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UNIVERSITY OF CINCINNATI

Date: April 24, 2007

I, Niranjan Deshpande ,

hereby submit this work as part of the requirements for the degree of:

Master of Science

in:

Environmental Engineering

It is entitled:

Dispersant Effectiveness on Oil Spills:

Impact of Environmental Factors

This work and its defense approved by:

Chair: Dr. George A. Sorial

Dr. Makram T. Suidan

Dr. Margaret J. Kupferle

DISPERSANT EFFECTIVENESS ON OIL SPILLS: Impact of Environmental Factors

A thesis submitted to the

Division of Research and Advanced Studies of the University of Cincinnati

In partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

In the department of Civil and Environmental Engineering Of the college of Engineering at the University of Cincinnati

2007

by

Niranjan Deshpande B.E. Civil Engineering, Pune University, 2004

Committee chair: Dr. George Sorial

i

ABSTRACT

When a dispersant is applied to an oil slick, its effectiveness in dispersing the

spilled oil depends on various factors such as oil properties, wave mixing energy,

temperature of both oil and water, and salinity of the water. Estuaries represent water

with varying salinities. In this study, three salinity values in the range of 10-34 ppt were

investigated, representing potential salinity concentrations found in typical estuaries.

Three oils were chosen to represent light refined oil, light crude oil and medium crude

oil. Each of the oils was tested at three weathering levels to represent maximum, medium

and zero weathering. Two dispersants were chosen for evaluation. A modified

trypsinizing flask termed the ‘Baffled Flask’ was used for conducting the experimental

runs. A full factorial experiment was conducted for each oil to investigate the effect of

salinity on three environmental factors: temperature (2 levels), oil weathering (3 levels)

and mixing energy (150,200 and 250 rpm). Each experiment was replicated four times in

order to evaluate the accuracy of the test. Evaluations were conducted to study the effect

of different variables like salinity, weathering, mixing speed and temperature on

dispersant effectiveness. Statistical analysis of the data was performed separately on each

of the nine oil-dispersant combinations, which revealed the significant factors for each of

the combinations. A linear regression model was fit to the experimental data collected.

Keywords: Baffled Flask, dispersant effectiveness, salinity, mixing speed, temperature.

iii

ACKNOWLEDGEMENTS

I would to thank first and foremost my family for all the motivation and support they

provided to me, especially my brother Nikhil, for the support and encouragement.

I would like to thank my advisor Dr. George Sorial for always being there for me when I

needed him, and for keeping an eye on me, and more importantly, being a very nice

person to work with. I cannot forget my group partners Qiuli Lu, Daekeun Kim, Hao

Zhang, Zhangli Cai (Charlie) Ashraf Hosni, Rangesh Srinivasan, and Rachel Rhodes for

all their help, support and friendship. They have really made the environmental chemistry

lab feel like home.

I would also like to thank Dr. Makram Suidan and Dr. Margaret Kupferle for serving on

my committee. I would also like to thank the EPA for the funding received during these

two years under USEPA Task Order 70.

A special thanks to Yogesh Kandlur, for all his help with statistics, and Pamela Heckel,

for proofreading my thesis. I really appreciate the time, effort and suggestions they have

given.

Of course I need to thank all my lab mates for helping me out, I wouldn’t have been able

to manage without any of you. In alphabetical order: Shirish Agarwal, Maria Antoniou,

iv

Ahmed Hosni, Gina Lamendella, Ian Laseke, Alicia Mansour, Ashok Matta, Marc-Andre

Philibert, Aditya Rastogi, Bhargavi Subramanian, and Jiefei Yu.

And finally I would like to mention the following people for giving me their friendship

and making my time in Cincinnati invaluable (also in alphabetical order): Ezgi Akpinar,

Maria Antoniou, Tejas Arurkar and the members of the UC cricket team, Emina

Atikovic, David Bailey and the members of my soccer team, Elif Bengu, Abhijeet

Deshpande, Hélène Deval, Yann Ferrand, Ines Ivicic, Gina Lamendella, Ian Laseke,

Chris Luedekar, Sujit Mahajan, Alicia Mansour, Amol Padmawar, Aniruddha Palsule,

Marc-Andre Philibert, Bhargavi Subramanian , Jiefei Yu, Rachel Zerkle, and YueChen

Zhao.

v

TABLE OF CONTENTS

ABSTRACT……………………………………………………………………………….i

ACKNOWLEDGEMENTS……………………………………………………………... iii

INDEX…………………………………………………………………………………….v

LIST OF TABLES……………………………………………………………………….vii

LIST OF FIGURES………………………………………………………………………ix

Chapter 1 Introduction

1.1 Introduction............................................................................................................... 1

1.2 Purpose of Study....................................................................................................... 2

1.3 Literature review....................................................................................................... 3

1.4 Research Objectives................................................................................................ 10

1.5 References............................................................................................................... 12

Chapter 2 Experimental Materials and Methods .......................................................... 16

2.1 Materials ................................................................................................................. 17

2.1.1 Analytical Instruments .................................................................................. 17

2.1.2 Reagents........................................................................................................ 18

2.2 Methods................................................................................................................... 21

2.2.1 Weathering of oils......................................................................................... 21

2.2.2 Oil Standards Procedure: .............................................................................. 21

2.2.3 Dispersant Effectiveness procedure:............................................................. 23

2.2.4 Sample Analysis............................................................................................ 23

2.2.5 QA/QC Checks ............................................................................................. 24

vi

2.2.6 Calculation Procedures for Experimental Samples....................................... 25

2.2.7 Viscosity measurements................................................................................ 26

Chapter 3 Dispersant Effectiveness at 10˚C................................................................... 28

3.1 Introduction............................................................................................................. 29

3.2 Dispersant Effectiveness procedure........................................................................ 29

3.3 Sample Analysis...................................................................................................... 30

3.4 Discussion ............................................................................................................... 30

Chapter 4 Dispersant Effectiveness at 16 ˚C.................................................................. 45

4.1 Introduction............................................................................................................. 46

4.2 Dispersant Effectiveness procedure........................................................................ 46

4.3 Sample Analysis...................................................................................................... 47

4.4 Discussion ............................................................................................................... 47

Chapter 5 Viscosity Determination of the Test Oils..................................................... 62

5.1 Abstract ................................................................................................................... 63

5.2 Introduction............................................................................................................. 63

5.3 Materials and Methods............................................................................................ 64

5.4 Experimental Results .............................................................................................. 65

5.5 Regression............................................................................................................... 66

5.6 References............................................................................................................... 73

Chapter 6 Statistical Analysis of Experimental Data .................................................... 74

6.1 Introduction............................................................................................................. 75

6.2 Factorial Experimental Design ............................................................................... 75

6.3 Analysis of Variance (ANOVA)............................................................................. 76

vii

6.4 Empirical Relationship............................................................................................ 77

6.5 Comparison with Previous study ............................................................................ 84

6.6 Correlation of Dispersant effectiveness to Oil viscosity......................................... 89

6.7 References............................................................................................................... 98

Chapter 7 Conclusions and Recommendations ............................................................ 99

7.1 Conclusions........................................................................................................... 100

7.2 Recommendations................................................................................................. 101

Appendix A1 Experimental Data.................................................................................. 103

Appendix A2 Results of ANOVA ................................................................................. 158

Appendix A3 Compositions and Physical properties of Oils ..................................... 164

Appendix A4 Results of ANOVA for Viscosity Correlation ....................................... 167

viii

LIST OF TABLES

Table 2.1 Major Ion Composition of “Instant Ocean” Synthetic Sea Salt........................ 20

Table 2.2: Six point calibration curve for three oils ......................................................... 22

Table 5.1 Calibration constants for Viscometers .............................................................. 66

Table 5.2 Viscosity measurements of oils at various temperatures .................................. 66

Table 5.3 Parameters obtained for the three test oils ........................................................ 67

Table 5.4 Comparison for South Louisiana Crude Oil (SLC) .......................................... 68

Table 5.5 Comparison for Prudhoe Bay Crude Oil (PBC) ............................................... 69

Table 5.6 Comparison for No.2 Fuel Oil (2FO) ............................................................... 70

Table 5.7 Comparison of Model with Reported Viscosities............................................. 71

Table 6.1 Significant Factors for Various Oil-Dispersant Combinations for 2

Temperatures (10&16 ˚C)................................................................................................. 77

Table 6.2 Coefficients of Regression equations ............................................................... 79

Table 6.3 Coefficients of Regression equations ............................................................... 91

ix

LIST OF FIGURES

Figure 2.1 Baffled Flask Test Apparatus .......................................................................... 19

Figure 2.2 Cannon-Fenske Viscometer............................................................................. 27

Figure 3.1 Effect of Salinity and Weathering of SLC for dispersant ‘A’ ......................... 36

Figure 3.2 Effect of Salinity and Weathering of SLC for dispersant ‘B’ ......................... 37

Figure 3.3 Effect of Salinity and Weathering of SLC for dispersant ‘C’ ......................... 38

Figure 3.4 Effect of Salinity and Weathering of PBC for dispersant ‘A’......................... 39

Figure 3.5 Effect of Salinity and Weathering of PBC for dispersant ‘B’ ......................... 40

Figure 3.6 Effect of Salinity and Weathering of PBC for dispersant ‘C’ ......................... 41

Figure 3.7 Effect of Salinity and Weathering of 2FO for dispersant ‘A’ ......................... 42

Figure 3.8 Effect of Salinity and Weathering of 2FO for dispersant ‘B’ ......................... 43

Figure 3.9 Effect of Salinity and Weathering of 2FO for dispersant ‘C’ ......................... 44

Figure 4.1 Effect of Salinity and Weathering of SLC for dispersant ‘A’ ......................... 53

Figure 4.2 Effect of Salinity and Weathering of SLC for dispersant ‘B’ ......................... 54

Figure 4.3 Effect of Salinity and Weathering of SLC for dispersant ‘C’ ......................... 55

Figure 4.4 Effect of Salinity and Weathering of PBC for dispersant ‘A’......................... 56

Figure 4.5 Effect of Salinity and Weathering of PBC for dispersant ‘B’ ......................... 57

Figure 4.6 Effect of Salinity and Weathering of PBC for dispersant ‘C’ ......................... 58

Figure 4.7 Effect of Salinity and Weathering of 2FO for dispersant ‘A’ ......................... 59

Figure 4.8 Effect of Salinity and Weathering of 2FO for dispersant ‘B’ ......................... 60

Figure 4.9 Effect of Salinity and Weathering of 2FO for dispersant ‘C’ ......................... 61

Figure 5.1 Comparisons of Viscosities of the Test Oils ................................................... 72

Figure 6.1 Comparison of Estimated & Experimental Dispersant Effectiveness-SLC .... 81

x

Figure 6.2 Comparison of Estimated & Experimental Dispersant Effectiveness-PBC.... 82

Figure 6.3 Comparison of Estimated & Experimental Dispersant Effectiveness-2FO .... 83

Figure 6.4 Comparison for No.2 Fuel Oil......................................................................... 86

Figure 6.5 Comparison for Prudhoe Bay Crude Oil ......................................................... 87

Figure 6.6 Comparison for South Louisiana Crude Oil .................................................... 88

Figure 6.7 Comparison of Estimated & Experimental dispersant effectiveness-2FO ...... 92

Figure 6.8 Comparison of Estimated & Experimental dispersant effectiveness-PBC...... 93

Figure 6.9 Comparison of Estimated & Experimental dispersant effectiveness-SLC...... 94

Figure 6.10 Comparison for No.2 Fuel Oil....................................................................... 95

Figure 6.11 Comparison for Prudhoe Bay Crude Oil ....................................................... 96

Figure 6.12 Comparison for South Louisiana Crude Oil…………………………….......97

Chapter 1

Introduction

1

1.1 Introduction

Transportation of petroleum products and offshore drilling around the world are

the most significant causes for oil spills in the environment. These spills can be results of

equipment malfunction, human carelessness, or natural causes. Oil spills at sea can affect

the water column, sediments and shorelines; oil spilled on water can harm organisms that

live on or around the water surface and also those that live under the water surface.

Effects depend in large part on the ultimate location of the oil as well as its

chemical composition at the time of interaction with the biota. Oil slicks usually spread

very rapidly to a large area due to the action of gravitational and viscous forces, and

require a quick response(Hoult 1972). Four cleanup strategies typically considered are (1)

mechanical cleanup or recovery, (2) burning, (3) bioremediation, and (4) treatment with

chemical dispersants (NRC 1989a; NRC 1989b).

The use of chemical dispersants to counter the effects of an oil spill has many

benefits when compared to other response options. Dispersants do not eliminate the

problem of an oil spill but reduce the overall impact of the spill on the environment.

Chemical dispersants are made up of surfactants, solvents, and additives, which are

usually sprayed onto the slick to remove the oil from the surface and disperse it into the

water column at very low concentrations. This accelerates the natural degradation of oils

and significantly reduces the impact on the shorelines and the aquatic habitat. The

essential components in dispersant formulations are surfactant, which contain both oil-

compatible (lipophilic) and water-compatible (hydrophilic) groups. Following successful

application of a chemical dispersant formulation to an oil slick, the surfactant molecules

will reside at oil-water interfaces and reduce the oil-water interfacial surface tension. The

2

presence of minimal mixing energy provided by wave or wind action disperses the oil as

small droplets into the underlying water column. Such dispersion leads to dilution of the

oil in the water and increased oil-water interfacial surface area, which favors microbial

degradation of the oil. The purpose is to remove oil from the water surface and dilute and

degrade it to non-problematic concentrations in an underlying water column.

Dispersant effectiveness is the ratio of oil that the chemical will disperse into the

water column compared to the amount of oil that remains on the surface. This is what

determines the selection and usage of dispersants. The National Contingency Plan (NCP)

Product schedule lists dispersants which are at least 45% effective (50 ± 5%) in

dispersing Prudhoe Bay and South Louisiana crude oils in the laboratory (Sorial et al.

2004c). Many factors influence dispersant effectiveness, including oil composition,

mixing energy, oil weathering, dispersant type and amount applied, temperature, and

salinity of water.

Salinity of the sea is considered to be constant between 34-35 ppt; however, the

salinity of water in estuaries varies due to the mixing of fresh water. To take into account

these differences, two other salinities (viz: 20 ppt and 10 ppt) were also considered.

1.2 Purpose of Study

To assess the impacts of dispersant usage on oil spills, the US EPA is developing

a simulation model called the EPA Research Object-Oriented Oil Spill (ERO3S) Model.

This model simulates a portion of the oil slick behavior. Due to physical and chemical

interactions between the oil and the sea, this behavior has to be based on empirical data.

3

Therefore the main aim of the project is to create a set of empirical data to serve as an

input to the ERO3S model. The first two phases of the project looked at the effectiveness

of the dispersion caused by changes in temperature, oil composition, oil weathering,

dispersant type, rotational speed of the Baffled Flask, and salinity. The results obtained

indicated the need for obtaining data that will more strongly establish the temperature

behavior (Chandrasekar 2004).

1.3 Literature review

The concept of applying chemical dispersants to combat oil spills has been around

for decades. Oil spill dispersants have been used to enhance the rate of natural dispersion

of oil spills at sea. Dispersants break up the oil slick from the water surface and dilute the

oil into small droplets into the water column. The large increase in the oil water interface

due to droplet formation increases the biodegradation of the oil by naturally occurring

micro-organisms. In 1973 (Canevari 1973)worked on developing “The Next Generation”

chemical dispersants. The idea was to develop dispersants requiring little or no mixing

energy, which approached spontaneous emulsification. Canevari identified mixing as the

limiting step rather than application. Thus came the era of self-mixing dispersants.

In 1989, the National Research Council (NRC) conducted a comprehensive

review of various laboratory, meso-scale, and field tests that have been used to assess

dispersant effectiveness (NRC 1989b). The report pointed out a wide range of conditions

of oil-dispersant mixing, turbulence, droplet size distribution, and droplet coalescence

and resurfacing. The review also noted that understanding the interactions among these

phenomena is fundamental to determining why dispersants work or do not work.

4

Furthermore, it was also noted that the relative complexity of a large scale apparatus

means that performance of multiple testing events in short periods of time is not possible.

A variety of factors influence the ability of dispersants to disperse oil into water.

Both crude and petroleum products are complex mixtures of hydrocarbon compounds.

(Bobra and Callaghan 1990) defined the five major compounds of any oil composition as

aliphatics, aromatics, asphaltenes, resins, and waxes. Interactions between aliphatics,

aromatics, asphaltenes, resins, and waxes in complex oil mixtures allow the compounds

to be maintained in a liquid-oil state.(Bobra 1991; Buist et al. 1989)

Brandvik and Daling (1998) found that the traditional blending rules based on the

hydrophilic-lipophilic-balance (HLB), which states that a dispersant should have a HLB

between 9 and 11, is not a useful tool in dispersant optimization. The concept fails to take

into account the strong molecular interactions between the surfactants, which are not

explained by this univariate concept.

Oil that is released onto the water surface will undergo rapid, dynamic changes in

both chemical composition and physical properties due to natural weathering processes.

(Payne et al. 1983). Lower molecular weight compounds (aromatics, aliphatics) that are

necessary for solvency interactions are lost due to evaporation and dissolution during

natural weathering processes. Water is rapidly incorporated into many oils to form stable

water in oil emulsions (mousse), which are characterized by substantially higher

viscosities (Payne et al. 1983). Studies by Buist and Ross (1986) and Daling (1988) have

shown that viscous mousse is more resistant to chemical dispersion than its less viscous

parent oil. Water in oil emulsions are formed rapidly in the field, making them important

for consideration in chemical dispersion. Therefore, the period of time or window of

5

opportunity during which chemical dispersants may be effectively used for an oil spill

may be relatively short.

Canevari (1982) noted that there may be two mechanisms to stabilize water in oil

emulsions: (1) actions of natural surfactants such as those addressed by Bridie et al.

(1980) and NRC (1985) and (2) the presence of bi-wetted solid particles (partly water

wetted and partly oil wetted) at oil- water interfaces that prevent emulsified water

droplets in oil from coalescing with each other.

Three mechanisms have been used for dispersant applications in lab tests: (1)

premixing of a dispersant with an oil before the test begins, (2) premixing of a dispersant

with the water before the oil is introduced into the system (Rewick et al. 2005; Rewick et

al. 1984), and (3) mixing of the dispersant with oil at the oil-air interface as a part of the

testing procedure itself. This situation is most representative of the situation likely to be

encountered at sea and ensures that dilution of a dispersant into oil is more gradual.

Fingas et al. (2005a) examined the natural dispersibility of 15 different types of

oil in the laboratory using the labofina rotating flask test and the Mackay-Nadeau-

Steelman test (MNS). Both of these tests impart substantial turbulence to test solutions.

Results show that the different oils were characterized by varying degrees of natural

dispersibility that are a function of the testing procedure. The ability of chemical

dispersants to disperse petroleum products will vary as a function of the chemical and

physical properties of oil. Oils characterized by higher viscosities will usually exhibit

lower capacities for chemical dispersion. Increasing viscosity appears to reduce

dispersion of oil droplets in two ways: first, migration of dispersant into oil-water

6

interface is retarded, and second, the energy required to shear off oil droplets from the

slick is increased (Clayton et al. 1993).

