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          The study involves using soya bean oil to determine the biodegradation of naphthalene. Naphthalene is the smallest of the polycyclic aromatic hydrocarbon (PAH) group. The soil sample investigated was collected from LAUTECH farm and it was characterized for total carbon (TC), total nitrogen (N), total phosphate (P), total potassium, P.H and moisture content.

          The total heterotrophic bacteria count (THB) and total hydrocarbon degrading bacteria (THDB) count was also determined. There is a steady increase in the THB and THDB count except for the control and the autoclaved experiment which recorded decrease in the THB and THDB. The autoclaved experiment has the lowest THB count.    

          There is variation in the value of THB and THDB of the different samples due to microbial growth in the soil which is influenced by the amount of nutrient and moisture content.

          Also the THB and THDB count for each sample is increasing from the first 5 days to 10 days, 15 days to20days to 25days. Thus it was deduced that microbial activities in the soil aid the degradation of the contaminants.




Environmental pollution is any discharge of material or energy into water, land, or air that causes or may cause acute (short-term) or chronic (long-term) detriment to the Earth’s ecological balance or that lowers the quality) of life. Pollutants may cause primary damage, with direct identifiable impact or the environment, or secondary damage in the form of minor perturbations in the delicate balance of the biological food web that are detectable only over long time periods, (Dorn P.B 2000).

Environmental pollution is considered to be our world’s most dangerous, and constant, threat; our world is exposed to hazardous pollutants and chemicals from different sources. These toxins affect our environmental resources such as air, water and soil. Slowly, our ecosystem is being thought down the impending danger of pollutants. These problems require immediate scientific attention to find an appropriate and cost effective solution, (Eriksson M 2001).

Pollution has been primarily a local problem. The industrialization of society, the introduction of motorized vehicles, and the explosion of the human population, however caused an exponential growth in goods and services. Coupled with this growth has been a tremendous increase in waste by­products. The indiscriminate discharge of untreated industrial and domestic wastes into waterways, the spewing of thousands of tons of particulates and airborne gases into the atmosphere, the “throwaway” attitude toward solid wastes, and the use of newly developed chemicals without considering potential consequences have resulted in major environmental disasters. Land pollution is the degradation of the Earth’s land surface through misuse of the soil by poor agricultural practices, mineral exploitation, industrial waste dumping, and indiscriminate disposal of urban waste. (Ricciardelli 1997)

The common methods of waste disposal include sanitary landfill, recycling and incineration. These processes of waste management have proven to be difficult and expensive. Incineration for example, is a method in which solid organic wastes are subjected to combustion so as to convert them into residue and gaseous products. Advanced incinerator use solid wastes as fuel, burning quantities refuse and utilizing the resultant heat to make steam for electricity generation. Problems remain, however; incinerator ash contains high ratios of heavy metals, becoming a hazardous waste in itself, and high efficiency incinerators may discourage the use of recycling and other waste reduction methods. Thus these concerns have continued to drive the need for the development and application of remediation techniques.

“Remediate” means to solve a problem, and “bio-remediate” means to use biological organisms to solve an environmental problem such as contaminated soil or groundwater. (Valaes T 1963)

In a non-polluted environment, bacteria, fungi, protists, and other microorganisms are constantly at work breaking down organic matter, what could occur if an organic pollutant such as oil contaminated this environment!, Some of the microorganisms would die, while others capable of eating the organic pollution would survive. Bioremediation works by providing these pollution-eating organisms with fertilizer, oxygen, and other conditions that encourage their rapid growth. These organisms would then be able to break down the organic pollutants correspondingly a faster rate. In fact, bioremediation is often used to help clean up oil spills. (Ricciardelli 1997).

Bioremediation of a contaminated site typically works in one of two ways. In the first case, ways are found to enhance the growth of whatever pollution-eating microbes might already be living at the contaminated site. In the second, less common case, specialized microbes are added to degrade the contaminants. Technologies can be generally classified as in situ or ex-situ. In situ bioremediation involves treating the contaminated material to be treated elsewhere. Some examples of bioremediation related technologies are phytoremediation, bioventing, bioleaching, land farming bioreactor, compositing, rhizofiltration, and biostimudation. (Mohn 2001)

Bioremediation can occur either through natural attenuation or intrinsic bioremediation or can be spread on via the addition of fertilizers to increase the bioavailability within the medium. Recent advancements have also proven successful via the addition of matched microbes’ strains to the medium to enhance the resident microbes population’s ability to break down contaminants. Microorganisms used to perform the function of bioremediation are known as bioremediators. (Senior 1992).

