ABSTRACT
The aim of this project is to remediate oil contaminated soil with the use of surfactants.
During the process of remediation, the chemical/physical properties of the soil was
determined before contamination to verify that the soil is fresh and doesn’t contain any
contaminant after which soil contamination in the laboratory was carried out manually
and the biological analysis was carried out on the contaminated soil to determine the type
of bacteria acting on the soil sample followed by the use of the surfactant (bio-solve) in
the remediation of the crude oil contaminated and the biological analysis was repeated to
determine the rate at which the bacteria responded the addition of surfactants
vi
TABLE OF CONTENT
Abstract………………………………………………………………………………I
Certification………………………………………………………………………………………………….II
Dedication……………………………………………………………………………………………………III
Acknowledgement…………………………………………………………………………………………IV
Table of content……………………………………………………………………………………………..VI
List of tables………………………………………………………………………………………………… IX
List of figures …………………………………………………………………………………………….. IX
CHAPTER ONE: INTRODUCTION
1.1 Crude oil pollution …………………………………………………………………………………………. 1
1.2 Effect of crude oil on soil ………………………………………………………………………………1 -2
1.3 Background study …………………………………………………………………………………………..2-
3
1.3.1 Surface-active compounds and their properties…………………………………………..3-
9
1.3.2 surfactants………………………………………………………………………………………………..3
1.3.3 critical micelle concentration…………………………………………………………………….5-
6
1.3.4 interfacial tension…………………………………………………………………………………….6-
7
1.3.5 solubilization …………………………………………………………………………………………..7
1.3.6 hydrophilic-lipophilic balance ………………………………………………………………..7-8
1.3.7 Types of surfactants…………………………………………………………………………………8
Cationic surfactants
Anionic surfactants
Non-ionic
vii
Zwitterionic
1.4 Aims and Objective …………………………………………………………………………………………9
1.5 Justification/relevance ……………………………………………………………………………………..9
1.6 Scope……………………………………………………………………………………………………………10
CHAPTER TWO: LITERATURE REVIEW
2.1 soil washing techniques…………………………………………………………11
2.2 surfactant based ex-situ washing…………………………………………….….14
2.3 soil treatment and categories…………………………………………………………………….17
CHAPTER THREE: MATERIALS AND METHODS
3.1 Materials………………………………………………………………………..21
3.1.1 Collection of soil sample
3.1.2 Surfactant type used
3.1.3 Sterilization of materials
3.2 Methods………………………………………………………………………..22
3.2.1 determination of physico-chemical properties of the soil………………..22
3.2.1.1 water (moisture) content
3.2.1.2 Potential hydrogen (PH)
3.2.1.3 Water holding capacity
3.2.1.4 organic matter
3.2.2 soil contamination process………………………………………………..28
3.2.2.1 biological analysis of the contaminated soil……………………….30
3.2.2.1.1 TPH (total petroleum hydrocarbon) analysis for a polluted soil
3.2.2.1.2 Isolation and enumeration of total heterotrophic bacteria (THB)
viii
3.2.2.1.3 Isolation and enumeration of hydrocarbon utilizing bacteria (HUB)
3.2.3. Soil remediation process………………………………………………………32
3.2.3.1 biological analysis of the remediated soil……………………………….33
3.2.3.1.1 TPH (total petroleum hydrocarbon) analysis for a polluted soil
3.2.3.2 Isolation and enumeration of total heterotrophic bacteria (THB)
3.2.3.1.3 Isolation and enumeration of hydrocarbon utilizing bacteria (HUB)
CHAPTER FOUR: RESULTS AND DISCUSSIONS……………………………36
4.1 results from the physico-chemical analysis of the soil
4.2 interpretation of the gas chromatography test
4.3 results from the biological analysis conducted on the polluted soil and remediated soil
4.4 discussions of the effects of the physico chemical and biological analysis conducted
on the soil sample.
