Modeling a Bioremediation Process of a Petroleum Contaminated Soil Enhanced With NPK Fertilizer and Animal/Plant Derived Organic Matter

In this study, the potential effects of animal derived organic manure (cow dung, poultry droppings), saw dust and NPK fertilizer on the bioremediation of petroleum hydrocarbon contaminated soil was investigated. The rate of biodegradation was studied for the period of 10 weeks under laboratory conditions. The biodegradation data were fitted to eight models, four of which are based on microbial growth rate and the other four based on order of reaction. Results obtained show that bioremediation with NPK fertilizer and poultry manure followed the logistic growth curve with a constant yield.While treatment with blend of poultry droppings+cow dung+saw dust, occurred with the logistic growth curve with varying yield. It was observed that at optimum addition of NPK fertilizer and poultry manure, the process obeyed same trend as observed when a combination of poultry droppings+cow dung+saw dust was applied. It also revealed bioremediation as basically a first order process at low and moderate addition of biostimulants. NPK fertilizer and poultry manure obeyed first order rate model with ultimate contaminant greater than zero. Again, it was observed that application of NPK fertilizer and animal manure at an increased quantity without combinations offer similar effect with poultry droppings+cow dung+saw dust. Consequently, the result of the percentage degradation of hydrocarbon for the soil sample studied revealed that the rate of hydrocarbon biodegradation was in the following order (83.5%) > (72.6%) > (68.31%) for biotreatment with blend of poultry droppings+cow dung+saw dust, poultry manure and NPK fertilizer respectively. The observations from the mathematical models, graphical and numerical fit results show that the proposed models employed in this work rather than the usual first order rate model were effective in predicting the bioremediation process.