1 

Characteristics, Behavior, & Response Effectiveness of Spilled Dielectric 

Insulating Oil in the Marine Environment 

Solicitation Number: M08PS00094 

Award Number: M09PC0002 

For 

U.S. Department of the Interior 

Bureau of Ocean Energy Management, Regulation and Enforcement 

(BOEMRE) 

Herndon, VA

By 

Louisiana State University 

Department of Environmental Sciences 

1285 Energy, Coast, and Environment Building 

Baton Rouge, Louisiana 70803 

MAR Incorporated 

P.O. Box 473 

Atlantic Heights, NL 07716 

June 2011 
2 

Table of Contents 

ABSTRACT ................................................................................................................................................ 3 

INTRODUCTION ...................................................................................................................................... 4 

OBJECTIVE ............................................................................................................................................... 7 

STUDY APPROACH ................................................................................................................................. 7 

MATERIALS & METHODS ..................................................................................................................... 8 

Artificial Weathering of Dielectric Fluid ................................................................................................ 8 

SFT and BFT Experiments ...................................................................................................................... 8 

Materials .............................................................................................................................................. 9 

Methods ............................................................................................................................................. 10 

Bioremediation Study ............................................................................................................................ 12 

Materials ............................................................................................................................................ 13 

Methods ............................................................................................................................................. 14 

Ohmsett MIDEL 7131 Field Study ....................................................................................................... 17 

Oleophilic Skimmer Testing .............................................................................................................. 18 

Wave Tank Dispersant Effectiveness Testing ................................................................................... 18 

RESULTS AND DISCUSSION ............................................................................................................... 19 

CONCLUSION ......................................................................................................................................... 23 

LITERATURE CITED ............................................................................................................................. 24 

APPENDIX A-LABORATORY FLASK STUDIES ............................................................................... 25 

APPENDIX B- OHMSETT SKIMMER & WAVE TANK STUDIES .................................................... 32 
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ABSTRACT 

Offshore wind power is a rapidly emerging form of renewable energy generation that is now 

being proposed in the United States (US). America’s first offshore wind farm, the Cape Wind 

project, is scheduled to begin construction in 2010. The Cape Wind project, located on 

Horseshoe Shoal in Nantucket Sound, will consist of 130 wind turbine generators (WTG) 

connected to a centralized electrical service platform (ESP). The Cape Wind project has the 

potential to spill roughly 67,000 gallons of dielectric fluids and oils into the marine ecosystem. 

In August 2006 the Cape Winds Associates LLC released the finding from a model study 

designed to estimate the trajectories of mineral oil spills from an ESP and calculate probable 

estimates of area coverage and minimal transit time for the oil slick. The spill trajectory model 

predicted the coasts of Cape Cod and Martha’s Vineyard would be severely impacted, possibly 

affecting many federally protected birds, turtles, and marine mammals. As a result, Bureau of 

Ocean Energy Management, Regulation and Enforcement (BOEMRE) recommended a thorough 

study be conducted to determine the dispersibility and biodegradability of dielectric fluid 

(MIDEL 7131) in the marine environment. 

Laboratory dispersibility and biodegradation tests were conducted at Louisiana State University 

(LSU) in Baton Rouge, Louisana. Large-scale skimmer and dispersibility tests were performed 

at the Ohmsett wave tank facility in Leonardo, New Jersey. Dispersant effectiveness was 

evaluated using the Swirling Flask Test (SFT), Baffled Flask Test (BFT), and Warren Springs 

Laboratory Test (WSLT) at various temperatures (4oC and 22oC), dispersant types (Corexit 9500 

and 9527), and dispersant-to-oil ratios (DOR 1:10 and 1:20). At 4°C, the SFT did not achieve 

greater than 21.1% effectiveness. The BFT and WSLT were comparable in effectiveness, 

ranging from 35.3 to 45.8% dispersant effectiveness at 4°C. At 22°C, the SFT never achieved 

greater than 45.7% effectiveness. The BFT and WSLT were comparable in effectiveness, 

ranging from 71.8 to 84.7% dispersant effectiveness at 22°C. All dispersant tests results 

indicated there was slightly higher dispersant effectiveness when MIDEL 7131 was dispersed at 

DOR 1:20, compared to DOR 1:10. It can be observed in figure 3 that the overall MIDEL 7131 

biodegradation rate is higher for product + nutrient than nutrient alone. The seawater control 

treatments averaged a 9.47% decrease over the 28 day test period. The nutrient and nutrient + 

product treatments averaged 50.0% and 78.0% MIDEL 7131 concentration decreases, 
4 

respectively. The Ohmsett skimmer tests utilized rope mop, drum, and disc skimmer systems in 

determining the oil recovery rates (ORR) and recovery efficiency (RE) of two (2) reference oils 

(diesel and hydrocal) and MIDEL 7131 test fluid. The disc skimmer exhibited the highest ORR 

for MIDEL 7131 at 6.4 gpm. The rope and drum skimmer had an ORR of 1.7 and 5.0 gpm, 

respectively. Further evaluation of MIDEL 7131 using Ohmsett’s wave tank system to 

determine the effectiveness of Corexit 900 was conducted. This report describes experiments to 

study the effect of different variables such as DOR, temperature, and dispersant type on 

dispersant effectiveness of MIDEL 7131. 