Fingas et al. (2005a) conducted studies on relationships between dispersant

effectiveness and mixing energy. The effect of dispersant type and oil type was also

considered. They found that each oil dispersant combination had a unique threshold or

onset of dispersion. The effectiveness increased linearly with mixing energy, expressed

as rotation speed. It was observed that effectiveness rises rapidly to 80 to 90 percent with

increasing energy for light oils treated with chemical dispersants, heavier oils dispersed

too, but to lesser effectiveness values.

Clayton et al. (1993) has shown that the salinity of receiving waters can impact

dispersion of oil. The specific intent of dispersant formulations for marine applications is

to provide maximum dispersion at normal seawater salinity.

Lower water temperatures increase the viscosity of both the oil and the dispersant.

A higher water temperature usually increases the solubility of dispersants in water, and

also affects the spilled oil temperature. Hence an increase in temperature reduces oil

viscosity and increases dispersion. Studies by Mackay and Szeto (1981), Byford et al.

(1983), and Fingas et al. (2005b) indicated an increase in dispersion efficiency with

temperature.

There have been conflicting results in the trends of dispersant effectiveness with

both increasing and decreasing water temperature. The results of the studies performed

by Byford et al. (1983) differed from those performed by Fingas (1991).

The swirling flask Test (SFT) was introduced by the US EPA to accept dispersant

products for use as an oil spill countermeasure in 1993. It was included in the final EPA

7

regulation in September 1994. In further testing, it was seen that the test gave widely

variable results among different labs (IT corporation, 1995). The errors were attributed to

the design of the flask, which led to partial remixing when the sample was being

extracted.

Blondina et al. (1999) studied the influence of salinity on dispersant effectiveness

using a modified version of the swirling flask. The flask was modified by placing a

stopcock at the bottom of the flask to facilitate the removal of the sample without

introducing mixing in the samples. The data demonstrated that the interaction between

receiving water salinity and the ability of dispersants to enhance dispersion into the water

column can be both oil and dispersant specific.

Venosa et al. (2005) identified the various factors that lead to the variance of the

SFT, and based on that information, designed a new test to give more realistic and

reproducible results. This study also showed that for the analyses of the crude oils, the

spectrophotometer and diode array demonstrated better instrument repeatability than the

GC at low concentrations (Sorial et al. 2001). The revised protocol, known as the Baffled

Flask Test (BFT), has a 150 ml trypsinizing flask with baffles, modified by placing a

stopcock at the bottom of the flask to facilitate the removal of the sample without

disturbance. The new design provides a different type of mixing regime that is more

analogous to the mixing provided by wave action in the open sea. A round robin testing

conducted by the EPA and eight international testing labs found that the BFT

performance was significantly improved over that of the SFT with regard to

reproducibility and repeatability (Sorial et al. 2004b).

8

Toxicity tests conducted on Corexit® dispersants (Clark and Ares 2000) revealed that

toxicity estimates were significantly affected by the test variables (species, life stage,

exposure duration, and temperature). The apparently greater toxicity of the oil dispersant

combination was due to the greater exposure of aquatic organisms to the dissolved and

dispersed components of the oil. The study concluded that the toxicity of the dispersant

did not add to the toxicity of the spilled oil, and asserted that it is more important to

consider the toxicity of the oil. This study alleviated any concerns over the use of

chemical dispersants for oil spill remediation.

Sorial et al. (2004a) studied the impact of operational variables (rotational speed,

mixing time, settling time, and oil to dispersant ratio) on dispersant effectiveness. It was

found that the effectiveness of the dispersant was strongly dependent on the type of oil

and type of flask. It was observed that it was difficult to differentiate between dispersants

at higher rotation speeds. (There was no significant difference in the amount of dispersion

between 200 rpm and 250 rpm). The effect of settling time was more pronounced at 150

rpm than at any other rotation speed studied. The rotation speeds above 200 rpm and

settling times above 10 minutes did not result in any further enhancement in dispersion.

The results indicated that for the Baffled Flask, the coefficient of variation for operator

repeatability was always less than ten percent. The factors most important for dispersion

were identified as rotational speed and dispersant to oil ratio. Mixing time and settling

time were found to have minor influences on the dispersion. A revised protocol with the

following operational variables was formed:

1. Rotational speed of 200 rpm

2. Mixing time of 10 min

9

3. Settling time of 10 min

4. Dispersant: oil ratio of 1:25

Sorial et al. (2004d) conducted further experiments to test the performance of the new

protocol. Experiments were run by three operators on 18 dispersants, by both the EPA

SFT and the BFT methods. The performance of the BFT was found to surpass that of the

SFT. The results further confirmed the reproducibility of the BFT as was previously

reported. Chandrasekar (2004) studied the dispersant effectiveness on three oils under

various simulated environmental conditions, viz: temperature, weathering, salinity, and

rotation speed. It was found that for light crude oil (SLC), temperature and mixing energy

were significant factors; for medium crude oil (PBC), temperature, mixing energy and

weathering were significant; and finally, for light refined oil (2FO), only temperature was

a significant factor. Statistical analyses of the experimental data (performed separately)

revealed that certain two way interactions exist between the factors. The percent

dispersion was found to increase as flask rotational speed increased from 150 to 250 rpm.

The percent dispersion was seen to decrease as the degree of weathering of the oil

increased. The impact of weathering was most pronounced in the case of PBC. When the

temperature was increased from 5 to 22C, dispersion increased in most cases. When the

temperature was increased from 22 to 35C, dispersion declined in most cases. It was

noted that temperature played a dual role: decreasing the viscosity, which increases the

dispersion; and increasing the weathering, which decreases the dispersion. A quadratic

regression model was fit to the experimental data obtained. The terms in the relationship

10

were chosen to include both linear and parabolic effects of each variable and all the

possible two and three factor interactions.

The temperature range studied was wide enough not to depict a clear picture (5, 22,

and 35 °C). Studying the dispersion at intermediate temperatures will help better

understand the impact of temperature on dispersion. Therefore, the main purpose of the

current study is to clearly establish the temperature behavior, to determine the

relationship of viscosity with dispersion at a different temperature and to provide a

comprehensive equation that will be able to predict oil dispersal.

1.4 Research Objectives

The overall objective of this research was to develop a set of empirical data on

three oils and two dispersants to serve as an input to the ERO3S model based on variation

in dispersant effectiveness caused by changes in temperature, oil type, oil weathering,

dispersant type, rotation speed of BFT, and salinity of sea water.

The specific objectives of the project were:

• To conduct a factorial experimental design in order to determine which of the

factors such as temperature, oil type, salinity, weathering, and flask speed are

related to the effectiveness of a dispersant used in oil remediation; the main

intention is to more strongly establish temperature behavior at intermediate

temperatures within the range studied previously by Chandrasekar (2004)

• Temperatures of 10 and 16 °C will be considered.

• To determine how the viscosity of the oil and weathered oil changes over the

temperature range

• To predict dispersion values using empirical relationships

11

• To draw a correlation between the trends observed in dispersant effectiveness to

the viscosity of the oils studied under simulated conditions (temperature and

weathering).

12

1.5 References

1. Blondina, G. J., Singer, M. M., Lee, I., Ouano, M. T., Hodgins, M., Tjeerdema, R.

S., and Sowby, M. L. (1999). "Influence of Salinity on Petroleum

Accommodation by Dispersants." Spill Science & Technology Bulletin 5(2), 127-

134.

2. Bobra, M. (1991)"Water in Oil Emulsification: A physicochemical Study." In

proceedings of International Oil Spill Conference, San Diego,CA, 483-488.

3. Bobra, M., and Callaghan, S. (1990). "A Catalogue of Crude Oil and Oil Product

Properties." Environment Canada, EE-125, 542.

4. Brandvik, P., and Daling, S. (1998). "Optimisation of oil spill dispersant

composition by mixture design and response surface methods." Chemometrics

and Intellegent Laboratory systems, 42, 63-72.

5. Bridie, A. L., Wanders, T. H., Zegveld, W., and van der Heijde, H. B. (1980).

"Formation, prevention and breaking of sea water in crude oil emulsions

`chocolate mousses'." Marine Pollution Bulletin, 11(12), 343-348.

6. Buist, I., S, P., D, M., and M, C. (1989)"Laboratory Studies on the Behaviour and

Cleanup of Waxy Crude Oil Spills." In proceedings of Oil Spill Conference,

Washington, D.C, 105-113.

7. Byford, D. C., Green, P. J., and Lewis, A. (1983) "Factors Influencing the

Performance and Selection of Low-Temperature Dispersants." In proceedings of

6th Arctic Marine Oilspill Program, Edmonton, Alberta, Canada, 140-150.

13

8. Canevari, G. P. (1973). "Development of the 'next generation' chemical

dispersants." In proceedings of Joint Conference on Prevention and Control of

Oil Spills, 231-240.

9. Canevari, G. P. (1982). "The formulation of an effective demulsifier for oil spill

emulsions." Marine Pollution Bulletin, 13(2), 49-54.

10. Chandrasekar, S. (2004). "Dispersant effectiveness data for a suite of

environmental conditions," MS Thesis University of Cincinnati, Cincinnati.

11. Chandrasekar, S., Sorial, G., and Weaver, J. (2005). "Dispersant effectiveness on

three oils under various simulated environmental conditions." Environmental

Engineering Science, 22(3), 324-336.

12. Clark, J., and Ares, G. (2000). "Aquatic toxicity of two Corexit dispersants."

Chemosphere, 40, 897-906.

13. Clayton, J. R., Payne, J., and Farlow, J. (1993). Oil Spill Dispersants Mechanisms

of Action and Laboratory Tests, C.K. Smoley, Boca Raton, FL.

14. Cormack, D. B., Lynch, W. J., and Dowsett, B. D. (1986/87). "Evaluation of

Dispersant effectiveness." Oil and Chemical Pollution, 3, 87-103.

15. Daling, S. (1988). "A Study of Chemical Dispersibility of Fresh and Weathered

Crude oil." In proceedings of 11th Artic Marine Oil Spill Program, 481-499.

16. Fingas, M. F., Kyle, D. A., Holmes, J. B., and Tennyson, E. J. "The effectiveness

of dispersants: Variation with energy." 2005 International Oil Spill Conference,

2273.

14

17. Fingas, M. F., Munn, D. L., White, B., Stoodley, R. G., and Crerar, I. D.

"Laboratory testing of dispersant effectiveness: The importance of oil-to-water

ratio and settling time." 2005 International Oil Spill Conference, 4257.

18. Hoult, D. P. (1972). "Oil Spreading on the Sea." Annu. Rev. Fluid Mech., 4, 341-

368.

19. Mackay, D., and Szeto, F (1981) "The Laboratory Determination of Dispersant

Effectiveness, Method Development and Results." In proceedings of Oil Spill

Conference, 11-17.

20. Mackay, D., and Wells, P. G. (1983) "Effectiveness, behavior, and toxicity of (Oil

Spill) dispersants." In Proceedings of Oil Spill Conference, San Antonio, TX, 65-

71.

21. Nes, H. (1984). "Effectiveness of Oil dispersants: Laboratory experiments."

NTNF, Oslo, Norway.

22. NRC. (1985). "Oil in the Sea: Inputs, Fates and Effects." National Research

Council, Washington, D.C.

23. NRC. (1989a). "Using Oil Spill Dispersants on the Sea." Report of the Committee

on Effectiveness of Oil Spill Dispersants, National Academy Press, Washington,

D.C.

24. NRC. (1989b). "Using Oil Spill Dispersants on the Sea." National Research

Council, National Academy Press, Washington, D.C.

25. Payne, J., Kirstein, B. E., G.D McNabb, J., and Lambach, J. L. "Multivariate

Analysis of Petroleum Hydrocarbon Weathering in the Subartic Marine

15

Environment." In Proceedings of Oil Spill Conference, San Antonio, TX, 423-

434.

26. Rewick, R. T., Sabo, K. A., Gates, J., Smith, J. H., and McCarthy Jr, L. T. "An

evaluation of oil spill dispersant testing requirements." 2005 International Oil

Spill Conference, 2765.

27. Rewick, R. T., Sabo, K. A., and Smith, J. H. "The Drop-weight Interfacial

Tension Method for Predicting Dispersant Performance in: Oil Spill Chemical

Dispersants, Research Experience and Recommendations, ASTM STP 840."

ASTM Special Technical Publication, 94-107.

28. Sorial, G., Koran, K., and Venosa, A. "Development of a rational oill spill

dispersant effectiveness protocol." International oil Spill conference, 471-478.

29. Sorial, G., Venosa, A., and Koran, K. (2004a). "Oil spill dispersant effectiveness

protocol I: Impact of operational variables." Journal of Environmental

Engineering, 130(10), 1073-1085.

30. Sorial, G., Venosa, A., and Koran, K. (2004b). "Oil spill dispersant effectiveness

protocol II: Performance of Revised protocol." Journal of Environmental

Engineering, 130(10), 1085-1093.

31. Venosa, A. D., Sorial, G. A., Uraizee, F., Richardson, T. L., and Suidan, M. T.

"Research leading to revisions in EPA's dispersant effectiveness protocol." 2005

International Oil Spill Conference, 6987.

32. Weaver, J. (2004). "Characteristics of Spilled Oils, Fuels, and Petroleum

Products: 3a. Simulation of Oil Spills and Dispersants Under Conditions of

Uncertainty." EPA 600/R-04/120, US. EPA, Raleigh, NC.

16

Chapter 2

Experimental Materials and Methods

17

2 EXPERIMENTAL MATERIALS AND METHODS

2.1 Materials

Modified 150 mL glass baffled trypsinizing flasks with screw caps at the top and Teflon

Stopcocks placed near the bottom were used in all the experiments (see Figure 1). An

orbital shaker (Lab-Line Instruments Inc, Melrose Park, IL) with a variable speed control

unit (40-400 rpm) and an orbital diameter of 0.75 inches (2 cm) was used in order to

provide turbulence to solutions in test flasks. The shaker has a control speed dial to

provide an rpm reading on a meter within the instrument. The accuracy is within ±10%.

A Brinkmann Eppendorf repeater plus pipettor (Fisher Scientific, Pittsburgh, PA) capable

of dispensing 4 μL of dispersant and 100 μL of oil with an accuracy of 0.3% and a

precision of 0.25% was used with 100 μL and 5mL syringe tip attachments. Glassware

consisting of graduated cylinders, 125 mL separatory funnels with Teflon stopcocks,

pipettes, 50 mL crimp style amber glass vials and 50, 100 and 1000 μL gas-tight syringes

were also used.

2.1.1 Analytical Instruments

A UVmini-1240 UV-VIS Spectrophotometer (UV-VIS spec) (Shimadzu Scientific

Instruments, Inc, Wood Dale, IL) capable of measuring absorbance at 340, 370 and 400

nm was used in all the experiments to measure the dispersed oil concentration after

extraction.

18

2.1.2 Reagents

The synthetic sea water “Instant Ocean” (Aquarium Systems, Mentor, OH) was used for

all the experiments at a concentration (salinity) of 34, 20, and 10 ppt, based on an ion

composition shown in table 2.1. Three types of oil samples provided by US EPA-SLC,

PBC, and 2FO were used in the study. The dispersants used for testing of test oils were

C9500, and SPC1000.

The hydrocarbon composition and physical characteristics of the test oils can be

found in Appendix A3.

19

Figure 2.1 Baffled Flask Test Apparatus

20

Table 2.1 Major Ion Composition of “Instant Ocean” Synthetic Sea Salt

Major Ion % Total Weight Ionic Concentration at

34 ppt salinity, mg/L

Chloride 47.5 18,700

Sodium 26.3 10,400

Sulfate 6.6 2,600

Magnesium 3.2 1,200

Calcium 1.0 400

Potassium 1.0 400

Bicarbonate 0.5 200

Boron 0.015 6

Strontium 0.001 8

Solids Total 86.1 34,000

Water 13.9

Total 100.0

21

2.2 Methods

2.2.1 Weathering of oils

The three oils Prudhoe Bay Crude Oil, South Louisiana Crude Oil and Number 2 Fuel

Oil were used in the study at three levels of volatilization (weathering). The weathering

of the oil was performed by bubbling air up through 1-L graduated cylinder filled with

oil. The volume of the oil remaining in the measuring cylinder was recorded with time.

The evaporative loss was then expressed as a volume percent.

%oilvolatilizedInitial volume Final volume

Initial volume = − ×100 …… (2.1)

Prudhoe Bay and South Louisiana Crude oil were weathered at 0%, 10%, and 20%

whereas Number 2 Fuel Oil was weathered at 0%, 3.8%, and 7.6%.

2.2.2 Oil Standards Procedure:

Standard solutions of oil for calibrating the UV-visible spectrophotometer were

prepared with the specific reference oils and dispersant used for a particular set of

experimental test runs.

For control treatments with no dispersant, i.e., oil control experiments, only oil was used

to make the standard solution. Initially, Oil Alone Stock Standard was prepared. The

density of the specific reference oil (2 mL) with 18 mL DCM added was measured by

using a 1 mL gas tight syringe and the concentration of the oil solution determined.

Specific volumes of Prudhoe Bay Crude Oil-DCM stock or South Louisiana Crude Oil-

DCM stock or Number 2 Fuel Oil-DCM stock were added to 30 mL of synthetic sea

22

water in a separatory funnel and extracted thrice with DCM. The volumes that were

added are given in table 2. The final DCM volume for the combined extracts was

adjusted to 20 mL with DCM. The extracts were then transferred to a 50 mL crimp style

glass vial with a Teflon/aluminum seal. The contents of the sealed vial were mixed by

inverting several times. The vials were stored at 4 ± 2 0C until time of analysis. Prior to

any analysis, the spectrophotometer ultraviolet lamp was turned on and allowed a 30-

minute warm-up period. For treatments with oil plus dispersant, Oil plus Dispersant

Stock Standard were first prepared. The density of 2 mL specific reference oil, 80 μL of

the dispersant and 18 mL DCM was measured using a 1 mL gas tight syringe and the

concentration determined. These stock solutions were used to prepare standard solutions

as mentioned above.

Table 2.2: Six point calibration curve for three oils

Calibration points

Oil 1 2 3 4 5 6

PBC 11 20 50 100 125 150

SLC 20 50 100 150 200 300

2FO 150 200 400 600 800 1000

* All numbers indicate volume of the stock solution in µL

23

2.2.3 Dispersant Effectiveness procedure:

The experimental procedure for each of the flask test runs was as follows:

120 mL of synthetic seawater equilibrated at the desired temperature was first added to

the modified trypsinizing flask (Baffled Flask), followed sequentially by addition of oil

and dispersant. A volume of 100 μL of oil was dispensed directly onto the surface of the

synthetic sea water using an Eppendorf repeater pipettor with a 5 mL syringe tip

attachment. The dispersant was then dispensed onto the center of the oil slick by using a

100 μL syringe tip attachment set to dispense 4 μL, giving a ratio of dispersant-to-oil of

1:25. The flask was then placed on the orbital shaker and mixed for 10 minutes at the

desired rotation speed. At the end of the shaking period, the flask was removed from the

shaker and allowed to remain stationary on the bench top for 10 minutes. At the end of

the settling time, the first 2 mL of sample are drained from the stopcock and discarded;

30 mL of sample are then collected in a 50 mL measuring cylinder. The 30 mL sample

was then transferred to a 125 mL separatory funnel and extracted 3 times with fresh 5 mL

DCM. The extract was then adjusted to a final volume of 20 mL and transferred to a 50

mL crimp style glass vial with an aluminum/Teflon seal. The vials were then stored at

4±2� C until the time of analysis.

