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UNIVERSITY OF CINCINNATI Date:___________________

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

in:

It is entitled:

This work and its defense approved by:

Chair: _______________________________ _______________________________ _______________________________ _______________________________ _______________________________

DISPERSANT EFFECTIVENESS DATA FOR A SUITE OF

ENVIRONMENTAL CONDITIONS

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

2004

by

Subhashini Chandrasekar

B.E., Chemical Engineering, Birla Institute of Technology & Science, India, 2001

Committee Chair: Dr. George Sorial

ABSTRACT

The use of chemical dispersants to combat the effects of oil spills has been gaining

worldwide acceptance recently. Dispersants are made of surfactants, solvents and additives.

When applied to an oil slick, dispersants reduce the interfacial surface tension and disperse

the oil into into tiny oil droplets in the underlying water column. To assess the impacts of

dispersant usage on oil spills, U.S EPA is developing a simulation model called the EPA

Research Object-Oriented Oil Spill (ERO3S) model to simulate a portion of the oil slick

behavior. Due to interactions between spilled oils and the sea however, the behavior of oil

spills must be based upon empirical data. So the main aim of this research work was to create

a set of empirical data on three oils and two dispersants that has the potential for use as an

input to the ERO3S model. Three oils representing a range of light refined oil, light crude oil

and medium crude oil were chosen for study. Two dispersants with similar characteristics but

supplied by different manufacturers were chosen for evaluation. A factorial experimental

design was conducted in order to determine which of the factors such as temperature, oil

type, oil weathering, dispersant type, rotation speed of the Baffled Flask Test (BFT) and

salinity of sea water are related to the effectiveness of a dispersant used in oil remediation.

Replicates were conducted for all the experiments. This research work has successfully

created a set of empirical data on three oils and two dispersants that could serve as an input to

the oil spill simulation models being developed by EPA. The empirical correlation for the

collected experimental data predicted within a good accuracy the effectiveness of the

dispersant. The results of this research are expected to provide a guidance to dispersant

usage on oil spills.

ACKNOWLEDGEMENTS

I would like to thank my advisor, Dr. George Sorial for his constant guidance, support and

valuable suggestions throughout the course of this research work. I would also like to thank Dr.

Makram Suidan and Dr. James W.Weaver for serving on my committee and for their insights

and suggestions.

I would like to thank the members of my research group, Qiuli Lu, Daekeun Kim, Pablo Campo,

Yi Zhou, Hao Zhang, Zhangli Cai and Balaji Ramakrishnan for their help, suggestions and

friendship. I would like to thank my friends and family for their love and support.

i

TABLE OF CONTENTS

TABLE OF CONTENTS…………………………………………………………………………..i

LIST OF TABLES……………………………………………………………………………......iv

LIST OF FIGURES…………………………………………………………………………….....v

1. INTRODUCTION……………………………………………………………………………...1

1.1 Introduction…………………………………………………………………………………2

1.2 Purpose of Study……………………………………………………………………………3

1.3 Background of Study…………………………………………………………………….....3

1.4 Research Objectives………………………………………………………………………...5

1.5 References…………………………………………………………………………………..7

2. DISPERSANT EFFECTIVENESS ON THREE OILS UNDER VARIOUS

SIMULATED ENVIRONMENTAL CONDITIONS………………………………………...11

2.1 Abstract…………………………………………………………………………………....12

2.2 Introduction………………………………………………………………………………..13

2.3 Materials and Methods…………………………………………………………………….16

2.3.1 Materials…………………………………………………………………………….16

2.3.2 Methods……………………………………………………………………………...17

2.4 Results…………………………………………………………………………………......21

2.5 General Discussion………………………………………………………………………..23

2.5.1 Factors Affecting Dispersion………………………………………………………..23

2.5.2 Empirical Relationships……………………………………………………………..26

2.5.3 Simple Model of Dispersant Action………………………………………………...28

ii

2.6 Summary and Conclusions………………………………………………………………..29

2.7 References…………………………………………………………………………………33

3. DISPERSANT EFFECTIVENESS ON OIL SPILLS – IMPACT OF SALINITY…………..49

3.1 Abstract……………………………………………………………………………………50

3.2 Introduction………………………………………………………………………………..51

3.3 Materials and Methods…………………………………………………………………….54

3.3.1 Materials and Reagents……………………………………………………………...54

3.3.2 Methods……………………………………………………………………………...55

3.4 Results and Discussion……………………………………………………………………59

3.4.1 Effect of Salinity at Different Mixing Energies…………………………………….60

3.4.2 Effect of Salinity at Different Temperatures………………………………………..61

3.4.3 Effect of Salinity at Different Weathering………………………………………......62

3.4.4 Empirical Relationships……………………………………………………………...65

3.5 Summary and Conclusions………………………………………………………………..67

3.6 References………………………………………………………………………………....70

4. IMPACT OF OIL VISCOSITY ON DISPERSANT EFFECTIVENESS………………..…...84

4.1 Abstract……………………………………………………...............................................85

4.2 Introduction………………………………………………………………………….........86

4.3 Materials and Methods……………………………………………………………………86

4.4 Results…………………………………………………………………………………….87

4.5 Discussion………………………………………………………………………………...88

4.6 Conclusions……………………………………………………………………………….90

iii

4.7 Reference…………………………………………………………………………………91

5. CONCLUSIONS AND RECOMMENDATIONS……………………………………………97

APPENDIX……………………………………………………………………………………...A1

5◦C Experiments…………………………………………………………………………….A2

22◦C Experiments………………………………………………………………………….A17

35◦C Experiments………………………………………………………………………….A33

Two-way Interactions………………………………………………………………….......A49

iv

LIST OF TABLES

2.1 Coefficients of Regression Equations with Terms Determined by Step-Wise Linear

Regression…………………………………………………………………………………...36

3.1 Significant Factors for Various Oil-Dispersant Combination……………………………….74

3.2 Effect of Salinity at Different Mixing Energies……………………………………………..74

3.3 Effect of Salinity at Different Temperatures………………………………………………..75

3.4 Effect of Salinity at Different Weathering………………………………………………...…75

3.5 Coefficients of Regression Equations………………………………………………………..76

4.1 Viscosity of Water at Various Temperatures………………………………………………...92

4.2 Calibration Constants for Viscometers………………………………………………………92

4.3 Viscosity Measurements of Oils at Various Temperatures…………………………………..92

v

LIST OF FIGURES

2.1 Baffled Flask Test Apparatus………………………………………………………………...37

2.2 Flask Speed vs Percent Effectiveness of Dispersant ‘A’ for SLC…………………………...38

2.3 Flask Speed vs Percent Effectiveness of Dispersant ‘A’ for PBC…………………………...39

2.4 Flask Speed vs Percent Effectiveness of Dispersant ‘A’ for 2FO…………………………...40

2.5 Flask Speed vs Percent Effectiveness of Dispersant ‘B’ for SLC…………………………...41

2.6 Flask Speed vs Percent Effectiveness of Dispersant ‘B’ for PBC…………………………...42

2.7 Flask Speed vs Percent Effectiveness of Dispersant ‘B’ for 2FO…………………………...43

2.8 Comparison of Measured and Estimated Values (Eq.9) of Dispersant Effectiveness

on South Louisiana Crude Oil………………………………………………………………..44


on Prudhoe Bay Crude Oil…………………………………………………………………...45


on Number Two Fuel Oil………………………………………………………….................46

2.11 Simulation of PBC dispersal at flask speed of 200 RPM and temperature of 20◦C……….47

2.12 Simulation of PBC dispersal at flask speed of 200 RPM and temperature of 5◦C -30◦C... 47

2.13 Simulation of PBC dispersal at flask speeds of 150 - 250 RPM and 20◦C………………...48

3.1 Flask Speed vs Percent Effectiveness of Dispersant ‘A’ at 22±1◦C………………………...77

3.2 Temperature vs Percent Effectiveness of Dispersant ‘A’ at 250 rpm………………………..78

3.3 Weathering vs Percent Effectiveness of Dispersant ‘A’ at 5±1◦C …………………..……...79

3.4 Weathering vs Percent Effectiveness of Dispersant ‘A’ at 35±1◦C ………………………...80

3.5 Comparison of Measured and Estimated Values (eq. 8) of Dispersant Effectiveness

vi

on South Louisiana Crude Oil………………………………………………………………..81


on Prudhoe Bay Crude Oil…………………………………………………………………...82


on Number Two Fuel Oil…………………………………………………………………….83

4.1 Cannon-Fenske viscometer…………………………………………………………………..93

4.2 Temperature (◦C ) vs Viscosity (cSt) for SLC……………………………………………....94

4.3 Temperature (◦C ) vs Percent Effectiveness of Dispersant ‘B’ on SLC (Salinity =

10ppt, flask speed = 250 rpm)……………………………………………………………….94

4.4 Temperature (◦C ) vs Viscosity (cSt) for PBC………………………………………………95

4.5 Temperature (◦C ) vs Percent Effectiveness of Dispersant ‘B’ on PBC (Salinity =


4.6 Temperature (◦C ) vs Viscosity (cSt) for 2FO………………………………………………96

4.7 Temperature (◦C ) vs Percent Effectiveness of Dispersant ‘B’ on 2FO (Salinity =


1

1. INTRODUCTION

2

1.1 Introduction

Transportation and consumption of petroleum products and offshore drilling around the

world have created the potential for oil spills into the environment. Spills may be caused by

human carelessness, equipment breakdown or natural disasters. Oil spills at sea can affect the

water column, sediments and shorelines. Slicks on water surface are dangerous to sea birds, fish

and marine mammals. Oil spills spread under the action of gravitational, viscous and surface

tension forces (Hoult 1972) and will most likely spread over a large area if a quick response is

not initiated. Some of the main oil spill cleanup strategies include: mechanical cleanup/recovery,

in-situ burning, bioremediation and treatment with chemical dispersants (NRC 1989).

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

advantages and could also result in a net environmental benefit when considered in relation to

other response options. Dispersants do not eliminate the problem of an oil spill but are intended

as a means of reducing the overall environmental impact of an oil slick at sea. Dispersants are

chemical formulations with an active ingredient called surfactants. Surfactants are specifically

designed chemicals that have both hydrophilic and lipophilic groups in the chemical compound.

These chemicals reduce the interfacial tension between the oil and water and helps the creation

of small oil droplets, which move into the water column facilitating quicker natural biological

breakdown (biodegradation) and dispersion. By decreasing the size of the oil droplets, and

dispersing the droplets in the water column, the oil surface area exposed to the water increases

and natural breakdown of the oil is enhanced.

Dispersant effectiveness is one of the major factors that determines the selection and

usage of dispersants. It is defined as the amount of oil that the dispersant puts into the water

column compared to the amount of oil that remains on the surface. Many factors influence

3

dispersant effectiveness, including oil composition, sea energy, state of oil weathering, the type

of dispersant used and the amount applied, temperature, and salinity of the water.

1.2 Purpose of Study

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

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

(Weaver 2003) . This model is for simulating a portion of the oil slick behavior. However, due to

the chemical and physical interactions between spilled oils and the sea, a portion of the behavior

of the oil spill must be based upon empirical data. The impacts of dispersants on oil slicks are

best characterized by empirical data. So the main aim of this research was to create a set of

empirical data on three oils and two dispersants that has the potential for use as an input to the

ERO3S model. Depending on the nature of the results, the data may be used to determine the

amount of oil that is dispersed at a given time in a spill scenario. Since oils have an inherent

tendency for “natural” dispersal, a set of control experiments was also conducted both for good

experimental practice and to assess the unaided dispersal of oil at sea.

1.3 Background of Study

Testing dispersant effectiveness in the laboratory is not a simple task. Many of the

complexities relate to the physical-chemical behavior and properties of dispersants. A dispersant

consists of three types of chemicals: surfactants, solvents, and additives. For an effective

dispersant, the most important component in the dispersant mixture is the surfactant. Surfactants

contain both oil-compatible and water-compatible groups. Because of their opposing solubility

tendencies, both groups will reside at the oil-water interface and will reduce the oil-water

4

interfacial surface tension, which will eventually promote dispersion of oil droplets into the

water column. The major factors affecting dispersion of oil include: (a) the method of

application of the dispersant to the oil; (b) the method of mixing of dispersant, oil, and water;

and (c) the subsequent dispersion of the dispersant/oil mixture in the water column

(Clayton et al. 1993).

Many different types of dispersant test procedures and apparatus have been described in

literature. In general, three approaches have been used for dispersant applications in these tests:

(1) premixing of a dispersant with the oil before the test begins (Fingas et al. 1989a) and

(U.S.EPA 1996);

(2) premixing of the dispersant with water before oil is introduced to the system

(Rewick et al. 1981) and (Rewick et al. 1984) and

(3) mixing of the dispersant with the oil at the oil-air interface as part of the testing procedure

itself.

Clayton et al. (1992) evaluated the performance of the revised standard EPA method

(U.S.EPA 1984) , Environment Canada’s Swirling Flask Test (SFT) (Fingas et al. 1987),

(Fingas et al. 1989a), (Blondina et al. 1997) and (Fingas et al. 1989b) and the IFP-Dilution test

(Desmarquest et al. 1985), (Bardot et al. 1984) and (Daling et al. 1990). They also evaluated

three versions of the SFT (premixed dispersant and oil, and 1-droplet and 2-droplet dispersant-to-

oil-slick addition). Based on their results, the SFT premixed procedure was recommended to

EPA for treating oil slicks due to its relative simplicity and straightforwardness.

Becker et al.(1991) studied the Exxon Dispersant Effectiveness Test (EXDET) for evaluating oil

spill dispersants and the results of this method were similar to the SFT. The SFT was adopted in

the final EPA regulation in September 1994. The method was different from the earlier standard

5

method of 1984. The SFT was reexamined after its first year of use (IT Corporation 1995).

However, due to discrepancies among researchers, a redesign of the test flask was considered by

EPA. The design of the new flask which is referred to as the Baffled Flask Test (BFT) and the

important experiments leading to major changes in the protocol reflecting a much more

reproducible and stable effectiveness test are addressed by Sorial et al. (2003a&b) . Use of the

BFT protocol was the basis for all experiments conducted. The BFT has the promise of being

able to overcome limitations of previous test methodologies which included non-reproducibility

and non-representativeness of field conditions, as reported by earlier researchers. In this

research, the variation in the effectiveness of dispersants caused by changes in temperature, oil

composition, oil weathering, dispersant type, rotation speed of the BFT and salinity of water has

been explored.

1.4 Research Objectives

The overall objective of this research was to create a set of empirical data on three oils and

two dispersants to serve as an input to the ERO3S model, by studying the variation in the

effectiveness of the dispersants caused by changes in temperature, oil type, oil weathering,

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

Specific objectives were:

To conduct a factorial experimental design for three oils, namely, South Louisiana Crude

Oil, Prudhoe Bay Crude Oil, and Number 2 fuel oil for determining the significance of

the above factors on the effectiveness of two dispersants referred to as Dispersant ‘A’ and

Dispersant ‘B’ in this study. Of the three oils chosen, Prudhoe Bay Crude Oil and South

Louisiana Crude Oil are medium weight reference oils and Number Two Fuel Oil is a

6

light refined oil. Two dispersants with similar characteristics but manufactured by two

different manufacturers were chosen for evaluation

To conduct a replicate study for all experiments

To determine empirical relationships between the amount of oil dispersed and the various

variables studied

To study the impact of oil viscosity on dispersant effectiveness.

7

1.5 References

Bardot, C., Bocard, C., Castaing, G., and Gatellier, C. 1984. The Importance of a Dilution

Process to Evaluate Effectiveness and Toxicity of Chemical Dispersants. Proceedings of

the Seventh Annual Arctic Marine Oilspill Program Technical Seminar, 1984, 179-201.

Becker, K. W., Coker, L. G., and Walsh, M. A.1991. A Method for Evaluating Oil Spill

Dispersants: Exxon Dispersant Effectiveness Test (EXDET). Proceedings of the Oceans

Conference, 1991, Honolulu, HI.

Blondina, G. J., Sowby, M. L., Ouano, M. T., Singer, M. M., and Tjeerdema, R. S. 1997.

Comparative Efficacy of Two Corexit Dispersants as Measured Using California's

Modified Swirling Flask Test. Proceedings of the 20th Arctic and Marine Oilspill

Program Technical Seminar, 1997, Ontario, 561-573.

Clayton, J. R., Tsang, S., Frank, V., Marsden, P., and Harrington, J. 1992. Chemical Dispersant

Agents-Evaluation of Three Laboratory Procedures for Estimating Performance. Final

Report on EPA Contract No.68-C8-0062, Work Assignment No.2/3-38, USEPA, New

Jersey.

Clayton, J. R., Payne, J. R., Farlow, J. S., and Sarwar, C. 1993. Oil Spill Dispersants

Mechanisms of Action and Laboratory Tests, CRC press, Boca Raton, Florida, 5, 55-87.

8

Daling, P. S., Mackay, D., Mackay, N., and Brandvik, P. J. 1990. Dropsize Distributions in

Chemical Dispersion of Oil Spills: Towards a Mathematical Model. Oil & Chemical

Pollution, 7, 173-198.

Desmarquest, J. P., Croquette, J., Merlin, F., Bocard, C., Castaing, G., and Gatellier, C.1985.

Recent Advances in Dispersant Effectiveness Evaluation: Experimental and Field

Aspects. Proceedings of the International Oil Spill Conference, 1985, Los Angeles, CA,

445-452.

Fingas, M. F., Hughes, K. A., and Schweitzer, M. A.1987. Dispersant Testing at the

Environmental Emergencies Technology Division. Tenth Arctic Marine Oilspill Program

Technical Seminar, Alberta, Canada, 343-356.

Fingas, M. F., Dufort, V. M., Hughes, K. A., Bobra, M. A., and Duggan, L. V. 1989a.

Laboratory Studies on Oil Spill Dispersants. Oil Spill Dispersants: New Ecological

Approaches, ASTM STP1018, American Society for Testing and Materials, Philadelphia,

PA, 207-219.

Fingas, M. F., Munn, D. L., White, B., Stoodley, R. G., and Crerar, I. D.1989b. Laboratory

Testing of Dispersant Effectiveness: The Importance of Oil-to-Water ratio and Settling

Time. Proceedings of the International Oil Spill Conference, 1989, San Antonio,TX, 365-

373.

9

Hoult, D. P. 1972. Oil Spreading on the Sea. Annu. Rev. Fluid Mech., 4, 341-368.

IT Corporation 1995. Investigation of Reported Problems with Swirling Flask Dispersant

Effectiveness Test-Final Report. Final Report on EPA Contract No. 68-C2-0108, Work

Assignment No. 3-53, JTN 816453, U.S.EPA, Edison, NJ 08837.

NRC 1989. Using Oil Spill Dispersants on the Sea. Report of the Committee on Effectiveness of

Oil Spill Dispersants, National Academy Press, Washington, D.C.

Rewick, R. T., Sabo, K. A., Gates, J., Smith, J. H., and McCarthy, L. T. 1981. An Evaluation of

Oil Spill Dispersant Testing Requirements. Proceedings of the International Oil Spill

Conference, 1981, Atlanta, GA, 5-10.

Rewick, R. T., Sabo, K. A., and Smith, J. H. 1984. The Drop-weight Interfacial Tension Method

for Predicting Dispersant Performance. Oil Spill Chemical Dispersants, Research

Experience and Recommendations, American Society for Testing Materials,

Philadelphia, PA, 94-107.

Sorial, G. A., Venosa, A. D., Koran, K. M., Holder, E., and King, D. 2003a. Oil Spill Dispersant

Effectiveness Protocol-Part I Impact of Operational Variables. Accepted for publication

in ACSE Journal of Environmental Engineering.

10

Sorial, G. A., Venosa, A. D., Koran, K. M., Holder, E., and King, D. 2003b. Oil Spill Dispersant

Effectiveness Protocol-Part II Performance of the Revised protocol. Accepted for

publication in ACSE Journal of Environmental Engineering.

U. S. EPA 1984. National Oil and Hazardous Substances Pollution Contingency Plan: Final

Rule. 40 CFR Part 300, Federal Report Register, Vol. 49, 29192-29207.

U. S. EPA 1996. Swirling Flask Dispersant Effectiveness Test. Title 40 Code of Federal

Regulations, Pt.300, appendix C, 245-250.

Weaver, J. W. 2003. EPA Research Object-Oriented Oil Spill model. U.S EPA Ecosystems

Research Page: http://www.epa.gov/athens/research/projects/eros/.

