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Background
Advances in science and technology since the industrial revolution have increasingly enabled mankind to exploit natural resources. Excavating fossil fuels for energy and the advent of gricultural chemicals and pharmaceuticals have facilitated the improvement of the standard of living of millions of people in the world. Unfortunately, many of these inventions have a downside: chemicals needed for such improvements may have adverse health effects and impacts on the environment and humans (Valentín et al., 2013). Relative to the pre-industrialization era, industrialization and intensive use of chemical substances such as petroleum hydrocarbons (e.g.,aliphatic, aromatic, polycyclic aromatic hydrocarbons (PAHs), BTEX (benzene, toluene, ethylbenzene, and xylenes), chlorinated hydrocarbons like polychlorinated biphenyls (PCBs), trichloroethylene (TCE), and perchloroethylene, nitroaromatic compounds, organophosphorus compounds, solvents, pesticides, and heavy metals are contributing to environmental pollution (Megharaj et al., 2011). Some chemical compounds, such as organochlorides and nitroaromatic compounds, are purposefully synthesised, while the production and incineration of some other commodities, such as polyvinyl chloride (PVC) plastic, create undesired toxic by-products. After the chemical products have served their purpose, they often end up in the environment. The final destination of persistent contaminants is often the soil, or if they pass through a water treatment plant, either sewage sludge or sediment at the bottom of rivers, lakes or the sea, where they may accumulate, thereby rendering the environment hazardous to life (Valentín et al., 2013).
PAHs and petroleum hydrocarbons are a major class of such hazardous and persistent organic pollutants released in to the environment, posing serious threat to terrestrial and aquatic ecosystems (Ite et al., 2013). The term PAH generally refers to hydrocarbons containing two orore fused benzene rings in linear, angular or clustered arrangements (Sims and Overcash, 1983) PAHs are ubiquitous in the natural environment and are highly recalcitrant molecules due to the strong soil sorption capacity, molecular stability, and hydrophobicity (Ortega-Calvo et al., 2013).Increased anthropogenic activities in the past 150 years have caused a significant increase of PAH concentrations in the natural environment (Cerniglia, 1992; Elliot, 2011).
Due to their high hydrophobicity and solid-water distribution ratio, PAHs in soil tend to interact with the non-aqueous phase and organic matter, and consequently become less available for further physicochemical or microbial removal (Johnsen et al., 2005). PAHs are highly resistant to degradation as they are hydrophobic, have a high solid-water distribution ratio, and contain dense π-electron clouds that protect them from nucleophilic attack (Johnsen et al., 2005; Belcher, 2012). PAHs have received increased attention in recent years in environmental pollution studies because some of these compounds are highly carcinogenic or mutagenic (Hong et al., 2016.). Eight PAHs typically considered as possible carcinogens are: benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene (B(a)P), dibenzo(a,h)anthracene, indeno(1,2,3-cd)pyrene and benzo(g,h,i) perylene. In particular, benzo(a)pyrene has been identified as being highly carcinogenic. The US Environmental Protection Agency (EPA) has promulgated 16 unsubstituted PAHs (EPA-PAH) as priority pollutants (Srogi, 2007).
Although PAHs originate from natural sources such as open burning, natural losses or seepage of petroleum or coal deposits, and volcanic activities, they are mainly derived from anthropogenic activities related to pyrolysis and incomplete combustion of organic matter (Abdel-Shafy and Mansour, 2015). Anthropogenic sources of PAH include burning of fossil fuel, coal tar, wood, garbage, refuse, used lubricating oil and oil filters, municipal solid waste incineration and petroleum spill and discharge (Haritash and Kaushik, 2009). PAHs are found in complex nonaqueous-phase liquids (NAPLs), such as creosote and coal tar, and soot-like materials, which are generally known as black carbon (Ortega-Calvo et al., 2013). Creosote, with a PAH mass fraction of 85% (Mueller et al., 1989), is an obvious source. Coal tar creosote is the most common wood preservative in the United States. Various kinds of creosote are used for road paving, roofing, coking, and aluminum smelting (ATSDR, 1997). Petroleum is another significant source, it is a complex mixture containing thousands of hydrocarbons including PAHs. It is estimated that the annual global input of petroleum hydrocarbons to the environment is 1.7 – 8.8 million metric tons with anthropogenic sources responsible for the majority of it (Dimitriou-Christidis, 2005). Used lubricating oil contains several toxic components including up to 30% aromatic hydrocarbons, with as much as 22 ppm benzo(a)pyrene (Abioye, 2011). Upshall et al. (1992) reported that motor oil had a density of 0.828 g/ml and contained 14% aromatics and 65.4% aliphatics (by weight). In their study, the sum of 26 individual PAHs represented 0.17% of the oil, or 1.2% of the aromatic fraction.