2.2.4 Sample Analysis

The experimental samples extracts and the standard solutions prepared were removed

from the cold room and allowed to equilibrate at the laboratory temperature. First, a blank

solution (DCM) was introduced. Then the standard solutions were introduced in the order

24

of increasing concentrations and the absorbance values were noted at wavelengths of 340,

370, and 400 nm. After this, the experimental samples were introduced. For the samples

that exceeded the highest calibration standard point, dilution was done. This was mostly

done in case of Prudhoe Bay Crude oil which was diluted 10 times. The sequence of

analysis was thus:

1 Solvent Blank

2 Six calibration standards for the specific test oils plus dispersant and

3 Experimental samples.

2.2.5 QA/QC Checks

Precision: Instrument precision objectives for the conducted dispersant effectiveness

tests were based on analyzing 5% of all spectrophotometric measurements in duplicate.

The acceptance criterion is based upon agreement of the four replicate samples within α

5% of their mean value. The operator precision objectives are determined by using the

relative standard deviation (RSD) for percent dispersant effectiveness based on four

replicate flasks. In case of viscosity determination, the RSD is based on three replicates

of time of travel for viscosity measurements. The acceptance criterion is based upon

RSD less than 15%

100*essEffectivenAverage

DeviationdardStanRSD = …… (2.2)

25

Accuracy:

The accuracy is determined by using a mid-point standard calibration check after every 5

experimental samples analyzed (4 experimental samples or 4 replicates + method blank)

or 4 experimental samples if a method blank is not analyzed. The acceptance criterion is

based on a percent recovery of 90-110%.

Method Detection Limit: The reporting limits (RLs) by UV-Spectrophotometer for

Alaska North Crude Oil, South Louisiana Crude Oil, and Number 2 Fuel Oil are 0.04,

0.05, and 0.09 mg/L, respectively. The RLs are the low end of the calibration curves for

the analytes. The analysis of all these oils will be measured within the calibration

concentration range. If the measured concentration of any of these oils is above the

range, the sample will be diluted, and will be again analyzed to quantify that particular oil

in the calibrated concentration range. If the measured concentration of any of these oils

is below the calibrated concentration range, the data will be reported as below detection

limits.

2.2.6 Calculation Procedures for Experimental Samples

The area under the absorbance vs. wavelength curve for the standards and experimental

samples between wavelengths 340 and 400 nm was calculated using the trapezoidal rule,

according to the following equation:

2

30)AbsAbs(

2

30)AbsAbs(Area 400370370340 +

++

= …. (2.3)

Where Abs340, Abs370, and Abs400 are the absorbance measured at wavelengths of

340, 370, and 400 nm, respectively.

26

The dispersant performance (i.e, percent of oil dispersed, or Effectiveness) based on the

ratio of oil dispersed in the test system to the total oil added to the system was determined

by:

100*Voil * oil

Dispersed Oil Total % Eff

ρ= ….. (2.4)

Where:

Total Oil Dispersed = Mass of Oil x ml30

ml120 …. (2.5)

Mass of Oil, g = Concentration of Oil x VDCM …. (2.6)

where ρoil is the density of the test oil (g/1), Voil is the volume of oil added, and VDCM is

the final volume of the DCM-extract of water sample (20 ml), and the concentration of

oil (g/l) is the area determined by

Concentration of the Oil, g/L = curven calibratio theof Slope

2.3equation by determined as Area …. (2.7)

2.2.7 Viscosity measurements

A Cannon-Fenske viscometer will be used in the study for viscosity measurements. The

sample whose viscosity is to be measured is introduced into the viscometer and the time

required for the liquid front to travel between the two timing marks on the viscometer=s

capillary tube, is noted. This procedure is repeated and a second time measurement taken

for accuracy in the reading. Then the kinematic viscosity of the test oil is calculated in

mm2/s according to the following equation:

27

Kinematic Viscosity mm2/s, = C*t .... (2.8)

Where:

C = Calibration constant of the viscometer (cSt/s),

t = Measured flow time, s.

(The calibration constant can be calculated using a liquid of known viscosity and

determining t)

Figure 2.2 Cannon-Fenske Viscometer

28

Chapter 3

Dispersant Effectiveness at 10˚C

29

3.1 Introduction In this chapter, the effect of rotation speed, weathering, and salinity on percent

dispersion of the three test oils, viz: SLC, PBC, and 2FO at a temperature of 10 ± 1 °C

has been studied. The parameters and the different levels considered are as follows:

1. Temperature – 1 Level (10 ± 1 °C)

2. Salinity – 3 Levels. (34, 20, and 10 ppt)

3. Weathering – 3 Levels. (0%, 10%, and 20% weathering)

4. Mixing speed – 3 Levels. (150, 200, and 250 rpm)

5. Dispersant – 3 Levels. (Dispersant ‘A’, ‘B’, and control ‘C’)

3.2 Dispersant Effectiveness procedure

The experimental procedure for each of the flask test runs is as follows:

120 mL of synthetic seawater equilibrated at the desired temperature was first added to

the modified trypsinizing flask (Baffled Flask), followed sequentially by addition of oil

and dispersant. A volume of 100 μL of oil was dispensed directly onto the surface of the


attachment. The dispersant was then dispensed onto the center of the oil slick by using a


1:25. The flask was then placed on the orbital shaker and mixed for 10 minutes at the

desired rotation speed. At the end of the shaking period, the flask was removed from the


the settling time, the first 2 mL of sample was drained from the stopcock and discarded;

30 mL of sample was then collected in a 50 mL measuring cylinder. The 30 mL sample

was then transferred to a 125 mL separatory funnel and extracted 3 times with fresh 5 mL

30

DCM. Next, the extract was adjusted to a final volume of 20 mL and transferred to a 50

mL crimp style glass vial with an aluminum/Teflon seal. Finally, the vials were stored at

4±2� C until the time of analysis.

3.3 Sample Analysis

The experimental sample extracts and the standard solutions prepared were removed


solution (DCM) was introduced. Then the standard solutions were introduced in order of

increasing concentrations and the absorbance values were noted at wavelengths of 340,


that exceeded the highest calibration standard point, dilution was performed. This was

primarily in the case of Prudhoe Bay Crude oil, which was diluted 10 times. The

sequence of analysis was thus:

1. Solvent Blank

2. Six calibration standards for the specific test oils plus dispersant and

3. Experimental samples.

3.4 Discussion

All of the data collected for dispersant effectiveness at a temperature of 10 ± 1 °C

are plotted to provide a better understanding of the effect of mixing speed, salinity, and

weathering on dispersion at this temperature. It is seen that percent dispersion increased

with increasing mixing speed in all of the cases. The effects of salinity and weathering on

the test oils (SLC, PBC, and 2FO) are shown in figures 3.1 through 3.9

31

Figure 3.1 shows the effect of salinity and weathering on the dispersion of SLC

and dispersant ‘A’ at the three salinities tested. It is seen that percent dispersion increased

from 10 ppt to 20 ppt for 0% weathered oil for the higher rotation speeds (200, 250 rpm),

but salinity did not affect dispersion significantly when it increased from 20 ppt to 34 ppt.

For SLC, the RSD values for dispersant effectiveness among the three salinities at the

three weathering levels studied at this temperature were 3.99, 4.88, and 2.60 at 150, 200,

and 250 rpm, respectively. Since our acceptance criteria for the four replicates is based on

RSD <15%, hence it can be deduced that the impact of salinity is nearly the same at the

three mixing speeds.


and dispersant ‘B’ at the three salinities tested. The results clearly demonstrated that

salinity affected dispersion at 0% weathering and 150 rpm; however, the effect of salinity

was not very significant for the other rotation speeds (200, 250 rpm). The RSD values for

dispersant effectiveness among the three salinities at the three weathering levels studied

at this temperature were 19.54, 5.46, and 3.98 at 150, 200, and 250 rpm, respectively.

Comparing the RSD of 19.54 with the other values could indicate a significant impact of

salinity at a mixing speed of 150 rpm.


and dispersant ‘C’ at the three salinities tested. The percent dispersion is very low for this

combination (control samples). Dispersion values were less than 1%; consequently, no

conclusions can be made based on the observations.

Figure 3.4 shows the effect of salinity and weathering on the dispersion of PBC

and dispersant ‘A’ at the three salinities tested. It is observed that for 0% weathered PBC

32

at 34 and 20 ppt and 150 rpm, dispersion was almost the same, but there was a drop as

the salinity reduced to 10 ppt. Also it is seen that dispersion increased as salinity

increased from 10 ppt to 34 ppt for higher rotation speeds (200, 250 rpm) at 0%

weathering. For 10% weathered PBC at higher rotation speeds (200, 250 rpm),

dispersion increased with salinity from 10 ppt to 20 ppt, whereas this increase is not

significant when salinity increased from 20 ppt to 34 ppt. For 20% weathered PBC at 150

rpm, dispersion remained the same at 10 and 20 ppt, but is higher at 34 ppt. At the higher

rotation speeds (200, 250 rpm), dispersion increased with salinity through the entire range

of 10 to 34 ppt. The RSD values for dispersant effectiveness among the three salinities at

the three weathering levels studied at this temperature were 38.15, 12.81, and 9.20 at 150,

200, and 250 rpm, respectively. Comparing the RSD of 38.15 with the other values

indicates a significant impact of salinity at a mixing speed of 150 rpm.


and dispersant ‘B’ at the three salinities tested. It is observed for 0% weathered PBC at

150 rpm that the dispersion decreased with salinity; however, at the higher rotation

speeds (200, 250 rpm), the dispersion is almost the same at 10 ppt and 20 ppt, but

increased for 34 ppt. For 10% weathered PBC, dispersion is almost the same at 10 ppt

and 20 ppt, but increased at 34 ppt for all three rotation speeds (150, 200, and 250 rpm).

For 20% weathered PBC, increased salinity (from 10 ppt to 34 ppt) caused a steady,

significant increase in dispersion. . The RSD values for dispersant effectiveness among

the three salinities at the three weathering levels studied at this temperature were 33.21,

8.04, and 7.43 at 150, 200, and 250 rpm, respectively. Comparing the RSD of 33.21 with

the other values indicates a significant impact of salinity at a mixing speed of 150 rpm.

33


and dispersant ‘C’ on the three salinities tested. The percent dispersion is very low for

this combination (control samples), less than 10%; because of this, no conclusions can be

drawn regarding weathering.

Figure 3.7 shows the effect of salinity and weathering on the dispersion of 2FO

and dispersant ‘A’ at the three salinities tested. For 0% weathered 2FO at 150 rpm, it is

seen that dispersion was nearly the same at 10 ppt and 20 ppt, but increased at 34 ppt;

however, at the higher rotation speeds (200, 250 rpm), the dispersion remained almost the

same for all three salinities. For 3.8% weathered 2FO at 250 rpm, dispersion remained

almost the same for 10 ppt and 20 ppt, but increased for 34 ppt. Overall, there is a

general decrease in dispersion with an increase in percent weathering. The RSD values

for dispersant effectiveness among the three salinities at the three weathering levels

studied at this temperature were 16.70, 14.15, and 12.41 at 150, 200, and 250 rpm,

respectively. Comparing the RSD of 16.70 with the other values could a significant

impact of salinity at a mixing speed of 150 rpm. However, since the RSD was very close

to 15% (our acceptance criteria) hence, no significant impact can be confirmed.


and dispersant ‘B’ at the three salinities tested. For 0% weathered 2FO, it is seen that the

dispersion remained almost the same at the three salinities except for 150 rpm. For 3.8%

weathered 2FO, it is seen that dispersion remained the same at 150rpm for the three

salinities, but at the higher rotation speeds (200, 250 rpm), dispersion is almost the same

for 10 ppt and 20 ppt but showed an increase at 34 ppt. For 7.6% weathered 2FO, it is

seen that at the higher rotation speeds (200, 250 rpm), the dispersion is lower overall than

34

that observed for 0% and 3.8% weathered 2FO. It is also observed for 7.6% weathering

at 150 rpm that there is an increase in dispersion from 10 ppt to 20 ppt, with little or no

change between 20 and 34 ppt. At the higher rotation speeds (200, 250 rpm), the

dispersion is similar at 10 ppt and 20 ppt as compared to a more marked increase at 34

ppt. The RSD values for dispersant effectiveness among the three salinities at the three

weathering levels studied at this temperature were 16.61, 14.15, and 12.41 at 150, 200,

and 250 rpm respectively. Since the RSD at 150 rpm is very close to 15% (our

acceptance criteria), one can conclude that no significant impact of salinity is observed.


and dispersant ‘C’ at the three salinities tested. The percent dispersion is low for this

combination (control samples). Salinity showed no impact for the different weathering

conditions and rotation speeds.

From the above discussion and plots, the following observations can be made:

1. Dispersant effectiveness is directly proportional to the mixing speed. As the

mixing speed increased, percent dispersion increased. The increase was very

significant when the speed increased from 150 rpm to 200 rpm, but less

significant when the speed increased from 200 rpm to 250 rpm.

2. In most of the combinations, percent dispersion decreased with an increase in

weathering.

3. Viscosity of the oil played a major role in dispersion. Light crude oil (SLC) and

refined oil (2FO) were dispersed more than the medium crude (PBC).

4. The RSD values for dispersant effectiveness among the three salinities at the three

weathering levels studied at this temperature indicate that the impact of salinity is

35

significant in most cases at 150 rpm. However it should be noted that at 150rpm,

the mixing speed does not impart enough energy to the oil to cause dispersion.

36

Dispersant Effectiveness for SLC Dispersant 'A' 0% weathering

Rotation Speed rpm150 200 250

% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 3.1 Effect of Salinity and Weathering of SLC for dispersant ‘A’

37

Dispersant Effectiveness for SLC Dispersant 'B' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 3.2 Effect of Salinity and Weathering of SLC for dispersant ‘B’

38

Dispersant Effectiveness for SLC Dispersant 'C' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 3.3 Effect of Salinity and Weathering of SLC for dispersant ‘C’

39

Dispersant Effectiveness for PBC Dispersant 'A' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 3.4 Effect of Salinity and Weathering of PBC for dispersant ‘A’

40

Dispersant Effectiveness for PBC Dispersant 'B' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 3.5 Effect of Salinity and Weathering of PBC for dispersant ‘B’

41

Dispersant Effectiveness for PBC Dispersant 'C' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 3.6 Effect of Salinity and Weathering of PBC for dispersant ‘C’

42

Dispersant Effectiveness for 2FO Dispersant 'A' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

3.8 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

7.6 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 3.7 Effect of Salinity and Weathering of 2FO for dispersant ‘A’

43

Dispersant Effectiveness for 2FO Dispersant 'B' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

3.8 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

7.6 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 3.8 Effect of Salinity and Weathering of 2FO for dispersant ‘B’

44

Dispersant Effectiveness for 2FO Dispersant 'C' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

3.8 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

7.6 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 3.9 Effect of Salinity and Weathering of 2FO for dispersant ‘C’

45

Chapter 4

Dispersant Effectiveness at 16 ˚C

46

4.1 Introduction In this chapter, the effect of rotation speed, weathering, and salinity on percent

dispersion of the three test oils viz: SLC, PBC, and 2FO at a temperature of 16 ± 1 °C

has been studied. The parameters and the different levels considered were as follows:

6. Temperature – 1 Level (16 ± 1 °C)

7. Salinity – 3 Levels. (34, 20, and 10 ppt)

8. Weathering – 3 Levels. (0%, 10%, and 20% weathering)

9. Mixing speed – 3 Levels. (150, 200, and 250 rpm)

10. Dispersant – 3 Levels. (Dispersant ‘A’, ‘B’, and control ‘C’)

4.2 Dispersant Effectiveness procedure

The experimental procedure for each of the flask test runs is as follows:

120 mL of synthetic seawater equilibrated at the desired temperature is first added to the

modified trypsinizing flask (Baffled Flask), followed sequentially by addition of oil and

dispersant. A volume of 100 μL of oil is dispensed directly onto the surface of the


attachment. The dispersant is then dispensed onto the center of the oil slick by using a


1:25. The flask is then placed on the orbital shaker and mixed for 10 minutes at the

desired rotation speed. At the end of the shaking period, the flask is removed from the


the settling time, the first 2 mL of sample are drained from the stopcock and discarded;

30 mL of sample are then collected in a 50 mL measuring cylinder. The 30 mL sample is

transferred to a 125 mL separatory funnel and extracted 3 times with fresh 5 mL DCM.

47

Next, the extract is adjusted to a final volume of 20 mL and transferred to a 50 mL crimp

style glass vial with an aluminum/Teflon seal. Finally, the vials are stored at 4±2�C until

the time of analysis.

4.3 Sample Analysis

The experimental samples extracts and the standard solutions prepared were removed


solution (DCM) was introduced. Then the standard solutions were introduced in the order

of increasing concentrations and the absorbance values were noted at wavelengths of 340,


that exceeded the highest calibration standard point, dilution was performed. This was

primarily done in case of Prudhoe Bay Crude oil which was diluted 10 times. The

sequence of analysis was thus:

1. Solvent Blank

2. Six calibration standards for the specific test oils plus dispersant and

3. Experimental samples.

4.4 Discussion

All of the data collected for dispersant effectiveness at a temperature of 16 ± 1 °C

are plotted to provide a better understanding of the effect of mixing speed, salinity, and

weathering on dispersion at this temperature. It is seen that percent dispersion increased

with increasing mixing speed in all the cases. The results and effects of salinity and

weathering on the test oils (SLC, PBC, and 2FO) are shown in figures 4.1 through 4.9.

48


and dispersant ‘A’ at the three salinities tested. It is seen that for 0% weathered SLC at

150 rpm, dispersion increased with salinity from 10 ppt to 34 ppt. For higher rotation

speeds (200, & 250 rpm) dispersion was almost the same at 10ppt and 20ppt, but it

increased at 34ppt. For 10% and 20% weathered SLC at 150 rpm, it is observed that

dispersion decreased from 34 ppt to 20 ppt, and increased from 20 ppt to 10 ppt. It is also

observed that dispersion decreased with increased level of weathering. The decrease was

more significant at a speed of 150 rpm, when the weathering was increased from 10% to

20%. The RSD values for dispersant effectiveness among the three salinities at the three

weathering levels studied at this temperature were 39.95, 6.66, and 3.53 at 150, 200, and

250 rpm, respectively. Since our acceptance criteria for the four replicates is based on

RSD <15%, comparing the RSD of 39.95 with the other values indicates a significant

impact of salinity at a mixing speed of 150 rpm.