11

2. DISPERSANT EFFECTIVENESS ON THREE OILS UNDER VARIOUS

SIMULATED ENVIRONMENTAL CONDITIONS1

1 Paper Submitted for Publication in Marine Environmental Research

12

2.1 Abstract

To assess the impacts of dispersant usage on oil spills, U.S EPA is developing and

evaluating models. However, due to the complexity of chemical and physical interactions

between spilled oils, dispersants and the sea, an empirical approach to the interaction between

the dispersant and oil slick may provide a guide to dispersant effects on oil slicks.

Recently, EPA developed an improved laboratory dispersant testing protocol, called the

baffled flask test (BFT). Use of this protocol was the basis for the experiments conducted in this

study. A factorial experimental design was conducted in order to determine which of the factors

temperature, oil type, oil weathering, dispersant type, and rotation speed of the shaker are related

to the effectiveness of a dispersant used in oil remediation. Statistical analyses of the

experimental data performed separately for the three oils revealed that certain two-way

interactions exist among the factors. For SLC, temperature and mixing energy were significant

factors, for PBC, temperature, mixing energy and weathering were significant and for 2FO, only

temperature was a significant factor. The replicate study revealed that the replicates were in close

agreement with the previously obtained results. An empirical simulation of the experiment with

dispersant addition at several times illustrated the effects of dispersants on oil slicks. Empirical

relationships between the amount of oil dispersed and the variables studied were also developed.

Keywords: baffled flask test, dispersant, dispersant effectiveness, oil spill, oil remediation.

13

2.2 Introduction

Transportation and consumption of petroleum products around the world has created the

potential for oil spills into the environment. Offshore drilling and production platforms are

another potential source of oil spills at sea. Oil spills at sea can affect the water surface, water

column, sediments and shorelines. Oil initially forms a slick at the water surface due to its

immiscibility. Water and wind actions disrupt the oil/water interface, resulting in the formation

of oil droplets that enter the water column. Oil spills spread under the action of gravitational,

viscous and surface tension forces (Hoult 1972) and will most likely spread over a large area if a

quick response is not initiated. So careful response planning and preparedness are essential for

successful response to oil spills at sea. In general, there are three major response operations for

cleanup of oil spills at sea: mechanical response, in-situ burning, and the use of chemical

dispersants (NRC 1989).

Chemical dispersants are made of mixtures of surfactants and other chemicals that are

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

column (Lessard and Demarco 2000). Surfactants are surface active agents that are dissolved in

one or more solvents. They have a chemical affinity for both oil (lipophilic) and water

(hydrophilic). When applied to an oil film, surfactants diffuse to the oil/water interface and align

themselves so that the lipophilic end of the molecule is attached to the oil phase and the

hydrophilic end extends into the water phase, thereby reducing the interfacial surface tension

between water and oil. This allows oil to mix in the top part of the water column as droplets and

thus may be useful to prevent the oiling of shorelines and aquatic animals. Because there are a

number of factors that may influence the ability of the dispersant to disperse an oil slick, this

study was undertaken to develop empirical data on the effectiveness of dispersants. This

14

information was expected to provide insight into the degree of reduction of shoreline impacts or

the need for repeat application of a dispersant.

Since chemical dispersants enhance the dispersion of oil slicks at sea as small oil droplets

in the water column, they could be used in oil spill response operations under appropriate

conditions. Recently, the U.S EPA developed an improved dispersant testing protocol, called the

baffled flask test (BFT) which was the basis of the experiments conducted in this study (Venosa

et al. 2002). The test is a refinement of the earlier testing protocol called the Swirling Flask Test

(SFT). The BFT has the advantage of overcoming limitations of SFT such as non-reproducibility

in the hands of various operators and limited mixing of the oil, dispersant and water (Venosa et

al. 2002). The BFT test procedure is also relatively simple and requires a minimum of

equipment. Using the BFT, the variations in the effectiveness of dispersants caused by changes

in oil composition, dispersant type, and the environmentally related variables of temperature, oil

weathering, and rotational speed of the BFT were studied. Dispersant effectiveness is defined as

the amount of oil that the dispersant puts into the water column compared to the amount of oil

that remains on the surface. The amount of dispersant is very important to effectiveness

(Delvigne 1987), (Fingas et al. 1997) and (Fingas et al. 1993b). Other factors such as oil

composition, sea energy, state of oil weathering, the type of dispersant used and the amount

applied, and temperature of sea water also influence dispersant effectiveness.

Mixing energy is required to disperse the oil slick as oil droplets after the addition of

dispersants. In a real spill situation, the sea state is one of the important factors that affect

dispersant effectiveness. In general, the more ‘rough’ the sea is, the better the mixing of the oil

and the dispersant and hence, greater the effectiveness. As reported by Clayton et al. (1993) the

applications of dispersants reduces the interfacial tension between oil and water, which results in

15

the formation of oil droplets. Initial drop size distribution is controlled by mixing energy, as well

as compositional parameters such as dispersant, oil, and dispersant-oil and oil-water ratio.

Clayton et al. (1993) and Fingas et al. (1993a) conducted experiments that indicated that mixing

energy reduces the size of the oil droplets. Emulsions begin to form when sea energy is sufficient

(Fingas et al. 1995).

In general, oil properties play an important role in the degree of dispersant effectiveness.

The chemical composition and physical properties of a crude oil determine the behavior of the

oil and the way its properties will change when the oil is spilled at sea. When oil is spilled at sea,

it undergoes physical and biological processes which change the properties of the oil. These

processes are collectively known by the term ‘weathering’. Weathering increases the viscosity of

the oil due to evaporation of the lighter components. High viscosity will limit the effectiveness of

chemical dispersants. Highly viscous oils resist the breakup of the oil into dispersed droplets and

hence the efficiency of dispersion decreases.

Usually, lower water temperatures increase the viscosity of both the oil and the dispersant.

As oil gets more viscous due to low water temperature or weathering, the energy requirement for

mixing the dispersant and oil also increases (Clayton et al. 1993). Higher water temperatures will

also affect the spilled oil temperature. So, theoretically, an increase in temperature will reduce oil

viscosity and hence improve dispersion. Mackay & Szeto (1981) conducted studies on the impact

of water temperature on the effectiveness of dispersants on spilled oil. Studies conducted

indicate an increase in dispersion efficiency with an increase in temperature. However, even

theory indicates that there have been conflicting results in the trend of dispersant effectiveness

with either increasing or decreasing water temperature. For example, studies performed by

Byford et al. (1983) varied from those conducted by Fingas (1991).

16

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

evaluating models (Weaver 2003). However, due to the complexity of chemical and physical

interactions between spilled oils, dispersants and the sea, an empirical approach to the interaction

between the dispersant and oil slick may provide a guide to dispersant effects on oil slicks. This

work represents the first step in developing a dataset as it seeks to elucidate the factors affecting

dispersant effects.

The overall objective of this project was to create a set of empirical data on three oils and

two dispersants, by studying the variation in the effectiveness of the dispersants caused by

changes in temperature, oil type, oil weathering, dispersant type, and rotation speed of the BFT.

The specific activities of this research were to: (1) design a factorial experimental setup to

determine which of the factors such as temperature, oil type, oil weathering, dispersant type and

rotation speed of the BFT are related to the effectiveness of a dispersant used in oil remediation,

(2) conduct a replicate study to determine the precision of the experimental results for the range

of variables studied, (3) determine empirical relationships between the amount of oil dispersed

and the various variables studied, and (4) perform simulations of dispersant additions to the flask

for illustrating behavior of the oil under a variety of environmental conditions.

2.3 Materials and methods

2.3.1 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 2.1). 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

17

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 :L of dispersant and 100 :L

of oil with an accuracy of 0.3% and a precision of 0.25% was used with 100 :L 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 :L

gas-tight syringes were also used.

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.

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

for all the experiments at a concentration (salinity) of 34 ppt. Three types of oil samples provided

by US EPA- South Louisiana Crude Oil (SLC), Prudhoe Bay Crude Oil (PBC), and Number 2

Fuel Oil (2FO) were used in the study. Of the three oils studied, SLC and PBC are light and

medium weight EPA/API standard reference oils respectively and 2FO is light refined oil. Two

dispersant samples that scored effectiveness above 85% by the BFT were used in the study

(Venosa et al. 2002). They are referred to as Dispersant ‘A’ and Dispersant ‘B’ here. The solvent

dichloromethane (DCM, pesticide quality), was used for extraction of all sample water and oil-

standard water samples.

2.3.2 Methods

18

Weathering of oils: The three oils namely, SLC, PBC and 2FO were used in the study at three

levels of weathering: 0%, 10% and 20%. The weathering of the oil was performed by bubbling

air up through a 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.

)1(100*%volumeInitial

volumeFinalvolumeInitialweatheredOil −=

SLC and PBC were weathered to 10% and 20% whereas 2FO was weathered to 3.8% and 7.6%

which represents the maximum weathering possible for this oil.

Oil standard procedure: Standard solutions of oil for calibrating the UV-VIS spec 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 2 mL of the specific reference oil with 18 mL DCM added was measured by using a 1 mL gas

tight syringe and the concentration of the oil solution was then determined. Specific volumes of

20, 50,100, 150, 200, 300 :L of SLC-DCM stock or 11, 20, 50, 100, 125, 150 :L of PBC-DCM

stock or 150, 200, 400, 600, 800, 1000 :L of 2FO-DCM stock were added to 30 mL of synthetic

sea water in a separatory funnel and extracted thrice with DCM. The final DCM volume for the

combined extracts was adjusted to 20 mL with DCM. The extracts were transferred to a 50 mL

crimp style glass vial with a teflon/aluminum seal, mixed by inverting many times and stored in

a refrigerator at 4±2 0C until time of analysis. For treatments with oil plus dispersant, oil plus

dispersant stock standard was first prepared. The density of 2 mL specific reference oil, 80 :L of

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

19

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

solutions as mentioned above.

Dispersant effectiveness procedure: 120 mL of synthetic sea water equilibrated at the desired

temperature was added to the test flask (Fig. 1), followed by the sequential addition of oil and

finally the dispersant. 100 :L of oil was dispensed directly onto the surface of the synthetic sea

water using an Eppendorf repeator pipettor with a 5 mL syringe tip attachment. The dispersant

was then dispensed onto the center of the oil slick by using a 100 :L syringe tip attachment that

was set to dispense 4 :L, giving a ratio of dispersant-to-oil ratio (DOR) of 1:25. The flask was

placed on an orbital shaker and mixed for 10 minutes at the desired rotation speed, at the end of

which it was removed from the shaker and allowed to remain stationary on the bench top for

another 10 minutes. At the end of the settling time, the first 2 mL of sample was drained from the

stopcock and discarded, and then 30 mL of sample was collected in a 50 mL measuring cylinder.

The 30 mL sample was then transferred to a 125 mL separatory funnel and extracted three 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 a Teflon/aluminum seal. These vials were stored at 4±2 0C

until the time of analysis (maximum of 5 days). The oil standards procedure and test procedures

were conducted according to the procedures given by Sorial et al. (2003).

The dispersant effectiveness is defined as the concentration of the dispersed oil in water

(which is determined through extraction by DCM as stated above) divided by the total

concentration of oil, i.e., based on the total volume of oil added.

20

Sample analysis: The experimental sample extracts and the standard solutions prepared were

removed from the refrigerator and allowed to equilibrate at the laboratory temperature. First, a

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

of increasing concentration and the absorbance values were noted at wavelengths of 340, 370

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

the highest calibration standard point, dilution was done. This was mostly done in the case of

PBC which was diluted 10 times. The sequence of analyses is thus: (1) solvent blank; (2) six

calibration standards for the specific test oil plus dispersant and (3) experimental samples.

Calculation procedure: The area under the absorbence vs wavelength curve for the

experimental samples between wavelengths 340 and 400 nm was calculated by using the

trapezoidal rule according to the following equation:

( ) ( )Area

Abs Abs *302

Abs Abs *302

340 370 370 400=+

++

(2)

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:

EffTotal oil dispersed

Voil oil

%*

*=ρ

100 (3)

where:

mLmLoilofMassdispersedoilTotal

30120*= (4)

Mass of oil, g = Concentration of oil * VDCM (5)

and

21

Concentration of oil, g / L = Area as determined by Equation 2

Slope of the calibration curve

(6)

Factorial experimental design: The main aim was to determine what factors are related to the

effectiveness of a dispersant used in oil remediation. The response variable for the experiment

was the percent effectiveness of the dispersant. The factors and levels of each of the factors are

as follows: weathering (0, 10, and 20% for SLC and PBC; and 0, 3.8 and 7.6% for 2FO),

dispersant (“A” and “B”), temperature (5◦C, 22◦C and 35◦C ), and flask speed (150, 200, and 250

rpm). With these levels for each of the factors, a factorial experiment was conducted. The

factorial experiment was also performed for each of the three crude oils separately, i.e., no

dispersant added.

2.4 Results

The results of the factorial experimental design are presented in Figures 2.2-2.7 which

show the percent effectiveness of dispersants ‘A’ and ‘B’ at various flask speeds, weathering

levels, and temperatures for all three oils. Statistical analyses of the experimental data were

performed separately for the three oils. The results of the factorial experiments were analyzed

using an analysis of variance (ANOVA) at α = 0.05 in order to determine which factors, or set of

factors, are related to percent effectiveness. A significant interaction means that the effect of one

input parameter varies at differing levels of another input parameter. Whenever a hypothesis test

showed an effect to be significant, least squares means were examined to determine the exact

nature of the difference. The p value from the General Linear Models (GLM) procedure was

used to measure the significance of a factor. The GLM procedure uses the method of least

squares to fit general linear models (SAS Institute Inc. 1999). The condition for significance as

22

determined by statistical analysis was that the p value should be less than 0.05 for a factor to be

significant.

The results showed that only 2 factors significantly affected dispersion effectiveness in

SLC, namely, temperature and mixing speed for which the respective p values were 0.0002 and

0.0001. Since the only response factor measured was dispersant effectiveness, only two-way

interactions involving the factor dispersant type with temperature or rotational speed were

considered for replicate study. For PBC, three factors (temperature, mixing speed, and

weathering) were found to give significant interactions with dispersant type (p=0.0024, p=0.0001,

and p=0.0162, respectively). In the case of 2FO, temperature was the only factor giving a two-

way interaction with dispersant type (p<0.001). For interactions that did not involve rotational

speed, the highest speed-250 rpm was used for subsequent replicate experiments. Similarly for

interactions that did not involve weathering, 0% was used, and for interactions that did not

involve temperature, 22 °C was used. The effect of these two-way interactions can also be seen

from Figures 2.2-2.7. For example, in the case of SLC, there is a significant change in the

percent effectiveness values with increase in temperature from 5 to 35 °C and with increase in

mixing energy from 150 to 250 rpm whereas there is not much change in the effectiveness values

with increase in weathering from 0 to 20% (Figures 2.2 and 2.5). Hence temperature and mixing

energy are indeed significant factors for SLC.

From Figures 2.3 and 2.6, it is also evident that for PBC, all three factors: temperature,

mixing energy and weathering produce significant change in the percent effectiveness values and

hence all these factors are termed significant. For 2FO, although mixing energy and temperature

produced a significant change in the effectiveness values, mixing energy vs dispersant did not

23

yield a significant statistical interaction. Hence only temperature was considered to be

significant.

In order to confirm the precision of the previously obtained results a replicate study was

conducted. Two replicates for each condition where we previously observed a two-way

interaction was conducted and 4 replicates for 2 of these experiments, namely, the ones studying

mixing speed and dispersant type for SLC and for PBC were conducted. Error bars are shown in

Figures 2.2-2.7 for experiments conducted in replicates. The precision objectives were

determined by using the relative standard deviation (RSD) for percent effectiveness based on

four replicate flasks and on relative percent difference (RPD) for percent effectiveness based on

two replicates. The acceptance criterion was based upon RSD or RPD less than 15%. The RSD

was calculated using:

)7(100*tanessEffectivenAverage

DeviationdardSRSD = and the RPD using:

)8(100*.

.replicatesofessEffectivenAvg

resultspreviousofessEffectivenreplicatesofessEffectivenAvgRPD −=

2.5 General Discussion

2.5.1 Factors affecting dispersion

Effectiveness of oil dispersion by chemical dispersants is governed by a range of

conditions and includes: type of oil, degree of weathering of the oil, type of dispersant used,

wave mixing energy and sea water temperature.

Mixing energy: Figures 2.2-2.7 show the results obtained for oil + dispersant combinations at 34

ppt salinity. From these figures, it is seen that for a given oil at a specified weathering condition,

24

as the speed of the orbital shaker increased from 150 to 250 rpm, the dispersion effectiveness

also increased. For example, for unweathered SLC with dispersant ‘A’, at 5±1°C and 150 rpm

flask speed, the effectiveness was 54.5%, whereas at 200 and 250 rpm, it was 77.3% and 89.6%,

respectively (see Figure 2.2a). Similarly, for unweathered PBC with dispersant ‘A’, 5±1oC

temperature and 150 rpm flask speed, dispersion effectiveness was 21.1%, whereas at 200 and

250 rpm, it was 58.9% and 69.7%, respectively (see Figure 2.3a). In the case of 2FO, the

increase in dispersant effectiveness with increase in flask speed from 150 to 250 rpm was quite

high at all the three temperatures of study and three weathering levels. This trend in dispersant

effectiveness with increase in flask speed was true for dispersant ‘B’ as well. Control

experiments (data not shown) showed the same trend although the effectiveness values were very

low. Overall, for SLC, at the three weathering levels and three temperatures, the RSD for

dispersant effectiveness values among different flask speeds ranged from 14-43% and 37-77%

for experiments with dispersants ‘A’ and ‘B’, respectively. Similarly for PBC, the RSD was

ranging between 23-51% and 24-112% for experiments with dispersants ‘A’ and ‘B’,

respectively. For 2FO, the RSD among dispersant effectiveness values was ranging between 17-

64% and 25-51%, for experiments with dispersants ‘A’ and ‘B’, respectively. If one postulates

that an RSD value less than 15% is insignificant, then these results imply that mixing energy has

a significant impact on dispersant effectiveness. This increase in dispersant effectiveness is due

to the fact that when the mixing energy increases, eddies formed from the energy dissipation are

smaller, which cause better breakup of oil droplets and thus better dispersion.

Weathering: The effect of weathering on dispersant effectiveness is observed by examining

Figures 2.2-2.7. In general, as the degree of weathering of the oil increases, dispersant

25

effectiveness decreases. For example, with unweathered SLC and dispersant ‘B’, at 5±1 oC and

250 rpm flask speed, the dispersion effectiveness was 83.1%, whereas at 10 and 20% weathering

it declined to 81.2% and 77.7%, respectively, at the same flask speed (Figure 2.5). The same

types of observations were evident with the other two oils at the different temperature settings.

Exceptions to the general conclusion that dispersion decreased with weathering occurred for SLC

at 200 rpm, PBC at 150 and 200 rpm, and 2FO at 150 and 200 rpm, all at 22±1 oC and with

dispersant ‘A’. The RSD for dispersant effectiveness values among different weathering levels

ranged from 3-14% and 1-6% for experiments with dispersants ‘A’ and ‘B’, respectively for SLC,

at all three flask speeds and temperatures. Similarly for PBC, the RSD was ranging between 2-

22% and 2-7% for experiments with dispersants ‘A’ and ‘B’, respectively. For 2FO, the RSD

among dispersant effectiveness values was ranging between 1-9% and 1-2%, for experiments

with dispersants ‘A’ and ‘B’, respectively. Hence, in contrast with the other two oils, the

weathering of PBC had a greater impact on dispersant effectiveness. This is consistent with the

results of statistical analysis which identified weathering as a significant factor for PBC.

Weathering had very less impact on the natural dispersion of oils, i.e., oil control experiments

(data not shown).

Temperature: The properties of spilled oils are determined by, among other things, their

chemical composition, which varies widely from one oil to another. For the purposes of

determining the utility of dispersants at various sea temperatures, one of the most important

properties is the viscosity of the spilled oil, which is inversely proportional to temperature. An

examination of the data presented in Figures 2.2-2.7 reveals some important relationships:

dispersant effectiveness increased as temperature increased, at least up to a point. As temperature

26

increased from 5 to 22 °C, dispersion increased in almost all cases. However, when the

temperature increased to 35 °C, dispersion declined in many cases. It is interesting to note that

temperature plays a dual role here: on one hand, it affects viscosity of the oils, which decreases

and thereby causes an increase in dispersion. On the other hand, it increases weathering, which

has a tendency to decrease dispersion effectiveness (35°C). As mentioned earlier, conflicting

trends in dispersant effectiveness with increase in temperature, have been observed by previous

researchers too. An in depth study of oil properties such as density, viscosity and surface tension

might provide a clearer understanding of the effect of temperature on dispersant effectiveness

because it is speculated that temperature variations cause a change in the physical properties of

oils as well as dispersants.

