IMPORTANCE OF MELLON SEED IN THE REMEDIATION OF SPENT ENGINE OIL POLLUTED SOIL
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND TO THE STUDY
Bioremediation is one of the most viable options for remediating soil contaminated by organic and inorganic compounds considered detrimental to environmental health. Bioremediation is a process defined as the use of microorganisms/plants to detoxify or remove organic and inorganic xenobiotics from the environment. It is a remediation option that offers green technology solution to the problem of hydrocarbon and heavy metals contamination. The main advantage of bioremediation is its reduced cost compared to conventional techniques. Besides cost-effectiveness, it is a permanent solution, which may lead to complete mineralization of the pollutant. Furthermore, it is a non-invasive technique, leaving the ecosystem intact (Perelo, 2010). Bioremediation can deal with lower concentration of contaminants where the cleanup by physical or chemical methods wouldnot be feasible. For bioremediation to be effective, microorganisms must enzymatically attack the pollutants and convert them to harmless products. Bioremediation can be effective only where environmental conditions permit microbial growth and activity, its application often involves the manipulation of environmental parameters to allow microbial growth and degradation to proceed at a faster rate (Vidali, 2001).
Hydrocarbon considered to be one of the major sources of energy supply across the world usually constitutes major contaminants to both aquatic and terrestrial ecosystems. Various techniques has been employed to remediate soil environment contaminated by hydrocarbons, ranging from physical, to chemical and mechanical forms of treating or removing the contaminants. Bioremediation offers a better technique for treatment and removal of these contaminants into an innocuous substance. Effective bioremediation of hydrocarbons in the soil environment can be achieved by either or both of the following techniques: Biostimulation and Bioaugmentation. Microorganisms play a significant and vital role in bioremediation of heavy metal contaminated soil and wastewater. Though when microorganisms especially bacteria are exposed to higher concentration of metal, it may have cidal effects on them. Hence, microorganisms are effective only at low metal concentration in the soil. Microorganisms are usually used for the removal of heavy metals. Microorganisms can interact with metals and radionuclides via many mechanisms, some of which may be used as the basis for potential bioremediation strategies (Lloyd et al., 2005). Mechanisms by which microorganisms act on heavy metals includes biosorption (metal sorption to cell surface by physiochemical mechanisms), bioleaching (heavy metal mobilization through the excretion of organic acids or methylation reactions), biomineralization (heavy metal immobilization through the formation of insoluble sulfides or polymeric complexes) intracellular accumulation, and enzyme-catalyzed transformation (redox reactions) (Lloyd, 2002). Biosorption seems to be the most common mechanisms (Haferburg and Knothe, 2007). It is the only option when dead cells are applied as bioremediation agent. However, systems with living cells allow more effective bioremediation processes as they can self-replenish and remove metals via different mechanisms (Malik et al., 2004). On the other hand, living cells shows higher sensitivity to environmental conditions and demand nutritional and energetic sources. Many genera of microbes like Bacillus,Enterobacter, Escherichia, Pseudomonas and also some yeasts and moulds help in bioremediation of metal and chromium-contaminated soil and water by bio-absorption and bioaccumulation of chromium (Kotas and Stasicka, 2000). The heavy metal removal by the bacteria Pseudomonas was attributed to the cellular growth of these organisms (Ray and Ray, 2009).
1.2 STATEMENT OF PROBLEMS
Bioremediation of engine oil polluted soil through agrommeral fertilizer and fermented melon seed reveals that spent engine oil harden inhibitory or toxic effect on the growth of crops. The degree of toxicity on crops is attributed to the contact of the volatile and water soluble hydrocarbons in waste engine oil with the tissue of the tender crop of absorption of soluble toxic substance by the plants.
1.3 PURPOSE OF THE STUDY
The objective of this study is to evaluate the effect of waste engine oil contaminated soil on plants growth. It is also aimed at ascertaining the effectiveness of fermented melon seed as a bioremediation agent.
1.4 SIGNIFICANCE OF THE STUDY
The study is of utmost importance to researchers; farmers; government and the society as a whole based on the threat of waste engine oil on the soil. In view of the above a high premium of remediation strategies is placed on the treatment of contaminated soil hence the concept of bioremediation.
1.5 SCOPE OF THE STUDY
This resear5ch work covers only a site at the College of Education, Ekiadolor-Benin.
1.7 DEFINITIONS OF TERMS
Bioremediation: A process of returning the environment altered by contaminants to its original condition biologically.
Contaminants: A substance that makes something impure.
Microorganism: A very small living thing that you can only see under a microscope.
Waste Engine Oil: Any oil that has been refine from crude or any synthetic oil that has been used and as a result of such use is contaminated by physical or chemical impurities