Figure 4.2 shows the effect of salinity and weathering on dispersion of SLC and

dispersant ‘B’ at the three salinities tested. It is seen that for 0% weathered SLC,

dispersion was similar at 10 ppt and 20 ppt, but increased at 34 ppt for all of the three

mixing speeds tested. With higher percentages of weathering, it is seen that dispersion

increased from 34 ppt to 20 ppt and decreased from 20 ppt to 10 ppt at speeds of 150 and

200 rpm. At 250 rpm dispersion remained almost the same. It is observed that in case of

34 ppt salinity at 150 rpm, dispersion decreased significantly with increasing weathering.

At 10 ppt salinity and 150 rpm, it is seen that dispersion at 10 and 20% weathered SLC

was lower than dispersion for 0% weathered SLC. The RSD values for dispersant

effectiveness among the three salinities at the three weathering levels studied at this

49

temperature were 35.38, 6.44, and 3.91 at 150, 200, and 250 rpm, respectively.

Comparing the RSD of 35.38 with the other values indicates a significant impact of

salinity at a mixing speed of 150 rpm.


and dispersant ‘C’ at the three salinities tested. The dispersion is very low for this

combination (control samples). It is observed that the dispersion decreased slightly with

increasing weathering. No specific trend is observed with salinity.


and dispersant ‘A’ at the three salinities tested. It is seen that for 0% weathered PBC,

dispersion was almost the same at 34 and 20 ppt, but decreased at 10 ppt, for 150 and 200

rpm. For the 10% weathered PBC at 150 and 200 rpm, there was a marked increase in

dispersion at 20 ppt as compared to dispersion at both 34 and 10 ppt; however, at 250

rpm, the dispersion remained the same at all of the three salinities tested. For 20%

weathered PBC, dispersion is higher at 20 ppt than at 34 or 10 ppt for all rotation speeds.

The RSD values for dispersant effectiveness among the three salinities at the three

weathering levels studied at this temperature were 31.75, 8.56, and 4.93 at 150, 200, and

250 rpm, respectively. Comparing the RSD of 31.75 with the other values indicates a

significant impact of salinity at a mixing speed of 150 rpm.


and dispersant ‘B’ at the three salinities tested. The dispersion for 150 rpm followed a

similar trend to that which was noted for dispersant ‘A’. That is, dispersion increased

from 34 ppt to 20 ppt then decreased from 20 ppt to 10 ppt, except in the case of 20%

weathered PBC at 10 ppt, which showed a remarkable increase. For 10% weathered PBC

50

at 200 and 250 rpm, dispersion decreased from 34 ppt to 20 ppt and then increased from

20 ppt to 10 ppt. For 20% weathered PBC at 150 and 250 rpm, the dispersion was similar

at 34 and 20 ppt, and increased only at 10 ppt. On the other hand, at 200 rpm, dispersion

increased with salinity from 34 to 10 ppt. The RSD values for dispersant effectiveness

among the three salinities at the three weathering levels studied at this temperature were

44.96, 8.18, and 6.79 at 150, 200, and 250 rpm, respectively. Comparing the RSD of

44.96 with the other values indicates a significant impact of salinity at a mixing speed of

150 rpm.

Figure 4.6 shows the effect of salinity and weathering on dispersion of PBC and

dispersant ‘C’ at the three salinities tested. The dispersion was very low for this

combination (control samples). It is seen that percent dispersion remained very low at all

salinities tested; thus, the impact of salinity cannot be verified.

Figure 4.7 shows the effect of salinity and weathering on dispersion of 2FO and

dispersant ‘A’ at the three salinities tested. For 0% weathered 2FO at 150 rpm, it is seen

that dispersion increased from 10 ppt to 20 ppt and decreased at 34 ppt. At 200 rpm for

the same percent weathering, it is seen that dispersion increased with salinity from 34 ppt

to 10 ppt, and at 250 rpm, dispersion was almost the same at all three salinities. For 3.8%

weathered 2FO, dispersion was almost the same for 10 and 20 ppt with an increase at 34

ppt, with the exception of 20 ppt at 200 rpm. For 7.6% weathered 2FO at 150 rpm,

dispersion increased from 10 ppt to 20 ppt, and almost remains the same at 34 ppt. At the

higher rotation speeds (200, & 250 rpm) dispersion increased with salinity from 10 ppt to

20 ppt to 34 ppt, also at these speeds weathering seems to have an impact on dispersion.

The RSD values for dispersant effectiveness among the three salinities at the three

51


and 250 rpm, respectively. Comparing the RSD of 18.92 with the other values indicates a

significant impact of salinity at a mixing speed of 150 rpm.

Figure 4.8 shows the effect of salinity and weathering on dispersion of 2FO and

dispersant ‘B’ at the three salinities tested. For 0% weathered 2FO at 150 rpm, it is seen

that dispersion was similar at 10 and 20 ppt but increased at 34 ppt; at 200 rpm, the

significant increase is between 20 and 34 ppt (18%); and at 250 rpm, dispersion remained

almost the same at the three salinities. For 3.8% weathered 2FO at 150 and 200 rpm,

there were no significant variations in dispersion at any of the three salinities; and at 250

rpm, dispersion is almost the same at 10 and 20 ppt but increased at 34 ppt. For 7.6%

weathered 2FO at 150 rpm, dispersion was almost the same at 10 and 20 ppt but

increased at 34 ppt; there is slightly less variation at higher rotation speeds (200, & 250

rpm). In general, dispersion for 7.6% weathered 2FO is lower than dispersion at 3.8%

2FO. The RSD values for dispersant effectiveness among the three salinities at the three


and 250 rpm respectively. As the RSD values are less than 15% (our acceptance criteria),

it is concluded that salinity played no significant role.


and dispersant ‘C’ at the three salinities tested. The dispersion is very low for this

combination (control samples), and no trends can be seen in the data. No specific trends

can be observed with salinity and weathering.

From the above discussion and plots the following observations can be made

52

1. Dispersant effectiveness is directly proportional to the mixing speed. As the

mixing speed increased, percent dispersion increased. The increase is very

significant when the speed increased from 150 rpm to 200 rpm, but less

significant when the speed increased from 200 rpm to 250 rpm.

2. Weathering is also an important factor in dispersion. In most of the combinations

it is observed that percent dispersion decreased with an increase in weathering.

3. Viscosity of the oil played a major role in dispersion. Light crude oil (SLC) and

refined oil (2FO) were dispersed more than the medium crude (PBC).

4. The RSD values for dispersant effectiveness among the three salinities at the three

weathering levels studied at this temperature indicate that the impact of salinity is

significant in most cases at 150 rpm. However it should be noted that at 150rpm,

the mixing speed does not impart enough energy to the oil to cause dispersion.

53

Dispersant Effectiveness for SLC Dispersant 'A' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 4.1 Effect of Salinity and Weathering of SLC for dispersant ‘A’

54

Dispersant Effectiveness for SLC Dispersant 'B' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 4.2 Effect of Salinity and Weathering of SLC for dispersant ‘B’

55

Dispersant Effectiveness for SLC Dispersant 'C' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 4.3 Effect of Salinity and Weathering of SLC for dispersant ‘C’

56

Dispersant Effectiveness for PBC Dispersant 'A' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 4.4 Effect of Salinity and Weathering of PBC for dispersant ‘A’

57

Dispersant Effectiveness for PBC Dispersant 'B' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 4.5 Effect of Salinity and Weathering of PBC for dispersant ‘B’

58

Dispersant Effectiveness for PBC Dispersant 'C' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

10 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

20 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 4.6 Effect of Salinity and Weathering of PBC for dispersant ‘C’

59

Dispersant Effectiveness for 2FO Dispersant 'A' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

3.8 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

7.6 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 4.7 Effect of Salinity and Weathering of 2FO for dispersant ‘A’

60

Dispersant Effectiveness for 2FO Dispersant 'B' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

3.8 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

7.6 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 4.8 Effect of Salinity and Weathering of 2FO for dispersant ‘B’

61

Dispersant Effectiveness for 2FO Dispersant 'C' 0% weathering


% Dis pers ion

0

20

40

60

80

100

34 ppt20 ppt10 ppt

3.8 % weathering


% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

7.6 % weathering

Rotation Speed rpm

150 200 250

% D

ispe

rsio

n

0

20

40

60

80

100

34 ppt20 ppt10 ppt

% D

ispe

rsio

n

Figure 4.9 Effect of Salinity and Weathering of 2FO for dispersant ‘C’

62

Chapter 5

Viscosity Determination of the Test Oils

63

5.1 Abstract

When oil is exposed to the atmosphere, it undergoes a number of physical and

chemical changes, collectively referred to as weathering. Weathering is essentially the

loss of lower weight molecular compounds, (viz: aromatics and aliphatics) due to

evaporation and dissolution. Weathering, along with temperature, tends to alter the oil

viscosity and interfere with effective dispersion of the oil. The effect of temperature and

weathering on viscosity has been studied and a correlation has been drawn for the same.

5.2 Introduction

The ability of a particular refined or crude petroleum product to be dispersed is a

function of the physical and chemical properties of that oil. Oils characterized by higher

viscosities usually exhibit lower abilities for chemical dispersion. Increasing viscosity

appears to reduce the dispersion of oil droplets in two ways (1) migration of dispersant

into oil-water interface is retarded, and (2) the energy required to shear off oil droplets

from the slick is increased (Clayton et al. 1993). Mackay and Wells (1983) noted that

there may be certain ranges of absolute viscosity (approximately 100 cP) where an

increase in viscosity may actually improve retention of dispersants by oil resulting in

enhanced dispersant performance. (Absolute viscosity in cP = kinematic viscosity in cSt

X density at that temperature). It is generally accepted that dispersants perform better for

oils with viscosities less than 2000 cSt, and essentially no dispersion will occur at

viscosities greater than 10,000 cSt. (Cormack et al.1986/87). Oil water interfacial surface

tension provides the principal resistive force to droplet formulation. Typically the surface

tension ranges from 20-30 dynes/cm for fresh oils. Oil spill dispersants may reduce this

64

value to 0.01 dyne/cm or less (Nes 1984), which facilitates the natural process of droplet

formulation. Sufficient mixing energy must be provided to deform the oil, deform the

water, and create a new surface area for the oil. For low viscosity oils, most of the mixing

energy is consumed in creating new surface area in the oil. For higher viscosity oils, a

relatively greater portion of the mixing energy is utilized in deforming the oil, meaning

less energy available for forming new surface area that result in dispersed oil droplets.

Higher oil viscosities will inhibit penetration and mixing of chemical dispersant into the

oil, leading to lower dispersion. To summarize, new surface area of oil will be higher (i.e.

resulting in more and smaller oil droplets) for low viscosity oils compared to more

viscous oils.(Clayton et al. 1993)

The main objective of this chapter was to measure the viscosity of the three oils

viz: SLC, PBC and 2FO at the three weathering conditions (0%, 10%, and 20% for SLC

and PBC, 0%, 3.8%, and 7.6% for 2FO) and the six temperatures (5, 10, 16, 22, 27, 35

°C) using a Cannon-Fenske viscometer, for studying the impact of oil viscosity on

dispersant effectiveness.

5.3 Materials and Methods A Cannon-Fenske viscometer (Fisher Scientific, Pittsburg, PA) was used in the

study for viscosity measurements. Five viscometer sizes, viz: 25, 100, 150, 300 and 400

units conforming to ASTM were used. The sample, for which viscosity was to be

measured was introduced into the viscometer, and the time required for the liquid front to

travel between the two timing marks on the viscometer’s capillary tube was noted. This

procedure was repeated and a second time measurement taken for accuracy in the

65

reading. The kinematic viscosity of the test oil was then calculated in mm2/s according to

the following equation:

Kinematic Viscosity mm2/s, = C*t .... (5.1)

Where:

C = Calibration constant of the viscometer (cSt/s) = mm2/s

t = Measured flow time, s.

(The calibration constant can be calculated using a liquid of known viscosity and

determining t)

5.4 Experimental Results The five viscometer sizes viz: 25, 100, 150, 300 and 400 units used are capable

of measuring viscosities in the range of 0.5-2, 3-15, 7-35, 50-250, and 240-1200

respectively. The calibration constants for the viscometers were calculated using a liquid

of known viscosity such as water, or oil in case of very viscous oils. The calibration

constants determined for the viscometers are listed in Table 5.1. These constants were

then used in the measurements of oil viscosities according to the above equation. The

viscosity of the 9 oils (3 test oils * 3 levels of weathering) were calculated at 6 different

temperatures (Viz: 5, 10, 16, 22, 27, and 35 °C). The data collected is listed in Table 5.2.

66

Table 5.1 Calibration constants for Viscometers Viscometer

Size Range Approx. Constant, cSt/s

units cSt

5°C 10°C 16°C 22°C 27°C 35°C

25 0.5-2 2.242* 10-3 NA 1.843*10-3 NA NA 1.918*10-3

100 3.0-15 0.01759 0.01591 0.01516 0.01512 0.01348 0.01532

150 7.0-35 0.03928 0.03023 0.03285 0.03174 0.02861 0.03064

300 50-250 0.25315 0.27502 0.18613 NA 0.21281 NA

400 240-1200 1.46645 1.28323 0.99897 1.28479 1.20480 1.04414

NA – At this temperature the viscometer was not used, hence not calibrated

Table 5.2 Viscosity measurements of oils at various temperatures Oil Viscosity (cSt) at temperature (°C)

5°C 10°C 16°C 22°C 27°C 35°C

SLC 0% 9.140 8.526 7.084 5.445 4.540 3.932

SLC 10% 19.117 12.920 11.048 8.691 6.381 5.055

SLC 20% 24.983 20.105 19.358 13.756 10.043 7.721

PBC 0% 108.517 96.166 36.296 32.548 24.969 15.717

PBC 10% 597.821 192.057 107.833 91.649 61.147 34.805

PBC 20% NA NA 325.998 248.394 144.174 66.825

2FO 0% 5.255 4.408 3.982 3.580 2.795 2.533

2FO 3.8% 5.847 5.357 4.396 3.781 3.020 2.717

2FO 7.6% 6.117 5.596 4.558 3.917 3.218 2.854

NA – At these temperatures the oils were so viscous that viscosity measurement

was not possible

5.5 Regression A correlation was established between the temperature, viscosity and weathering

to determine the effect of temperature and weathering on the viscosity of the three test

67

oils. We used Minitab R14 (2003) for obtaining the correlation. The equation takes the

form:

cb wta ∗∗= η …… (5.2)

In the logarithmic form

)log()log()log( wctba ++=η …… (5.3)

Where: η = Viscosity of the test oils,

w = % weathering of the test oils,

t = Temperature °C

Table 5.3 Parameters obtained for the three test oils Parameters

Oil Const Log W level Log temp R2 Durbin -Watson

SLC 1.47 -3.93 -0.565 93.4 1.045

PBC 3.15 -8.65 -1.26 94.2 1.665

2FO 1.04 -1.84 -0.394 91.5 1.279

Tables 5.4 through 5.6 contain data comparing the experimental values and

predicted values of viscosity as obtained from the regression. It is seen that the

correlation provides very close estimates of viscosity for all three oils (see the RPD

values in Tables 5.4-5.6). Figure 5.1 compares the experimental values to the predicted

values of viscosity for the three oils as obtained from the correlation.

68

Table 5.4 Comparison for South Louisiana Crude Oil (SLC)

Oil Weathering Temperature Viscosity

Estimated

Viscosity

%

RPD‡

SLC 0%† 5 9.1390 11.9536 23.546

SLC 0% 10 8.5251 8.0816 5.487

SLC 0% 16 7.0843 6.1987 14.288

SLC 0% 22 5.4450 5.1785 5.148

SLC 0% 27 4.5405 4.6132 1.576

SLC 0% 35 3.9319 3.9838 1.304

SLC 10%† 5 19.1161 18.0801 5.730

SLC 10% 10 12.9181 12.2236 5.682

SLC 10% 16 11.0484 9.3756 17.842

SLC 10% 22 8.6916 7.8325 10.969

SLC 10% 27 6.3812 6.9775 8.547

SLC 10% 35 5.0548 6.0256 16.112

SLC 20%† 5 24.9804 28.7144 13.004

SLC 20% 10 20.1048 19.4133 3.562

SLC 20% 16 19.3598 14.8902 30.017

SLC 20% 22 13.7562 12.4394 10.586

SLC 20% 27 10.0438 11.0815 9.364

SLC 20% 35 7.7215 9.5697 19.314

†- The weathering levels have been referred to in the model as 1, 0.9, 0.8 for 0%, 10%, 20% weathering respectively.

‡ - Relative Percent Difference (RPD) = Value Estimated

Value alExperimentValue Estimated −

69

Table 5.5 Comparison for Prudhoe Bay Crude Oil (PBC)


Estimated

Viscosity

%

RPD

PBC 0%† 5 108.5176 185.7804 41.588

PBC 0% 10 96.1612 77.4997 24.079

PBC 0% 16 36.2994 42.8450 15.277

PBC 0% 22 32.5462 28.6748 13.501

PBC 0% 27 24.9689 22.1462 12.746

PBC 0% 35 15.7181 15.9661 1.554

PBC 10%† 5 597.8607 462.2746 29.330

PBC 10% 10 192.0437 192.8413 0.414

PBC 10% 16 107.8450 106.6105 1.158

PBC 10% 22 91.6431 71.3510 28.440

PBC 10% 27 61.1505 55.1061 10.969

PBC 10% 35 34.8017 39.7283 12.401

PBC 20%† 5 NA* 1280.8551 NA

PBC 20% 10 NA* 534.3182 NA

PBC 20% 16 325.9868 295.3929 10.357

PBC 20% 22 248.3705 197.6970 25.632

PBC 20% 27 144.1783 152.6863 5.572

PBC 20% 35 66.8190 110.0779 39.298

* NA – At these temperatures the oils were so viscous that viscosity measurement

was not possible.

†- The weathering levels have been referred to in the model as 1, 0.9, 0.8 for 0%,

10%, 20% weathering respectively.

70

Table 5.6 Comparison for No.2 Fuel Oil (2FO)


Estimated

Viscosity

%

RPD

2FO 0%† 5 5.2546 5.8135 9.614

2FO 0% 10 4.4077 4.4247 0.384

2FO 0% 16 3.9821 3.6769 8.300

2FO 0% 22 3.5800 3.2435 10.375

2FO 0% 27 2.7954 2.9921 6.574

2FO 0% 35 2.5327 2.7014 6.244

2FO 3.8%† 5 5.8468 6.2437 6.356

2FO 3.8% 10 5.3571 4.7519 12.735

2FO 3.8% 16 4.3964 3.9489 11.332

2FO 3.8% 22 3.7810 3.4835 8.543

2FO 3.8% 27 3.0202 3.2135 6.017

2FO 3.8% 35 2.7166 2.9013 6.367

2FO 7.6%† 5 6.1166 6.7248 9.044

2FO 7.6% 10 5.5958 5.1182 9.330

2FO 7.6% 16 4.5582 4.2533 7.167

2FO 7.6% 22 3.9171 3.7520 4.402

2FO 7.6% 27 3.2179 3.4612 7.031

2FO 7.6% 35 2.8544 3.1249 8.656

†- The weathering levels have been referred to in the model as 1, 0.962, 0.934 for

0%, 3.8%, 7.6 % weathering respectively.