Overall, for SLC, at the three weathering levels and three flask speeds, the RSD for

dispersant effectiveness values at different temperatures ranged from 14-37% and 7-31% for

experiments with dispersants ‘A’ and ‘B’, respectively. Similarly for PBC, the RSD was ranging

between 16-53% and 16-36% for experiments with dispersants ‘A’ and ‘B’, respectively. For

2FO, the RSD among dispersant effectiveness values was ranging between 14-65% and 15-39%,

for experiments with dispersants ‘A’ and ‘B’, respectively. Again, if an RSD value greater than

15% is considered to be significant, it can be concluded that temperature plays an important role

in determining dispersant effectiveness, for all three oils which is also evident from the results of

statistical analysis.

2.5.2 Empirical relationships

A quadratic regression model was fit to the experimental data obtained, for each of the

oil/dispersant combinations. The model takes the following form:

27

)9()(2

)(2

)(2

)(2

)(2

)(2

)(2

)(2

)(2

)(2

)(2

)(2

)()()()()()()()()(

)()()(0

222

222222

222

isitivstv

isitstisivsvitivtv

issittivv

isitivvtsisittsisivvsitivvt

issittivvi

xxx

xxxxxx

xxx

xxxxxxxxx

xxxy

β

βββ

βββ

ββββ

ββββ

+

+++

+++

++++

+++=

for i=1,....n

Where yi is the effectiveness value at the corresponding levels of the factors (x), $0 is the

intercept, $v is the oil weathering effect, $t is the temperature effect, $s is the speed effect, $vt is

the effect of the weathering by temperature interaction, $vs is the effect of the weathering by

speed interaction, $ts is the effect of temperature by speed interaction, and $vts is the effect of the

three way interaction between all of the factors. The terms were chosen to include both linear

and parabolic effects of each variable and all possible two and three factor interactions. If all

were statistically significant, the model would include 15 terms. Since there were no more than

27 data points for each oil/dispersant combination, no additional interaction or non-linear terms

were included in the model. Data from the replicate study were used to enhance the regressions

i.e, each non-replicated point was replaced by the average result from the replicate study. As

seen in the results (Table 2.1), only a few terms were significant for a given oil/dispersant

combination as determined by step-wise multiple regression with an acceptance/rejection level of

0.05. This is evident from Table 2.1 which gives the coefficients of regression equations. For

example, for SLC with dispersant ‘A’, the significant terms include both linear and parabolic

effects of temperature, and temperature by speed interaction as seen in Table 2.1. Also, the step-

wise regression showed that adding more of the 15 possible terms does not improve the fits.

28

The various $ parameters for the various oil-dispersant combinations are given in Table

2.1 together with R2 values. These R2 values indicate a good fit of the model. Except 2FO with

no dispersant, i.e., oil control (86.9%) all the R2 values were above 90%.

Figure 2.8 shows a comparison of measured and estimated values (as determined by

equation 9), of dispersant effectiveness on SLC. Each of the plots shows the data cluster along

the 1:1 line, indicating a close match between estimated and measured values. Figure 2.8a for

SLC with no dispersant and Figure 2.8c for SLC with dispersant ‘B’ show an especially good

match between measured and estimated values due to the high R2 values. Similarly, Figure 2.9

shows a comparison of measured and estimated values of dispersant effectiveness on PBC. In the

case of PBC, there is tight clustering along the 1:1 line for almost all the three cases i.e, no

dispersant, with dispersant ‘A’ and with dispersant ‘B’ for which the R2 values were 91.1%,

97.5% and 98.2%, respectively.

Figure 2.10 shows a comparison of measured and estimated value of dispersant

effectiveness on 2FO. Figures 2.10b and 2.10c with dispersants ‘A’ and ‘B’ show an especially

tight cluster along the 1:1 line for 2FO, for which the R2 values were as high as 96.7% and

94.8%, respectively.

2.5.3 Simple Model of Dispersant Action

Dispersant effectiveness under the investigated conditions is illustrated through

simulation of the following experiment: Oil is placed in the baffled flask apparatus that is

rotated at a certain speed and held at a certain temperature. Evaporation of the oil is allowed to

occur, causing weathering of the oil. Two dispersant applications are then made four hours apart.

Evaporative losses of the oil are assumed to follow an empirical relationship developed by

29

(Wang et al. 2003) for an Alaska North Slope oil. The percent evaporated (%E) is given by as a

function of time in minutes (t) and temperature (T ◦C).

%E = (2.86 + 0.045 T ) ln(t). (10)

Figure 2.11 shows predicted percents remaining based on the empirical equations 4 and 5. There

is an initial dispersal of 3.9% due to the natural dispersal at a temperature of 20◦C and 200 RPM

as determined from the control experiments. Oil evaporation occurs until the dispersant “A” is

added at 1 hr followed by a second application at 5 hrs. Dispersant application is also simulated

at five other pairs of times. Although the oil weathers due to evaporation, the amount of

dispersal is very similar for each case because the initial weathering occurs before the first

simulated dispersant application at 1 hour. Figure 2.12 shows the predicted dispersal for

temperatures from 5◦C to 30◦C for a flask speed of 200 RPM and dispersant application at 6 hr

and 10 hr. The final dispersal of the oil depends on temperature. As shown in table 2.1, dispersal

of PBC oil with dispersant “A” was higher at 22◦C than 35◦C, this behavior is also shown in

Figure 2.6 as the minimum dispersal shown is for the temperature of 25◦C. Figure 2.13 shows

the effect of rotational speed at a temperature of 20◦C. The highest speed gives the highest

dispersal of the oil.

2.6 Summary and Conclusions

Laboratory experiments using a baffled flask made from a trypsinizing flask were

conducted to determine the effectiveness of two dispersants on three oils. The oils used were

South Louisiana Crude Oil, Prudhoe Bay Crude Oil, and Number 2 Fuel Oil. The main aim was

to determine which of the factors temperature, oil type, oil weathering, dispersant type, and

30

shaker rotational speed influence dispersion effectiveness and to what degree each is important

in the process.

Results from the BFT experiments conducted revealed the following general

observations: dispersion efficiency (1) increases with increase in mixing energy; (2) decreases

with increase in the level of weathering, and (3) does not follow a particular trend with increase

in temperature i.e, it increases at low and intermediate temperatures but decreases at high

temperature. A detailed study of oil properties might provide more insight on the effect of

temperature on dispersant effectiveness. Statistical analyses of experimental data revealed that

certain two-way interactions exist among the factors. For SLC, temperature and mixing energy

were significant factors, for PBC, temperature, mixing energy and weathering were significant

and for 2FO, only temperature was significant. The replicate study revealed that the replicates

were in close agreement with the previously obtained results. An empirical simulation of the

experiment with dispersant addition at several times illustrated the effects of dispersants on oil

slicks.

The effect of environmental factors on dispersant effectiveness has been studied in this

research. It should be noted that both the physical properties of the oil (viscosity, pour point,

specific gravity or density, surface tension) and its chemical constituent, as well as the chemical

properties of the dispersant will impact the dispersion of the oil and the effectiveness of a

particular dispersant. In a real spill situation, the impacts of dispersants on oil slicks are best

characterized by empirical data because of the complex interactions that take place between the

spilled oils and the sea. This research work has created a set of empirical data on three oils and

two dispersants that could serve as an input to the oil spill simulation models being developed by

EPA. The empirical correlation for the collected experimental data predicted within a very good

31

accuracy the effectiveness of the dispersant. The results of this research are expected to provide a

guidance to dispersant usage on oil spills.

32

Acknowledgment

This research study was supported by the U.S. Environmental Protection Agency (U.S EPA)

under CONTRACT NO. 68-C-00-159. The findings and conclusions expressed in this

publication are solely those of the authors and do not necessarily reflect the views of the agency.

33

2.7 References

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

Selection of Low-temperature Dispersants." Proceedings of the Sixth Arctic Marine Oil

Spill Program, Edmonton, Canada.

Clayton, J. R., Payne, J. R., Farlow, J. S., and Sarwar, C. (1993). "Oil Spill Dispersants:

Mechanisms of Action and Laboratory Tests (pp.31-36). Boca Raton, Florida: CRC press.

Delvigne, G. A. L. (1987). "Droplet Size Distribution of Naturally Dispersed Oil." In Fate and

Effects of Oil in Marine Ecosystem, (pp.29-40). Dordrecht, The Netherlands.

Fingas, M. F. (1991). "Dispersants: A Review of Effectiveness Measures and Laboratory

Physical Studies." Environmental Emergencies Technology Division, Environment

Canada, Ottawa, Ontario.

Fingas, M. F., Kyle, D. A., Holmes, J. B., and Tennyson, E. J. (1993a). "The Effectiveness of

Dispersants: Variation with Energy." Proceedings of the1993 International Oil Spill

Conference (pp.567-572). Washington, D.C: American Petroleum Institute.

Fingas, M. F., Kyle, D. A., and Tennyson, E. J. (1993b). "Physical and Chemical Studies on

Dispersants: The Effect of Dispersant Amount and Energy." Proceedings of the Sixteenth

Arctic and Marine Oil Spill Program Technical Seminar (pp.861-876). Environment

Canada, Ottawa, Ontario.

34

Fingas, M. F., Fieldhouse, B., and Mullin, J. V. (1995). "Water-in-oil Emulsions: How They are

Formed and Broken." Proceedings of the Eighteenth Arctic Marine Oil Spill Program

Technical Seminar (pp.21-42).Environment Canada, Ottawa, Ontario.

Fingas, M. F., Huang, E., Fieldhouse, B., Wang, L., and Mullin, J. V. (1997). "The Effect of

Energy, Settling Time and Shaking Time on the Swirling Flask Dispersant Apparatus."

Proceedings of the Twentieth Arctic Marine Oilspill Program Technical Seminar

(pp.541-550).Environment Canada, Ottawa, Ontario.

Hoult, D. P. (1972). "Oil Spreading on the Sea." In Annu. Rev. Fluid Mech., 4, 341-368.

Lessard, R. R., and Demarco, G. (2000). "The Significance of Oil Spill Dispersants." Spill

Science and Technology Bulletin, 6(1), 59-68.

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

Method Development and Results." Proceedings of the 1981 Oil Spill Conference

(pp.331-337). Washington, D.C: American Petroleum Institute.

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

of Oil Spill Dispersants (pp.78-80). Washington, D.C: National Academy Press.

SAS Institute Inc.(1999). "The GLM Procedure." Department of Economic, University of

Missouri homepage: http://rite.econ.missouri.edu:7071/saspdf/stat/chap30.pdf.

35

Sorial, G. A., Venosa, A. D., Koran, K. M., Holder, E., and King, D. (2003). "Oil Spill

Dispersant Effectiveness Protocol-Part I Impact of Operational Variables." Accepted for

publication in ASCE Journal of Environmental Engineering.

Venosa, A. D., King, D. W., and Sorial, G. A. (2002). "The Baffled Flask Test for Dispersant

Effectiveness: A Round Robin Evaluation of Reproducibility and Repeatability." Spill

Science and Technology Bulletin, 7(Nos.5-6), 299-308.

Wang, Z., Hollebone, B. P., Fingas, M., Fieldhouse, B., Sigouin, L., M, L., Smith, P., Noonan, J.,

and Thouin, G. (2003). "Characteristics of Spilled Oils, Fuels, and Petroleum Products: 1.

Composition and Properties of Selected Oils." EPA/600/R-03/072, United States

Environmental Protection Agency.

Weaver, J. W. (2003). "EPA Research Object-Oriented Oil Spill model."

http://www.epa.gov/athens/research/projects/eros/.

36

Table 2.1. Coefficients of Regression Equations with Terms Determined by Step-Wise Linear Regression

South Louisiana Crude Oil Prudhoe Bay Crude Oil Number Two Fuel Oil Factor (a) No Disp (b) Disp A Disp B No Disp Disp A Disp B No Disp Disp A Disp B

$0 -17.250 41.39 -69.24 -5.9325 -264.6 -15.16 1.490 -112.0 -17.65 $v $t -0.13812 -8.873 -9.149 1.2090 4.222 3.506 10.67 3.032 $s 0.16800 0.1680 1.322 2.609 0.6617 $vt -6.391e-3 -8.386e-3 $vs -1.631e-3 -2.452e-3 $ts 7.656e-4 4.092e-2 4.132e-2 -4.120e-3 -8.386e-3 -1.4089e-3 -2.435e-2 $vts -4.845e-5 $v2 -1.038e-2 $t2 4.382e-3 0.1516 0.1178 -1.979e-2 -9.697e-2 -2.817e-2 6.996e-3 -0.200 -6.313e-2 $s2 -3.375e-4 -2.970e-3 1.468e-4 -5.409e-3 1.433e-3 9.871e-5 1.256e-3 $v2t2 9.99e-6 $v2s2 5e-8 1.39e-6 $t2s2 -2.87e-6 -2.26e-6 2.6e-7 9e-8 1.30e-6 $v2t2s2

R2 98.2% 90.8% 98.6% 91.1% 97.5% 98.2% 86.9% 96.7% 94.8% a v=weathering, t=temperature, s=speed b disp=dispersant

37

Figure 2.1. Baffled Flask Test Apparatus

38

0

20

40

60

80

100

5 oC22 oC35 oC

a. SLC 0% weathering

Flask speed (rpm)

Perc

ent E

ffec

tiven

ess

0

20

40

60

80

100

b. SLC 10% weathering

100 150 200 250 3000

20

40

60

80

100

Flask speed (rpm)

c. SLC 20% weathering

Figure 2.2. Flask Speed vs Percent Effectiveness of Dispersant ‘A’ for SLC

39

0

20

40

60

80

100

5 oC22 oC35 oC

a. PBC 0% weathering

Perc

ent E

ffec

tiven

ess

0

20

40

60

80

100 b. PBC 10% weathering

Flask speed (rpm)100 150 200 250 300

0

20

40

60

80

100

c. PBC 20% weathering

Figure 2.3. Flask Speed vs Percent Effectiveness of Dispersant ‘A’ for PBC

40

0

20

40

60

80

100

5 oC22 oC35 oC

a. 2FO 0% weathering

Perc

ent E

ffec

tiven

ess

0

20

40

60

80

100

b. 2FO 3.8% weathering

Flask speed (rpm)100 150 200 250 300

0

20

40

60

80

100

c. 2FO 7.6% weathering

Figure 2.4. Flask Speed vs Percent Effectiveness of Dispersant ‘A’ for 2FO

41

0

20

40

60

80

100

5 oC22 oC35 oC

a. SLC 0% weathering

Perc

ent E

ffec

tiven

ess

0

20

40

60

80

100

b. SLC 10% weathering

Flask speed (rpm)100 150 200 250 300

0

20

40

60

80

100

c. SLC 20% weathering

Figure 2.5. Flask Speed vs Percent Effectiveness of Dispersant ‘B’ for SLC

42

0

20

40

60

80

100

5 oC22 oC35 oC

a. PBC 0% weathering

Perc

ent E

ffect

iven

ess

0

20

40

60

80

100

b. PBC 10% weathering

Flask speed (rpm)100 150 200 250 300

0

20

40

60

80

100

c. PBC 20% weathering

Figure 2.6. Flask Speed vs Percent Effectiveness of Dispersant ‘B’ for PBC

43

0

20

40

60

80

100

5 oC22 oC35 oC

a. 2FO 0% weathering

Perc

ent E

ffec

tiven

ess

0

20

40

60

80

100 b. 2FO 3.8% weathering

Flask speed (rpm)100 150 200 250 300

0

20

40

60

80

100 c. 2FO 7.6% weathering

Figure 2.7. Flask Speed vs Percent Effectiveness of Dispersant ‘B’ for 2FO

44

Figure 2.8. Comparison of Measured and Estimated values (eq. 9) of Dispersant Effectiveness on South Louisiana Crude Oil

Measured

0 5 10 15

Estim

ated

0

5

10

15

a. SLC with No Dispersant

Measured

0 20 40 60 80 100

Estim

ated

0

20

40

60

80

100

b. SL C with Dispersant 'A'

Measured

0 20 40 60 80 100

Estim

ated

0

20

40

60

80

100

c. SLC with Dispersant 'B'

45

Figure 2.9. Comparison of Measured and Estimated values (eq. 9) of Dispersant Effectiveness on Prudhoe Bay Crude Oil

Measured

0 5 10 15

Estim

ated

0

5

10

15

a. PBC with No Dispersant

Measured

0 20 40 60 80 100

Estim

ated

0

20

40

60

80

100

b. PBC with Dispersant 'A'

Measured

0 20 40 60 80 100

Estim

ated

0

20

40

60

80

100

c. PBC with Dispersant 'B'

46

Figure 2.10. Comparison of Measured and Estimated values (eq. 9) of Dispersant Effectiveness on Number Two Fuel Oil

Measured

0 5 10 15

Estim

ated

0

5

10

15

a. 2FO with No Dispersant

Measured

0 20 40 60 80 100

Estim

ated

0

20

40

60

80

100

b. 2 FO with Dispersant 'A'

Measured

0 20 40 60 80 100

Estim

ated

0

20

40

60

80

100

c. 2FO with Dispersant 'B'

47

0 4 8 12Time (hr)

0

20

40

60

80

100

% O

il Sl

ick

Rem

aini

ng

Weathering/Timing1 hr/5 hr2 hr/6 hr3 hr/7 hr4 hr/8 hr5 hr/9 hr6 hr/10 hr

Figure 2.11. Simulation of PBC dispersal at flask speed of 200 RPM and temperature of 20◦C. Weathering follows empirical relationship of Wang et al. (2003) with dispersant “A” added at 6 pairs of times.

0 4 8 12Time (hr)

0

20

40

60

80

100

% O

il Sl

ick

Rem

aini

ng

Temperature Effects5 C10 C15 C20 C25 C30 C

Figure 2.12. Simulation of PBC dispersal at flask speed of 200 RPM and temperature of 5◦C to 30◦C. Weathering follows empirical relationship of Wang et al. (2003) with dispersant “A” added at 6 hrs and 10 hrs.

48

0 4 8 12Time (hr)

0

20

40

60

80

100

% O

il Sl

ick

Rem

aini

ng

Rotational Speed150 RPM175 RPM200 RPM225 RPM250 RPM

Figure 2.13. Simulation of PBC dispersal at flask speeds of 150 RPM to 250 RPM and temperature of 20◦C. Weathering follows empirical relationship of Wang et al. (2003) with dispersant “A” added at 6 hrs and 10 hrs

49

3. DISPERSANT EFFECTIVENESS ON OIL SPILLS – IMPACT OF

SALINITY2

2 Paper Submitted for Publication in Marine Pollution Bulletin

50

3.1 Abstract

When a dispersant is applied to an oil slick, the dispersion depends on various factors

such as oil properties, wave mixing energy, temperature and salinity of the water. Estuaries

represent water with varying salinities. In this study three salinities were selected to represent a

range of 10-34 ppt. Three oils were chosen to represent light refined oil, light crude oil and

medium crude oil. Each oil was tested at three weathering levels to represent maximum, medium

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

termed as ‘Baffled Flask’ was used for conducting the experimental runs. A full factorial

experiment was conducted for each oil for investigating the effect of salinity on three

environmental factors namely, temperature, oil weathering and mixing energy. Salinity was

found to play an important role in determining the significance of temperature and mixing energy

on dispersant effectiveness for almost all the oil-dispersant combinations. The impact of salinity

on weathering was only significant for South Louisiana Crude Oil with dispersant ‘A’. Each

experiment was replicated four times in order to evaluate the accuracy of the test. Statistical

analyses of the experimental data were performed separately for each of the three oils three times

(with or without dispersant). A linear regression model representing the main factors (salinity,

temperature, oil weathering and flask speed) and interaction terms among the factors was fit to

the experimental data.

Keywords: baffled flask test, dispersant, dispersant effectiveness, environmental factors, oil spill,

oil remediation.

51

3.2 Introduction

In the event of unintentional releases of oil into coastal waters, oil from slicks can have

deleterious impacts to biota in exposed ecosystems. Effects will 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 (NRC, 1985). Oil slicks usually spread very rapidly to a large area due to the action of

gravitational and viscous forces and hence quick response has to be initiated (Hoult, 1972). Four

cleanup strategies that frequently receive consideration include: (1) mechanical cleanup or

recovery, (2) burning, (3) bioremediation, and (4) treatment with chemical dispersants (NRC,

1989).

