The technology known as land farming exhibits a high capacity of biodegradation for soils contaminated by petroleum hydrocarbons,
Tests at laboratory scale were conducted using pans filled with two types of soil, one contaminated with crude oil and the other with diesel. Both samples were collected at the respective occurrence site. The microbial activity was stimulated by aeration and by successive addition of a solution enriched in nutrients. The soils were weekly sampled in order to control and monitorize the following parameters: pH, moisture content, microbial population density, nutrient concentrations and the grade of the contaminants. The efficiency of degradation reached for both soils was satisfactory, 80% for the crude and 76% for the diesel.
The kinetics of the biodegradation was also studied based on the experimental results. Several models were considered in order to determine the best fitting for the experimental data. The first order decay model shows a reasonable fit to the results, with a specific rate of 0.021 day-1 for the crude oil and 0.019 day-1 for the diesel. The logistic model applied to the time evolution of the microbial population density did not revealed to be a wise choice, specially because there no data available for the biomass concentration on the stationary phase. It was also developed a theoretical dynamic model for the diffusion of the oxygen in soils wich shows the importance of the aeration in landfarming. Finally, it was used a complex dynamic model which simultaneously describes the time evolution of the biomass and the contaminant degradation, both for the biotic and the abiotic components. The fitting to the experimental results was adequate and the model exhibits a fair robustness and flexibility.