CHAPTER ONE
1.1 BACKGROUND
1.2 STATEMENT OF THE PROBLEM
1.3 SCOPE OF THE STUDY
1.4 RESEARCH HYPOTHESIS .
1.6 THESIS ORGANIZATION
CHAPTER TWO
2.1 BACKGROUND
2.2 BIOREMEDIATION OF POLYCYCLIC AROMATIC AND PETROLEUM HYDROCARBONS
2. 3 ENHANCING BIOAVAILABILITY OF PAHS USING SURFACTANTS
2.4 TYPES OF SURFACTANTS
2.5 INFLUENCE OF BIOSURFACTANTS ON THE BIOAVAILABILITY AND SUBSEQUENT DEGRADATION OF HYDROPHOBIC ORGANIC COMPOUNDS
2.6 BIOSURFACTANT PRODUCTION
CHAPTER THREE MATERIALS AND METHODS
3.1 MATERIALS AND METHODS
3.2 BACTERIAL STRAIN
3.3 MICROBIOLOGICAL METHODS
3.4. BIOSURFACTANT PRODUCTION AND CHARACTERIZATION
3.5 BIOSURFACTANT ASSISTED MASS TRANSFER EXPERIMENTS
3.6 MICROBIAL DEGRADATION EXPERIMENTS OF PETROLEUM SLUDGE, MOTOR OIL AND PAHS
3.7 ANALYTICAL METHODS
3.8 DATA ANALYSIS
CHAPTER FOUR APPLICATION OF BIOSURFACTANT FOR ENHANCING PETROLEUM SLUDGE AND USED MOTOR OIL BIOREMEDIATION
4.1 APPLICATION OF BIOSURFACTANT PRODUCED BY OCHROBACTRUM INTERMEDIUM CN3 FOR ENHANCING PETROLEUM SLUDGE BIOREMEDIATION
4.2 PRODUCTION AND APPLICATIONS OF LIPOPEPTIDE BIOSURFACTANT FOR BIOREMEDIATION AND OIL RECOVERY BY BACILLUS SUBTILIS CN2
4.3 SUMMARY
CHAPTER FIVE BIOSURFACTANT FROM PAENIBACILLUS DENDRITIFORMIS AND ITS APPLICATION IN ASSISTING PAH AND MOTOR OIL SLUDGE REMOVAL FROM CONTAMINATED SOIL AND SAND MEDIA
5.1 INTRODUCTION
5. 2 ISOLATION OF BACTERIAL ISOLATES FOR BIOSURFACTANT PRODUCTION
5.3 PHYSICAL PROPERTIES OF THE BIOSURFACTANT.
5.4 CHEMICAL CHARACTERIZATION OF THE BIOSURFACTANT
5.5 BATCH DESORPTION STUDY
5.6 PAH DESORPTION KINETICS
5.7 APPLICATION OF THE BIOSURFACTANT IN OIL REMOVAL FROM SAND
5.8 SUMMARY
CHAPTER SIX PYRENE BIODEGRADATION ENHANCEMENT POTENTIAL OF LIPOPEPTIDE BIOSURFACTANT PRODUCED BY PAENIBACILLUS DENDRITIFORMIS CN5 STRAIN
CHAPTER SEVEN THE ROLE OF LIPOPEPTIDE BIOSURFACTANT ON MICROBIAL REMEDIATION OF AGED POLYCYCLIC AROMATIC HYDROCARBON (PAHS)-CONTAMINATED SOIL
8.1 CONCLUSIONS
REFERENCES