Chemical dispersants are made of surfactants that are usually sprayed onto oil slicks to

remove oil from the surface and disperse it into the water column at very low concentrations

(Lessard and Demarco, 2000). This accelerates the degradation of oil by natural processes and

significantly reduces the impact on shorelines and habitats. 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 on water, the surfactant molecules will reside at oil-water interfaces

and reduce the oil-water interfacial surface tension. In the presence of minimal mixing energy

(provided by wave or wind action), this will result in dispersion of 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 removal of oil from the water surface, followed by dilution and degradation of the oil

to non-problematic concentrations in an underlying water column.

52

Since chemical dispersants enhance the dispersion of oil slicks at sea as small oil droplets

in the water column, they could be used in oil spill response operations. Recently, the U.S EPA

developed an improved dispersant testing protocol, called the baffled flask test (BFT) which was

the basis of the experiments conducted in this study. Using the BFT, the variations in the

effectiveness of dispersants caused by changes in oil composition, dispersant type, and the

environmentally related variables of salinity of sea water, temperature, oil weathering and

rotational speed of the BFT were studied.

The salinity of sea water plays an important role in determining dispersant effectiveness.

Studies have shown that salinity of receiving waters can impact dispersion of oil by chemical

dispersants (Clayton et al., 1993). Specifically, the intent of dispersant formulations for marine

use is to provide maximum dispersion at normal seawater salinities. Mackay et al. (1984) note

that higher salinities will increase dispersion by dispersants by deterring migration of surfactant

molecules into the water phase, which is equivalent to a salting-out effect for the surfactant from

the saline medium. Such a situation will tend to promote association of surfactant molecules with

oil at oil-water interfaces, which is important for lowering oil-water interfacial surface tensions

in the oil-dispersant mixture. In general, increasing salinity will decrease the solubility of

dispersants in water resulting in more surfactant being available to interact and mix with the oil.

Experimental studies have demonstrated a general increase in dispersant effectiveness with

increasing salinity. Clayton et al. (1993) and Byford et al. (1983) performed tests to determine

the effect of salinity on dispersant effectiveness under low temperatures and low energy

conditions using the Labofina rotating flask test method. These tests were conducted using

seven different dispersants and two types of crude oil. The test conditions were such to simulate

those commonly found in the Arctic environment. Experimental results indicated an overall

53

increase in dispersion with an increase in salinity in five of the dispersants tested. Clayton et al.

(1993)and Fingas (1991) studied the role of salinity on the effectiveness of three dispersants on

three types of crude oil using the swirling flask test method. These tests also showed an increase

in dispersion with an increase in salinity from 0 to 45 parts per thousand (ppt).

A number of other factors such as mixing energy, oil weathering and temperature also

influence dispersant effectiveness. Emulsions begin to form when sea energy is sufficient

(Fingas, 1991)and (Fingas et al., 1995). After addition of the dispersants, mixing energy is

further required to disperse the oil droplets formed. As reported by Clayton et al. (1993), the

applications of dispersants reduces the interfacial tension between oil and water, which results in

the formation of oil droplets. Experimental studies performed by a number of scientists indicated

that the sizes of the oil droplets are inversely related to the amount of mixing energy input into

test vessels. For example, Clayton et al. (1993) and Fingas et al. (1993) conducted experiments

that indicated that mixing energy reduces the size of the oil droplets. The chemical composition

and physical properties of a crude oil also determine the behavior of the oil and the way its

properties will change when the oil is spilled at sea (Kristiansen et al., 1997). Weathering

increases the viscosity of the oil due to evaporation of the lighter components. Oil viscosity has

been perceived as a major factor affecting the dispersibility of oil (Canevari et al., 2001). As the

oil weathers and the viscosity increases, it has been demonstrated that the effectiveness of the

chemical dispersant declines (Daling, 1988). Lower water temperatures increase the viscosity of

both the oil and the dispersant. Higher water temperatures usually increase the solubility of

dispersants in water. Higher water temperatures will also affect the spilled oil temperature. So,

an increase in temperature will reduce oil viscosity and hence improve dispersion. Mackay and

Szeto (1981), Byford et al. (1983), Lentinen and Vesala (1984) and Fingas (1991) conducted

54

studies which indicated an increase in dispersion efficiency with an increase in temperature.

However, there have been conflicting results in the trend of dispersant effectiveness with either

increasing or decreasing water temperature. For example, studies performed by Byford et al.

(1983) varied from those conducted by Fingas (1991).

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

and evaluating models (Weaver, 2003). Because of the complexity of chemical and physical

interactions between spilled oils, dispersants and the sea, an empirical approach to the interaction

between the dispersant and oil slick may provide a useful or practical approach for including

dispersants in these models. The overall objective of this project was to create a set of empirical

data on three oils and two dispersants, by studying the variation in the effectiveness of the

dispersants caused by changes in salinity of sea water, temperature, oil type, oil weathering,

dispersant type and rotation speed of the BFT. The specific objectives of this research were: (1)

designing a factorial experimental setup to determine which of the factors such as salinity,

temperature, oil type, oil weathering, dispersant type and rotation speed of the BFT are related to

the effectiveness of a dispersant used in oil remediation, (2) conducting a four replicate study for

all the experiments and (3) determining empirical relationships between the amount of oil

dispersed and the various variables studied.

3.3 Materials and methods

3.3.1 Materials and Reagents

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 2.1). 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

55

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 :L of dispersant and 100 :L

of oil with an accuracy of 0.3% and a precision of 0.25% was used with 100 :L 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 :L

gas-tight syringes were also used. 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.

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

the experiments at a concentration (salinity) of 10, 20 and 34 ppt. The synthetic sea water was

prepared by adding sufficient water to 10, 20 or 34 grams of the salt to make 1L of the solution.

Three types of oil samples provided by U.S EPA- South Louisiana Crude Oil (SLC), Prudhoe

Bay Crude Oil (PBC), and Number 2 Fuel Oil (2FO) were used in the study. Of the three oils

studied, SLC and PBC are light and medium weight EPA/API standard reference crude oils and

2FO is light refined oil. Two dispersant samples that scored effectiveness above 85% by the BFT

were used in the study (Venosa et al., 2002). They are referred to as Dispersant ‘A’ and

Dispersant ‘B’ here. The solvent dichloromethane (DCM, pesticide quality), was used for

extraction of all sample water and oil-standard water samples.

3.3.2 Methods

56

Weathering of oils: The three oils were used in the study at three levels of weathering:

unweathered condition, intermediate and maximum weathering. The weathering of the oil was

performed by bubbling air up through a 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.

)1(100*%volumeInitial

volumeFinalvolumeInitialweatheredOil −=

SLC and PBC were weathered to 10% and 20% whereas 2FO was weathered to 3.8% and 7.6%

which represents the maximum weathering possible for this oil.

Oil standard procedure: Standard solutions of oil for calibrating the UV-VIS spec 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 2 mL of the specific reference oil with 18 mL DCM added was measured by using a 1 mL gas

tight syringe and the concentration of the oil solution was determined. Specific volumes of 20,

50,100, 150, 200, 300 :L of SLC-DCM stock or 11, 20, 50, 100, 125, 150 :L of PBC-DCM

stock or 150, 200, 400, 600, 800, 1000 :L of 2FO-DCM stock were added to 30 mL of synthetic

sea water in a separatory funnel and extracted thrice with DCM. The final DCM volume for the

combined extracts was adjusted to 20 mL with DCM. The extracts were transferred to a 50 mL

crimp style glass vial with a teflon/aluminum seal, mixed by inverting many times and stored in

a refrigerator at 4±2 0C until time of analysis (maximum of 5 days) For treatments with oil plus

dispersant, oil plus dispersant stock standard was first prepared. The density of 2 mL specific

reference oil, 80 :L of the dispersant and 18 mL DCM was measured using a 1 mL gas tight

57

syringe and the concentration was then determined. These stock solutions were used to prepare

standard solutions as mentioned above.

Dispersant effectiveness procedure: 120 mL of synthetic sea water equilibrated at the desired

temperature was added to the test flask (Fig. 1), followed by the sequential addition of oil and

finally the dispersant. 100 :L of oil was dispensed directly onto the surface of the synthetic sea

water using an Eppendorf repeator pipettor with a 5 mL syringe tip attachment. The dispersant

was then dispensed onto the center of the oil slick by using a 100 :L syringe tip attachment that

was set to dispense 4 :L, giving a ratio of dispersant-to-oil ratio (DOR) of 1:25. The flask was

placed on an orbital shaker and mixed for 10 minutes at the desired rotation speed, at the end of

which it was removed from the shaker and allowed to remain stationary on the bench top for

another 10 minutes. At the end of the settling time, the first 2 mL of sample was drained from the

stopcock and discarded, and then 30 mL of sample was collected in a 50 mL measuring cylinder.

The 30 mL sample was then transferred to a 125 mL separatory funnel and extracted three 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 a Teflon/aluminum seal. These vials were stored at 4±2 0C

until the time of analysis (maximum of 5 days). The oil standards procedure and test procedures

were conducted according to the procedures given by (Sorial et al., 2003).

Sample analysis: The experimental sample extracts and the standard solutions prepared were

removed from the refrigerator and allowed to equilibrate at the laboratory temperature. First, a

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

58

of increasing concentration and the absorbance values were noted at wavelengths of 340, 370

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

Calculation procedure: The area under the absorbence vs wavelength curve for the

experimental samples between wavelengths 340 and 400 nm was calculated by using the

trapezoidal rule according to the following equation:

( ) ( )Area

Abs Abs *302

Abs Abs *302

340 370 370 400=+

++

(2)

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:

EffTotal oil dispersed

Voil oil

%*

*=ρ

100 (3)

where:

mLmLoilofMassdispersedoilTotal

30120*= (4)

Mass of oil, g = Concentration of oil * VDCM (5)

and

Concentration of oil, g / L = Area as determined by Equation 2

Slope of the calibration curve

(6)

Factorial experimental design: The main aim was to determine what environmental factors are

related to the effectiveness of a dispersant used in oil remediation. The response variable for the

experiment was the percent effectiveness of the dispersant. The factors and levels of each of the

factors are as follows: salinity (10, 20 and 34 ppt), weathering (0, 10, and 20% for SLC and

59

PBC; and 0, 3.8 and 7.6% for 2FO), dispersant (“A” and “B”), temperature (5 0C, 22 0C and 35

0C ) and flask speed (150, 200, and 250 rpm). A complete factorial experiment was conducted

with these levels for each of the factors. The total number of experimental samples prepared was

648 for each oil: 3 salinity * 3 weathering levels * 3 temperatures * 3 flask speeds * 4 replicates

* 2 dispersants. The factorial experiment was also performed for each of the three crude oils

separately, i.e., no dispersant added. The total number of oil control experimental samples

prepared was 324 for each oil: 3 salinity * 3 weathering levels * 3 temperatures * 3 flask speeds

* 4 replicates.

3.4 Results and Discussion

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 results were

analyzed using analysis of variance with "=0.05. The highest order interaction in all cases was

assumed to be non-significant and its degrees of freedom used for error determination. A

significant interaction means that the effect of one input parameter varies at differing levels of

another input parameter. The t-test from the REG procedure was used to test the level of

significance for each factor studied. The REG (regression) procedure is a general-purpose

procedure that performs linear regression analysis (SAS Institute Inc., 2000). The condition for

significance as determined by statistical analysis was that the probability of a run being greater

than the corresponding student t-test value should be less than 0.0001. Using this, significant

factors were determined for each oil-dispersant combination (see Table 3.1).

A four replicate study was also conducted for all the experiments. The precision

objectives were determined by using the relative standard deviation (RSD) for percent

60

effectiveness based on four replicate flasks. The acceptance criterion was based upon RSD less

than 15% (Venosa et al., 2002). The RSD was calculated using:

)7(100*tanessEffectivenAverage

DeviationdardSRSD =

The experimental design was conducted in four replicates in order to determine the

precision of the experimental results for the range of variables studied.

3.4.1 Effect of salinity at different mixing energies

In the experiments conducted in the laboratory, this mixing energy was provided

in the form of revolutions per minute (rpm) of the orbital shaker. Figure 3.1 shows the results for

percent effectiveness of dispersant ‘A’ for the three oils at their unweathered condition (0%

weathering) and at room temperature (22±10C). From Figure 3.1, it is seen that for a given oil, at

a specific weathering condition and salinity, as the speed of the orbital shaker increases from 150

to 250 rpm, the percent effectiveness also increases. For example, for SLC 0% and 10 ppt

salinity, the dispersant effectiveness at 150, 200 and 250 rpm were 49.2, 76.5 and 86.8%,

respectively.

This trend in dispersant effectiveness with increase in flask speed is true for oil +

dispersant ‘B’ experiments as well as oil control experiments (results not shown). From Figure

3.1 it is also seen that dispersant effectiveness increases with increase in salinity from 10 to 34

ppt for all three oils at a specific flask speed. For SLC, the RSD values for dispersant

effectiveness among the three salinities were 7.6, 6.7 and 5.6 at 150, 200 and 250 rpm flask

speed, respectively. So in the case of SLC, the impact of salinity on dispersant effectiveness is

more pronounced at 150 and 200 rpm than at 250 rpm. For PBC, the RSD values for dispersant

effectiveness among different salinities were 4.01, 15.1 and 2.6 at 150, 200 and 250 rpm flask

61

speed, respectively. This implies that for PBC, salinity has a significant impact at the

intermediate flask speed of 200 rpm than at 150 or 250 rpm. This is evident from the bar plot

(Figure 3.1). In the case of 2FO, the RSD values for dispersant effectiveness among different

salinities were 8.4, 5.9 and 1.4 at 150, 200 and 250 rpm flask speed, respectively. So in the case

of 2FO too, the impact of salinity on dispersant effectiveness is more pronounced at 150 and 200

rpm flask speed than at 250 rpm.

3.4.2 Effect of salinity at different temperatures

Figure 3.2 shows the results for percent effectiveness of dispersant ‘A’ for the three oils

at their maximum weathering level (20% for SLC and PBC and 7.8% for 2FO) and at maximum

flask speed (250 rpm). In the case of SLC, at 10 and 34 ppt salinity, the percent effectiveness

increases with increase in temperature from 5±1oC to 22±1oC, but decreases at 35±1oC. For

example, the dispersant effectiveness values at 5±1oC, 22±1 oC and 35±1 oC, were 73.3, 81.5 and

77.7%, respectively at 10 ppt and 84.1, 92.8 and 90.7 %, respectively at 34 ppt. However, the

results obtained at 20 ppt salinity show that percent effectiveness increases with increase in

temperature. For example, the dispersant effectiveness values at 5±1oC, 22±1 oC and 35±1 oC,

were 77.1, 80.9 and 84.7%, respectively. From Figure 3.2a it is also seen that dispersant

effectiveness increases with increase in salinity from 10 to 34 ppt at 5±1oC and 35±1 oC. Also,

for SLC, the RSD values for dispersant effectiveness among different salinities were 6.9, 7.9 and

7.7 at 5±1oC, 22±1 oC and 35±1 oC temperature, respectively. Hence the impact of salinity is

more pronounced at the higher temperatures of 22±1oC and 35 ±1oC as compared to the lower

temperature of 5±1oC in the case of SLC.

62

For PBC, it is seen that at all three salinities, the percent effectiveness first increases with

increase in temperature from 5±1oC to 22±1oC and then decreases at 35±1oC. This means that

PBC which is a medium crude oil resists dispersion even at high temperature and at high salinity

of 34 ppt. It is speculated that this behavior might be due to weathering of the oil at 35 oC. For

PBC, the RSD values for dispersant effectiveness among different salinities were 5.1, 2.3 and 5.8

at 5±1oC, 22±1 oC and 35±1 oC temperature, respectively. Hence for PBC too, the impact of

salinity is more pronounced at the higher temperature of 35±1oC.

In the case of 2FO, at 10 and 34 ppt salinity, the percent effectiveness increases with

increase in temperature from 5±1oC to 22±1oC, but decreases at 35±1oC. However, the results

obtained at 20 ppt salinity show that percent effectiveness increases with increase in temperature.

For 2FO, the RSD values for dispersant effectiveness among different salinities were 5.6, 15.3

and 10.9 at 5±1oC, 22±1 oC and 35±1 oC temperature, respectively. Hence the significance of

salinity on dispersant effectiveness is more pronounced at the higher temperatures of 22±1oC and

35±1oC than at 5±1oC in the case of 2FO too.

3.4.3 Effect of salinity at different weathering

The effect of salinity on weathering can be seen from Figures 3.3-3.4 which show the

results for percent effectiveness of dispersant ‘A’ on all three oils, at an intermediate flask speed

of 200 rpm and at 5±1oC and 35±1oC temperature. Figure 3.3 shows the results for percent

effectiveness of dispersant ‘A’ on all three oils, at a flask speed of 200 rpm and at a temperature

of (5±1oC). In general, it is seen that for any oil at a specific salinity, as the degree of weathering

of the oil increases, the dispersant effectiveness decreases. For example, for SLC at 200 rpm

flask speed and 10 ppt salinity, the dispersant effectiveness at 0, 10 and 20% weathering were

63

72, 61.5 and 60.9%, respectively. This is true for oil + dispersant ‘B’ experiments as well as oil

control experiments conducted (results not shown). From Figure 3.3, it is also seen that

dispersant effectiveness increases with increase in salinity from 10 to 34 ppt for all three oils at a

specific weathering. For SLC, the RSD values for dispersant effectiveness among different

salinities were 3.6, 7.6 and 6.7 at 0, 10 and 20% weathering, respectively. This implies that

salinity has an impact on dispersant effectiveness at the higher weathering levels of 10 and 20%

as compared to 0%. For PBC, the RSD values for dispersant effectiveness among different

salinities were 6.1, 7.0 and 6.5 at 0, 10 and 20% weathering, respectively. For 2FO, the RSD

values for dispersant effectiveness among different salinities were 7.7, 5.0 and 6.0 at 0, 3.8 and

7.6% weathering, respectively. In the case of 2FO, the impact of salinity on dispersant

effectiveness is more pronounced at 0% weathering for the example shown in Figure 3.3.

Figure 3.4 shows the results for percent effectiveness of dispersant ‘A’ on all the three

oils at an intermediate flask speed of 200 rpm and at high temperature (35±1oC). Once again, it is

seen that as the degree of weathering of the oil increases, the dispersant effectiveness decreases.

For SLC, the RSD values for dispersant effectiveness among different salinities were 6.8, 14.8

and 11.4 at 0, 10 and 20% weathering, respectively. This implies that salinity has an impact on

dispersant effectiveness at the higher weathering levels of 10 and 20% as compared to 0%, in the

case of SLC. For PBC, the RSD values for dispersant effectiveness among different salinities

were 11.5, 11.6 and 10.8 at 0, 10 and 20% weathering, respectively. For 2FO, the RSD values for

dispersant effectiveness among different salinities were 17.7, 16.6 and 13.9 at 0, 3.8 and 7.6%

weathering, respectively. In the case of 2FO, it is seen that with increase in salinity from 10 to 20

ppt, the percent dispersant effectiveness increases but decreases at 34 ppt at all three levels of

weathering.

64

General discussion: Table 3.2 shows the impact of salinity on mixing energy. The percent

effectiveness values for each oil-dispersant combination and oil control experiments is shown in

the table. The range in effectiveness values is shown for all temperatures and weathering levels.

The corresponding RSD values were calculated. Overall, for SLC, the RSD among dispersant

effectiveness values varied between 9-46%, 18-51% and 26-110%, for experiments with

dispersants ‘A’, ‘B’ and oil controls, respectively. Similarly for PBC, the RSD ranged between

20-53%, 17-54% and 24-100%, for experiments with dispersants ‘A’, ‘B’ and oil controls,

respectively. For 2FO, the RSD among dispersant effectiveness values ranged between 17-64%,

24-54% and 15-52%, for experiments with dispersants ‘A’, ‘B’ and oil controls, respectively. If

an RSD value greater than 15% is considered to be significant, it can be concluded that salinity

plays an important role in determining the significance of flask speed on dispersant effectiveness

for all three oils. This is also evident from Table 3.1 which lists the significant factors for each of

the oil-dispersant combinations. Speed was also found to be a significant factor for SLC and

PBC oil control experiments.

The effect of salinity at different temperatures is shown in Table 3.3. The percent


Table 3.3. The range in effectiveness values is shown for all flask speeds and weathering levels.

The corresponding RSD values for these results were calculated. In the case of SLC, the RSD

among dispersant effectiveness values varied between 3-23%, 3-30% and 44-124%, for

experiments with dispersants ‘A’ and ‘B’ and oil controls, respectively. Similarly for PBC, the

RSD ranged between 10-54%, 1-44% and 3-80% for experiments with dispersants ‘A’, ‘B’ and

oil controls, respectively. For 2FO, the RSD among dispersant effectiveness values ranged

between 8-65%, 14-45% and 3-82%, for experiments with dispersants ‘A’, ‘B’ and oil controls

65

respectively. Again, if an RSD value greater than 15% is considered to be significant, it can be

concluded that salinity plays an important role in determining the significance of temperature on

dispersant effectiveness, on all three oils except for SLC with dispersant ‘A’ experiments which

gave comparatively less RSD than the other experiments. This is also evident from table 1 which

shows that temperature is indeed a significant factor for all oil-dispersant combinations except

SLC with dispersant ‘A’. Temperature was also found to be a significant factor for SLC oil

control experiments.

