLOT, amongst the main functions of MATHLAB was used. Results: From the proposed model, it was observed that biodegradation augments when there was increase in the number of bacterial population. This was quite conspicuous in the delay of crude oil breakdown that occurred because the microorganisms that degrade the substrate must grow first of all and increase in number. When the biomass was sufficient, the crude oil was quickly biodegraded. There was growth in the biomass as the microorganisms utilized the electron acceptors (oxygen and nitrate). Conclusion: The modification of the biodegradation component in the NOSM shows the involvement of microorganisms and use of electron acceptors which is a reflection of natural systems. This proposed model addresses the limitation in NOSM where oil biodegraded is proportional to the initial mass of oil and an empirical decay coefficient.