71

Table 5.7 shows a comparison of the viscosities estimated by the regression model for

0% weathered PBC and SLC at a temperature of 40 °C as reported in Appendix C of the

EPA Swirling Flask Test (SFT) protocol.

Table 5.7 Comparison of Model with Reported Viscosities

Oil Weathering Temperature °C Kinematic Viscosity Reported Viscosity % RPD

cSt(eqn 5.1) cSt (EPA, SFT Appendix C)

PBC 0% 40 13.5333 14.09 3.95087

SLC 0% 40 3.6714 3.582 2.43603

It can be observed that the model estimated within 4% accuracy the viscosity at 40 °C,

indicating the versatility of the model.

72

South Louisiana Crude Oil

Log (Experimental Data)

0.4 0.6 0.8 1.0 1.2 1.4 1.6

Log

( F

it D

ata)

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Log SLC Exp vs Log SLC Fit

Prudhoe Bay Crude Oil

Log (Experimental Data)1.0 1.5 2.0 2.5 3.0

Log

(Fit

Dat

a)

1.0

1.5

2.0

2.5

3.0

Log PBC Exp vs Log PBC Fit

No.2 Fuel Oil

Log(Experimental Data)

0.4 0.6 0.8 1.0

Log

(Fit

Dat

a)

0.4

0.6

0.8

1.0

Log 2FO Exp vs Log 2FO Fit

Figure 5.1 Comparisons of Viscosities of the Test Oils

73

5.6 References

1. Clayton, J. R., Payne, J., and Farlow, J. (1993). Oil Spill Dispersants

Mechanisms of Action and Laboratory Tests, C.K. Smoley, Boca Raton, FL.

2. Cormack, D. B., Lynch, W. J., and Dowsett, B. D. (1986/87). "Evaluation of

Dispersant effectiveness." Oil and Chemical Pollution, 3, 87-103.

3. Mackay, D., and Wells, P. G. (1983) "Effectiveness, behavior, and toxicity of (Oil

Spill) dispersants." In Proceedings of Oil Spill Conference, San Antonio, TX. 65-

71.

4. Nes, H. (1984). "Effectiveness of Oil dispersants: Laboratory experiments."

NTNF, Oslo, Norway.

5. Minitab. (2003). "Meet Minitab Release14." Minitab Inc., User Manual.

74

Chapter 6

Statistical Analysis of Experimental Data

75

6.1 Introduction

Data for regression can be collected in two ways, viz: observationally (where the

values of independent variables are uncontrolled) and experimentally (where the values

of the variables are controlled). It is important to note that with observational data, a

statistically significant relationship between a response and a predictor does not imply a

cause and effect relationship. It is critical to have good data, but it is essential to

minimize the number of experimental runs at the same time. To achieve this, a solid

experimental design is required. This chapter deals with the statistical analysis of the data

collected in chapters 3 and 4.

6.2 Factorial Experimental Design

The response variable for the experiments conducted was the percent

effectiveness of the dispersant. The factors and levels of each of the factors were as

follows: weathering (0, 10 and 20% for SLC and PBC; 0, 3.8 and 7.6% for 2FO),

dispersant (Corexit 9500 ('A'), SPC 1000 ('B'), and oil control (‘C’)), temperature (10,

and 16°C), flask speed (150, 200 and 250 rpm) and salinity (10, 20 and 34 ppt). Using

these levels for each of the factors, a complete factorial experiment of 2 x 3 4 runs (where

the base stands for number of levels, and the exponent stands for the number of factors;

i.e., in this study the factors are temperature at two levels, weathering, dispersant, salinity

and speed at three levels), was replicated four times for the three different oils requiring a

total of 1944 experimental runs.

76

6.3 Analysis of Variance (ANOVA)

Statistical analysis was performed separately on each of the nine oil-dispersant

combinations, i.e., three oils, with dispersants (‘A’ or ‘B’) and the oils alone. The

response of percent dispersant effectiveness to the following five factors was observed:

• Temperature

• Oil Weathering

• Salinity

• Mixing Speed

• Dispersant type

The results were subjected to analysis of variance (ANOVA) in order to quantify the

main and interaction effects of the factors considered in the study using statistical

analysis software. The response (percent dispersion) was set at 95% confidence limit. The

probability, P, is compared with α=0.05 (95% confidence limit) to evaluate the main

effects and interaction effects of factors on percent dispersion. If the P value is less than

0.05, it can be concluded that the effect is significant at 95% confidence. We used the

SAS (Statistical Analysis System, version 9.1.3) for all statistical analysis. The results of

the ANOVA revealed the number of significant factors for each oil and dispersant

combination and are listed in Table 6.1. The results of the ANOVA conducted for each

oil dispersant combination can be found in Appendix A2.

77

Table 6.1 Significant Factors for Various Oil-Dispersant Combinations for 2 Temperatures (10&16 ˚C)

Oil Oil control

Experiments

Oil + dispersant ‘A’

Experiments

Oil + dispersant

‘B’ Experiments

SLC Temperature, Rotation

speed, Weathering,

Salinity by temperature

Rotation speed, Weathering,

Temperature by Weathering

Rotation speed,

Weathering

PBC Salinity, Rotation speed,

Weathering, Salinity by

Rotation speed,

Temperature by Rotation

speed

Salinity, Temperature, Rotation

speed, Weathering, Salinity by

Temperature, Temperature by

Weathering, Temperature by

Rotation speed

Rotation speed,

Weathering

2FO Rotation speed ,

weathering

Salinity, temperature, Rotation

speed, weathering

Salinity, Rotation

speed, Weathering

6.4 Empirical Relationship

A linear regression model was fit to the experimental data collected, for each of

the nine oil-dispersant combinations. All of the factors and their interactions were

considered for the model, regardless of their significance. The model takes the following

form:

iiRiTTRiWiTTWiRiSSRiTiSST

iWWiRRiSSiWWiRRiTTisSoi

xxxxxxxx

xxxxxxxy

εββββ

ββββββββ

+++++

+++++++=

)()()()()()()()(

)()()()()()()( 222222

..(6.1)

For i= 1,…n

78

Where yi is the effectiveness value at the corresponding levels of the factors (x), β0 is the

intercept, βS is the salinity effect, βT is the temperature effect, βR is the speed effect, βW

is the oil weathering effect, βS2 is the effect of second order interaction of salinity, βR

2 is

the effect of second order interaction of rotation speed, βW2 is the effect of second order

interaction of weathering, βST is the effect of temperature by salinity interaction, βSR is the

effect of speed by salinity interaction, βTW is the effect of the weathering by temperature

interaction, and βTR is the effect of temperature by speed interaction. The factors were

entered into the equation in the following form: Salinity as 10, 20, and 34 ppt,

Temperature as 10 and 16 °C, Mixing speed as 150, 200, and 250 rpm, and Weathering

as 0, 10, and 20 for SLC and PBC and 0, 3.8, and 7.6 for 2FO. The equation contains all

main effects and second order interactions for all factors. The various β parameters for

the various oil-dispersant combinations are given in Table 6.2 together with R2 values

which indicate the linearity of the model. With the exception of oil control experiments

for SLC and 2FO, all the R2 values were very close to or more than 90%.

79

Table 6.2 Coefficients of Regression equations

No. 2 Fuel Oil South Louisiana Crude Prudhoe Bay Crude

Factor Control Dispersant A

Dispersant B Control

Dispersant A

Dispersant B Control

Dispersant A

Dispersant B

Intercept 4.026 -231.87 -279.53 -33.049 -255.46 -258.26 -16.743 -280.96 -295.77 Salinity -0.8547 -0.6296 -1.043 0.456 -0.3124 1.4288 -0.0957 1.9786 0.2292 Temperature -1.1808 0.8115 1.1074 0.7631 -1.3249 0.4411 -0.1152 -1.8738 -2.1491 Rotation speed 0.2081 2.6556 3.1858 0.2078 3.0536 2.8216 0.1603 2.8901 3.3117 Weathering -0.5994 -3.3016 -3.2888 -0.0658 1.2092 1.108 0.0491 -2.149 -1.0854 Salinity2 0.013 0.0051 0.0225 -0.0007 -0.0039 -0.0281 0.0033 -0.0233 0.0108 Rotation speed2 -0.0004 -0.0053 -0.0066 -0.0003 -0.0068 -0.0059 -0.0002 -0.0063 -0.0073 Weathering2 -0.0824 0.0006 0.1586 0.0019 -0.0143 -0.0699 0.0002 0.0351 -0.0125 Salinity* Temperature 0.0184 0.0408 -0.0247 -0.0226 0.0151 -0.0196 0.0009 -0.0591 -0.07 Salinity* Rotation 0.0003 0.0007 0.0028 0.0007 0.0021 0.0008 -0.0005 0.0007 0.0015 Temperature* Weathering 0.0722 0.1194 0.0359 -0.0031 -0.0944 0.0044 -0.0018 0.096 0.0744 Temperature* Rotation 0.0031 -0.0007 -0.0066 -0.0003 0.0076 -0.0003 0.0003 0.0141 0.0129 R2 ANOVA 0.652 0.9008 0.8993 0.8386 0.9078 0.8924 0.9457 0.943 0.9324 R2 Regression 0.6354 0.8832 0.8957 0.8184 0.9021 0.8766 0.9169 0.9383 0.9321

80

Figures 6.1 through 6.3 show a comparison of measured and estimated values of

dispersant effectiveness for the three oils.

The correlations for SLC and PBC oils provided good estimates for dispersion,

and this can be seen from the clutter of points along the 1:1 line. It is seen that for SLC

with oil control the correlation estimated slightly higher dispersion values for the higher

salinities (34 and 20 ppt) and very good estimates at the lower salinity (10 ppt).

It is observed that for 2FO with dispersant ‘A’, the values predicted by the

correlation were slightly higher than those obtained experimentally for both temperatures

studied. In the case of 2FO with dispersant ‘B’, the values are closely matched, which

was evident by the clutter of points along the 1:1 line. It is interesting to note that for 2FO

with oil control, the correlation provided a satisfactory estimate of dispersion as was

determined by the clutter of points along the 1:1 line; this correlation had the lowest R2 of

63.54%.

81

SLC 34 ppt

Experimental Dispersal Effectiveness, %

0 20 40 60 80 100 120

Pre

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Eff

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enes

s, %

0

20

40

60

80

100

120

Exp vs pred

SLC 20 ppt


0 20 40 60 80 100 120

Pre

dict

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Eff

ectiv

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s, %

0

20

40

60

80

100

120

Exp vs pred

SLC 10 ppt


0 20 40 60 80 100 120

Pre

dict

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ispe

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Eff

ectiv

enes

s, %

0

20

40

60

80

100

120

Exp vs pred

Figure 6.1 Comparison of Estimated and Experimental Dispersant Effectiveness for SLC

82

PBC 34 ppt


0 20 40 60 80 100 120

Pre

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s, %

0

20

40

60

80

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Exp vs pred

PBC 20 ppt


0 20 40 60 80 100 120

Pre

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Eff

ectiv

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s, %

0

20

40

60

80

100

120

Exp vs pred

PBC 10 ppt


0 20 40 60 80 100 120

Pre

dict

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ispe

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Eff

ectiv

enes

s, %

0

20

40

60

80

100

120

Exp vs pred

Figure 6.2 Comparison of Estimated and Experimental Dispersant Effectiveness for PBC

83

2 FO 34 ppt


0 20 40 60 80 100 120

Pre

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s, %

0

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40

60

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Exp vs pred

2 FO 20 ppt


0 20 40 60 80 100 120

Pre

dict

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Eff

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s, %

0

20

40

60

80

100

120

Exp vs pred

2 FO 10 ppt


0 20 40 60 80 100 120

Pre

dict

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ispe

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Eff

ectiv

enes

s, %

0

20

40

60

80

100

120

Exp vs pred

Figure 6.3 Comparison of Estimated and Experimental Dispersant Effectiveness for 2FO

84

6.5 Comparison with Previous Study In this section a comparison is made with previously conducted studies on

dispersant effectiveness. The linear regression model created by Chandrasekar et al.

(2004) is used for sake of comparison. The previous study looked at dispersant

effectiveness on oil spills under various simulated conditions at three temperatures, viz: 5

°C, 22 °C and 35°C.

In the previous study a linear regression model was fit to the experimental data

obtained for each of the oil-dispersant combinations. All factor terms and their

interactions were included in the model regardless of their significance. The model takes

the following form:

iiSSiWWiTTiRRiWiSSWiSiRRSiSiTTS

iRiTTRiRiWWRiTiWWTiSSiRRiTTiWWi

xxxxxxxxxx

xxxxxxxxxxy

εβββββββββββββββ

++++++++

+++++++=

22222222 )()()()()()()()()()(

)()()()()()()()()()(0

…(6.2)

for i=1,....n


intercept, βW is the oil weathering effect, βT is the temperature effect, βR is the speed

effect, βS is the salinity effect, βWT is the effect of the weathering by temperature

interaction, βWR is the effect of the weathering by speed interaction, βTR is the effect of

temperature by speed interaction, βTS is the effect of temperature by salinity interaction,

βRS is the effect of speed by salinity interaction, βSW is the effect of salinity by weathering

interaction, βR2

is the effect of second order interaction of speed, βT2

is the effect of

second order interaction of temperature, βW2 is the effect of second order interaction of

weathering and βS2 is the effect of second order interaction of salinity. The factors were

85

entered into the equation in the following form: Salinity as 10, 20, and 34 ppt,

Temperature as 5, 10, 16, 22, and 35 °C, Mixing speed as 150, 200, and 250 rpm, and

Weathering as 0, 10, and 20 for SLC and PBC and 0, 3.8, and 7.6 for 2FO. The equation

contains all main effects and second order interactions for all factors.

In the current study, the two temperatures studied were in between those studied

by Chandrasekhar et al. (2004) viz: 10°C, and 16 °C. The model created by

Chandrasekhar et al. was used to estimate dispersant effectiveness at the two

temperatures for this study. These estimates were compared with the experimentally

collected data in order to verify the universality of the model.

Figures 6.4 through 6.6 illustrate the comparison between experimental and

predicted values of dispersion for both studies. The comparison was made by means of

95% confidence lines on both sides of the 1:1 line. It is observed that a sizeable chunk of

data lie outside the 95% confidence line on the lower side. Subsequently, 90% confidence

lines were included for the comparison. It is seen that there are still certain outliers

beyond the 90% confidence line. In the case of SLC, it is observed that most of the

estimated data for higher rotation speeds for the current study lie just outside the 90%

confidence line. Except for PBC at 20 ppt salinity, the model gives very good estimates

for the lower mixing speed. However the model was under predicting data for higher

rotation speeds, especially 200 rpm.

In this model the authors have included all of the terms irrespective of their

significance. Although this increases the R2 for the model and reduces the errors in the

estimates, it tends to tailor the model to the particular data set and gives erroneous results

for other conditions.

86

2FO 34 ppt


0 20 40 60 80 100 120

Pre

dict

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Effe

ctiv

enes

s, %

0

20

40

60

80

100

120Current StudyPrevious data(Chandrashekhar, 2004)95% Conficence90% Confidence

2FO 20ppt


0 20 40 60 80 100 120

Pre

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Effe

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s, %

0

20

40

60

80

100

120

Current StudyPreviousdata(Chandrashekhar, 2004)95% Confidence90% Confidence

2FO 10ppt

Experimental Dispersal Effectiveness, %0 20 40 60 80 100 120

Pre

dict

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rsal

Effe

ctiv

enes

s, %

0

20

40

60

80

100

120Current studyPrevious Data (Chandrashekar,2004)95% Confidence90% Confidence

Figure 6.4 Comparison for No.2 Fuel Oil

87

PBC 34 ppt


0 20 40 60 80 100 120

Pre

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s, %

0

20

40

60

80

100

120

Current StudyPrevious Data(Chandrashekar,2004)95% Confidence90% Confidence

PBC 20ppt


0 20 40 60 80 100 120

Pre

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Eff

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enes

s, %

0

20

40

60

80

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120


PBC 10ppt


Pre

dict

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Eff

ectiv

enes

s, %

0

20

40

60

80

100

120

Current StudyPrevious Data (Chandrashekar,2004)95% Confidence90% Confidence

Figure 6.5 Comparison for Prudhoe Bay Crude Oil

88

SLC 34 ppt


0 20 40 60 80 100 120

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Eff

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enes

s, %

0

20

40

60

80

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120

Current StudyPrevious Data (Chandrashekhar,2004)95% Confidence90% Confidence

SLC 20ppt


0 20 40 60 80 100 120

Pre

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Eff

ectiv

enes

s, %

0

20

40

60

80

100

120


SLC 10ppt


Pre

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Eff

ectiv

enes

s, %

0

20

40

60

80

100

120

Current StudyPrevious Data, (Chandrashekar,2004)95% Confidence90% Confidence

Figure 6.6 Comparison for South Louisiana Crude Oil

89

6.6 Correlation of Dispersant Effectiveness to Oil Viscosity This section draws a correlation between dispersant effectiveness and oil viscosity

as determined by the regression model discussed in chapter 5 (equation 5.3). This

correlation uses viscosity as the dependent variable and temperature and oil weathering as

the independent variables. The correlation obtained in chapter 5 (equation 5.3) was

inserted into the regression equation discussed in section 6.4 (equation 6.1); in order to

simplify and generalize it. The main motive was to develop a correlation that was a more

general form of the equation obtained in section 6.4.

The two linear regression equations were solved simultaneously and a linear

regression model was fit to the experimental data obtained, for each of the oil-dispersant

combinations. An ANOVA analysis revealed that all the factor terms and their

interactions were significant and included in the model. The results of the ANOVA can

be found in Appendix A4. The model takes the following form:

iiRiVVRiViSSViRiSSR

iVViRRiSSiVViRRisSoi

xxxxxx

xxxxxxy

εβββ

βββββββ

++++

++++++=

)()()()()()(

)()()()()()( 222222

… (6.3)

for i=1,....n


intercept, βS is the salinity effect, βV is the oil viscosity effect, βR is the speed effect, βS2

is the effect of second order interaction of salinity, βV2 is the effect of second order

interaction of viscosity, βR2 is the effect of second order interaction of rotation speed. βSR

is the effect of salinity by speed interaction, βSV is the effect of viscosity by salinity

90

interaction, and βVR is the effect of viscosity by rotation speed. The factors were entered

into the equation in the following form: Salinity as 10, 20, and 34 ppt, mixing speed as

150, 200, and 250 rpm, and Viscosity as estimated by equation 5.3. The equation contains

all main effects and second order interactions for all factors. The various β parameters

for the various oil-dispersant combinations are given in Table 6.3 together with R2 values

which indicate the linearity of the model. If the R2 values are compared to the R2 values

for the previous correlations (6.1), it is observed that the values dropped significantly for

the oil-control combinations; (SLC about 16%, PBC about 19% and 2FO about 6%). In

the other combinations the reduction in R2 values was not very significant (less than 5%).