The impact of salinity at different weathering can be seen from Table 3.4. The percent


table 4. The range in effectiveness values is shown for all flask speeds and temperatures. The

corresponding RSD values for these results were calculated. Overall, for dispersant ‘A’

experiments, the RSD among dispersant effectiveness values varied between 3-36% for SLC, 1-

12% for PBC and 1-14% for 2FO. For dispersant ‘B’ experiments, the RSD among dispersant

effectiveness values varied between 1-6% for SLC, 1-9% for PBC and 1-9% 2FO. For oil

control experiments, the RSD among dispersant effectiveness values varied between 1-15% for

SLC, 1-11% for PBC and 1-14% 2FO. Based on these RSD values, it is seen that the impact of

salinity at different weathering was significant for SLC with dispersant ‘A’ experiments alone

(also evident from Table 3.1). The impact of weathering had very less impact on the natural

dispersion of oils in the case of oil control experiments.

3.4.4 Empirical relationships

66

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:

iillivvittissivillvisisslilittl

isittsisivvsitivvtillissittivvi

xxxxxxxxxx

xxxxxxxxxxy

εβββββββ

ββββββββ

++++++++

+++++++=

)(2

)(2

)(2

)(2

)()()()()()(

)()()()()()()()()()(0 (8)

for i=1,....n

Where yi is the effectiveness value at the corresponding levels of the factors (x), $0 is the

intercept, $v is the oil weathering effect, $t is the temperature effect, $s is the speed effect, $vt is

the effect of the weathering by temperature interaction, $vs is the effect of the weathering by

speed interaction, $ts is the effect of temperature by speed interaction, $tl is the effect of

temperature by salinity interaction, $sl is the effect of speed by salinity interaction, $lv is the

effect of salinity by weathering interaction, $s2

is the effect of second order interaction of speed,

$t2

is the effect of second order interaction of temperature, $v2 is the effect of second order

interaction of weathering and $l2 is the effect of second order interaction of salinity. The

equation contains all main effects and second order interactions for all factors. The various $

parameters for the various oil-dispersant combinations are given in Table 3.5 together with R2

values which indicate the linearity of the model. Except oil control experiments all the R2 values

were above 90%.

Figure 3.5 shows a comparison of measured and estimated values of dispersant

effectiveness on SLC. Each of the plots show the data cluster along the 1:1 line, indicating a

close match between estimated and measured values. Figure 3.5b for SLC with dispersant ‘A’

and Figure 3.5c for SLC with dispersant ‘B’ especially show a good match between measured

and estimated values due to the high R2 values. Similarly, Figure 3.6 shows a comparison of

67

measured and estimated values of dispersant effectiveness on PBC. In the case of PBC, there is

tight clustering along the 1:1 line for PBC with dispersant ‘A’ and with dispersant ‘B’ for which

the R2 values were 91.37% and 98.03%, respectively.

Figure 3.7 shows a comparison of measured and estimated value of dispersant

effectiveness on 2FO. Figures 3.7b and 3.7c with dispersants ‘A’ and ‘B’ especially show a tight

cluster along the 1:1 line for 2FO, for which the R2 values were as high as 92.09% and 95.88%,

respectively.

3.5 Summary and Conclusions

A full factorial experiment with four replicates was conducted for determining the impact

of salinity on three environmental factors namely, mixing energy, temperature and oil

weathering. All experiments were analyzed using an analysis of variance with "=0.05. The REG

procedure was used to perform linear regression analysis.

Results from the BFT experiments conducted revealed the following general

observations:

1. Dispersion efficiency increases with increase in mixing energy with no exceptions.

Salinity plays an important role in determining the significance of mixing energy on

dispersant effectiveness for all three oils.

2. Dispersion efficiency does not follow a general trend with increase in temperature and is

different for each oil depending on its properties. The impact of salinity on dispersant

effectiveness is more pronounced at higher temperature than at lower temperature i.e, the

significance of salinity on dispersant effectiveness increases with increase in temperature

for all three oils. In general, salinity plays an important role in determining the

68

significance of temperature on dispersant effectiveness for all oil-dispersant combinations

except SLC with dispersant ‘A’.

3. Dispersion efficiency decreases with increase in the level of weathering. The impact of

weathering is only significant for SLC with dispersant ‘A’.

4. In general, dispersion efficiency increases with increase in salinity for most of the oil-

dispersant combinations.

5. This research work has successfully created a set of empirical data on three oils and two

dispersants that could serve as an input to the oil spill simulation models being developed

by EPA. The empirical correlation for the collected experimental data predicted within a

good accuracy the effectiveness of the dispersant. The results of this research are

expected to provide a guidance to dispersant usage on oil spills.

69

Acknowledgment

This research study was supported by the U.S. Environmental Protection Agency (U.S EPA)

under CONTRACT NO. 68-C-00-159. The findings and conclusions expressed in this

publication are solely those of the authors and do not necessarily reflect the views of the agency.

70

3.6 References

Byford, D.C., Green, P.J. & Lewis, A.1983. Factors Influencing the Performance and Selection

of Low-temperature Dispersants. Proceedings of the Sixth Arctic Marine Oil Spill

Program. Environmental Protection Service, Environment Canada., Edmonton, Alberta,

Canada, 140-150.

Canevari, G.P., Calcavecchio, P., Becker, K.W., Lessard, R.R.& Fiocco, R.J. 2001. Key

Parameters Affecting the Dispersion of Viscous Oil. Proceedings of the International Oil

Spill Conference, Tampa, Florida, 11-20.

Clayton, J.R., Payne, J.R., Farlow, J.S. & Sarwar, C. 1993. Oil Spill Dispersants Mechanisms of

Action and Laboratory Tests, pp 90-103. Boca Raton, Florida: CRC press.

Daling, P.S.1988. A Study of the Chemical Dispersibility of Fresh and Weathered Crude Oils. In

Eleventh Arctic and Marine Oilspill Program, pp. 481-499. Ottawa, Ontario:

Environment Canada.

Fingas, M.F. 1991. Dispersants: A Review of Effectiveness Measures and Laboratory Physical

Studies. Environmental Emergencies Technology Division, Environment Canada, Ottawa,

Ontario, Canada.

71

Fingas, M.F., Kyle, D.A., Holmes, J.B. & Tennyson, E.J. 1993. The Effectiveness of Dispersants:

Variation with Energy. Proceedings of the International Oil Spill Conference, pp. 567-

572. Washington, D.C.: American Petroleum Institute.

Fingas, M.F., Fieldhouse, B. & Mullin, J.V. 1995. Water-in-oil Emulsions: How They are

Formed and Broken. Proceedings of the Eighteenth Arctic Marine Oil Spill Program

Technical Seminar, pp.21-42. Ottawa, Ontario: Environment Canada.

Hoult, D.P.1972. Oil Spreading on the Sea. In Annu. Rev. Fluid Mech., 4: 341-368.

Kristiansen, T.S., Lewis, A., Daling, P.S., Hokstad, J.N. & Singsaas, I. 1997. Weathering and

Dispersion of Naphthenic, Asphaltenic, and Waxy Crude Oils. Proceedings of the

International Oil Spill Conference. Washington, D.C.: American Petroleum Institute.

Lehtinen, C.M. & Vesala, A.M. 1984. Effectiveness of Oil Dispersants at Low Salinities and

Low Water Temperatures. In Oil Spill Chemical Dispersants -Research Experience and

Recommendations, pp.108-121. Philadelphia, PA: American Society for Testing and

Materials.

Lessard, R.R. & Demarco, G. 2000. The Significance of Oil Spill Dispersants. In Spill Science

and Technology Bulletin, 6(1): 59-68.

72

Mackay, D. & Szeto, F. 1981. The Laboratory Determination of Dispersant Effectiveness-

Method Development and Results. Proceedings of the International Oil Spill Conference,

Atlanta, GA, pp.331-337. Washington, D.C.: American Petroleum Institute.

Mackay, D., Chau, A., Hossain, K. & Bobra, M. 1984. Measurement and Prediction of the

Effectiveness of Oil Spill Chemical Dispersants. In Oil Spill Chemical Dispersants,

Research, Experience and Recommendations, pp. 38-54. Philadelphia, PA: American

Society for Testing and Materials.

NRC, 1985. Oil in the Sea: Inputs, Fates and Effects. National Research Council, 601-605.

NRC, 1989. Using Oil Spill Dispersants on the Sea. Report of the Committee on Effectiveness of

Oil Spill Dispersants, pp.78-80. Washington, D.C.: National Academy Press.

SAS Institute Inc. 2000. "The REG Procedure Overview." SAS/STAT User's Guide:

http://www.id.unizh.ch/software/unix/statmath/sas/sasdoc/stat/chap55/sect1.htm

Sorial, G.A., Venosa, A.D., Koran, K.M., Holder, E., & King, D. 2003. Oil Spill Dispersant

Effectiveness Protocol-Part I Impact of Operational Variables. Accepted for publication

in ASCE Journal of Environmental Engineering.

73

Venosa, A.D., King, D.W. & Sorial, G.A. 2002. The Baffled Flask Test for Dispersant

Effectiveness: A Round Robin Evaluation of Reproducibility and Repeatability. In Spill

Science and Technology Bulletin, 7(Nos.5-6): 299-308.

Weaver, J.W. 2003. EPA Research Object-Oriented Oil Spill model. US Environmental

Protection Agency, Ecosystems Research Page:

http://www.epa.gov/athens/research/projects/eros/.

74

Table 3.1. Significant Factors for Various Oil-Dispersant Combination

Oil Oil Control Experiments

Oil + Dispersant ‘A’ Experiments

Oil + Dispersant ‘B’ Experiments

SLC Temperature, speed, temperature by speed

interaction

Weathering, speed Temperature, speed, speed by salinity interaction

PBC Salinity, temperature by speed interaction,

temperature by salinity interaction, speed by salinity interaction

Temperature, speed Temperature, temperature by weathering interaction,

temperature by speed interaction

2FO Temperature by salinity interaction

Temperature, speed, temperature by speed

interaction

Temperature, speed

Table 3.2. Effect of Salinity at Different Mixing Energies

Percent Effectiveness

Salinity

Oil-

Dispersant

10 ppt 20 ppt 34 ppt

150

rpm

200

rpm

250

rpm

150

rpm

200

rpm

250

rpm

150

rpm

200

rpm

250

rpm

SLC-A 24-63 53-84 70-91 44-65 62-88 77-91 34-81 69-91 84-98

SLC-B 42-63 62-75 74-89 44-61 64-78 75-90 26-51 70-77 77-92

SLC* 1-7 1-11 2-13 2-7 1-12 2-13 1-5 2-10 4-11

PBC-A 17-47 48-85 57-96 17-58 50-69 60-94 20-60 55-86 64-97

PBC-B 20-58 42-66 69-86 22-64 43-67 73-87 26-63 46-69 80-87

PBC* 1-2 1-8 3-11 1-2 3-6 3-11 2-9 2-10 3-12

2FO-A 17-56 37-89 65-95 16-48 38-79 70-94 18-61 41-87 73-98

2FO-B 20-55 40-75 66-93 23-46 42-74 70-95 24-56 47-78 72-98

2FO* 1-2 2-5 3-7 1-4 2-6 3-7 2-7 1-7 2-10

*-oil control experiments

75

Table 3.3. Effect of Salinity at Different Temperatures


Salinity

Oil-

Dispersant


5°C 22°C 35°C 5°C 22°C 35°C 5°C 22°C 35°C

SLC-A 41-83 24-86 52-90 44-85 44-91 57-91 50-89 34-97 73-98

SLC-B 42-79 50-87 54-89 44-81 52-88 55-90 46-83 26-90 41-92

SLC* 1-3 5-13 6-13 1-4 2-7 7-14 1-5 1-9 4-12

PBC-A 17-61 37-96 30-85 17-66 36-94 48-86 20-69 40-95 31-75

PBC-B 20-71 47-81 49-86 22-78 47-84 53-87 26-84 47-87 56-89

PBC* 1-3 1-11 1-12 1-6 2-5 2-11 2-7 2-6 2-11

2FO-A 17-74 41-95 42-76 16-77 45-94 45-94 18-79 48-98 32-89

2FO-B 20-67 31-91 34-93 23-71 32-93 44-95 24-73 33-98 41-98

2FO* 1-3 1-8 2-6 1-4 2-7 4-8 1-5 1-7 6-11

Table 3.4. Effect of Salinity at Different Weathering


Salinity


Oil-

Dispersant

Weathering

0% 10% 20% 0% 10% 20% 0% 10% 20%

SLC-A 49-90 24-79 30-81 51-91 44-85 44-84 54-98 34-97 39-92

SLC-B 45-89 44-87 42-83 49-90 47-89 44-85 28-92 27-91 26-88

SLC* 1-13 2-12 1-13 1-13 1-13 1-13 1-11 1-9 1-11

PBC-A 18-91 17-96 17-92 19-94 18-91 17-88 21-95 33-97 20-90

PBC-B 21-86 21-80 20-82 27-87 24-83 22-82 30-89 28-85 26-83

PBC* 1-11 1-9 1-10 1-11 1-10 2-9 1-12 1-11 1-10

Weathering

0% 3.8% 7.6% 0% 3.8% 7.6% 0% 3.8% 7.6%

2FO-A 18-92 18-95 17-75 20-94 18-90 16-86 21-95 19-97 18-98

2FO-B 20-93 21-91 22-91 23-95 23-93 23-93 24-98 24-97 23-96

2FO* 1-6 1-5 1-7 1-7 1-7 1-7 2-10 1-10 1-10

*-oil control experiments

76

Table 3.5. Coefficients of Regression Equations

South Louisiana Crude Oil Prudhoe Bay Crude Oil Number Two Fuel Oil Factor (a) No Disp (b) Disp A Disp B No Disp Disp A Disp B No Disp Disp A Disp B

$0 -20.05044 -115.96645 -66.77451 -6.23968 -180.85008 -11.00662 -0.64197 -109.75982 -101.66665

$v -0.10360 -2.03166 -0.05252 0.03741 0.76673 -0.12229 0.04481 1.91720 -0.32559

$t 0.30690 -0.07442 0.77095 0.10179 4.16418 3.7982 -0.02456 5.74749 2.98224

$s 0.19971 1.5252 1.00915 0.00239 1.52901 -0.10247 -0.01378 0.72230 0.75067

$l -0.21127 0.08709 -0.35897 0.31155 0.35435 -0.09902 0.12144 -0.14205 0.84530

$v2 0.00193 0.06792 -0.00830 0.00234 -0.01261 0.00198 0.00996 -0.14260 0.16016

$t2 -0.00369 0.01891 -0.00775 -0.00438 -0.07657 -0.03229 -0.0007854 -0.09288 -0.05608

$s2 -0.0004423 -0.00283 -0.00194 0.0001129 -0.00252 0.00151 0.00009731 -0.000426 -0.000704

$l2 0.00410 0.00827 -0.02081 0.0001460 0.00516 0.00123 -0.00216 -0.00809 -0.01018

$vt -0.00103 -0.00274 0.00173 -0.00180 -0.00293 -0.01012 0.00027196 -0.00968 -0.00576

$vs 0.00031019 0.00038116 -0.0009320 -0.0003129 -0.00183 0.00019923 0.00005556 -0.01146 -0.00353

$lv 0.00059386 0.01226 0.00913 0.0002707 -0.01077 0.00123 -0.00649 0.05541 -0.000317

$ts 0.00100 -0.00234 -0.0000826 0.00157 -0.00186 -0.00814 0.00036340 -0.00596 0.00176

$tl -0.00308 0.00927 -0.00936 -0.00444 -0.00197 -0.00226 0.00383 -0.00477 -0.01265

$sl 0.00005366 -0.0009232 0.00654 -0.00143 -00009026 0.00184 0.00008335 0.00286 -0.0004338

R2 0.8958 0.9246 0.9409 0.8729 0.9137 0.9803 0.8421 0.9209 0.9588 a v=weathering, t=temperature, s=speed bdisp=dispersant

77

0

20

40

60

80

100

10 ppt20 ppt34 ppt

a. SLC 0%

Perc

ent E

ffec

tiven

ess

0

20

40

60

80

100b. PBC 0%

Flask speed (rpm)100 150 200 250 300

0

20

40

60

80

100c. 2FO 0%

Figure 3.1. Flask speed vs Percent Effectiveness of Dispersant ‘A’ at 22±1◦C

78

0

20

40

60

80

100

10 ppt20 ppt34 ppt

a. SLC 20%

Perc

ent E

ffec

tiven

ess

0

20

40

60

80

100b. PBC 20%

Temperature (0C)

5 22 350

20

40

60

80

100c. 2FO 7.6%

Figure 3.2. Temperature vs Percent Effectiveness of Dispersant ‘A’ at 250 rpm

79

0

20

40

60

80

100

10 ppt20 ppt34 ppt

a. SLC 200 rpm

Perc

ent E

ffec

tiven

ess

0

20

40

60

80

100b. PBC 200 rpm

Weathering (%)0.0 3.8 7.6

0

20

40

60

80

100c. 2FO 200 rpm

Figure 3.3. Weathering vs Percent Effectiveness of Dispersant ‘A’ at 5±◦C

80

0

20

40

60

80

100

10 ppt20 ppt34 ppt

a. SLC 200 rpm

Perc

ent E

ffec

tiven

ess

0

20

40

60

80

100

b. PBC 200 rpm

Weathering (%)0.0 3.8 7.6

0

20

40

60

80

100

c. 2FO 200 rpm

Figure 3.4. Weathering vs Percent Effectiveness of Dispersant ‘A’ at 35±1◦C

81

Measured0 5 10 15

0

5

0

5

a. SLC with No DispersantMeasured

0 20 40 60 80 100

Est

imat

ed

0

20

40

60

80

100

b. SLC with Dispersant 'A'

Measured

0 20 40 60 80 100

Est

imat

ed

0

20

40

60

80

100

c. SLC with Dispersant 'B'

Figure 3.5. Comparison of Measured and Estimated values (eq. 8) of Dispersant Effectiveness on South Louisiana Crude Oil

82

Measured

0 20 40 60 80 100

Est

imat

ed

0

20

40

60

80

100

a. PBC with Dispersant 'A'

Measured

0 20 40 60 80 100

Est

imat

ed

0

20

40

60

80

100

c. PBC with Dispersant 'B'

Figure 3.6. Comparison of Measured and Estimated values (eq. 8) of Dispersant

Effectiveness on Prudhoe Bay Crude Oil

Measured

0 5 10 15

Estim

ated

0

5

10

15

a. PBC with No Dispersant

83

Measured

0 5 10 15

Est

imat

ed

0

5

10

15

a. 2FO with No Dispersant

Measured

0 20 40 60 80 100

Est

imat

ed

0

20

40

60

80

100

b. 2FO with Dispersant 'A'

Measured

0 20 40 60 80 100

Est

imat

ed

0

20

40

60

80

100

c. 2FO with Dispesant 'B'

Figure 3.7. Comparison of Measured and Estimated values (eq. 8) of Dispersant Effectiveness on Number Two Fuel Oil

84

4. IMPACT OF OIL VISCOSITY ON DISPERSANT EFFECTIVENESS

85

4.1 Abstract

Oil properties such as viscosity has been perceived as an important factor that determines

dispersant effectiveness. The viscosity of oil at the three weathering conditions and three

temperatures studied in chapters 2 and 3, were determined by using a Cannon-Fenske

viscometer. The impact of oil viscosity on dispersant effectiveness was studied. It was found that

an increase in oil weathering increased the viscosity and hence decreased the dispersant

effectiveness.

Keywords: oil, viscosity, Cannon-Fenske viscometer, oil weathering, temperature

86

4.2 Introduction

Temperature affects the viscosities and pour points of both oils and dispersants. This can

be critical at lower temperatures because penetration and mixing of dispersants with more

viscous oil generally will be less effective. Specifically, increasing viscosity appears to reduce

dispersion of oil droplets in two ways: (1) migration of the dispersant to the oil-water interface is

retarded (i.e, the dispersant is unable to penetrate and homogeneously mix into a viscous oil) and

(2) the energy required to shear off oil droplets from a slick is increased (Clayton et al., 1993).