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION
5.1 Conclusion………………………………………………………………………41
5.2 recommendations…………..……………………………………………………42
REFERENCES………………………………………………………………………43
LIST OF TABLES
Table 4.1 …………………………………………………………37
Table 4.2 …………………………………………………………37
Table 4.3 …………………………………………………………38
Table 4.4 …………………………………………………………38
LIST OF FIGURES
ix
Figure 3.1 …………………………………………………………21
Figure 3.2 …………………………………………………………22
Figure 3.3 …………………………………………………………25
Figure 3.4 …………………………………………………………26
Figure 3.5 …………………………………………………………27
Figure 3.6(a) ………………………………………………………29
Figure 3.6(b) ………………………………………………………29
Figure 3.7 …………………………………………………………31
Figure 3.8 …………………………………………………………32
Figure 3.9 …………………………………………………………33
1
CHAPTER ONE
1.0 INTRODUCTION
1.1 Crude Oil Pollution
Petroleum hydrocarbons are widespread in our environment as fuel and chemical
Compounds. The uncontrolled release of petroleum hydrocarbons negatively impacts
many of our soi1 and water resources. The contamination can result from leaking
Underground Storage tanks (UST), petroleum refineries and bulk storage facilities,
broken oil pipelines, spills of petroleum products in chemical plants and transportation
processes (Sheman and Stroo, 1989). The risks of explosion and fire are also serious
threats to the environment. The US. Environmental Protection Agency (EPA) has
reported that there were about 1.6 million of USTs and 37,000 hazardous tanks in 1992.
Approximately 320.000 USTs are leaking, and 1,000tanks are confirmed as new release
each week (Cole, 1994). Approximately 200,000 USTs are in use in Canada, it leads to a
considerable amount of petroleum hydrocarbon leaks and contamination in soi1 and
groundwater (Scheibenbogen et al., 1994). As reported by Gruiz and Kriston (1995) an
amount of 6,000,000 tons petroleum waste enter the environment each year causing
serious environmental problems.
Even if the problems associated with fuel storage and distribution are solved,
contamination incidental to production and commercial usage would continue to threaten
ground water supplies. Many manufacturing processes necessarily produce water and
sledges that are contaminated with hydrocarbons. At a typical oil refinery facility, more
than 23 different waste streams have been identified, several of which have been
classified a hazardous waste (Sims, 1990).
Since the contamination of soil and groundwater by uncontrolled releases of petroleum
products has become a significant problem, a number of technologies have been tested to
remediate the polluted sites.
1.2 Effect of The Crude Oil on the Soil
According to Cole (1994), in the US, about 16,000 sites are treated each year by the states
and responsible parties treatment processes have incorporated physical, chemical,
biological methods, or a combination of them.
2
Remedial action on a contaminated site can involve in situ or ex situ action. The
remediation methods include excavation and landfill disposal or incineration. However,
these methods are expensive and only transfer the contamination from one place to
another.
According to Arora (1989) and Reed et al. (2000), soil is an unconsolidated surface
material that is formed from natural bodies made up of living materials, organic and nonorganic materials produced by the disintegration of rocks. Studies conducted on soils by
American Society for Testing and Materials (ASTM 1994), Dorn et al. (1998), Howard
(2002), Okieimen and Okieimen (2002) have focused on the effects that soil types will
have within our environment when polluted with crude oil and other oily related materials.
Generally, soil function at its potential in an ecosystem with respect to the maintenance of
biodiversity, nutrient cycling, biomass production and water quality. When contaminated
with crude oil, soil will have insufficient aeration due to the displacement of air from the
spaces or pores between the soil particles. Crude oil with low-density tends to penetrate
the topsoil rapidly, whereas heavier oils with higher viscosity tend to contaminate the soil
more slowly resulting in greater contamination at the surface. Moreover, during the
penetration process, crude oil may not change physically. However, when left in the soil
for a long time and subjected to weathering it will result in cleanup difficulties. Many
properties influence the behavior of crude oil mixed with soil. Viscosity of crude oil
affects its rate of movement and the degree to which it will penetrate soil. Schramm
(1992) has studied the measurement of oil viscosity and has used it to correlate with
temperature. Like density, viscosity is affected by temperature: as temperature decreases,
viscosity increases. Viscosity and the forces of attraction between crude oil and soil at the
interface affect the rate at which oil will spread. Jokuty et al. (1995) noted that density
and viscosity of oils shows systematic variations with temperature and degree of
evaporation whereas, interfacial tensions do not show any correlation with viscosity.
1.3 Background Study
The global demand for crude petroleum has contributed to detrimental effects on
surrounding ecosystems. Petroleum is predominantly made up of hydrocarbons, organic
molecules that can be lethal in ecological contexts (Tang, 2011). Large tanker oil spills
and other accidental discharges of petroleum have negatively impacted sea life and
3
polluted land near the spills, creating crude oil contaminated soils (Shaw, 1992).