The model was used to estimate dispersant effectiveness and a comparison was

made between estimated and experimentally obtained dispersion values. Figures 6.7

through 6.9 show a comparison of measured and estimated values of dispersant

effectiveness for the three oils. It is observed that the model provided very good estimates

for dispersant effectiveness.

The model was then used to estimate dispersion for the temperatures studied by

Chandrasekhar et al. (2004) viz: 5°C, 22°C, and 35 °C. These estimates were compared

with the experimentally collected data to give us an idea as to how universal is the model.

Figures 6.10 through 6.12 show the comparison of experimental and predicted values of

dispersion for both studies. The comparison was made by means of 95% confidence and

90% confidence lines on both sides of the 1:1 line. It is observed that the model was able

to estimate dispersion within 90% confidence for most of the data collected.

91

Table 6.3 Coefficients of Regression equations

No. 2 Fuel Oil South Louisiana Crude Prudhoe Bay Crude

Factor Control

Dispersant

A

Dispersant

B Control

Dispersant

A

Dispersant

B Control

Dispersant

A

Dispersant

B

Intercept -76.345 -136.25 -179.54 -10.392 -165.37 -130.67 -10.517 -206.39 -103.3

Salinity -0.2314 0.016 -1.1401 -0.411 -0.014 -0.1395 -0.0332 0.2658 -0.9119

Rotation speed 0.1216 1.3243 1.895 0.2088 2.1383 1.7582 0.0949 2.2375 1.3837

Predicted Viscosity 31.887 18.249 15.114 -0.7008 -1.4865 -0.3374 -0.0012 -0.0359 -0.0662

Salinity2 0.0081 -0.0005 0.0061 0.0004 0.0006 -0.0183 0.0022 -0.0049 0.0053

Rotation speed2 -0.0001 -0.0027 -0.0034 -0.0004 -0.0046 -0.0037 -4.37E-05 -0.0044 -0.0025

Predicted Viscosity2 -3.2699 -3.5807 -2.3226 0.0082 0.0107 -0.0235 1.20E-06 1.70E-05 1.98E-05

Rotation * Predicted

Viscosity -0.0048 0.0408 -0.0157 -0.0005 0.004 0.0019 -2.43E-05 -2.76E-05 0.0001

Salinity* Rotation 0.0009 0.0017 0.0015 0.001 0.0023 0.0045 -0.0006 0.0011 0.0041

Salinity * Predicted

Viscosity -0.0408 -0.0176 0.1635 0.0129 -0.0094 0.0107 0.0001 0.0001 0.0003

R2 ANOVA 0.9611 0.9686 0.9655 0.9661 0.9746 0.945 0.9529 0.9694 0.9753

R2 Regression 0.5792 0.8353 0.8681 0.6539 0.8027 0.8145 0.7245 0.842 0.8114

92

2 FO 34 ppt


0 20 40 60 80 100 120

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Exp vs pred

2 FO 20 ppt


0 20 40 60 80 100 120

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Exp vs pred

2 FO 10 ppt


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s, %

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Exp vs pred

Figure 6.7 Comparison of Estimated and Experimental dispersant effectiveness for 2FO

93

PBC 34 ppt


0 20 40 60 80 100 120

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Exp vs pred

PBC 20 ppt


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Exp vs pred

PBC 10 ppt


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s, %

0

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60

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Exp vs pred

Figure 6.8 Comparison of Estimated and Experimental dispersant effectiveness for PBC

94

SLC 34 ppt


0 20 40 60 80 100 120

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Exp vs pred

SLC 20 ppt


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60

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Exp vs pred

SLC 10 ppt


0 20 40 60 80 100 120

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s, %

0

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60

80

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120

Exp vs pred

Figure 6.9 Comparison of Estimated and Experimental dispersant effectiveness for SLC

95

2FO 34 ppt


0 20 40 60 80 100 120

Pre

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Effe

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s, %

0

20

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60

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120Current StudyPrevious data(Chandrashekhar, 2004)95% Conficence90% Confidence

2FO 20ppt


0 20 40 60 80 100 120

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Current StudyPreviousdata(Chandrashekhar, 2004)95% Confidence90% Confidence

2FO 10ppt


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60

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120Current studyPrevious Data (Chandrashekar,2004)95% Confidence90% Confidence

Figure 6.10 Comparison for No.2 Fuel Oil

96

PBC 34 ppt


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PBC 20ppt


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PBC 10ppt


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Figure 6.11 Comparison for Prudhoe Bay Crude Oil

97

SLC 34 ppt


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60

80

100

120

Current StudyPrevious Data (Chandrashekhar,2004)95% Confidence90% Confidence

SLC 20ppt


0 20 40 60 80 100 120

Pre

dict

ed D

ispe

rsal

Eff

ectiv

enes

s, %

0

20

40

60

80

100

120


SLC 10ppt


Pre

dict

ed D

ispe

rsal

Eff

ectiv

enes

s, %

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40

60

80

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120

Current StudyPrevious Data, (Chandrashekar,2004)95% Confidence90% Confidence

Figure 6.12 Comparison for South Louisiana Crude Oil

98

6.7 References

1. Statistical Analysis System, version 9.1.3 Cary, NC, SAS Institute, 2005

2. Chandrasekar, S. (2004) “Dispersant Effectiveness Data for a Suite of

Environmental Conditions”. MS Thesis. University of Cincinnati.

99

Chapter 7

Conclusions and Recommendations

100

7.1 Conclusions In the above chapters, we looked at the effectiveness of two dispersants on three oils

under different simulated environmental conditions. A full factorial experimental design

was studied to determine the impact of salinity, temperature, mixing speed, oil type, and

oil weathering on the effectiveness of the two dispersants. All the experiments were

analyzed with analysis of variance with α = 0.05. The REG procedure was used to

perform regression analysis on the experimental data collected during the study. An

empirical relationship was drawn between oil viscosity, temperature and weathering for

the test oils. The experimental data collected in this study was verified using the

dispersion model prepared in a previous study. The correlation between oil weathering

and temperature was combined with the correlation for dispersion and simplified, in

terms of input parameters. The model was used to verify data collected in a previous

study. The experimental results obtained from this study reveal the following

1. Dispersant effectiveness is not dependent on one or two factors alone, but it also

depends on certain interactions between the factors. These interactions need not

be the same for each oil dispersant combination.

2. Dispersant effectiveness is directly proportional to the mixing speed with no

exceptions.

3. Salinity has a significant impact on dispersion at a rotation speed of 150 rpm.

However it should be noted that at a mixing speed of 150 rpm does not impart

enough energy to the oil to be dispersed.

4. Oil weathering has a significant effect on dispersion in all the oil dispersant

combinations. Percent dispersion decreases with an increase in oil weathering.

101

5. Temperature has a significant impact on dispersion for oil + dispersant ‘A’

experiments, and was not significant for most of the other oil dispersant

combinations.

6. Overall the significance of the factors can be ranked in the decreasing order as:

Mixing speed, weathering, temperature and salinity.

7. Temperature and weathering have a significant role in determining the viscosity

of the oil. The correlation developed predicted within a good accuracy the

viscosity of the oil.

8. The empirical correlation developed for the experimental data for dispersant

effectiveness predicted with good accuracy the dispersant effectiveness.

9. The model developed by Chandrasekhar (2004) estimated data collected in this

study at a little less than 90% confidence.

10. The model developed in this study, for accounting oil viscosity estimated data

collected by Chandrasekhar (2004) between 90 – 95 % confidence limits.

11. This study has successfully collected empirical data and developed correlations

which have the potential to serve as input for the ERO3S model.

7.2 Recommendations

The effect of various environmental factors such as mixing energy, weathering,

temperature and salinity on the effectiveness of two dispersants has been studied in detail

in this project. In all the experiments conducted, all these factors were studied at three

varying levels. In order to better predict the behavior of dispersants, more levels in each

102

of these factors could be considered and incorporated in the factorial experimental

design.

Experiments need to be conducted at temperature of 27 ˚C in order to have a

better understanding of the temperature dependence of dispersant effectiveness between

22˚C and 35 ˚C since it was noted that there was a drop in dispersant effectiveness at 35

˚C.

It is worthwhile to conduct a study for estimating the dispersibility of a synthetic

mixture of the crude oil that contains a mixture of selected alkanes, and polyaromatic

hydrocarbons (PAH’s) that are common in the three oils studied. This will help to

determine if the dispersibility of the synthetic oil can be predicted from the dispersibility

of its different components.

103

Appendix A1

Experimental Data

104

Table A1-1 Dispersant Effectiveness Test (Temperature = 10 ± 1 °C, Salinity 10 ppt)

Oil Dispersant Flask

Speed

% Effectiveness of replicate samples

R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 0% A 150 32.07 35.03 34.64 37.82 34.89 6.75

2FO 0% A 200 92.21 98.95 80.29 92.58 91.18 8.58 2FO 0% A 250 79.06 96.10 95.43 95.43 91.50 9.07

2FO 0% B 150 39.11 39.48 48.71 48.71 44.00 12.35

2FO 0% B 200 96.75 95.29 89.52 84.66 91.56 6.067

2FO 0% B 250 92.44 96.32 95.35 97.90 95.50 2.40

2FO 0% C 150 9.34 9.22 9.45 11.65 9.92 11.73

2FO 0% C 200 15.95 14.55 18.38 19.54 17.10 13.25

2FO 0% C 250 22.73 19.48 18.73 22.73 20.92 10.11

105



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 0% A 150 32.07 35.03 34.64 37.82 34.89 6.75

2FO 0% A 200 89.06 83.36 90.06 90.79 88.32 3.82

2FO 0% A 250 99.67 92.75 91.96 94.09 94.62 3.68

2FO 0% B 150 32.19 40.75 29.09 37.41 34.86 14.96

2FO 0% B 200 78.95 93.29 87.94 94.14 88.58 7.87

2FO 0% B 250 89.22 97.54 96.02 99.60 95.60 4.70

2FO 0% C 150 12.00 10.03 10.32 10.90 10.81 8.05

2FO 0% C 200 19.42 18.79 19.13 16.87 18.55 6.20

2FO 0% C 250 18.61 20.47 18.96 17.97 19.00 5.56

106



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 0% A 150 37.32 48.55 49.39 49.72 46.25 12.91

2FO 0% A 200 90.45 86.04 88.56 92.02 89.27 2.88

2FO 0% A 250 98.33 99.39 99.45 95.15 98.08 2.06

2FO 0% B 150 36.68 39.9 42.76 38.08 39.36 6.66 2FO 0% B 200

96.26 94.99 95.23 95.35 95.46 0.58 2FO 0% B 250 99.48 95.05 92.33 95.34 95.55 8.22 2FO 0% C 150 12.29 10.90 8.70 10.90 10.70 13.89

2FO 0% C 200 21.86 17.28 20.06 16.00 18.80 14.10

2FO 0% C 250 19.08 19.95 23.37 22.38 21.19 9.50

107



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 3.8% A 150 47.18 34.65 38.29 35.38 38.87 14.80

2FO 3.8% A 200 68.51 69.57 75.23 74.64 71.99 4.77

2FO 3.8% A 250 97.49 77.86 77.12 77.63 82.53 12.09

2FO 3.8% B 150 30.32 37.34 36.15 40.53 36.19 11.90

2FO 3.8% B 200 75.98 92.42 83.45 87.54 84.85 8.19

2FO 3.8% B 250 84.20 91.37 95.80 95.70 91.77 5.94

2FO 3.8% C 150 11.60 15.73 14.74 16.13 14.56 14.05

2FO 3.8% C 200 16.33 20.55 18.56 16.08 17.88 11.74

2FO 3.8% C 250 19.70 19.21 20.85 21.94 20.42 5.97

108



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 3.8% A 150 27.87 22.16 22.81 21.84 23.67 11.96

2FO 3.8% A 200 67.45 70.12 68.14 69.75 68.87 1.85

2FO 3.8% A 250 78.28 82.70 82.10 77.35 80.11 3.35

2FO 3.8% B 150 28.83 30.43 36.90 34.85 32.75 11.47

2FO 3.8% B 200 66.12 65.43 62.04 82.56 69.04 13.3

2FO 3.8% B 250 82.95 87.19 83.95 85.05 84.78 2.14

2FO 3.8% C 150 10.67 7.79 10.17 10.77 9.85 14.18

2FO 3.8% C 200 12.16 14.10 15.09 12.16 13.38 10.92

2FO 3.8% C 250 22.19 20.95 18.02 19.06 20.05 9.32

109



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 3.8% A 150 41.56 39.02 40.59 40.36 40.38 2.58

2FO 3.8% A 200 80.21 75.37 77.26 77.63 77.62 2.56

2FO 3.8% A 250 84.82 98.13 94.68 87.77 91.35 6.70

2FO 3.8% B 150 32.07 33.31 34.36 32.46 33.05 3.06

2FO 3.8% B 200 92.96 84.45 90.17 88.23 88.95 4.02

2FO 3.8% B 250 96.00 95.45 99.69 93.16 96.08 2.81

2FO 3.8% C 150 11.22 13.65 12.06 12.06 12.25 8.29

2FO 3.8% C 200 18.91 19.51 18.76 16.93 18.53 6.01

2FO 3.8% C 250 21.89 22.53 19.75 20.05 21.06 6.47

110

Table A1- 7 Dispersant Effectiveness Test (Temperature = 10 ± 1 °C, Salinity 10 ppt)


Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 7.6% A 150 32.40 39.63 36.35 30.41 34.70 11.85

2FO 7.6% A 200 68.83 67.74 68.13 62.85 66.89 4.07

2FO 7.6% A 250 67.89 67.74 69.14 70.04 68.70 1.58

2FO 7.6% B 150 29.31 37.37 28.03 32.14 31.71 13.07

2FO 7.6% B 200 74.86 59.89 54.98 65.12 63.71 13.35

2FO 7.6% B 250 76.74 72.63 70.75 72.63 73.19 3.45

2FO 7.6% C 150 9.34 9.75 11.61 9.22 9.98 11.10

2FO 7.6% C 200 15.33 17.44 13.59 15.70 15.51 10.15

2FO 7.6% C 250 16.75 18.37 15.90 15.53 16.64 7.57

111



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 7.6% A 150 35.29 40.22 33.42 40.18 37.28 9.28

2FO 7.6% A 200 61.44 67.54 62.15 62.34 63.37 4.43

2FO 7.6% A 250 77.94 80.20 70.32 76.26 76.18 5.55

2FO 7.6% B 150 36.42 40.52 36.42 48.03 40.35 13.56

2FO 7.6% B 200 68.67 71.77 54.32 72.31 66.74 12.63

2FO 7.6% B 250 78.69 74.39 78.93 82.62 78.65 4.30

2FO 7.6% C 150 7.93 9.34 7.32 8.25 8.21 10.2

2FO 7.6% C 200 15.33 14.81 14.85 14.24 14.81 3.01

2FO 7.6% C 250 15.21 14.97 15.01 16.16 15.34 3.64

112



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 7.6% A 150 29.78 39.16 30.64 35.57 33.79 13.01

2FO 7.6% A 200 74.11 71.10 70.47 73.44 72.28 2.44

2FO 7.6% A 250 73.21 73.17 72.31 70.86 72.39 1.51

2FO 7.6% B 150 37.77 39.09 40.48 41.71 39.76 4.28

2FO 7.6% B 200 55.51 56.26 72.05 55.43 59.81 13.65

2FO 7.6% B 250 88.39 94.95 86.68 88.55 89.65 4.05

2FO 7.6% C 150 9.02 12.22 10.60 9.59 10.36 13.53

2FO 7.6% C 200 9.63 11.37 11.69 9.99 10.67 9.48

2FO 7.6% C 250 11.41 11.41 10.88 10.56 11.06 3.78

113



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 0% A 150 53.06 41.28 45.44 54.78 48.64 13.08

SLC 0% A 200 73.59 73.06 86.92 73.93 78.87 8.72

SLC 0% A 250 96.32 91.31 83.82 93.19 91.16 5.82

SLC 0% B 150 27.65 28.32 34.08 33.31 30.84 10.77

SLC 0% B 200 88.86 88.93 85.88 86.59 87.56 1.78

SLC 0% B 250 95.64 92.66 95.35 94.19 94.46 1.43

SLC 0% C 150 0.67 0.62 0.55 0.73 0.64 12.13

SLC 0% C 200 7.40 6.41 6.71 8.47 7.25 12.58

SLC 0% C 250 10.08 9.78 9.57 11.51 10.24 8.57

114



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 0% A 150 53.59 53.90 52.71 42.13 50.58 11.18

SLC 0% A 200 87.68 89.09 94.26 91.66 90.67 3.2

SLC 0% A 250 98.55 97.72 99.35 97.63 98.31 0.82

SLC 0% B 150 58.60 54.35 51.57 48.49 53.25 8.06

SLC 0% B 200 93.75 86.80 90.89 90.03 90.37 3.16

SLC 0% B 250 99.84 92.85 93.63 92.95 94.82 3.54

SLC 0% C 150 0.22 0.18 0.21 0.18 0.20 11.35

SLC 0% C 200 6.48 7.08 6.89 8.95 7.35 14.9

SLC 0% C 250 13.63 10.54 11.56 11.81 11.89 10.81

115



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 0% A 150 50.34 50.79 47.81 50.43 49.84 2.75

SLC 0% A 200 87.98 89.11 91.35 92.37 90.20 2.23

SLC 0% A 250 93.12 96.68 97.19 98.89 96.47 2.51

SLC 0% B 150 62.84 62.81 68.15 60.97 63.69 4.86

SLC 0% B 200 77.29 80.85 83.80 82.11 81.01 3.41

SLC 0% B 250 96.29 94.72 99.62 98.50 97.28 2.26

SLC 0% C 150 2.10 1.78 1.60 1.52 1.75 14.78

SLC 0% C 200 7.66 5.43 6.74 7.36 6.80 14.54

SLC 0% C 250 8.82 11.21 12.16 10.14 10.58 13.57

116



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 10% A 150 55.38 57.51 47.79 50.51 52.80 8.41

SLC 10% A 200 90.12 87.13 87.85 85.79 87.72 2.07

SLC 10% A 250 96.67 94.05 96.29 95.11 95.53 1.24

SLC 10% B 150 60.78 57.11 56.29 48.75 55.73 9.06

SLC 10% B 200 87.43 91.75 90.42 89.61 89.80 2.02

SLC 10% B 250 96.15 97.25 94.42 96.19 96.00 1.22

SLC 10% C 150 0.56 0.66 0.63 0.52 0.59 10.64

SLC 10% C 200 6.37 5.30 6.91 5.12 5.92 14.52

SLC 10% C 250 8.31 7.96 7.08 7.53 7.72 6.88

117



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 10% A 150 43.67 51.25 46.38 46.45 46.94 6.71

SLC 10% A 200 88.58 84.28 90.03 88.23 87.78 2.80

SLC 10% A 250 95.47 95.64 95.49 91.52 94.53 2.12

SLC 10% B 150 53.70 54.70 46.41 55.26 52.52 7.85

SLC 10% B 200 90.89 89.94 91.37 94.19 91.60 1.99

SLC 10% B 250 98.75 98.80 99.43 99.67 99.16 0.46

SLC 10% C 150 0.60 0.50 0.51 0.52 0.53 9.38

SLC 10% C 200 9.29 7.12 7.20 7.64 7.81 12.96

SLC 10% C 250 14.63 14.62 12.70 12.31 13.57 9.09

118



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 10% A 150 45.34 50.92 57.02 49.67 50.74 9.51