It is seen that with increase in temperature, the viscosity of the oil decreases. The more

viscous the oil is, the more it will oppose the action of the dispersant i.e, the lesser the dispersant

effectiveness. Theoretically, an increase in temperature should favor an increase in dispersant

effectiveness. The viscosity of an oil is affected by both weathering of the oil and the

temperature. Hence an increase in weathering of the oil will cause an increase in viscosity and

hence dispersant effectiveness declines.

The main objective was to measure the viscosity of three oils namely, SLC, PBC and

2FO at the three weathering conditions and three temperatures studied in Chapters 2 and 3 using

a Cannon-Fenske viscometer, for the purpose of studying the impact of oil viscosity on

dispersant effectiveness.

4. 3 Materials and Methods

Materials: A Cannon-Fenske viscometer (Fisher Scientific, Pittsburgh, PA) was used in the

study for viscosity measurements of all the oils at their weathered conditions (see Figure 4.1).

87

Three sizes namely, 25, 100 and 150 were used. These sizes can measure viscosities in the range

of 0.5-2, 3-15 and 7-35 cSt, respectively. A stop watch was also used to take time measurements.

Viscosity Measurement Procedure: The oil whose viscosity was to be measured was

introduced into the viscometer and the time required for the oil front to travel between the two

timing marks on the viscometer’s capillary tube, was noted. This procedure was repeated twice

and measurements taken for accuracy in the reading. Then the viscosity of the test oil was

calculated in cSt, from the viscometer constant and the measured flow time according to the

following equation:

where:

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

t = Measured flow time, s

The calibration constant was calculated using a liquid of known viscosity (water) and

determining t (see Table 4.1)

4.4 Results

Table 4.2 shows the results for calibration constants of viscometers which were

calculated by using a liquid of known viscosity such as water. These calibration constants were

then used in the measurements of oil viscosities according to equation 1. Results are shown in

Table 4.3.

Vis ity cSt C tcos , * ( )= 1

88

4.5 Discussion

SLC: For SLC, the decrease in viscosity values with increase in temperature has been found to

be more prominent from 5 to 22◦C than from 22 to 35◦C. This implies that dispersant

effectiveness too should increase significantly with increase in temperature from 5 to 22◦C. From

the experimental results, it is seen that this is true for most of the SLC with dispersant ‘B’

experiments. For example, Figure 4.2 shows temperature vs viscosity and Figure 4.3 shows

temperature vs dispersant effectiveness, for SLC with dispersant ‘B’, at 10 ppt salinity and 250

rpm flask speed. From the figure, it is seen that the increase in dispersant effectiveness with

increase in temperature, is more from 5 to 22◦C than from 22 to 35◦C. In general, it is also seen

that with increase in temperature, the dispersant effectiveness of both ‘A’ and ‘B’ on SLC

increases but the trend is not linear. Exceptions to this general trend were SLC 10% and 20%

with dispersant ‘A’ at 10 ppt and 34 ppt (data presented in chapters 2 and 3). From Figure 4.3, it

is also seen that with increase in weathering of SLC, the percent effectiveness decreases.

However, a closer look at Figure 4.3 reveals the fact that by choosing more temperatures

between 5 and 35◦C, and conducting experiments at these temperatures would provide more

points on the plot and would allow for generating a correlating function.

PBC: There is a significant decrease in viscosity values for PBC 0 and 10% with increase in

temperature from 5 to 35◦C. This means that the dispersant effectiveness values for PBC 0 and

10% should increase significantly. This is true in the case of experiments with dispersant ‘B’.

Exceptions to this trend were observed in the case of PBC with dispersant ‘A’ experiments at 10

and 34 ppt salinity where the percent effectiveness first increased with increase in temperature

from 5 to 22◦C and then decreased at 35◦C (data presented in Chapters 2 and 3). Figure 4.4 shows

89

temperature vs viscosity for PBC 0 and 10%. Figure 4.5 shows temperature vs percent

effectiveness of dispersant ‘B’ on PBC at 10 ppt salinity and 250 rpm flask speed. From the

example shown, it is seen that dispersant effectiveness increases significantly with increase in

temperature but the trend is not linear. From Figure 4.4, it is also seen that with increase in

weathering, the viscosity of PBC increases significantly. However, there is no significant

decrease in dispersant effectiveness values with increase in weathering as seen from Figure 4.5.

It is speculated that the oil chemical properties played a major role in determining dispersant

effectiveness. Again, more experiments need to be conducted between 5 and 35 ºC in order to

develop an accurate relationship between dispersant effectiveness and temperature.

2FO: In the case of 2FO too, there is a decrease in viscosity values with increase in temperature.

So theoretically, there should be an increase in dispersant effectiveness values with increase in

temperature from 5 to 35◦C. From the BFT experimental results, it is seen that this trend is true

for most cases of 2FO. Exceptions to this general trend were 2FO with dispersant ‘A’

experiments at 10 ppt and 34 ppt salinity (data presented in Chapters 2 and 3). Figure 4.6 shows

temperature vs viscosity for 2FO. Temperature vs percent effectiveness of dispersant ‘B’ on 2FO

at 10 ppt salinity and 250 rpm flask speed is shown in Figure 4.7. From the example shown, it is

again seen that dispersant effectiveness increases sharply with increase in temperature from 5 to

22 ºC and then at 35 ºC a very slight increase is noticed. It is also seen that with increase in

weathering, percent effectiveness decreases.

It should be noted that both the physical properties of the oil such as viscosity, pour point,

specific gravity or density, surface tension, and its chemical constituent plus the chemical

90

properties of the dispersant will impact the dispersion of the oil and the effectiveness of a

particular dispersant.

4.6 Conclusions

Temperature and weathering affect the viscosity of oils. The trend observed in the

effectiveness of dispersant ‘B’ on all three oils has been presented here at a salinity of 10 ppt and

flask speed of 250 rpm. Overall for all three oils, with increase in viscosity, the dispersant

effectiveness declines. The impact of viscosity is more pronounced between temperatures 5 and

22 ºC for the three oils at the three levels of weathering than at 35 ºC.

91

4.7 Reference

Clayton, J.R., Payne, J.R., Farlow, J.S. & Sarwar, C. 1993. Oil Spill Dispersants Mechanisms of

Action and Laboratory Tests, pp 90-103. Boca Raton, Florida: CRC press.

92

Table 4.1 Viscosity of Water at Various Temperatures

Temperature (◦C) Viscosity (cSt) 5 1.528 22 1.001 35 0.811

Table 4.2 Calibration Constants for Viscometers

Approx. Constant, cSt/s Size Range, cSt

5 ◦C 22 ◦C 35 ◦C

25 0.5-2 2.242 * 10-3 1.675 * 10-3 1.918 * 10-3

100 3-15 0.0186 0.0147 0.0154

150 7-35 0.044 0.03125 0.0328

Table 4.3 Viscosity Measurements of Oils at Various Temperatures

Oil Viscosity at 5 ◦C, cSt Viscosity at 22 ◦C,

cSt

Viscosity at 35 ◦C,

cSt

SLC 0% 12.747 6.350 4.681

SLC 10% 17.155 7.594 6.385

SLC 20% 27.5 9.0993 7.4536

PBC 0% 91.622 34.416 20.139

PBC 10% 202.356 78.614 49.571

PBC 20% -- -- --

2FO 0% 5.480 3.8171 2.854

2FO 3.8% 5.995 4.106 3.151

2FO 7.6% 6.789 4.253 3.8192

93

Figure 4.1 Cannon-Fenske Viscometer

94

0

5

10

15

20

25

30

5 22 35

Temperature (C)

Visc

osity

(cSt

)

SLC 0%SLC 10%SLC 20%

Figure 4.2 Temperature (◦C ) vs Viscosity (cSt) for SLC

70

75

80

85

90

95

100

5 22 35

Temperature (C)

Perc

ent E

ffec

tiven

ess

SLC 0%SLC 10%SLC 20%

Figure 4.3 Temperature (◦C ) vs Percent Effectiveness of Dispersant ‘B’ on SLC (Salinity = 10ppt, flask speed = 250 rpm)

95

0

50

100

150

200

250

5 22 35

Temperature (C)

Visc

osity

(cSt

)

PBC 0%PBC 10%

Figure 4.4 Temperature (◦C ) vs Viscosity (cSt) for PBC

60

65

70

75

80

85

90

95

100

5 22 35

Temperature (C)

Perc

ent E

ffec

tiven

ess

PBC 0%PBC 10%

Figure 4.5 Temperature (◦C ) vs Percent Effectiveness of Dispersant ‘B’ on PBC (Salinity = 10ppt, flask speed = 250 rpm)

96

0

2

4

6

8

5 22 35Temperature (C)

Visc

osity

(cSt

)

2FO 0%2FO 3.8%2FO 7.6%

Figure 4.6 Temperature (◦C ) vs Viscosity (cSt) for 2FO

60

65

70

75

80

85

90

95

100

5 22 35

Temperature (C)

Perc

ent E

ffec

tiven

ess

2FO 0%2FO 3.8%2FO 7.6%

Figure 4.7 Temperature (◦C ) vs Percent Effectiveness of Dispersant ‘B’ on 2FO (Salinity = 10ppt, flask speed = 250 rpm)

97

5. CONCLUSIONS AND RECOMMENDATIONS

98

In the previous chapters, the effectiveness of two selected dispersants on three oils was

shown for a suite of simulated environmental conditions. A factorial experimental design for

determining the impact of temperature, oil type, oil weathering, rotation speed and salinity on the

effectiveness of two dispersants were studied in two phases. All experiments were analyzed

using an analysis of variance with "=0.05. The REG procedure was used to perform regression

analysis on combined data from both phases of study. The experimental results obtained in this

study reveal the following:

(1) Dispersion efficiency increases with increase in mixing energy with no exceptions.

(2) Dispersion efficiency does not follow a general trend with increase in temperature and is

different for each oil depending on its properties. Temperature was found to a significant

factor for all experiments except SLC with dispersant ‘A’.

(3) Dispersion efficiency decreases with increase in the level of weathering. The impact of

weathering is only significant for SLC with dispersant ‘A’.

(4) In general, dispersion efficiency increases with increase in salinity for most of the oil-

dispersant combinations. The impact of salinity on dispersant effectiveness is more

pronounced at higher temperature than at lower temperature i.e, the significance of

salinity on dispersant effectiveness increases with increase in temperature for all three

oils. In general, salinity plays an important role in determining the significance of

temperature on dispersant effectiveness for all oil-dispersant combinations except SLC

with dispersant ‘A’.

(5) Overall, the significance of the factors can be ranked from most significant to least

significant as: Mixing Energy, Temperature, Salinity and Weathering.

99

(6) The empirical correlation for the collected experimental data from both phases of study,

predicted within a good accuracy the effectiveness of the dispersant. These correlations

have the potential to serve as an input parameter to the ERO3S model.

(7) Viscosity is one of the most important oil properties determining dispersant behavior.

This chapter deals with further work that need to be performed and also some

recommendations that would throw light on the behavior of dispersants. In the experiments

conducted, all the environmental factors were studied at three varying levels. In order to better

predict the behavior of dispersants, more levels in each of these factors could be considered and

incorporated in the factorial experimental design.

< In the case of mixing energy for example, there was a large variation in percent

effectiveness results and the trend observed was linear in all the cases. Hence the no: of

levels for mixing energy could be fixed at 3 i.e, 150, 200 and 250 rpm.

< In the case of weathering, three levels of 0, 10 and 20% for SLC and PBC and 0, 3.8 and

7.6% for 2FO were chosen. The trend in dispersant effectiveness values due to the impact

of weathering can be better predicted if more intermediate levels of weathering (between

0 and 20%) are chosen, especially in the case of SLC and PBC. This would give a clear

trend in dispersant effectiveness values with increase in weathering levels.

< In the case of temperature, it is seen in some cases that percent effectiveness increases

with increase in temperature from 5 to 22◦C and then suddenly decreases at 35◦C. So in

order to get a clear trend in effectiveness values with increase in temperature, more

100

intermediate values could be chosen especially between 22 and 35◦C. This would explain

whether the relationships are linear or not.

< Figures 3.1-3.4 clearly reveal the trend in dispersant effectiveness with increase in

salinity. A close look at the plots reveals the fact that more levels in salinity values

between 10 and 34 ppt would provide a better trend in dispersant effectiveness. From the

results discussed in chapter 3, it is seen that there is a pronounced impact of salinity on

dispersant effectiveness at 35◦C and at 22◦C whereas, there is not much impact at the

lower temperature of 5◦C. Hence more intermediate levels of temperature could be

chosen especially between 5 and 22◦C and the impact of salinity could also be studied at

these new temperatures.

A1

APPENDIX

Experimental Data

A2

Oil Control Experiments (Temperature = 5±1 0C, Salinity=10 ppt)

Oil Weathering Condition

Flask speed % Effectiveness of the replicate samples R1 R2 R3 R4

Average effectiveness

RSD

SLC 0 % 150 0.30 0.31 0.33 0.30 0.31 4.50

SLC 0% 200 1.92 1.88 1.86 1.90 1.88 1.30

SLC 0% 250 2.93 2.93 2.96 2.90 2.93 0.79

SLC 10% 150 0.33 0.35 0.36 0.35 0.34 3.68

SLC 10% 200 1.83 1.86 1.77 1.77 1.80 2.61

SLC 10% 250 2.80 2.89 2.83 2.91 2.85 1.8

SLC 20% 150 0.38 0.37 0.34 0.35 0.36 3.69

SLC 20% 200 1.73 1.77 1.75 1.74 1.75 1.05

SLC 20% 250 2.70 2.72 2.70 2.70 2.70 0.38

PBC 0% 150 0.00 0.00 0.01 0.01 0.005 115.47

PBC 0% 200 0.65 0.76 0.69 0.65 0.69 8.01

PBC 0% 250 2.85 2.83 3.01 2.61 2.82 5.86

PBC 10% 150 0.00 0.01 0.01 0.00 0.005 115.47

PBC 10% 200 0.79 0.83 0.78 0.86 0.81 4.13

PBC 10% 250 2.95 2.78 2.73 2.72 2.79 3.79

A3

Oil Control Experiments (Temperature = 5±1 0C, Salinity=10 ppt) (Cont’d)




RSD

PBC 20% 150 0.00 0.00 0.00 0.00 0.00 0.00

PBC 20% 200 0.83 0.75 0.80 0.80 0.79 4.33

PBC 20% 250 2.66 2.70 2.71 2.73 2.69 1.12

2FO 0% 150 1.42 1.22 1.22 1.42 1.31 8.88

2FO 0% 200 2.03 1.82 2.09 2.03 1.99 5.87

2FO 0% 250 3.24 2.90 3.31 3.17 3.15 5.62

2FO 3.8% 150 1.51 1.35 1.46 1.51 1.45 5.44

2FO 3.8% 200 2.02 1.85 1.79 2.02 1.92 6.02

2FO 3.8% 250 3.14 3.08 2.86 3.19 3.06 4.80

2FO 7.6% 150 1.58 1.53 1.58 1.48 1.54 3.16

2FO 7.6% 200 1.94 1.99 1.89 2.04 1.96 3.35

2FO 7.6% 250 3.17 3.01 3.11 3.11 3.10 2.07

A4

Oil + dispersant ‘A’ experiments (Temperature = 5±1 0C, Salinity=10 ppt)




RSD

SLC 0 % 150 48.25 47.82 50.21 51.62 49.48 3.57

SLC 0% 200 70.26 73.06 71.80 72.89 72.00 1.79

SLC 0% 250 83.72 83.88 83.51 84.26 83.84 0.38

SLC 10% 150 41.83 41.85 42.87 42.64 42.30 1.26

SLC 10% 200 61.71 62.01 60.71 61.51 61.49 0.90

SLC 10% 250 72.33 74.16 73.09 76.27 73.96 2.31

SLC 20% 150 42.77 42.22 40.79 40.28 41.51 2.82

SLC 20% 200 62.22 61.46 58.61 61.47 60.94 2.61

SLC 20% 250 72.43 74.32 73.25 73.43 73.36 1.05

PBC 0% 150 18.21 17.86 18.08 17.98 18.04 0.82

PBC 0% 200 52.72 51.81 52.61 51.30 52.11 1.29

PBC 0% 250 60.40 60.16 64.41 62.93 61.97 3.30

PBC 10% 150 18.37 17.90 17.83 17.69 17.95 1.64

PBC 10% 200 49.25 49.44 52.14 48.72 49.89 3.07

PBC 10% 250 60.24 58.08 58.61 59.77 59.17 1.69

A5

Oil + dispersant ‘A’ experiments (Temperature = 5±1 0C, Salinity=10 ppt) (Cont’d)




RSD

PBC 20% 150 16.73 17.12 16.72 17.40 16.99 1.93

PBC 20% 200 47.93 49.44 51.39 46.56 48.83 4.24

PBC 20% 250 59.18 57.33 56.67 58.09 57.82 1.87

2FO 0% 150 18.70 18.38 18.57 17.88 18.38 1.94

2FO 0% 200 39.33 37.71 39.52 40.77 39.33 3.19

2FO 0% 250 72.28 72.85 78.79 72.85 74.19 4.14

2FO 3.8% 150 18.13 17.45 18.65 17.87 18.02 2.77

2FO 3.8% 200 38.13 38.85 38.54 39.27 38.70 1.25

2FO 3.8% 250 67.47 70.64 70.02 71.37 69.83 2.42

2FO 7.6% 150 17.11 17.24 17.28 17.97 17.44 2.24

2FO 7.6% 200 37.16 36.21 37.25 38.51 37.28 2.53

2FO 7.6% 250 66.77 64.99 68.29 63.86 65.98 2.95

A6

Oil + dispersant ‘B’ experiments (Temperature = 5±1 0C, Salinity=10 ppt)




RSD

SLC 0 % 150 45.58 44.93 45.25 44.42 45.05 1.09

SLC 0% 200 68.32 67.07 68.69 71.59 68.91 2.77

SLC 0% 250 80.04 77.62 78.86 79.84 79.09 1.40

SLC 10% 150 45.37 44.05 43.42 45.01 44.46 2.00

SLC 10% 200 66.88 67.82 67.79 68.25 67.69 0.85

SLC 10% 250 80.40 77.69 77.55 79.44 78.77 1.76

SLC 20% 150 43.34 41.23 44.58 42.67 42.96 3.25

SLC 20% 200 61.90 62.14 61.88 62.23 62.04 0.28

SLC 20% 250 73.68 76.09 75.02 74.17 74.74 1.41

PBC 0% 150 21.88 21.16 22.36 21.85 21.81 2.27

PBC 0% 200 43.18 43.28 43.39 42.69 43.14 0.71

PBC 0% 250 74.18 72.46 69.33 68.78 71.19 3.61

PBC 10% 150 22.16 21.39 22.25 20.88 21.67 3.01

PBC 10% 200 42.91 44.46 42.54 44.26 43.54 2.20

PBC 10% 250 72.32 72.19 70.22 68.78 70.88 2.39

A7

Oil + dispersant ‘B’ experiments (Temperature = 5±1 0C, Salinity=10 ppt) (Cont’d)




RSD

PBC 20% 150 20.61 20.85 20.57 20.23 20.57 1.25

PBC 20% 200 42.83 42.17 42.52 42.79 42.58 0.71

PBC 20% 250 69.96 68.96 69.05 68.87 69.21 0.73

2FO 0% 150 20.91 20.39 21.35 21.13 20.95 1.97

2FO 0% 200 40.04 40.48 42.19 41.67 41.09 2.44

2FO 0% 250 68.88 66.66 65.17 70.21 67.73 3.32

2FO 3.8% 150 21.62 21.54 22.55 20.54 21.56 3.81

2FO 3.8% 200 41.80 42.51 37.99 41.44 40.93 4.91

2FO 3.8% 250 69.66 68.51 65.71 64.13 67.43 3.75

2FO 7.6% 150 22.85 21.67 20.62 21.88 22.13 4.13

2FO 7.6% 200 43.90 37.63 40.13 39.79 40.36 6.45

2FO 7.6% 250 69.54 68.00 64.10 63.68 66.33 4.35

A8

Oil control experiments (Temperature = 5±1 0C, Salinity=20 ppt)




