Bioremediation Potential Of Fractionated Fuel Spills On Clay And Sandy Loam Soils

The purpose of the present study was to investigate possible methods to enhance the rate of aerobic biodegradation of hydrocarbons (ex–situ treatments). In this work, the bioremediation processes were applied to a clay and sandy soil with a high level of contamination originated from the leakage of a diesel oil underground storage tank at a petrol station. Laboratory scale experiments (Bartha biometer flasks) were used to evaluate the biodegradation of the diesel oil. Enhancement of biodegradation was carried out through biostimulation (addition of nitrogen and phosphorus solutions or Tween 80 surfactant) and bioaugmentation (bacterial consortium isolated from a landfarming system). To investigate interactions between optimizing factors, and to find the right combination of these agents, the study was based on full factorial experimental design. Efficiency of biodegradation was simultaneously measured by two methods: respirometric (microbial CO2 production) and gas chromatography. Acute toxicity tests with Daphnia similis were applied for examination of the efficiency of the processes in terms of the generation of less toxic products. Results showed that all bioremediation strategies enhanced the natural bioremediation of the contaminated soil and the best results were obtained when treatments had nutritional amendment. Respirometric data indicated a maximum hydrocarbon mineralization of 19.8%, obtained through the combination of the three agents, with a total petroleum hydrocarbons (TPH) removal of 45.5% in 55 days of treatment. At the end of the experiments, two predominant bacteria species were isolated and identified (Staphylococcus hominis and Kocuria palustris).

 

CHAPTER ONE

1.0                           INTRODUCTION

1.1                 BACKGROUND OF THE STUDY

Oil product leakages from underground storage tanks, distribution facilities and various industrial operations represent an important source of soil and aquifer contamination. This fuel is a complex mixture of normal, branched and cyclic alkanes, and aromatic compounds obtained from the middle–distillate fraction during petroleum separation (14).

Among several clean–up techniques available to remove petroleum hydrocarbons from the soil and groundwater, bioremediation processes are gaining ground due to their simplicity, higher efficiency and cost–effectiveness when compared to other technologies (3). These processes rely on the natural ability of microorganisms to carry out the mineralization of organic chemicals, leading ultimately to the formation of CO2, H2O and biomass (12).

Strategies to accelerate the biological breakdown of hydrocarbons in soil include stimulation of the indigenous microorganisms by optimizing the nutrients and oxygen supply and the temperature and pH conditions (biostimulation), and through inoculation of an enriched mixed microbial consortium into soil (bioaugmentation). In addition to provide these optimum conditions, it is also important to know that the pollutant degradation in soil is influenced by mass transfer phenomena. Providing a way to reduce the sorption of the hydrophobic organic contaminants to the soil matrix can increase the rate and extent of biodegradation (26). For this purpose, the addition of surfactants into the soil aims to enhance the emulsification of hydrocarbons and therefore they have the potential to solubilize hydrocarbons and increase their bioavailability and subsequent biodegradation (20,24,25,30).

In biological treatments it is always necessary to perform laboratory feasibility tests to determine the microbial potential to degrade the pollutants and to evaluate strategies to optimize the degradation rates before the design of real scale in–situ or ex–situ (bioreactors, landfarming and others) treatments. Thus, the purpose of the present study was to investigate possible methods to enhance the rate of aerobic biodegradation (ex–situ treatments) of diesel oil in soil. In this work, the bioremediation processes were applied to a sandy soil contaminated by the leakage of an underground storage tank at a petrol station. Biodegradation of diesel oil was performed using laboratory scale experiments (Bartha biometer flasks). Enhancement of biodegradation was carried out through biostimulation (addition of nitrogen and phosphorus solutions and Tween 80 surfactant) and bioaugmentation (treatment with inoculation of a bacterial consortium isolated from a landfarming). To investigate interactions between optimizing factors, and to find the right combination of these agents, the study was based on full factorial experimental design. Efficiency of biodegradation was simultaneously measured by two methods: respirometric (microbial CO2 production) and gas chromatography to evaluate the biodegradation of total petroleum hydrocarbons (TPH). Acute toxicity tests with Daphnia similis were applied to examine the efficiency of the processes in terms of the generation of less toxic products. The results of this study aim to contribute towards current demands for the development of new processes able to reduce the time usually required for bioremediation.

1.2                       PROBLEM STATEMENT

Soil that is accidentally contaminated by petroleum fuel spills is classified as hazardous waste. When the amounts of contaminated soil are large, the currently accepted disposal methods of incineration or burial in secure chemical landfills can become prohibitively expensive. This often results in cleanup delays while the contaminated soil continues to pollute scarce groundwater resources. Land treatment disposal of oily refinery sludges has been practiced for decades with generally good results. The currently used physical and chemical treatments are effective for the degradation of petroleum products but they lag behind in the desired properties, apart they frequently produce many hazardous compounds which are potent immunotoxicants and carcinogenic for living beings. In contrast, bioremediation is effective treatment in terms of efficacy, safety on long terms use, cost and simplicity of administration.

1.3            AIM AND OBJECTIVE OF THE STUDY

The main aim of this study is to investigate possible methods to enhance the rate of aerobic biodegradation of hydrocarbons (ex–situ treatments). Objectives are:

 

1. 1. To determine the rate of soil pollution by oil products

 

1. 1. To use bioremediation processes to a clay and sandy soil with a high level of contamination originated from the leakage of a diesel oil underground storage tank at a petrol station.

 

 

 

• • To reduce the level of soil pollution

 

1.4                                    SCOPE OF THE STUDY

This project was designed to test, on the laboratory scale, what type of fuel spills could be cleaned up by a cost-effective bioremediation approach based on a land treatment process optimized for oily sludges. In addition to five different fuels, the variables included three contamination levels, three incubation temperatures, and three different soil types. Petroleum hydrocarbon disappearance rates were compared in contaminated but otherwise untreated soil,in bioremediationtreated soil, and in soil poisoned in order to suppress biodegradation.

1.5                                                        LIMITATION OF THE STUDY

As we all know that no human effort to achieve a set of goals goes without difficulties, certain constraints were encountered in the course of carrying out this project and they are as follows:-

 

1. 1. Difficulty in information collection: I found it too difficult in laying hands of useful information regarding this work and this course me to visit different libraries and internet for solution.

 

1.6                                             RESEARCH METHODOLOGY

In the course of carrying this study, numerous sources were used which most of them are by visiting libraries, consulting journal and news papers and online research which Google was the major source that was used.

1.7                                   PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.