SLC 10% A 200 88.90 92.25 85.56 83.43 87.53 4.42

SLC 10% A 250 94.67 94.22 94.93 96.55 95.09 1.07

SLC 10% B 150 52.93 51.47 48.46 44.42 49.32 7.63

SLC 10% B 200 96.48 96.95 90.75 92.04 94.06 3.32

SLC 10% B 250 99.69 99.41 98.73 93.60 97.84 2.92

SLC 10% C 150 0.49 0.37 0.43 0.40 0.42 11.57

SLC 10% C 200 6.78 8.58 6.38 7.16 7.23 13.25

SLC 10% C 250 10.14 10.37 12.07 13.06 11.41 12.21

119



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 20% A 150 39.87 50.74 49.19 50.53 47.58 10.90

SLC 20% A 200 84.64 87.01 87.91 91.55 87.78 3.27

SLC 20% A 250 93.85 90.65 93.28 91.24 92.25 1.68

SLC 20% B 150 44.57 37.56 43.03 49.76 43.73 11.48

SLC 20% B 200 84.55 76.32 88.75 82.82 83.11 6.21

SLC 20% B 250 92.18 85.10 92.22 92.25 90.43 3.93

SLC 20% C 150 0.30 0.32 0.25 0.25 0.28 12.80

SLC 20% C 200 6.77 4.93 6.13 5.23 5.76 14.60

SLC 20% C 250 6.99 7.21 7.13 7.72 7.26 4.39

120



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 20% A 150 52.48 48.99 52.34 44.95 49.69 7.14

SLC 20% A 200 91.43 92.02 92.97 86.85 90.82 2.99

SLC 20% A 250 89.98 90.85 91.76 91.31 90.98 0.83

SLC 20% B 150 41.25 44.90 39.05 43.34 42.14 6.03

SLC 20% B 200 85.61 82.28 79.87 78.83 81.80 3.75

SLC 20% B 250 88.27 86.96 86.41 84.89 86.63 1.62

SLC 20% C 150 0.77 0.74 0.95 0.71 0.79 13.52

SLC 20% C 200 4.75 6.42 5.54 5.87 5.64 12.38

SLC 20% C 250 7.87 5.81 6.86 6.05 6.65 13.99

121



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 20% A 150 52.31 45.58 42.36 47.45 46.92 8.87

SLC 20% A 200 90.54 86.17 91.35 86.92 88.75 2.91

SLC 20% A 250 96.19 90.98 95.12 94.77 94.26 2.41

SLC 20% B 150 43.27 44.79 42.64 46.41 44.28 3.80

SLC 20% B 200 85.77 83.60 85.19 79.41 83.49 3.44

SLC 20% B 250 93.26 96.08 91.86 93.27 93.62 1.89

SLC 20% C 150 0.32 0.40 0.39 0.30 0.35 14.22

SLC 20% C 200 8.95 8.65 7.97 8.18 8.44 5.29

SLC 20% C 250 9.29 11.89 10.25 12.18 10.90 12.55

122



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 0% A 150 31.08 25.61 30.36 35.18 30.56 12.84

PBC 0% A 200 62.93 62.89 61.39 63.30 62.63 1.35

PBC 0% A 250 78.63 73.91 69.02 73.86 73.85 5.30

PBC 0% B 150 37.67 46.14 48.36 46.24 44.60 10.60

PBC 0% B 200 77.84 77.54 65.70 79.53 75.15 8.46

PBC 0% B 250 73.40 84.92 86.65 87.73 83.18 7.96

PBC 0% C 150 0.14 0.14 0.17 0.16 0.15 9.06

PBC 0% C 200 5.16 5.71 5.85 5.63 5.59 5.34

PBC 0% C 250 7.18 6.47 6.44 7.50 6.90 7.65

123



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 0% A 150 43.66 34.87 38.14 42.80 39.87 10.34

PBC 0% A 200 70.22 70.31 70.83 69.78 70.28 0.61

PBC 0% A 250 87.40 79.97 80.93 82.84 82.78 3.98

PBC 0% B 150 40.67 32.74 39.39 37.07 37.47 9.30

PBC 0% B 200 80.30 64.64 82.56 81.68 77.30 10.98

PBC 0% B 250 86.69 87.42 85.75 85.93 86.44 0.88

PBC 0% C 150 0.13 0.14 0.11 0.12 0.12 12.37

PBC 0% C 200 5.75 5.19 4.22 5.33 5.12 12.63

PBC 0% C 250 4.99 5.41 5.72 5.99 5.53 7.75

124



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 0% A 150 41.31 46.62 37.90 34.10 39.98 13.29

PBC 0% A 200 73.37 79.99 79.22 77.51 77.52 3.8

PBC 0% A 250 85.80 88.01 82.26 87.99 86.02 3.14

PBC 0% B 150 29.86 30.00 36.18 36.38 33.11 11.08

PBC 0% B 200 80.71 82.49 90.26 84.25 84.43 4.91

PBC 0% B 250 87.86 98.81 89.62 94.69 92.74 5.36

PBC 0% C 150 0.23 0.25 0.29 0.24 0.25 10.53

PBC 0% C 200 3.37 4.17 3.59 3.14 3.57 12.34

PBC 0% C 250 5.47 5.81 7.30 5.44 6.01 14.69

125



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 10% A 150 23.47 30.29 28.53 24.43 26.68 12.2

PBC 10% A 200 48.45 55.29 61.67 50.21 53.85 10.85

PBC 10% A 250 67.72 67.26 68.00 66.89 67.47 0.72

PBC 10% B 150 25.02 23.95 25.00 24.87 24.71 2.05

PBC 10% B 200 74.27 78.96 77.42 73.34 76.00 3.47

PBC 10% B 250 93.49 83.67 87.05 84.80 87.25 5.03

PBC 10% C 150 0.19 0.21 0.19 0.18 0.19 6.61

PBC 10% C 200 4.90 6.02 4.65 4.54 5.03 13.45

PBC 10% C 250 8.19 9.01 8.41 7.21 8.21 9.11

126



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 10% A 150 15.52 17.95 16.64 15.94 16.44 7.05

PBC 10% A 200 54.38 68.44 58.98 70.38 63.04 12.10

PBC 10% A 250 78.12 79.60 80.40 83.23 80.41 2.53

PBC 10% B 150 25.79 22.08 25.90 18.98 23.19 14.31

PBC 10% B 200 78.24 72.75 73.31 74.11 74.60 3.33

PBC 10% B 250 84.24 89.63 84.60 84.70 85.80 2.99

PBC 10% C 150 0.25 0.27 0.19 0.24 0.24 14.76

PBC 10% C 200 4.35 4.47 4.75 4.50 4.52 3.71

PBC 10% C 250 5.96 5.56 4.50 5.27 5.32 11.56

127



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 10% A 150 22.82 20.61 18.85 18.59 20.22 9.65

PBC 10% A 200 67.33 65.36 67.90 63.14 65.93 3.26

PBC 10% A 250 81.94 82.99 82.82 77.37 81.28 3.26

PBC 10% B 150 32.91 28.66 31.55 37.08 32.55 10.75

PBC 10% B 200 83.55 76.88 75.19 78.03 78.24 4.76

PBC 10% B 250 91.68 87.86 93.39 87.97 90.23 3.05

PBC 10% C 150 0.15 0.19 0.18 0.14 0.16 12.99

PBC 10% C 200 4.27 4.15 4.42 4.23 4.27 2.65

PBC 10% C 250 6.14 5.78 5.83 5.87 5.91 2.72

128



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 20% A 150 16.69 14.98 15.65 16.53 15.96 4.99

PBC 20% A 200 54.85 54.82 54.19 55.35 54.80 0.87

PBC 20% A 250 65.61 63.39 69.99 61.12 65.03 5.82

PBC 20% B 150 12.54 10.12 10.37 12.28 11.33 11.13

PBC 20% B 200 70.04 64.95 51.75 67.63 63.59 12.84

PBC 20% B 250 69.50 71.17 74.37 75.02 72.51 3.62

PBC 20% C 150 0.38 0.36 0.38 0.34 0.36 5.00

PBC 20% C 200 7.19 5.53 5.26 5.55 5.88 14.98

PBC 20% C 250 8.00 9.06 7.11 6.75 7.73 13.36

129



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 20% A 150 13.35 13.39 15.64 15.12 14.38 8.21

PBC 20% A 200 58.66 59.21 71.27 57.15 61.57 10.60

PBC 20% A 250 73.84 84.55 75.96 71.94 76.57 7.27

PBC 20% B 150 20.47 21.56 27.99 25.14 23.79 14.46

PBC 20% B 200 60.86 80.45 66.32 63.31 67.73 12.94

PBC 20% B 250 76.78 80.30 78.50 74.07 77.41 3.42

PBC 20% C 150 0.18 0.18 0.22 0.24 0.21 14.85

PBC 20% C 200 4.95 4.40 4.36 4.84 4.64 6.50

PBC 20% C 250 6.56 6.95 8.24 8.40 7.54 12.17

130



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 20% A 150 29.84 32.88 29.34 31.42 30.87 5.19

PBC 20% A 200 64.87 79.50 81.21 78.48 76.02 9.88

PBC 20% A 250 85.40 91.47 80.07 66.29 80.81 13.29

PBC 20% B 150 34.35 38.57 36.65 31.19 35.19 9.02

PBC 20% B 200 71.98 71.70 69.55 82.96 74.05 8.16

PBC 20% B 250 84.40 79.00 89.37 76.06 82.21 7.16

PBC 20% C 150 0.22 0.21 0.22 0.22 0.22 2.65

PBC 20% C 200 5.89 4.68 5.02 4.85 5.11 10.51

PBC 20% C 250 6.94 7.52 7.57 8.62 7.66 9.11

131



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 0% A 150 76.26 76.65 76.82 65.93 73.92 7.21

2FO 0% A 200 82.13 86.38 90.12 87.44 86.52 3.83

2FO 0% A 250 91.57 96.94 89.56 90.06 92.03 3.67

2FO 0% B 150 50.71 43.97 59.46 49.92 51.02 12.5 2FO 0% B 200 86.91 90.49 89.04 86.61 88.26 2.08 2FO 0% B 250 94.26 96.39 90.98 96.20 94.46 2.65

2FO 0% C 150 8.58 10.49 11.77 10.61 10.36 12.7

2FO 0% C 200 15.89 19.08 15.71 17.28 16.99 9.17

2FO 0% C 250 20.87 18.26 20.18 19.54 19.71 5.63

132



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 0% A 150 48.22 53.64 54.03 60.34 54.05 9.17

2FO 0% A 200 89.62 98.61 90.96 96.38 93.89 4.57

2FO 0% A 250 96.49 99.90 96.32 89.45 95.54 4.58

2FO 0% B 150 29.88 34.56 29.33 31.82 31.40 7.52

2FO 0% B 200 84.66 81.99 88.85 79.44 83.74 4.8

2FO 0% B 250 98.75 96.45 99.67 99.85 98.68 1.58 2FO 0% C 150 12.52 12.41 12.12 14.50 12.89 8.43

2FO 0% C 200 19.42 20.76 19.13 22.44 20.44 7.38

2FO 0% C 250 22.85 21.05 21.34 26.38 22.90 10.7

133



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 0% A 150 53.97 45.03 49.72 45.59 48.58 8.56

2FO 0% A 200 76.21 63.52 85.54 65.37 72.66 14.10

2FO 0% A 250 93.30 88.61 94.64 99.51 94.02 4.76

2FO 0% B 150 44.76 39.90 48.59 42.64 43.97 8.33

2FO 0% B 200 60.37 61.4 61.16 60.73 60.92 0.75

2FO 0% B 250 98.94 94.36 97.66 90.08 95.26 4.15

2FO 0% C 150 8.12 8.70 7.83 8.12 8.19 4.45

2FO 0% C 200 14.44 13.22 13.22 17.92 14.70 15.1

2FO 0% C 250 18.38 17.28 18.21 14.38 17.06 10.9

134



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 3.8% A 150 44.46 46.35 35.75 42.62 42.29 10.9

2FO 3.8% A 200 88.50 86.71 85.42 82.47 85.77 2.96

2FO 3.8% A 250 86.80 87.17 85.00 85.05 86 1.33

2FO 3.8% B 150 43.27 38.34 31.32 43.57 39.12 14.64 2FO 3.8% B 200 68.56 77.38 66.32 70.76 70.76 6.74

2FO 3.8% B 250 78.12 72.60 69.96 84.60 76.32 8.49

2FO 3.8% C 150 13.30 12.66 12.36 14.24 13.14 6.35

2FO 3.8% C 200 17.27 14.74 17.67 14.34 16.01 10.7

2FO 3.8% C 250 24.77 24.57 26.90 21.09 24.33 9.88

135



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 3.8% A 150 43.81 36.95 37.80 35.92 41.42 7.66 2FO 3.8% A 200 69.52 75.46 69.15 70.12 71.07 4.16 2FO 3.8% A 250 86.98 89.61 85.92 83.57 86.52 2.89

2FO 3.8% B 150 39.14 31.32 33.46 33.81 34.43 9.66

2FO 3.8% B 200 71.85 77.33 77.73 70.46 74.34 5.01

2FO 3.8% B 250 80.27 78.22 81.36 75.68 78.88 3.16

2FO 3.8% C 150 9.73 8.34 8.09 8.88 8.76 8.28

2FO 3.8% C 200 12.46 11.47 12.71 11.71 12.09 4.89

2FO 3.8% C 250 13.40 14.99 13.30 15.29 14.24 7.3

136



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 3.8% A 150 54.41 42.66 41.97 43.35 45.60 12.9

2FO 3.8% A 200 95.74 92.28 91.50 88.96 92.12 3.04

2FO 3.8% A 250 92.19 98.04 93.76 98.59 95.64 3.3 2FO 3.8% B 150 36.10 26.59 31.32 30.27 31.07 12.67

2FO 3.8% B 200 70.41 76.38 75.93 76.38 74.78 3.9

2FO 3.8% B 250 90.57 98.09 87.24 84.75 90.16 6.43

2FO 3.8% C 150 8.39 8.34 9.23 8.19 8.54 5.52

2FO 3.8% C 200 22.19 15.73 21.64 20.95 20.13 14.8

2FO 3.8% C 250 25.07 29.68 27.35 25.36 26.86 7.94

137



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 7.6% A 150 29.82 29.43 24.98 23.92 27.04 11.2

2FO 7.6% A 200 65.23 61.68 59.37 60.39 61.67 4.15

2FO 7.6% A 250 61.76 63.87 61.56 60.31 61.87 2.38

2FO 7.6% B 150 28.71 28.27 30.98 25.23 28.30 8.35

2FO 7.6% B 200 68.64 68.68 63.60 70.59 67.88 4.41

2FO 7.6% B 250 79.86 71.07 67.52 64.88 70.83 9.22

2FO 7.6% C 150 12.30 10.36 10.80 10.64 11.02 7.88

2FO 7.6% C 200 13.67 15.70 13.15 10.96 13.37 14.5

2FO 7.6% C 250 15.82 18.69 18.81 19.42 18.18 8.85

138



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 7.6% A 150 53.86 47.76 55.42 42.76 49.95 11.7

2FO 7.6% A 200 65.08 66.13 63.44 64.76 64.85 1.71

2FO 7.6% A 250 75.08 94.12 77.35 82.43 82.25 10.3

2FO 7.6% B 150 42.51 41.71 39.56 30.82 38.65 13.9

2FO 7.6% B 200 73.12 58.17 57.54 60.28 62.28 11.8

2FO 7.6% B 250 74.79 60.48 60.92 60.08 64.07 11.2

2FO 7.6% C 150 7.24 7.16 7.28 6.92 7.15 2.28

2FO 7.6% C 200 10.88 11.41 13.51 11.93 11.93 9.52

2FO 7.6% C 250 15.37 16.18 15.25 13.84 15.16 6.43

139



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

2FO 7.6% A 150 54.80 56.95 41.82 48.47 50.51 13.5

2FO 7.6% A 200 73.64 77.12 75.75 78.44 76.24 2.69

2FO 7.6% A 250 97.99 93.06 87.71 91.66 92.60 4.58

2FO 7.6% B 150 43.06 32.96 39.17 34.91 37.53 12

2FO 7.6% B 200 79.09 87.40 77.34 77.70 80.38 5.9

2FO 7.6% B 250 73.00 96.94 82.47 74.99 81.85 13.3

2FO 7.6% C 150 16.83 16.02 17.96 18.28 17.27 6.04

2FO 7.6% C 200 22.69 16.95 20.83 17.72 19.55 13.7

2FO 7.6% C 250 25.40 28.56 24.56 20.83 24.84 12.8

140



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 0% A 150 52.74 53.57 50.89 55.01 53.05 3.24

SLC 0% A 200 84.69 81.08 83.41 81.18 82.59 2.14

SLC 0% A 250 94.55 92.20 93.78 94.26 93.7 1.12

SLC 0% B 150 58.37 58.00 58.25 57.95 58.14 0.35

SLC 0% B 200 74.7 74.77 75.41 75.07 74.99 0.43

SLC 0% B 250 89.20 87.35 89.41 88.61 88.64 1.04

SLC 0% C 150 7.08 6.43 7.30 6.91 6.93 5.32

SLC 0% C 200 9.92 10.80 10.25 9.99 10.24 3.91

SLC 0% C 250 12.67 11.91 11.19 12.60 12.09 5.71

141



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 0% A 150 60.51 58.05 58.59 59.06 59.05 1.79

SLC 0% A 200 83.70 79.95 87.01 79.88 82.63 4.14

SLC 0% A 250 93.28 91.45 95.74 89.42 92.47 2.91

SLC 0% B 150 60.84 61.09 61.37 60.97 61.07 0.37

SLC 0% B 200 77.87 78.12 86.58 77.44 80.0 5.49

SLC 0% B 250 90.85 90.63 90.61 90.36 90.61 0.23

SLC 0% C 150 8.54 8.07 8.75 8.76 8.53 3.78

SLC 0% C 200 10.58 10.90 10.64 11.19 10.83 2.57

SLC 0% C 250 11.30 10.74 11.07 11.03 11.03 2.08

142



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 0% A 150 47.54 36.10 42.69 50.96 44.32 14.54 SLC 0% A 200 85.84 95.20 90.55 93.90 91.37 4.57 SLC 0% A 250 98.06 99.32 98.84 99.98 99.05 0.82

SLC 0% B 150 47.54 36.10 42.69 50.96 44.32 14.54

SLC 0% B 200 86.09 92.44 86.36 92.91 89.45 4.17 SLC 0% B 250 99.48 97.99 96.91 98.99 98.34 1.16 SLC 0% C 150 1.05 0.96 1.32 1.10 1.11 1.16 SLC 0% C 200 5.21 6.06 4.65 5.29 5.30 10.91