Many techniques have been discovered and examined for treatment and one of the most
applicable methods is soil washing by surfactants. Among the soil washing methods, bio
surfactants use is promising because of its efficiency for remediation of oil- contaminated
soils and less environmental impacts from residue compared to surfactants (Zhang et al.,
2011).
1.3.2 Surfactants
Surface-active agent are amphiphilic molecules with both hydrophilic and hydrophobic
moieties, which show a wide range of properties, including the lowering of surface and
interfacial tension of liquids, and the ability to form micelles and micro emulsions
between two different phases. The hydrophilic moiety of a surfactant is defined as the
“head”, while the hydrophobic one is referred to as the “tail” of the molecule, which
generally consists of a hydrocarbon chain of varying length. Surfactants are classified as
anionic, cationic, non-ionic and zwitterionic, according to the ionic charge of the
hydrophilic head of the molecule (Christofi et al., 2002)
An important description of chemico-physical properties of surfactants is related to the
balance between their hydrophilic and hydrophobic moieties.
Thus, surfactants can also be classified according to their Hydrophile-Lipophile Balance
(HLB) (Tiehm, 1994)
The HLB value indicates whether a surfactant will produce a water-in-oil or oil-in-water
emulsion: emulsifiers with a lower HLB value of 3-6 are lipophilic and promote water-inoil emulsification, while emulsifiers with higher HLB values between 10 and 18 are more
hydrophilic and promote oil-in-water emulsions (Desai and Banat, 1997).
A classification based on HLB values has been used to evaluate the suitability of
different surfactants for various applications. For example, it has been reported that the
most successful surfactants in washing oil-contaminated soils are those with a HLB value
above 10 (Volkering et al., 1998).
As the name suggests and due to their chemico-physical structure, “surfactants” partition
preferentially at the interface between phases with different degrees of polarity and
4
hydrogen bonding such as oil/water and air/liquid interfaces. The presence of surfactant
molecules at the interfaces results in a reduction of the interfacial tension of the solution.
In the presence of a non-aqueous phase liquid (NAPL), the surfactant molecules also
aggregate at the liquid-liquid interface, thus reducing the interfacial tension (Volkering et
al., 1998).
Another fundamental property of surfactants is the ability to form micelles, which is
responsible for the excellent detergency and dispersing properties of these compounds.
When dissolved in water in very low concentrations, surfactants are present as monomers.
In such conditions, the hydrophobic tail, unable to form hydrogen bonding disrupts the
water structure in its vicinity, thus causing an increase in the free energy of the system. At
higher concentrations, when this effect is more pronounced, the free energy can be
reduced by the aggregation of the surfactant molecules into micelles, where the
hydrophobic tails are located in the inner part of the cluster and the hydrophilic heads are
exposed to the bulk water phase. The concentration above which the formation of
micelles is thermodynamically favored is called Critical Micelle Concentration (CMC)
(Haigh, 1996). The number of molecules necessary to form a micelle generally varies
between 50 and 100; this is defined as the aggregation number. As a general rule, the
greater the hydrophobicity of the molecules in the aqueous solution, the greater is the
aggregation number (Rosen, M.J. 1989). CMC is commonly used to measure the
efficiency of a surface-active agent (Desai and Banat, 1997). The CMC of surfactants in
aqueous solution can vary depending on several factors, such as molecule structure,
temperature, presence of electrolytes and organic compounds in solution. At soil
temperatures, the CMC typically varies between 0.1 and 1 mM (Volkering et al., 1998).
The size of the hydrophobic region of the surfactant is particularly important for the
determination of the CMC: in fact the CMC decreases with increasing hydrocarbon chain
length, i.e. increasing hydrophobicity. The addition of a CH2- group to the chain has been
shown to decrease the CMC by a factor of 3, according to the Traube’s rule (Fan et al.,
1997)
However, anionic surfactants have higher CMCs than nonionic surfactants even when
they share the same hydrophobic group. Electrolytes in solution can reduce the CMC by
shielding the electrical repulsion among the hydrophilic heads of the molecules; such
effect is more pronounced with anionic and cationic surfactants than with nonionic
5
compounds (Haigh, 1996). At concentrations above the CMC, additional quantities of
surfactant in solution will promote the formation of more micelles. The formation of
micelles leads to a significant increase in the apparent solubility of hydrophobic organic
compounds, even above their water solubility limit, as these compounds can partition into
the central core of a micelle. The effect of such a process is the enhancement of
mobilization of organic compounds and of their dispersion in solution (Perfumo et al.,
2010.)
