Abstract

This research is aimed at determining the growth and capacity of microorganisms to degrade crude oil following biostimulationwith NPK fertilizer and sawdust amendment. The contaminated soil was treated simultaneously with the nutrient amendment in treatments A, B, C, D, E, F, G, H and I and the population of microorganisms involved in the degradation of TPH monitored.Optimum conditions for effective degradation of the contaminant were determined and the kinetics of the process evaluated. Physicochemical and biological parameters like soil pH, texture, total petroleum hydrocarbon (TPH), total nitrogen, totalphosphorus, hydrocarbon-degrading bacteria (HDB), and hydrocarbon-degrading fungi (HDF) in the native, control and treatedsoils were analyzed using standard analytical method and procedures. The HDB/HDF population measured for TPH degradationat intervals established the efficiency and kinetics of the bioremediation process. However, HDB growth rate in the treatmentswere between 0.1840 and 0.1931. The utilization of nitrogen and phosphorus by microorganisms was between 81.5% and 92.8%.TPH degradation in the treatments was between 98.14% and 99.05% and degradation rates between -0.0419 day-1 and -0.0479day-1. However, optimum treatment was achieved in 105 days with an efficiency of 99.05% in the first-order kinetics at degradation constant of -0.0479 day-1, degradation half-life of 14.47 days, the microbial growth rate of 0.1921 day-1, and biomass doubling time; 3.61 days. Arousal of the population of indigenous microorganisms at the study site through the application of nutrients and a permeable medium resulted in massive biotransformation of the pollutants to non-toxic environmentally friendly forms.

Highlights

  • Pollution by crude oil is a persistent occurrence where it is exploited, transported or refined

  • The degree of success of biodegradation of spilt oil is predicated on the growth and population of hydrocarbon-degrading microorganisms [2]

  • This study evaluates the growth of indigenous hydrocarbon degrading microorganisms in a polluted soil following nutrient application and the resultant degradation of the pollutant

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Summary

Introduction

Pollution by crude oil is a persistent occurrence where it is exploited, transported or refined. Permeability of the affected soil and viscosity of the impacting crude oil determines the extent of spread on land. The concomitant adverse alteration of the physical, chemical and biological properties of land, water and air [3] by crude oil constitutes a threat to living organisms and humans [4, 5]. By these effects, crude oil is classified as priority environmental pollutant by the United States Environmental Protection Agency (USEPA) and calls for sustainable technologies to mitigate the associated risks. Enhancement of the capacity of the autochthonous microorganisms to degrade the pollutant without adverse ecological effect is the most veritable option

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