Effect Of Bioremediation On The Compaction Parameters, CBR, And Permeability Of Oil Polluted Soil

1.0 Introduction

1.1 Background of the Research.

1.1.1. Bioremediation Concept:

Bioremediation can be defined as any process that uses microorganism or their enzymes to reform the environment altered by contaminants to its original condition. Bioremediation may be employed in order to attack specific contaminants, such as oil spills that are broken down using multiple techniques including the addition of fertilizer to facilitate the decomposition of crude oil by bacteria. Such treatment will go a long way to improving the engineering properties of such soil and enhance its suitability.

Generally, bioremediation technologies can be classified as insitu or exsitu. Insitu bioremediation involves treating the contaminated material at the site while exsitu involves the removal of the contaminated material to be treated elsewhere.

Often, bioremediation can be accomplished without human intervention by microorganisms that are naturally found in the contaminated matrix. For this approach to be used, it is usually necessary for the rate of contaminant degradation to exceed the rate of contaminant migration. This is called intrinsic bioremediation.

In some cases, it may be desirable to construct engineered systems to supply nutrients, electron acceptors, or other materials that enhance the rate or extent of contaminant degradation. This is desirable when the rate of contaminant migration, the location of environmental receptors or other liability issues dictate that steps to be taken to optimize the rate of contaminant degradation in order to mitigate contaminant migration.

1.1.2. Engineering Properties of Soil

Soil materials are a critical component of engineering design within the construction of buildings and roads. The mechanical aspect of soil in terms of how it moves when subjected to certain conditions derives from the physical and chemical properties of a particular soil type. Understanding different soil compositions, their respective strengths and structural make ups enables engineers to treat soil as a construction material.

These engineering properties, some of which are discussed below play vital role in the determination of the suitability of a particular soil sample, for a particular purpose.

1.1.2.1. Compaction:

Compaction means pressing the soil particles close to each other by mechanical methods.

During compaction, air is expelled from the void space in the soil mass and, therefore, the mass density is increased. Compaction of a soil mass is done to improve the engineering properties. Compaction generally increases the shear strength of the soil, and hence the stability and bearing capacity. It also plays a vital role in reducing the compressibility and permeability of the soil.

1.1.2.2. California Bearing Ratio: The California Bearing Ratio

(CBR) test is a type of test developed by the California division of highway in 1929.The test is used in evaluating the suitability of sub-grade and the materials used in sub-base and base courses. The test results have been correlated with the thickness of the various materials required for flexible pavements.

The (CBR) test is a penetration resistance test used extensively in highway design methods. It is a standardized and popular design parameter for highway and air field pavements.

1.1.2.3. Permeability:

The property of a soil which permits flow of water or any liquid through it is called the permeability. In order words, the permeability of soil is the ease with which water can flow through it. A soil sample is highly porous when water can flow through it easily and as such the permeability of such soil sample is said to be high .In an impervious soil, the permeability is very low and water cannot easily flow through it .

Permeability is a very important engineering property of soil. Knowledge of permeability is very essential in a number of soil engineering problems, such as settlement of buildings, yield of wells, seepage through and below the earth structures. It controls the hydraulic stability of soil masses. The knowledge of the permeability of soil is also required in the design of filters used to prevent piping in hydraulic structures.

1.2. Objectives of the Study

Environmental pollution with petroleum and petroleum products has attracted much attention in recent decades. Spillage of used motor oils such as diesel, lubricating oil, or jet fuel contaminates our natural environment with hydrocarbon. Hydrocarbon contamination of the soil attracts public attention because toxic material could be released. Such contamination equally results in the soil losing its engineering properties.

This research consisted of two experimental tasks. The first project involved investigating how the engineering properties of oil polluted soil are affected by bioremediation.

The second part of the project involved the comparison of the effect produced on engine oil polluted sample to that of diesel polluted samples.

Hence, the objectives of the research are to;

• Test the engineering properties of the two polluted samples.
• Set up closed systems to evaluate the biodegradation of the contaminated soil sample.
• Evaluate the effects of the bioremediation on the engineering properties of both the engine oil polluted and the diesel polluted sample.
• Compare the rate of bioremediation of engine oil polluted sample to that of diesel polluted sample, by considering the values of the engineering properties at some stages of biodegradation.

1.3. Scope of the Research

Bioremediation as it affects the engineering properties of oil polluted soil samples is too vast. Hence, the scope of this research would be based on the available and accessible material and facilities.

The research will be carried out, using laterite sample collected from the ‘Ugwuaji’ borrow pit in Enugu, Nigeria. The soil sample would be contaminated with used engine oil and diesel fuel, used separately.

The process of bioremediation would be initiated by injecting enriched pseudomonas, isolated from the sample polluted with the same petroleum products mentioned above. Bioremediation as it affects the engineering properties of oil polluted soil will be verified by determining the following properties, at intervals, as the incubation proceeds;

• The compaction parameters; which include the maximum dry density (MDD) and the optimum moisture content (OMC).
• The strength characteristics, using the California Bearing Ratio (CBR) as the test study.
• The ease with which water flows through the soil sample, described as the sample coefficient of permeability.

From the data obtained from the experiments, regression models for the estimation of the test parameters for the type of polluted lateritic soils with the same physicochemical properties would be established.