This effect is also achieved by the lowering of the interfacial tension between immiscible
phases. In fact, this contributes to the creation of additional surfaces, thus improving the
contact between different phases (Christofi and Ivshina, 2002.). The reduction effect of
interfacial tension is particularly relevant when the pollutant is present in soil as a nonaqueous phase liquid.
In summary, the main surfactant- mediated mechanisms, which may potentially enhance
hydrophobic organic compound remediation, include the reduction of interfacial tension,
Micellar solubilization and phase transfer between soil particles and the pseudo-aqueous
phase.
1.3.3 Critical micelles concentration
When there is a large concentration of surfactant solution in water there may not be
enough area at the water surface for all the surfactant molecules to gather, then the
surfactant will begin to cluster together in clumps called micelles. The concentration at
which micelles first begin to form is known as the critical micelle concentration (CMC).
Many physical properties depend on surfactant CMC. As surfactant activities are best
described in aqueous solutions, their CMC depends on temperature, surfactant chemical
structure and ionic characteristics. The surfactants behavior can be explained at
concentrations below and above CMC. Holmberg (2002), Elvers et al. (1994) and Rosen
(1989) made the following observations about surfactant CMC dependence on chemical
structures:
As the hydrocarbon alkyl group increases, surfactant CMC increases. Depending
on the alkyl length the CMC of non-ionic surfactants are about two folds less than
that of the ionic surfactants. However, the cationic surfactants have a higher
6
CMC than the anionic ones.
Increase in temperature decreases the CMC of some non-ionic surfactants
whereas the solubility of ionic surfactants increases.
Salt addition reduces the CMC of ionic surfactant while those of non-ionic are
slightly affected.
The temperature at which the solubility value of anionic surfactants equals the
CMC is known as the Kraft point.
The temperature at which cloud occur for the non-ionic surfactant solutions is
known as cloud point.
1.3.4 Interfacial tension
It is an obvious statement that water and oil don’t mix and upon vigorous shaking will
eventually separate to achieve a minimum surface area between the two distinct phases
(the same can be said of any two immiscible bulk liquids). Interfacial tension exists in the
boundary region between the two bulk liquid phases. Interfacial tension is the property of
a liquid/liquid interface exhibiting the characteristics of a thin elastic membrane acting
along the interface in such a way as to reduce the total interfacial area by an apparent
contraction process (Myers, 1992).
Thermodynamically, interfacial tension is the excess of free energy resulting from an
imbalance of forces acting upon the molecules of each phase. Atoms or molecules at an
interface between two immiscible liquids will generally have a higher potential energy
than those in the bulk of the two phases. Their location at the interface means they will
experience a net force due to the nearest neighbor interactions significantly different from
those in the bulk phases. For two immiscible liquid phases, surface molecules will
normally interact more strongly with those in the bulk rather than those in the adjacent
phase. Interfacial tension is normally defined in units of dyne/cm or mN/m as a force per
unit length, which is equal to energy per unit area (Eamon, 2008).
1.3.5 Solubilization
The aqueous solubility of oil is the apparent solubilization due to the bringing together of
volume of oil and water to equilibrium, then analysing the water rich phase for oil content.
The solubilization rate of single or double components of petroleum hydrocarbon
7
components in aqueous surfactant solution can be used to assess surfactants’ tendency in
removing oil from a contaminated media (Bai et al. (1997), Gabr et al. (1998), Zheng and
Obbard (2002), Pennell et al. (1997) and Kommalapati et al. (1997)). These authors noted
that surfactant have greater capacity to solubilize polarizable hydrocarbons than
extremely hydrophobic compounds such as crude oil. This seems to suggest the reason
why the aqueous solubility of crude oil in surfactants has not yet been explored unlike
those of the different components of petroleum hydrocarbons as noted in NAS (1985).
1.3.6 Hydrophilic-Lipophilic Balance
The Hydrophilic-Lipophilic Balance (HLB) enables surfactants to be arranged on a value
scale from 0 to 40. This arrangement indicates the solubility and behavior of surfactant
solutions in water. Surfactants with high HLB (from about 8 to 15) are hydrophilic in
nature, thus water-loving and more water-soluble. They can be used to form oil-water
emulsions, with good wetting, detergency and cleaning properties. Surfactants with low
HLB (i.e. between 0 and 6) are hydrophobic in nature, will partition into an oil phase and
are more oil soluble. Rosen (1989), Elvers et al. (1994), Kosaric et al. (1987) argued that
they are insoluble in water, form water-in-oil emulsions and act as good emulsifiers.