SLC 0% C 250 9.32 8.28 8.20 7.37 8.29 9.65

143



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 10% A 150 57.32 56.83 54.09 61.67 57.48 5.45

SLC 10% A 200 82.15 72.38 75.74 69.33 74.90 7.34

SLC 10% A 250 87.96 83.08 87.63 87.46 93.91 1.81

SLC 10% B 150 56.06 53.76 57.73 55.08 55.66 3.0

SLC 10% B 200 94.00 95.51 95.80 95.76 96.63 1.73

SLC 10% B 250 97.64 98.15 98.96 96.96 97.93 0.86 SLC 10% C 150

1.11 1.11 1.26 1.13 1.15 6.19 SLC 10% C 200 8.97 7.84 7.29 8.26 8.09 8.78 SLC 10% C 250

20.92 21.72 21.17 20.02 20.96 3.39

144



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 10% A 150 48.38 44.58 43.07 52.51 47.14 8.96 SLC 10% A 200 90.15 90.63 93.82 91.21 91.45 1.79 SLC 10% A 250 92.04 93.40 94.15 89.93 92.38 2.01

SLC 10% B 150 60.42 65.80 66.16 57.23 62.41 6.95 SLC 10% B 200 89.51 97.04 96.63 87.93 92.85 5.19 SLC 10% B 250 99.07 99.16 97.32 95.76 97.83 1.65 SLC 10% C 150 2.31 2.89 2.53 3.15 2.72 13.72

SLC 10% C 200 11.23 10.72 13.80 11.26 11.75 11.78

SLC 10% C 250 11.76 11.58 13.29 11.52 12.04 7.00

145



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 10% A 150 58.71 56.08 68.57 64.51 61.97 9.10

SLC 10% A 200 89.61 86.91 90.26 88.87 88.92 1.63 SLC 10% A 250

90.13 88.10 90.91 94.11 90.81 2.75 SLC 10% B 150 64.67 51.45 66.97 50.25 58.93 14.93 SLC 10% B 200

90.77 79.87 84.76 93.67 87.27 7.08 SLC 10% B 250

94.40 99.51 94.17 98.99 96.76 2.97 SLC 10% C 150 0.51 0.54 0.50 0.39 0.48 13.48 SLC 10% C 200 3.87 4.18 4.21 4.63 4.22 7.35 SLC 10% C 250

12.58 11.85 12.92 12.01 12.34 4.01

146



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 20% A 150 27.87 28.11 28.05 27.47 27.88 1.03

SLC 20% A 200 87.80 85.06 85.30 83.73 85.47 1.99

SLC 20% A 250 91.66 92.23 90.91 93.35 92.04 1.12

SLC 20% B 150 16.82 18.21 21.59 21.48 19.52 12.24

SLC 20% B 200 86.59 87.37 87.59 86.87 87.11 0.52

SLC 20% B 250 89.72 90.48 92.24 91.46 90.98 1.21

SLC 20% C 150 0.88 0.91 1.20 0.92 0.98 15.21

SLC 20% C 200 6.15 5.34 6.20 7.21 6.23 12.27

SLC 20% C 250 15.01 15.15 15.70 15.42 15.32 1.99

147



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 20% A 150 17.83 20.44 16.05 15.31 17.41 13.10

SLC 20% A 200 91.42 88.56 88.82 87.18 89.00 1.99 SLC 20% A 250

91.66 92.23 90.91 93.35 92.04 1.12 SLC 20% B 150

61.33 63.70 65.99 55.87 61.72 7.03 SLC 20% B 200 88.54 89.34 89.56 88.83 89.07 0.52 SLC 20% B 250

96.81 93.37 96.81 96.96 95.99 1.82 SLC 20% C 150 0.91 0.94 1.24 0.95 1.01 15.21 SLC 20% C 200 4.85 3.64 4.20 4.87 4.39 13.37 SLC 20% C 250

12.69 12.93 13.15 12.74 12.88 1.62

148



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

SLC 20% A 150 20.77 19.32 21.28 18.88 20.07 5.70

SLC 20% A 200 85.90 92.29 92.63 89.09 89.98 3.50

SLC 20% A 250 95.85 93.25 95.62 96.00 95.18 1.36

SLC 20% B 150 22.72 17.40 21.59 19.83 20.38 11.38

SLC 20% B 200 84.34 81.07 85.60 85.23 84.06 2.45

SLC 20% B 250 96.04 96.93 97.31 97.28 96.89 0.61

SLC 20% C 150 0.89 0.98 0.88 1.05 0.95 8.40

SLC 20% C 200 5.24 4.50 4.19 5.53 4.86 12.85

SLC 20% C 250 12.31 13.49 12.26 13.03 12.77 4.64

149



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 0% A 150 10.60 10.65 10.62 11.20 10.77 2.67

PBC 0% A 200 77.62 64.22 71.34 63.22 69.10 9.74

PBC 0% A 250 84.55 78.91 84.39 79.67 81.88 3.67

PBC 0% B 150 9.04 11.34 9.53 9.41 9.83 10.44 PBC 0% B 200 81.11 79.92 75.07 86.05 80.54 5.60

PBC 0% B 250 92.94 89.47 87.81 89.01 89.63 2.09

PBC 0% C 150 0.15 0.18 0.17 0.18 0.17 7.57

PBC 0% C 200 3.37 2.53 3.18 2.80 2.97 12.69

PBC 0% C 250 6.95 7.79 7.13 7.15 7.26 5.053

150



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 0% A 150 20.57 21.44 23.70 20.80 21.63 6.60

PBC 0% A 200 85.35 80.21 82.58 78.56 81.68 3.61

PBC 0% A 250 87.78 85.75 81.78 86.61 85.48 3.04

PBC 0% B 150 19.10 19.68 15.09 14.93 17.20 14.77

PBC 0% B 200 81.07 68.49 84.67 74.56 77.19 9.26

PBC 0% B 250 89.85 92.40 95.22 90.14 91.90 2.70

PBC 0% C 150 0.29 0.36 0.37 0.28 0.33 14.373

PBC 0% C 200 3.15 3.36 3.34 3.14 3.25 3.60

PBC 0% C 250 6.69 5.88 4.98 5.35 5.73 12.94

151



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 0% A 150 16.72 20.82 23.7 20.80 20.51 13.99

PBC 0% A 200 75.85 79.59 77.94 77.66 77.76 1.96

PBC 0% A 250 81.41 93.35 92.31 87.78 88.71 6.12

PBC 0% B 150 15.20 11.89 15.09 14.22 14.10 10.9

PBC 0% B 200 73.72 86.72 77.83 89.68 81.99 9.10

PBC 0% B 250 94.11 95.29 94.49 93.52 94.35 0.78

PBC 0% C 150 0.49 0.42 0.54 0.41 0.46 13.04

PBC 0% C 200 2.87 2.74 3.35 2.52 2.87 12.23

PBC 0% C 250 6.30 5.84 7.31 7.15 6.65 10.51

152



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 10% A 150 17.72 23.27 23.59 23.85 22.13 13.31

PBC 10% A 200 60.75 56.51 67.45 74.16 64.72 11.95

PBC 10% A 250 77.72 78.66 75.49 79.15 77.75 2.08

PBC 10% B 150 30.75 23.43 29.21 30.92 28.58 12.30

PBC 10% B 200 65.03 76.36 61.68 74.40 69.37 10.26

PBC 10% B 250 90.78 88.65 84.37 80.31 86.03 5.40

PBC 10% C 150 0.4 0.36 0.34 0.32 0.35 9.55

PBC 10% C 200 2.93 3.38 2.46 2.80 2.89 13.15

PBC 10% C 250 8.53 10.55 8.69 11.06 9.71 13.27

153



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 10% A 150 44.30 35.93 35.11 36.99 38.08 11.06 PBC 10% A 200 72.70 68.37 72.01 73.97 71.76 3.34 PBC 10% A 250 78.43 80.48 80.71 78.78 79.60 1.41

PBC 10% B 150 42.13 30.75 36.10 39.43 37.10 13.20 PBC 10% B 200 66.90 67.95 67.31 68.25 67.60 0.90

PBC 10% B 250 77.96 74.79 80.38 82.09 78.81 4.01

PBC 10% C 150 0.35 0.29 0.29 0.30 0.31 9.65

PBC 10% C 200 3.08 3.76 3.17 3.99 3.5 12.73

PBC 10% C 250 5.71 6.23 7.86 7.15 6.74 14.21

154



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 10% A 150 31.33 31.99 36.97 25.95 31.56 14.28

PBC 10% A 200 72.76 57.68 64.44 53.03 61.98 13.84

PBC 10% A 250 84.17 86.64 72.88 73.25 79.23 9.08

PBC 10% B 150 32.34 31.42 25.61 28.50 29.47 10.34 PBC 10% B 200 72.49 79.11 67.05 64.27 70.73 9.25 PBC 10% B 250 83.38 86.69 90.37 87.86 87.08 3.33

PBC 10% C 150 0.51 0.54 0.50 0.39 0.48 13.48

PBC 10% C 200 3.22 2.52 2.53 2.48 2.69 13.32

PBC 10% C 250 7.31 8.38 6.52 6.68 7.22 11.65

155



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 20% A 150 25.50 20.99 18.55 21.84 21.72 13.27 PBC 20% A 200 76.43 65.79 79.35 69.56 72.78 8.53 PBC 20% A 250 87.56 89.64 78.59 85.40 85.30 5.62

PBC 20% B 150 38.54 37.65 35.66 44.54 39.10 9.77

PBC 20% B 200 83.60 83.15 67.86 73.99 77.89 10.89

PBC 20% B 250 84.64 94.68 78.70 84.56 85.64 7.74

PBC 20% C 150 0.26 0.28 0.25 0.28 0.27 5.26

PBC 20% C 200 4.98 5.58 6.15 6.10 5.70 9.629

PBC 20% C 250 6.84 7.63 7.35 7.47 7.32 4.67

156



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 20% A 150 28.27 27.67 27.25 26.36 27.39 2.93

PBC 20% A 200 65.56 72.69 82.38 81.01 75.66 9.81

PBC 20% A 250 85.77 88.44 91.12 90.34 88.92 2.67

PBC 20% B 150 19.75 19.46 19.09 14.66 18.24 13.173

PBC 20% B 200 72.25 70.58 74.94 71.01 72.19 2.71

PBC 20% B 250 79.64 68.44 83.27 80.66 78.00 8.40

PBC 20% C 150 0.28 0.25 0.24 0.30 0.27 10.24

PBC 20% C 200 4.19 3.48 3.55 3.30 3.63 10.77 PBC 20% C 250 5.18 6.94 6.56 5.66 6.08 13.32

157



Speed


R1 R2 R3 R4

Average

Effectiveness

RSD

PBC 20% A 150 23.34 23.04 23.22 23.31 23.23 0.59

PBC 20% A 200 65.74 56.31 72.95 79.77 68.69 14.62

PBC 20% A 250 87.03 86.19 82.40 85.66 85.32 2.37

PBC 20% B 150 16.51 15.07 15.63 18.71 16.48 9.72

PBC 20% B 200 68.61 57.87 69.36 61.72 64.39 8.60

PBC 20% B 250 78.26 81.35 74.77 85.31 79.92 5.61

PBC 20% C 150 0.42 0.34 0.43 0.46 0.41 12.64

PBC 20% C 200 3.77 2.85 3.27 3.35 3.31 11.37

PBC 20% C 250 6.87 6.77 7.25 6.30 6.80 5.73

158

Appendix A2

Results of ANOVA

159

Table A2-1 ANOVA Results No.2 Fuel Oil and Oil Control

Source DF Type I SS Mean

Square F

value Pr>F Salinity 2 168.232675 84.116337 9.07 0.0002

Temperature 1 24.759245 24.759245 2.67 0.1039 Rotation 2 2724.251203 1362.125601 146.88 <.0001

Weathering Levels 2 238.577908 119.288954 12.86 <.0001 Salinity*Temperature 2 92.405173 46.202587 4.98 0.0077

Salinity*Rotation 4 16.904139 4.226035 0.46 0.7682 Temperature*W_Levels 2 130.758679 65.379339 7.05 0.0011 Temperature*Rotation 2 44.304456 22.152228 2.39 0.0944

Table A2-2 ANOVA Results No.2 Fuel Oil and dispersant ‘A’


Square F

Value Pr>F Salinity 2 1667.51797 833.75899 15.74 <.0001

Temperature 1 978.47997 978.47997 18.47 <.0001 Rotation 2 83056.7286 41528.3643 784.01 <.0001



160

Table A2-3 ANOVA Results No.2 Fuel Oil and dispersant ‘B’


Square F





Table A2-4 ANOVA Results South Louisiana Crude oil and Oil Control


Square F

Value Pr>F Salinity 2 47.540062 23.770031 6.88 0.0013


Weathering Levels 2 68.503401 34.2517 9.91 <.0001 Salinity*Temperature 2 114.063303 57.031651 16.5 <.0001


161

Table A2-5 ANOVA Results South Louisiana Crude oil and dispersant ‘A’


Square F




Salinity*Rotation 4 662.99488 165.74872 3.28 0.0125 Temperature*W_Levels 2 1170.17456 585.08728 11.57 <.0001 Temperature*Rotation 2 264.24253 132.12126 2.61 0.0758

Table A2-6 ANOVA Results South Louisiana Crude oil and dispersant ‘B’


Square F





162

Table A2-7 ANOVA Results Prudhoe Bay Crude oil and Oil Control


Square F




Salinity*Rotation 4 23.508107 5.877027 11.94 <.0001 Temperature*W_Levels 2 3.591284 1.795642 3.65 0.0278 Temperature*Rotation 2 32.882534 16.441267 33.4 <.0001

Table A2-8 ANOVA Results Prudhoe Bay Crude oil and dispersant ‘A’


Square F



Weathering Levels 2 1156.6174 578.3087 14.62 <.0001 Salinity*Temperature 2 888.3369 444.1685 11.23 <.0001

Salinity*Rotation 4 62.9993 15.7498 0.4 0.8099 Temperature*W_Levels 2 1292.5284 646.2642 16.34 <.0001 Temperature*Rotation 2 916.5409 458.2705 11.58 <.0001

163

Table A2-9 ANOVA Results Prudhoe Bay Crude oil and dispersant ‘B’


Square F





164

Appendix A3

Compositions and Physical properties of Oils

165

Table A3-1 Oil Composition – Prudhoe Bay Crude

Concentration % weight Component Weathering 0% 10% 22.50% Saturates 75 72.1 69.2 Aromatics 15 16 16.5 Resins 6.1 7.4 8.9 Asphaltenes 4 4.4 5.4 Waxes 2.6 2.9 3.3

Table A3-2 Oil Composition – South Louisiana Crude

Concentration % weight Component Weathering 0% 11% 19.70% Saturates 80.8 80.4 78.4 Aromatics 12.6 12.3 12.5 Resins 5.9 6.4 8.0 Asphaltenes 0.8 0.9 1.1 Waxes 1.7 1.8 2.0

Table A3-3 Oil Composition – No. 2 Fuel Oil

Concentration % weight Component Weathering 0% 7% 14.20% Saturates 88.2 86.1 86.1 Aromatics 10.2 11.9 11.7 Resins 1.7 2.0 2.2 Asphaltenes 0.0 0.0 0.0 Waxes 1.7 1.8 2.0

*Source- (Weaver 2004)

166

Table A3-4 Properties of test oils- SLC and PBC

Characteristic Prudhoe Bay

Crude South Louisiana

Crude

Specific Gravity* 0.894 kg/l 0.840 kg/l

API Gravity* 26.8 degrees 37.0 degrees Sulfur 1.03 % wt 0.23 % wt

Nitrogen 0.20 % wt 0.031 % wt Vanadium 21 mg/l 0.95 mg/l

Nickel 11 mg/l 1.1 mg/l Pour point 25° F 0 ° F Viscosity at 40 C 1409 cSt 3.582 cSt at 100 C 4.059 cSt 1.568 cSt

Index 210 **

* At 15 C ** Not calculable when viscosity at 100 C is less than 2.0

Table A3-5 Properties of test oil- 2FO

2FO Characteristic Maximum Minimum

API Gravity 32.1

degrees 42.8

degrees Kinematic Viscosity 100

°F 2.35 cSt 3.00 cSt Flash Point ° F -- 0 Cloud Point ° F -- 10

Sulfur % wt -- 0.35 Aniline point ° F 125 180

Carbon residue % wt -- 0.16 Aromatics % vol. 10 15

*Source - http://www.setonresourcecenter.com/cfr/40CFR/P300_090.HTM

167

Appendix A4

Results of ANOVA for Viscosity Correlation

168

Table A4-1 ANOVA Results No. 2 Fuel oil and oil control


Square F

Value Pr > F Salinity 2 1876.28941 938.1447 443.99 <.0001 Rotation 2 2654.61641 1327.3082 628.17 <.0001

Pred Viscosity 14 13209.04705 943.50336 446.53 <.0001 Salinity* Pred Viscosity 28 1322.13728 47.21919 22.35 <.0001

Salinity*Rotation 4 65.47105 16.36776 7.75 <.0001 Rotation* Pred Viscosity 28 758.97461 27.10624 12.83 <.0001

Table A4-2 ANOVA Results No. 2 Fuel oil and dispersant ‘A’


Square F Value Pr > F Salinity 2 6142.5106 3071.2553 157.77 <.0001 Rotation 2 156070.8083 78035.4042 4008.74 <.0001

Pred Viscosity 14 50610.5914 3615.0422 185.71 <.0001 Salinity* Pred Viscosity 28 8195.2531 292.6876 15.04 <.0001

Salinity*Rotation 4 842.0891 210.5223 10.81 <.0001 Rotation*Pred Viscosity 28 13242.8346 472.9584 24.3 <.0001

169

Table A4-3 ANOVA Results No. 2 Fuel oil and dispersant ‘B’

Source DF Type I SS Mean Square F Value Pr > F Salinity 2 2792.9025 1396.4512 60.48 <.0001 Rotation 2 194048.5526 97024.2763 4201.99 <.0001

Pred Viscosity 14 40130.1646 2866.4403 124.14 <.0001 Salinity*Pred Viscosity 28 4193.666 149.7738 6.49 <.0001

Salinity*Rotation 4 460.593 115.1482 4.99 0.0006 Rotation*Pred Viscosity 28 11992.4301 428.3011 18.55 <.0001

Table A4-4 ANOVA Results Prudhoe Bay Crude Oil and oil control

Source DF Type I SS Mean Square F Value Pr > F Salinity 2 63.848446 31.924223 60 <.0001 Rotation 2 2681.202225 1340.601113 2519.74 <.0001



170

Table A4-5 ANOVA Results Prudhoe Bay Crude oil and dispersant ‘A’





Table A4-6 ANOVA Results Prudhoe Bay Crude oil and dispersant ‘B’




171

Table A4-7 ANOVA Results South Louisiana Crude Oil and oil control





Table A4-9 ANOVA Results South Louisiana Crude oil and dispersant ‘A’




172

Table A4-9 ANOVA Results South Louisiana Crude oil and dispersant ‘B’




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