RSD

SLC 0 % 150 0.45 0.43 0.45 0.43 0.44 1.65

SLC 0% 200 2.49 2.49 2.50 2.45 2.48 0.75

SLC 0% 250 4.01 3.92 3.86 3.91 3.92 1.66

SLC 10% 150 0.43 0.45 0.51 0.49 0.47 7.38

SLC 10% 200 2.42 2.47 2.45 2.38 2.42 1.71

SLC 10% 250 3.87 3.74 3.73 3.82 3.78 1.78

SLC 20% 150 0.47 0.48 0.44 0.45 0.46 3.88

SLC 20% 200 2.37 2.42 2.52 2.21 2.38 5.42

SLC 20% 250 3.71 3.61 3.68 3.64 3.65 1.13

PBC 0% 150 0.00 0.00 0.00 0.01 0.002 200

PBC 0% 200 1.11 1.07 0.97 1.09 1.06 5.72

PBC 0% 250 2.64 2.65 2.65 2.58 2.62 1.15

PBC 10% 150 0.01 0.00 0.01 0.00 0.004 115.47

PBC 10% 200 1.31 1.39 1.38 1.32 1.34 2.75

PBC 10% 250 3.56 3.71 3.54 3.67 3.61 2.32

A9

Oil control experiments (Temperature = 5±1 0C, Salinity=20 ppt) (Cont’d)