More so, Kosaric et al. (1987) have used the HLB to assess surfactant effect in enhanced
oil recovery and displacement from porous media. Results obtained through this study
have been used to correlate the surfactant molecular weight, emulsification and oil
recovery from different wells.
1.3.7 Types of surfactants
Anionic surfactants
Anionic surfactants are the largest class of surfactants in general use today and have a
head group composed of highly electronegative atoms making these groups strongly polar
a small counter ion is also present which is usually small Cation such as a sodium ion.
This class of surfactant can be divided into subgroups such as alkali carboxylates or soaps
(RCOO-M
+
); sulphates (ROSO3
-M
+
) such as sulphate ester surfactants, fatty alcohol
sulphates and sulphated fats and oils; sulphonates (RSO3
-M
+
) such as aliphatic and
alkylaryl sulphonates and to a lesser degree phosphates (Mayers, 1992).
8
Cationic surfactants
Cationic surfactants as the name suggests, possess positively charged head groups, which
usually contain a nitrogen atom, or an amide group. There are two important categories of
cationic surfactants which differ mainly in the nature of the nitrogen-containing group [5].
The first consists of alkyl nitrogen compounds such as ammonium salts containing at
least one long chain alkyl group, with halide, sulphate or acetate counter-ions.
The second category contains heterocyclic components within which is an amino group
or a nitrogen atom. An example of this type is alkyl substituted pyridine salts shown in
Figure 1.6. Other cationic functionalities are possible but are less common.
Non-ionic surfactants
The two previously mentioned surfactants dissociate in water to produce a net charge on
the head group of the molecule. This is not a necessary requirement for the existence of
surface activity and non-ionic surfactants can offer advantages over ionic surfactants i.e.
the effect of solution pH is lessened and the degree of water solubility can be controlled
by controlling the polarity and size of the head group. Non-ionic surfactants can be
further divided into sub groups such as block copolymer non-ionic surfactants;
derivatives of polyglycerols and other polyols; and polyoxyethylene based ==surfactants
like polyoxyethylene 23-lauryl ether (CH3(CH2)10CH2(OCH2CH2)23OH) which are the
most numerous and widely used. (Eamon McEvoy, 2008).
Zwitterionic surfactants
Zwitterionic or amphoteric surfactants contain or have the potential to form both positive
and negative functional groups under specified conditions. The zwitterionic nature of
these surfactants makes them very much compatible with other forms of surfactants.
There are in general four classes of functionalities with potential for producing
zwitterionic surfactants; imidazole derivatives such as fatty acid/amino-ethyl ethanolamine condensates (RCONHCH2CH2NR’R’’), betaines and sulpho-betaines such as
dodecylbetaine (C12H25(CH3)2N
+CH2COO-
), amino acid derivatives, and lecithin. (Eamon,
9
2008).
1.3 Aims and Objectives
This research project is aimed at applying surfactant (non-ionic) to enhanced treating oil
contaminated soil.
This aim can be achieved by the following objectives
The chemical/physical properties of the soil
Soil contamination in the Laboratory
Soil remediation using bio solve
1.4 Relevance/Justification
This study would reveal the type of surfactant used in enhancing the remediation of oil
contaminated soil, how surfactants improve remediation by increasing the apparent
solubility of the contaminant in the soil which improves the mass removal per pore
volume, and also by reducing the interfacial tension between the water and the nonaqueous phase liquid increasing the mobility of contaminants.
It is expected that this project will be of relevance in the petroleum industry generally
considering the fact that they manage the hydrocarbon resources which includes
exploration, refining, transporting etc.
This research work is aimed at using surface-active agents in removing the crude oil that
has contaminated water (waste water, surface water or ground water) in other to reduce
pollution and render the environment safe.
1.5 Scope
This research is going to be based on the application of surfactants in treating crude oil
contaminated soil. The removal of oil from polluted soil-using surfactant.
The scope of this work is limited to the laboratory work by conducting a physico-
10
chemical analysis on the soil to determine its properties and biological analysis to monitor
the rate of bacteria growth in the sample discussed in five chapters. This present chapter
gives a general overview of different oil-contaminated soil treatment methods. A
comprehensive literature review is presented in Chapter 2. Detailed description on
surfactants and surfactant properties, as well as the combined effects of surfactants, soil
and oil are also presented. The overview of soil washing in different settings and
mechanisms of oil removal in soil washing using aqueous surfactant solutions are
reviewed
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