Nonetheless, bioremediation provides a technique for cleaning up pollution by enhancing the same biodegradation processes that occur in nature. Depending on the site and its contaminants, bioremediation may be safer and less expensive than alternative solutions such as incineration or land filling of the contaminated materials. It also has the advantage of treating the contamination in place so that large quantities of soil, sediment or water do not have to be dug up pumped out of the ground for treatment. (Senior 1992).

Bioremediation can be implemented in various ways. The first is natural attenuation, in which the native soil microbial community grows and develops around the contaminants in the soil. This method is usually slow and degradation is unreliable. Another method, bioaugmentation, introduces bacteria capable of degrading the pollutant into the ecosystem. Bioaugmentation has been successful in laboratory and field settings but involves the introduction of a non-native population in the microbial community, a cause which limits its use. A third methods, biostimulation, uses microbial communities already present but stimulates those bacteria capable of the desired degradation by adding suitable electron donors or electron acceptors that are not available in high concentrations in the soil. Limited fields’ studies have been performed to date but information gathered through laboratory simulation can aid in determining the applications 4of biostimulations on pollutant remediation. (Miller 2010).

Biostimulation is a form of in situ bioremediation which uses an electron donor or acceptor to encourage growth of bacteria capable of degrading environmental pollutants. Successful biostimulation has degraded polycyclic aromatic hydrocarbons, polychlorinated ethylene, and petroleum, and reduced uranium and other heavy metals. Overcoming difficulties such as the loss of the stimulants to other processes, biofouling, and co-contamination will allow biostimulation to become more effective at preventing ground water contamination. (Miller 2010).

Biostimulation involves the modification of the environment to stimulate existing bacteria capable of bioremediation. This can be done by addition of various forms of rate limiting nutrients and electron acceptors, such as phosphorus, nitrogen, oxygen, or carbon (e.g. in the form of molasses). Additives are usually added to the subsurface through injection wells, although injection well technology for biostimulation purposes is still emerging. Removal of the contaminated material is also option, albeit an expensive one. Biostimulation can be enhanced by bioaugmentation. This process, overall, is referred to as bioremediation and is an EPA- approved method for reversing the presence of oil or gas spills. (Miller 2010).

The primary advantage of biostimulation is that bioremediation will be undertaken by already present native microorganisms that are well-suited to the subsurface environment, and are well distributed spatially within the surface. The primary disadvantage is that the delivery of additives in a manner that allows the additives to be readily available to subsurface lithology (tight clays or other fine-grained material) makes it difficult to spread additives throughout the affected area. Fractures in the subsurface create preferential pathways in the subsurface which additives preferentially follow, preventing even distribution of additives.

Not all contaminants, however, are easily treated by bioremediation using

Microorganisms. For example, heavy metals such as cadmium and lead are not readily absorbed or captured by microorganisms the assimilation of metals such as food chain may worsen matters



          Naphthalene is the smallest of the polycyclic aromatic hydrocarbon (PAH) group, containing two benzene rings. Its molecular formula is C10H8. It is a white crystalline solid that can be found in the form of scales, balls, powder or cakes. It has the strong aromatic odour this is associated with mothball. PAHS are a class of organic compounds consisting of over 100 individual molecules composed of two or more fused aromatic rings. Some PAHS have been known to possess carcinogenic characteristics and their release and subsequent accumulation in terrestrial environments is cause for concern (Cerniglia 1992).    



          Soya bean oil is a vegetable oil extracted from the seeds of the soya bean (Glycine max). It is one of the most widely consumed cooking oils. As a drying oil, processed soya bean is also used as a base for printing inks and oil plants.

          Per 100g of soya bean oil, 16g of saturated fat, 23g of mono saturated fat and 58g of poly saturated fat. The major unsaturated fatty acid in soya bean oil is triglycerides are the poly unsaturated alphalinolenic acid (David, BM 1986). 

          Soya bean can be used as biostimulant in the treatment of soil contaminated with PHAS such as Naphthalene.   



          Using soya bean oil to access the biodegradation of Naphthalene in LAUTECH soil. 



1.3.1 AIM

          The aim of this study is to use Soya bean oil to access the biodegradation of Naphthalene in the soil.



  • To determine the rate of biodegradation of Naphthalene contaminated soil by using biostimulation.
  • To evaluate the growth of microorganism in the contaminated soil.
  • To investigate the effect of time on the biodegradation process.



It is important to address the problem of soil contaminated with PAHS (Naphthalene been the major constituent) since the contamination poses great threat to live and our environment at large



The need for remediation of contaminated soil plays an important role in economic development and adequate quality fertile land for agricultural and other usage. This research work is limited to ex-situ remediation (i.e. removal of contaminate material to be treated else where) of soil sample polluted with Naphthalene.