RSD

PBC 20% 150 0.00 0.00 0.00 0.00 0.00 0.00

PBC 20% 200 1.30 1.28 1.26 1.35 1.29 3.19

PBC 20% 250 3.30 3.32 3.25 3.29 3.29 0.95

2FO 0% 150 1.89 1.82 2.09 1.96 1.94 5.94

2FO 0% 200 3.24 3.24 2.90 3.38 3.19 6.31

2FO 0% 250 5.67 6.35 4.93 5.74 5.67 10.24

2FO 3.8% 150 1.85 1.68 1.74 1.79 1.76 4.09

2FO 3.8% 200 3.20 3.08 3.42 3.25 3.23 4.32

2FO 3.8% 250 5.72 4.77 4.82 5.22 5.13 8.58

2FO 7.6% 150 2.09 1.94 2.09 2.04 2.03 3.53

2FO 7.6% 200 3.26 3.36 3.31 3.31 3.31 1.25

2FO 7.6% 250 5.10 5.20 4.89 5.05 5.05 2.51

A10





RSD

SLC 0 % 150 51.89 52.36 50.83 50.21 51.32 1.90

SLC 0% 200 76.22 74.85 77.12 73.92 75.53 1.88

SLC 0% 250 85.08 85.65 85.42 85.51 85.41 0.28

SLC 10% 150 44.70 44.10 44.90 45.44 44.78 1.23

SLC 10% 200 65.97 66.61 66.04 66.41 66.26 0.46

SLC 10% 250 77.80 79.06 78.62 78.67 78.54 0.67

SLC 20% 150 44.85 43.79 43.85 44.52 44.25 1.17

SLC 20% 200 66.85 65.74 65.09 66.20 65.97 1.12

SLC 20% 250 78.32 75.81 76.94 77.20 77.07 1.33

PBC 0% 150 18.88 19.52 18.11 19.46 18.99 3.45

PBC 0% 200 55.79 53.40 55.17 56.13 55.12 2.20

PBC 0% 250 65.84 66.22 67.92 65.01 66.25 1.84

PBC 10% 150 17.67 17.86 18.53 18.06 18.03 2.04

PBC 10% 200 51.86 53.66 53.26 53.60 53.10 1.58

PBC 10% 250 64.01 61.49 62.71 62.21 62.60 1.69

A11





RSD

PBC 20% 150 17.77 16.98 16.92 17.34 17.25 2.26

PBC 20% 200 50.22 51.72 49.22 51.03 50.55 2.12

PBC 20% 250 59.56 60.84 62.83 60.18 60.85 2.33

2FO 0% 150 20.86 19.85 20.61 19.47 20.20 3.20

2FO 0% 200 42.16 41.15 41.97 39.32 41.15 3.15

2FO 0% 250 78.13 75.85 78.19 78.25 77.60 1.50

2FO 3.8% 150 17.49 18.16 18.42 18.26 18.08 2.27

2FO 3.8% 200 39.89 41.44 44.08 40.66 41.51 4.38

2FO 3.8% 250 77.55 74.18 75.06 77.29 76.34 2.16

2FO 7.6% 150 15.70 16.22 16.96 17.09 16.34 3.98

2FO 7.6% 200 39.52 38.74 38.00 39.00 38.81 1.62

2FO 7.6% 250 71.62 70.54 70.71 68.11 70.24 2.13

A12





RSD

SLC 0 % 150 48.64 49.76 48.39 50.87 49.42 2.30

SLC 0% 200 72.96 72.76 70.05 71.09 71.71 1.93

SLC 0% 250 81.94 79.13 83.00 81.79 81.46 2.02

SLC 10% 150 48.20 48.40 47.57 47.60 47.94 0.87

SLC 10% 200 68.53 69.04 67.70 69.13 68.60 0.95

SLC 10% 250 80.34 77.75 78.75 82.43 79.82 2.55

SLC 20% 150 44.06 45.42 44.26 43.88 44.40 1.56

SLC 20% 200 64.58 65.26 65.36 64.28 64.87 0.80

SLC 20% 250 76.51 73.62 75.19 76.65 75.49 1.87

PBC 0% 150 27.44 26.80 27.12 27.26 27.15 0.99

PBC 0% 200 46.59 46.85 47.10 46.17 46.68 0.84

PBC 0% 250 80.51 75.48 77.55 79.12 78.17 2.76

PBC 10% 150 24.63 25.05 25.18 24.49 24.84 1.32

PBC 10% 200 45.51 46.52 44.59 45.62 45.56 1.73

PBC 10% 250 74.07 75.47 75.40 73.67 74.66 1.22

A13





RSD

PBC 20% 150 22.73 22.76 22.91 23.06 22.86 0.67

PBC 20% 200 45.17 44.16 42.91 42.99 43.81 2.45

PBC 20% 250 73.22 73.38 74.51 72.58 73.42 1.09

2FO 0% 150 22.88 23.77 24.59 22.73 23.49 3.66

2FO 0% 200 45.69 42.06 42.36 46.36 44.12 5.03

2FO 0% 250 70.06 73.39 72.13 68.35 70.98 3.13

2FO 3.8% 150 24.25 23.17 23.39 22.89 23.42 2.50

2FO 3.8% 200 45.20 42.98 41.27 45.56 43.75 4.60

2FO 3.8% 250 71.52 71.31 68.95 70.30 71.04 1.65

2FO 7.6% 150 23.17 24.00 23.03 22.82 23.33 2.22

2FO 7.6% 200 44.18 42.86 41.45 43.28 42.94 2.64

2FO 7.6% 250 71.59 72.15 70.90 69.09 70.93 1.87

A14



Percent Effectiveness at 150 rpm



SLC 0 % 0.51 2.73 4.42

SLC 10% 0.51 2.66 4.40

SLC 20% 0.52 2.65 4.24

PBC 0% 0.00 1.58 4.45

PBC 10% 0.00 1.52 4.06

PBC 20% 0.00 1.52 3.80

2FO 0% 2.24 3.73 6.44

2FO 3.8% 2.18 3.63 5.86

2FO 7.6% 2.31 3.54 5.80

A15






SLC 0 % 54.50 77.32 89.65

SLC 10 52.51 71.60 85.90

SLC 20% 50.91 69.65 84.09

PBC 0% 21.10 58.91 69.71

PBC 10% 20.96 57.31 65.75

PBC 20% 20.36 55.34 64.04

2FO 0% 21.09 45.67 79.29

2FO 3.8% 19.21 42.67 77.90

2FO 7.6% 18.65 41.92 73.77

A16






SLC 0 % 51.80 72.59 83.13

SLC 10% 50.99 71.75 81.25

SLC 20% 46.52 70.71 77.73

PBC 0% 30.02 48.85 84.11

PBC 10% 28.23 48.76 83.48

PBC 20% 26.67 46.44 81.21

2FO 0% 24.18 48.14 73.06

2FO 3.8% 24.42 47.12 72.75

2FO 7.6% 24.41 47.01 72.25

A17


Oil

Weathering Condition

Flask speed % Effectiveness of the replicate samples R1 R2 R3

R4


RSD

SLC 0 % 150 7.74 7.25 7.36 7.24 7.40 3.16

SLC 0% 200 10.89 13.44 11.6 10.39 11.58 11.54

SLC 0% 250 13.35 13.42 12.48 12.57 12.96 3.84

SLC 10% 150 6.32 6.72 6.62 5.03 6.17 12.67

SLC 10% 200 11.52 10.68 10.52 10.03 10.69 5.80

SLC 10% 250 12.56 11.26 12.64 12.38 12.21 5.29

SLC 20% 150 4.48 5.30 5.55 5.74 5.27 10.58

SLC 20% 200 12.26 12.43 12.05 13.24 12.49 4.16

SLC 20% 250 13.96 13.92 12.95 14.04 13.72 3.76

PBC 0% 150 1.39 1.57 1.83 1.63 1.60 11.46

PBC 0% 200 5.7 5.96 5.52 5.59 5.69 3.40

PBC 0% 250 10.82 11.51 11.43 11.53 11.32 2.99

PBC 10% 150 1.99 1.90 2.02 2.01 1.98 2.82

PBC 10% 200 4.79 4.76 4.87 5.03 4.86 2.55

PBC 10% 250 7.22 7.27 7.36 7.11 7.24 1.42

A18





RSD

PBC 20% 150 1.07 1.26 1.00 1.20 1.13 10.62

PBC 20% 200 7.88 8.39 8.17 7.75 8.05 3.57

PBC 20% 250 10.88 11.40 10.70 10.97 10.99 2.74

2FO 0% 150 1.63 1.84 1.84 1.63 1.73 6.79

2FO 0% 200 3.88 3.67 3.60 3.88 3.76 3.73

2FO 0% 250 4.42 4.83 5.37 5.30 4.98 8.94

2FO 3.8% 150 1.90 1.96 1.90 1.96 1.93 1.89

2FO 3.8% 200 4.24 4.43 5.38 5.19 4.81 11.62

2FO 3.8% 250 5.70 5.45 6.02 6.46 5.91 7.39

2FO 7.6% 150 2.16 2.28 2.47 2.65 2.39 8.80

2FO 7.6% 200 4.81 6.07 5.29 4.99 5.29 10.53

2FO 7.6% 250 8.24 7.76 7.64 7.28 7.73 5.14

A19





RSD

SLC 0 % 150 48.87 49.64 47.16 50.97 49.16 3.23

SLC 0% 200 78.48 75.13 77.30 75.23 76.53 2.14

SLC 0% 250 87.62 85.44 86.91 87.35 86.83 1.12

SLC 10% 150 24.03 24.33 25.72 24.39 24.61 3.05

SLC 10% 200 54.01 54.08 52.63 52.30 53.25 1.73

SLC 10% 250 70.58 70.42 70.07 70.13 70.30 0.34

SLC 20% 150 30.33 30.13 30.24 31.75 30.61 2.50

SLC 20% 200 80.03 80.54 80.21 78.81 79.90 0.94

SLC 20% 250 80.92 81.79 82.15 81.27 81.53 0.67

PBC 0% 150 37.71 37.77 37.72 37.81 37.75 0.12

PBC 0% 200 59.96 58.24 58.25 60.40 59.21 1.91

PBC 0% 250 94.75 92.14 86.56 91.08 91.13 3.75

PBC 10% 150 46.89 46.94 46.76 46.89 46.87 0.16

PBC 10% 200 84.70 83.39 82.12 81.06 77.85 3.02

PBC 10% 250 96.88 94.78 97.51 97.96 96.79 1.45

A20





RSD

PBC 20% 150 47.44 47.15 47.39 47.62 47.40 0.41

PBC 20% 200 85.39 84.75 85.56 86.44 85.53 0.81

PBC 20% 250 91.24 95.95 92.15 92.53 92.97 2.21

2FO 0% 150 39.36 39.42 42.74 46.38 41.98 7.94

2FO 0% 200 91.25 86.55 88.75 90.13 89.17 2.27

2FO 0% 250 93.95 92.19 93.07 92.07 92.82 0.94

2FO 3.8% 150 56.02 54.30 57.42 57.37 56.28 2.61

2FO 3.8% 200 81.50 80.00 83.53 81.45 81.62 1.78

2FO 3.8% 250 98.93 99.34 88.84 92.89 95.00 5.32

2FO 7.6% 150 44.82 45.03 60.37 51.00 50.30 14.5

2FO 7.6% 200 68.38 60.41 63.85 66.64 64.82 5.37

2FO 7.6% 250 76.00 76.00 76.70 72.91 75.40 2.24

A21





RSD

SLC 0 % 150 57.38 57.01 57.25 56.95 57.15 0.35

SLC 0% 200 73.43 73.49 74.12 73.79 73.71 0.43

SLC 0% 250 87.68 85.86 87.88 87.10 87.14 1.04

SLC 10% 150 54.63 54.60 55.90 55.54 55.17 1.18

SLC 10% 200 73.69 72.88 72.26 71.75 72.65 1.15

SLC 10% 250 83.25 83.33 83.47 86.49 84.13 1.87

SLC 20% 150 50.68 50.49 50.37 49.80 50.33 0.75

SLC 20% 200 70.72 70.49 71.57 69.63 70.61 1.12

SLC 20% 250 82.29 83.44 83.14 82.02 82.73 0.81

PBC 0% 150 51.97 52.04 51.86 51.99 51.97 0.14

PBC 0% 200 63.80 62.39 63.71 63.82 63.43 1.09

PBC 0% 250 79.84 82.13 81.44 81.43 81.21 1.19

PBC 10% 150 50.11 50.13 49.88 50.10 50.05 0.23

PBC 10% 200 58.55 59.00 57.92 59.57 58.76 1.19

PBC 10% 250 80.50 80.90 77.33 79.05 79.44 2.03

A22





RSD

PBC 20% 150 47.21 47.17 47.28 47.38 47.26 0.19

PBC 20% 200 57.45 57.48 57.90 57.68 57.63 0.35

PBC 20% 250 82.15 82.30 81.82 83.32 82.40 0.78

2FO 0% 150 44.74 45.49 43.04 46.15 44.86 2.98

2FO 0% 200 69.49 69.71 69.93 70.15 69.82 0.41

2FO 0% 250 91.19 90.75 90.53 91.41 90.97 0.44

2FO 3.8% 150 31.58 31.58 31.01 31.43 31.40 0.86

2FO 3.8% 200 71.35 72.35 72.35 72.28 72.08 0.67

2FO 3.8% 250 88.74 89.31 87.53 89.45 88.76 0.98

2FO 7.6% 150 54.88 55.73 55.03 56.16 55.45 1.08

2FO 7.6% 200 73.68 73.75 73.39 73.18 73.50 0.35

2FO 7.6% 250 92.40 90.84 90.35 92.47 91.51 1.18

A23





RSD

SLC~ 0 %~ 150~ 3.17 3.20 3.28 3.21 3.22 1.47

SLC 0% 200 5.96 5.95 5.99 6.30 6.05 2.75

SLC 0% 250 6.69 6.91 7.04 6.87 6.88 2.06

SLC~ 10%~ 150~ 2.92 2.87 2.96 2.88 2.91 1.35

SLC 10% 200 5.62 5.39 5.41 5.87 5.57 3.98

SLC 10% 250 6.19 6.26 6.31 8.00 6.69 13.11

SLC~ 20%~ 150~ 2.81 2.84 2.55 2.80 2.75 4.85

SLC 20% 200 5.81 6.68 6.05 6.13 6.17 5.97

SLC 20% 250 7.69 7.76 7.58 7.36 7.6 2.32

PBC 0% 150 2.15 2.11 2.31 2.12 2.17 4.18

PBC 0% 200 3.26 3.21 3.35 3.31 3.28 1.86

PBC 0% 250 5.20 4.69 4.79 5.25 4.98 5.66

PBC 10% 150 2.03 2.10 2.13 1.96 2.06 3.77

PBC 10% 200 3.21 3.13 3.22 3.11 3.17 1.70

PBC 10% 250 4.87 5.49 4.92 4.83 5.03 6.17

A24





RSD

PBC 20% 150 2.06 2.01 1.98 1.97 2.00 2.12

PBC 20% 200 3.16 3.12 3.06 3.06 3.10 1.65

PBC 20% 250 4.55 4.42 4.51 4.36 4.46 1.83

2FO 0% 150 2.31 2.38 2.24 2.18 2.28 3.85

2FO 0% 200 4.69 4.49 4.56 4.76 4.63 2.68

2FO 0% 250 6.87 6.26 6.67 6.60 6.60 3.85

2FO 3.8% 150 2.21 2.08 2.27 2.34 2.22 4.84

2FO 3.8% 200 4.36 4.73 4.54 4.73 4.59 3.94

2FO 3.8% 250 6.56 6.44 6.63 6.44 6.52 1.45

2FO 7.6% 150 2.16 2.28 2.10 2.28 2.21 4.08

2FO 7.6% 200 4.81 4.57 4.39 4.45 4.55 4.08

2FO 7.6% 250 6.55 6.55 6.61 8.05 6.94 10.68

A25





RSD

SLC 0 % 150 55.81 53.54 54.04 54.48 54.47 1.78

SLC 0% 200 82.58 82.84 83.00 82.63 82.76 0.23

SLC 0% 250 91.10 91.85 91.79 92.54 91.82 0.64

SLC 10% 150 45.21 45.12 45.34 44.90 45.14 0.41

SLC 10% 200 68.79 68.54 68.32 67.86 68.38 0.57

SLC 10% 250 76.34 79.16 77.85 77.92 77.82 1.48

SLC 20% 150 45.17 45.10 44.01 43.61 44.47 1.75

SLC 20% 200 69.57 68.37 68.72 68.90 68.89 0.73

SLC 20% 250 78.04 76.69 77.22 91.91 80.96 9.03

PBC 0% 150 40.34 40.11 39.81 39.61 39.97 0.80

PBC 0% 200 69.39 69.79 69.62 69.50 69.57 0.24

PBC 0% 250 96.73 92.04 92.61 95.68 94.26 2.43

PBC 10% 150 36.92 37.60 37.56 38.03 37.53 1.21

PBC 10% 200 63.89 66.97 65.49 64.10 65.11 2.18

PBC 10% 250 90.72 91.13 90.69 92.35 91.22 0.85

A26





RSD

PBC 20% 150 36.64 36.27 36.49 36.04 36.36 0.72

PBC 20% 200 64.01 63.98 62.35 63.81 63.54 1.25

PBC 20% 250 89.58 89.95 89.61 85.70 88.71 2.27

2FO 0% 150 48.99 48.99 48.43 48.12 48.63 0.89

2FO 0% 200 79.02 78.77 79.34 80.53 79.41 0.97

2FO 0% 250 92.85 97.73 94.04 93.23 94.46 2.36

2FO 3.8% 150 47.90 47.49 48.63 48.01 48.01 0.98

2FO 3.8% 200 73.99 74.88 75.08 75.45 74.85 0.82

2FO 3.8% 250 88.26 86.75 85.39 87.22 87.41 1.36

2FO 7.6% 150 43.76 45.80 45.80 48.11 45.89 3.86

2FO 7.6% 200 71.33 71.85 70.55 70.90 71.16 0.79

2FO 7.6% 250 77.54 78.41 77.71 78.02 77.92 0.48

A27





RSD

SLC 0 % 150 59.12 59.37 59.63 59.24 59.35 0.37

SLC 0% 200 75.67 75.91 84.13 75.25 77.75 5.49

SLC 0% 250 88.29 88.07 88.05 87.80 88.06 0.22

SLC 10% 150 58.12 57.67 57.62 57.96 57.85 0.41

SLC 10% 200 74.95 74.69 74.62 73.37 74.41 0.95

SLC 10% 250 84.95 85.06 84.71 85.45 84.91 0.36

SLC 20% 150 51.77 53.04 52.80 52.61 52.55 1.04

SLC 20% 200 74.63 73.90 72.67 72.08 73.32 1.57

SLC 20% 250 84.41 84.31 84.23 82.71 83.92 0.95

PBC 0% 150 52.94 52.61 52.61 52.78 52.73 0.30

PBC 0% 200 66.02 67.95 66.92 67.11 67.00 1.18

PBC 0% 250 82.16 83.78 83.42 86.90 84.07 2.39

PBC 10% 150 50.71 50.77 50.89 50.89 50.82 0.17

PBC 10% 200 62.21 62.38 61.50 60.12 61.55 1.67

PBC 10% 250 84.82 83.10 81.32 82.92 83.04 1.72

A28





RSD

PBC 20% 150 47.46 47.63 47.76 47.59 47.61 0.25

PBC 20% 200 59.31 60.14 58.82 58.11 59.10 1.44

PBC 20% 250 84.08 82.33 82.22 81.41 82.51 1.36

2FO 0% 150 46.31 47.79 44.09 46.01 46.05 3.29

2FO 0% 200 70.09 69.80 70.17 70.17 70.06 0.25

2FO 0% 250 90.70 90.99 91.66 91.51 91.22 0.49

2FO 3.8% 150 31.61 32.25 33.24 31.53 32.16 2.46

2FO 3.8% 200 74.03 74.53 73.96 74.46 74.24 0.39

2FO 3.8% 250 89.12 88.33 89.26 88.83 88.89 0.46

2FO 7.6% 150 56.3 56.72 56.65 56.01 56.42 0.57

2FO 7.6% 200 74.06 74.2 73.64 73.64 73.88 0.39

2FO 7.6% 250 91.68 92.59 93.43 94.55 93.06 1.31

A29



Natural Dispersency

150 rpm

Natural Dispersency at

200 rpm

Natural Dispersency at

250 rpm

SLC 0 % 1.26 5.77 7.07

SLC 10% 1.10 4.19 5.44

SLC 20% 1.61 5.19 8.45

PBC 0% 3.86 2.43 3.81

PBC 10% 3.44 4.89 6.29

PBC 20% 3.25 4.63 5.58

2FO 0% 3.24 5.70 7.12

2FO 3.8% 0.00 0.60 2.78

2FO 7.6% 2.63 5.57 7.02

A30






SLC 0 % 57.19 87.64 97.31

SLC 10% 34.21 69.76 89.80

SLC 20% 39.79 91.97 92.88

PBC 0% 40.82 80.12 95.95

PBC 10% 60.55 84.33 97.94

PBC 20% 43.20 86.00 90.61

2FO 0% 48.99 82.93 95.52

2FO 3.8% 58.25 84.07 97.85

2FO 7.6% 69.28 87.38 98.76

A31






SLC 0 % 28.64 76.67 90.68

SLC 10% 26.99 75.45 86.03

SLC 20% 26.42 73.54 88.99

PBC 0% 52.32 69.18 87.96

PBC 10% 49.24 63.47 85.15

PBC 20% 47.69 62.34 83.53

2FO 0% 48.94 78.00 98.24

2FO 3.8% 33.38 76.49 92.79

2FO 7.6% 56.39 75.89 94.75

A32





RSD

SLC 0 % 150 8.02 7.49 7.40 7.94 7.71 4.07

SLC 0% 200 11.43 12.78 11.69 11.61 11.88 5.15

SLC 0% 250 13.46 13.64 13.72 13.26 13.52 1.52

SLC 10% 150 6.90 6.91 6.57 7.34 6.93 4.53

SLC 10% 200 12.02 11.03 11.98 12.03 11.76 4.14

SLC 10% 250 12.91 12.41 12.58 13.11 12.75 2.50

SLC 20% 150 6.61 6.22 6.43 6.38 6.41 2.46

SLC 20% 200 11.12 11.36 11.56 10.96 11.25 2.31

SLC 20% 250 13.02 11.97 12.26 11.90 12.29 4.15

PBC 0% 150 1.83 1.54 1.46 1.69 1.63 10.00

PBC 0% 200 6.01 6.05 6.01 6.09 6.04 0.63

PBC 0% 250 11.25 11.00 11.38 11.33 11.24 1.51

PBC 10% 150 1.81 1.76 1.72 1.79 1.77 2.33

PBC 10% 200 5.31 5.36 5.30 5.36 5.33 0.60

PBC 10% 250 9.77 9.25 9.28 9.51 9.45 2.54

A33





RSD

PBC 20% 150 1.70 1.69 1.72 1.56 1.67 4.37

PBC 20% 200 5.07 4.91 5.01 5.04 5.01 1.38

PBC 20% 250 8.92 9.12 8.82 8.77 8.91 1.71

2FO 0% 150 2.17 2.04 2.10 2.31 2.15 5.37

2FO 0% 200 2.71 2.78 2.71 2.92 2.78 3.45

2FO 0% 250 6.38 6.17 6.04 5.97 6.14 2.92

2FO 3.8% 150 2.35 1.97 1.90 2.16 2.09 9.58

2FO 3.8% 200 3.04 3.23 3.04 2.92 3.06 4.27

2FO 3.8% 250 6.28 5.96 5.77 5.77 5.94 4.02

2FO 7.6% 150 2.59 2.59 2.16 2.46 2.45 8.10

2FO 7.6% 200 3.61 3.37 3.19 3.13 3.32 6.50

2FO 7.6% 250 6.43 5.89 6.01 5.71 6.01 5.10

A34





RSD

SLC 0 % 150 62.45 64.00 64.48 63.23 63.54 1.40

SLC 0% 200 85.24 83.95 85.83 83.16 84.54 1.43

SLC 0% 250 91.70 89.98 91.41 90.66 90.94 0.85

SLC 10% 150 53.50 54.15 53.41 53.46 53.63 0.64

SLC 10% 200 71.19 73.05 70.58 71.97 71.70 1.48

SLC 10% 250 78.27 79.03 79.82 80.21 79.33 1.08

SLC 20% 150 52.63 52.84 52.76 51.44 52.42 1.25

SLC 20% 200 71.55 70.61 71.97 70.07 71.05 1.21

SLC 20% 250 77.46 77.31 77.81 78.25 77.71 0.54

PBC 0% 150 35.42 35.69 35.35 35.97 35.61 0.79

PBC 0% 200 57.40 57.54 58.09 58.51 57.89 0.88

PBC 0% 250 88.52 78.91 85.53 89.33 85.57 5.52

PBC 10% 150 33.28 33.55 33.34 33.68 33.46 0.55

PBC 10% 200 57.67 55.89 57.80 55.96 56.83 1.84

PBC 10% 250 79.53 81.56 81.33 83.75 81.54 2.12

A35





RSD

PBC 20% 150 30.38 30.40 31.12 30.70 30.65 1.12

PBC 20% 200 55.72 54.97 57.33 53.22 55.31 3.09

PBC 20% 250 78.31 76.95 78.25 77.21 77.68 0.90

2FO 0% 150 50.03 45.58 48.97 41.44 46.51 8.32

2FO 0% 200 62.45 64.01 61.44 61.57 62.37 1.90

2FO 0% 250 75.11 75.42 77.31 78.81 76.66 2.25

2FO 3.8% 150 44.44 45.32 43.19 47.82 45.19 4.33

2FO 3.8% 200 55.52 57.40 56.20 58.07 56.80 2.02

2FO 3.8% 250 74.57 75.76 69.47 72.28 74.20 3.74

2FO 7.6% 150 41.96 43.19 42.80 41.12 42.09 2.19

2FO 7.6% 200 53.79 54.50 53.66 54.55 54.13 0.85

2FO 7.6% 250 69.56 70.58 70.22 69.83 70.05 0.63

A36





RSD

SLC 0 % 150 58.93 59.49 57.72 57.86 58.50 1.46

SLC 0% 200 75.09 75.28 74.89 74.70 74.99 0.33

SLC 0% 250 90.53 87.94 88.91 89.45 89.21 1.20

SLC 10% 150 56.58 54.42 56.64 56.05 55.92 1.85

SLC 10% 200 71.95 73.67 72.59 72.67 72.72 0.98

SLC 10% 250 88.40 87.79 87.34 86.99 87.84 0.69

SLC 20% 150 53.44 54.85 53.48 54.73 54.12 1.42

SLC 20% 200 71.48 71.19 72.48 70.84 71.50 0.98

SLC 20% 250 83.24 85.45 82.03 82.91 83.41 1.74

PBC 0% 150 57.96 58.05 58.12 58.12 58.06 0.13

PBC 0% 200 66.28 65.92 66.26 67.98 66.61 1.39

PBC 0% 250 87.25 86.47 86.61 85.90 86.56 0.64

PBC 10% 150 54.39 56.15 54.56 54.90 55.00 1.44

PBC 10% 200 63.01 63.18 60.13 62.52 62.21 2.27

PBC 10% 250 81.83 81.13 79.98 81.01 80.99 0.94

A37





RSD

PBC 20% 150 49.44 49.58 50.15 49.65 49.71 0.61

PBC 20% 200 60.51 64.22 58.80 61.47 61.25 3.70

PBC 20% 250 74.72 72.92 74.85 73.04 73.88 1.41

2FO 0% 150 39.27 40.24 38.76 40.46 39.68 2.02

2FO 0% 200 78.85 78.18 73.45 79.07 77.38 3.42

2FO 0% 250 95.34 96.15 90.46 92.31 93.56 2.83

2FO 3.8% 150 34.59 33.81 33.81 33.95 34.04 1.09

2FO 3.8% 200 74.57 75.57 74.93 75.50 75.14 0.63

2FO 3.8% 250 90.48 91.55 91.19 92.97 91.55 1.14

2FO 7.6% 150 34.38 34.24 33.76 33.62 34.00 1.09

2FO 7.6% 200 74.89 74.75 74.75 74.20 74.65 0.41

2FO 7.6% 250 89.37 89.86 91.46 89.86 90.13 1.01

A38





RSD

SLC 0 % 150 8.32 7.95 7.62 6.98 7.72 7.32

SLC 0% 200 12.86 12.73 11.64 12.81 12.51 4.67

SLC 0% 250 13.80 13.55 12.07 12.59 13.00 6.24

SLC 10% 150 8.34 7.51 7.26 6.50 7.40 10.27

SLC 10% 200 11.59 11.94 12.09 11.25 11.72 3.19

SLC 10% 250 12.92 12.74 12.97 13.55 13.05 2.68

SLC 20% 150 7.41 7.58 7.29 6.77 7.26 4.84

SLC 20% 200 11.26 11.74 11.17 11.21 11.34 2.32

SLC 20% 250 13.18 13.33 12.84 13.80 13.29 3.01

PBC 0% 150 1.95 2.27 2.22 2.02 2.12 7.30

PBC 0% 200 6.21 6.18 6.16 6.48 6.26 2.36

PBC 0% 250 11.41 11.48 11.65 11.49 11.51 0.86

PBC 10% 150 1.90 2.02 2.06 2.15 2.03 5.03

PBC 10% 200 5.57 5.71 5.90 6.09 5.82 3.93

PBC 10% 250 9.91 10.03 9.90 10.16 10.00 1.22

A39





RSD

PBC 20% 150 2.07 2.09 2.20 2.17 2.13 2.93

PBC 20% 200 5.60 5.56 5.42 5.61 5.55 1.57

PBC 20% 250 9.17 9.19 9.45 9.25 9.27 1.40

2FO 0% 150 4.27 3.93 4.47 4.40 4.27 5.65

2FO 0% 200 6.44 6.23 6.57 6.44 6.42 2.17

2FO 0% 250 8.34 7.59 8.06 7.86 7.96 3.96

2FO 3.8% 150 4.56 4.04 4.81 3.91 4.33 9.79

2FO 3.8% 200 6.67 6.10 6.22 5.84 6.21 5.62

2FO 3.8% 250 8.15 7.64 7.76 7.89 7.86 2.78

2FO 7.6% 150 4.83 4.29 4.47 4.29 4.47 5.73

2FO 7.6% 200 6.95 5.98 5.56 5.32 5.95 12.08

2FO 7.6% 250 7.97 7.37 7.19 7.49 7.50 4.47

A40





RSD

SLC 0 % 150 64.67 65.38 64.26 65.89 65.05 1.11

SLC 0% 200 87.19 86.51 86.74 88.73 87.29 1.14

SLC 0% 250 91.06 90.72 90.39 91.86 91.01 0.69

SLC 10% 150 57.62 58.99 57.66 58.57 58.21 1.16

SLC 10% 200 77.13 74.96 75.23 76.09 75.85 1.28

SLC 10% 250 83.41 84.92 88.52 86.04 85.72 2.51

SLC 20% 150 57.34 56.15 57.17 57.69 57.09 1.15

SLC 20% 200 73.79 74.24 73.60 74.42 74.01 0.52

SLC 20% 250 84.11 84.89 81.59 88.12 84.68 3.18

PBC 0% 150 57.39 57.62 58.70 58.30 58.00 1.04

PBC 0% 200 68.39 68.49 73.60 68.65 69.78 3.64

PBC 0% 250 87.29 87.33 84.98 87.05 86.66 1.30

PBC 10% 150 53.85 54.14 53.90 53.91 53.95 0.23

PBC 10% 200 61.92 62.43 61.98 62.53 62.22 0.49

PBC 10% 250 79.33 80.04 84.08 79.54 80.75 2.77

A41





RSD

PBC 20% 150 48.95 49.05 48.63 48.98 48.90 0.37

PBC 20% 200 59.69 59.25 60.94 61.49 60.34 1.73

PBC 20% 250 79.12 77.47 82.49 74.40 78.37 4.30

2FO 0% 150 47.49 46.68 46.43 46.86 46.86 0.96

2FO 0% 200 67.89 69.01 69.14 67.64 68.42 1.11

2FO 0% 250 96.53 88.67 93.91 99.22 94.58 4.75

2FO 3.8% 150 47.81 44.74 46.77 47.03 46.59 2.80

2FO 3.8% 200 61.07 62.74 64.04 72.67 65.13 7.94

2FO 3.8% 250 91.19 86.93 99.10 92.13 90.08 5.60

2FO 7.6% 150 45.39 44.99 46.80 47.37 45.92 2.46

2FO 7.6% 200 58.62 58.71 61.18 60.52 59.75 2.15

2FO 7.6% 250 90.86 79.26 90.90 85.66 86.67 6.37

A42





RSD

SLC 0 % 150 60.98 61.58 60.48 61.24 61.07 0.75

SLC 0% 200 77.53 77.35 79.49 77.99 78.09 1.24

SLC 0% 250 89.38 92.39 90.68 90.03 90.62 1.42

SLC 10% 150 58.41 59.28 59.61 59.35 59.16 0.88

SLC 10% 200 75.38 75.44 76.11 75.99 75.73 0.49

SLC 10% 250 92.40 88.51 88.96 86.78 89.96 2.62

SLC 20% 150 55.61 55.15 53.76 56.29 55.20 1.94

SLC 20% 200 74.13 73.50 74.17 74.74 74.14 0.68

SLC 20% 250 85.18 84.68 83.20 88.41 85.37 2.57

PBC 0% 150 60.66 61.11 61.06 72.28 63.78 8.89

PBC 0% 200 65.26 65.62 64.45 71.80 66.78 5.06

PBC 0% 250 87.66 90.37 86.49 86.29 87.70 2.14

PBC 10% 150 56.12 55.91 56.16 56.36 56.14 0.33

PBC 10% 200 64.00 60.93 66.97 65.30 64.30 3.97

PBC 10% 250 83.60 84.61 82.74 84.01 83.74 0.93

A43





RSD

PBC 20% 150 53.20 52.67 53.02 53.21 53.02 0.47

PBC 20% 200 62.03 64.86 61.01 60.60 62.12 3.08

PBC 20% 250 79.42 82.07 79.60 82.07 80.79 1.83

2FO 0% 150 46.49 46.49 47.45 46.94 46.84 0.97

2FO 0% 200 68.26 69.59 73.87 72.03 70.94 3.52

2FO 0% 250 96.01 95.42 91.88 98.08 95.35 2.70

2FO 3.8% 150 46.01 45.09 42.34 43.40 44.21 3.74

2FO 3.8% 200 70.68 69.26 67.92 68.77 69.16 1.67

2FO 3.8% 250 96.40 94.64 91.81 92.02 93.72 2.35

2FO 7.6% 150 45.67 44.42 44.77 44.28 44.78 1.39

2FO 7.6% 200 72.18 68.78 68.92 66.35 69.06 3.46

2FO 7.6% 250 95.30 93.56 91.69 91.55 93.02 1.90

A44



Natural Dispersion at

150 rpm


200 rpm


250 rpm

SLC 0 % 4.92 8.90 11.09

SLC 10% 4.12 8.25 9.68

SLC 20% 5.39 10.39 11.94

PBC 0% 0.53 1.77 5.47

PBC 10% 1.04 1.63 4.76

PBC 20% 1.06 1.74 4.46

2FO 0% 6.89 7.84 10.81

2FO 3.8% 6.23 7.50 10.73

2FO 7.6% 7.44 7.33 10.22

A45






SLC 0 % 81.64 96.28 98.17

SLC 10% 74.12 94.20 97.41

SLC 20% 73.81 87.64 90.69

PBC 0% 33.62 72.21 75.92

PBC 10% 33.06 71.47 72.79

PBC 20% 31.93 68.46 71.68

2FO 0% 34.60 47.92 89.79

2FO 3.8% 34.19 46.55 76.87

2FO 7.6% 32.19 45.11 75.62

A46






SLC 0 % 42.88 76.69 92.06

SLC 10% 42.68 77.57 91.39

SLC 20% 41.60 76.11 87.76

PBC 0% 63.59 67.69 89.23

PBC 10% 58.23 67.02 82.34

PBC 20% 56.29 66.87 80.79

2FO 0% 41.74 53.13 98.92

2FO 3.8% 41.53 52.67 97.98

2FO 7.6% 41.71 52.64 96.06

A47

Two-way interaction: Dispersant by temperature interaction (Flask speed =250 rpm, Weathering =0%, Salinity=34 ppt)

Oil Temp (0C) Dispersant

% Eff. of replicates R1 R2

Avg. effectiveness RSD

%Eff. of previous samples RPD

SLC 22 A 96.25 98.96 97.60 1.96 97.35 0.26

SLC 35 A 98.69 98.33 98.51 0.25 98.17 0.35

SLC 6 A 90.18 90.11 90.15 0.05 89.65 0.55

SLC 22 B 92.82 88.60 90.71 3.28 90.68 0.03

SLC 35 B 91.29 83.73 87.51 6.11 92.06 5.19

SLC 6 B 85.58 85.74 85.66 0.13 83.13 2.96

PBC 22 A 96.20 94.05 95.12 1.59 95.95 0.87

PBC 35 A 80.32 74.20 77.26 5.59 75.92 1.74

PBC 6 A 71.41 87.01 79.21 13.92 69.71 11.99

PBC 22 B 88.66 84.76 86.71 3.18 87.96 1.44

PBC 35 B 95.62 94.38 94.99 0.92 89.23 6.07

PBC 6 B 82.41 70.04 76.22 11.47 84.11 10.34

2FO 22 A 95.97 95.87 95.92 0.07 95.63 0.30

2FO 35 A 74.28 81.60 77.94 6.65 89.79 15.20

2FO 6 A 75.11 64.06 69.58 11.22 79.29 13.95

2FO 22 B 90.64 92.13 91.39 1.15 98.24 7.50

2FO 35 B 90.79 96.84 88.82 3.14 98.92 11.37

2FO 6 B 74.26 75.08 74.66 0.77 73.06 2.15

A48

Two-way interaction: Dispersant by volatilization interaction (Flask speed =250 rpm, Temperature = 22±10C, Salinity=34 ppt)

Oil Weathering Dispersant

% Effectiveness of replicates

R1 R2 Avg.

effectiveness RSD %Eff. of previous

samples RPD

PBC 0% A 89.96 93.76 91.86 2.92 95.95 4.45

PBC 10% A 99.82 96.88 98.35 2.11 97.94 0.42

PBC 20% A 90.08 94.72 92.40 3.55 90.61 1.93

PBC 0% B 89.89 86.19 88.04 2.96 87.96 0.09

PBC 10% B 87.21 86.63 86.92 0.47 85.15 2.03

PBC 20% B 83.91 88.84 86.37 4.04 83.53 3.29

A49

Two-way interaction: Dispersant by speed interaction (Weathering = 0%, Temperature = 22±10C, Salinity=34 ppt)

Oil Speed Dispersant % Effectiveness of replicates

R1 R2 R3 R4 Avg.

effectiveness RSD %Eff. of previous

samples RPD

SLC 150 A 54.69 55.7 55.18 69.97 58.88 12.56 57.21 2.87

SLC 200 A 88.70 92.51 87.71 87.88 89.20 2.52 87.45 1.98

SLC 250 A 99.52 98.40 98.05 96.90 98.20 1.09 97.35 0.88

PBC 150 A 51.25 46.37 48.00 46.38 48.00 4.78 40.82 14.96

PBC 200 A 79.38 82.43 81.28 78.99 80.52 2.01 80.12 0.49

PBC 250 A 99.05 95.80 96.05 98.10 97.20 1.60 95.95 1.33

SLC 150 B 30.48 30.18 31.47 28.79 30.23 3.67 28.64 5.40

SLC 200 B 71.38 72.29 71.79 70.98 71.61 0.78 76.67 7.06

SLC 250 B 91.03 93.74 89.38 99.74 93.47 4.86 90.68 3.03

PBC 150 B 49.73 49.87 49.70 48.76 49.51 1.03 52.32 5.51

PBC 200 B 76.09 76.15 72.15 72.21 74.15 3.07 69.18 6.70

PBC 250 B 92.46 88.49 93.77 97.78 93.12 4.11 87.96 5.54

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