INTRODUCTION 

The Cape Wind project, located on Horseshoe Shoal in Nantucket Sound, will consist of 130 

wind turbine generators (WTG) connected to a centralized electrical service platform (ESP). 

Electrical power from the individual wind turbine units will be routed through four (4) step-up 

transformers on the ESP to reduce loss of voltage in transmission. The ESP will contain 

approximately 40,000 gallons of dielectric insulating oil and approximately 2,000 gallons of 

assorted oil-based fluids (diesel fuel, lubricating oils, etc.) stored on site for facility maintenance. 

The Cape Wind project would contain an additional 25,000 gallons of dielectric insulating oil in 

the 130 wind turbines (190 gallons per turbine). Worst case scenario, the Cape Wind project has 

the potential to spill roughly 67,000 gallons of oils and fluid into the marine ecosystem. The 

dielectric insulating fluid used in the ESP and turbines is typically a mineral oil, but vegetablebased oils (soybean oil) may also be used. 

Several concerns have been raised by regulatory agency and environmental conservancy groups 

as to the environmental effects of a possible oil spill due to accidental vessel collision or natural 

catastrophe. The two (2) main concerns addressed were probability of oiling and the minimum 

transit time of the oil to areas and resources at risk. An oil spill trajectory analysis study funded 

by Cape Winds Associates LLC indicated a release from an ESP would severely impact the 

central and western area of the Cape Cod coast and the east and northeast coasts of Martha’s 

Vineyard 1

. The shortest transit times for each of the multiple oil spill scenarios ranged from 4.8 

to 11.3 hours. Nantucket Sound is home to many different species of wildlife, including 
5 

federally protected birds, turtles, and marine mammals. The Sound is also located in a 

geographical region known as the Atlantic Flyway, one of the largest migratory bird routes in the 

world. 

Numerous toxicological and biodegradation studies have been performed on mineral and 

vegetable-based oils over the last decade 2,3,4,5,6. The recent increase in fuel costs has sparked an 

interest in alternative fuel options, such as vegetable-based biodiesels. These biodiesels have oil 

properties and characteristics (e.g. specific gravity and toxicity) similar to the dielectric 

transformer oils used on ESPs. Mineral and vegetable-based oils display low direct toxicity 

because they do not contain the water–soluble and multi-ringed polynuclear aromatic 

hydrocarbons (PAH) typically found in petroleum-based oils. Due to their low toxicity and 

usage, little research has been performed on the response options available to cleanup a spill of 

dielectric fluids on the marine environment. New concerns of direct contact oiling of marine 

birds and mammals and persistence in the environment have risen with the proposed installation 

of wind turbines and ESPs off the northeastern and mid-Atlantic US coastlines. Model studies 

have showed significant adverse environmental and economic impacts to Nantucket Sound and 

surrounding areas, including impacts to wildlife and shellfish from a spill incident. 

Should this extremely unlikely spill event occur, what would the fluid be like that would leak out 

into the ocean? How would the dielectric insulating oil be removed from our oceans and 

shorelines? How persistent are these oils in the marine environment? The answers to these 

questions are unknown, but must be addressed prior to startup of the Cape Wind project. The 

residences of this region are still mindful of the fuel oil spill that occurred in 2003 near Buzzards 

Bay, MA. The single-hulled Bouchard No. 120 barge, bound for the oil-fired Mirant power plant 

in Sandwich, spilled approximately 98,000 gallons of No. 6 residual fuel oil after striking rocks 

near the entrance to Buzzards Bay. The toxic and persistent fuel oil impacted wildlife, shellfish 

beds and beaches in Buzzards Bay several years following the spill 7

. 

Due to its non-hazardous nature, little research has been performed on the fate and effect of 

spilled insulating fluids and mineral oils. LSU performed an online literature review and 

governmental database search for ESP, dielectric insulating fluids, and mineral oils. The results 

concluded there is little or no relevant research information concerning the weathering behavior, 
6 

and window of opportunity for using short-term response options for removal of spilled 

dielectric fluids in the marine environment. Research publications from the National Park 

Service and USEPA Environmental Fate & Effects Division have determined mineral oils not to 

be acutely toxic 8

. Toxicity data is available, but it is general and non-conclusive. 

In 2004, Cape Wind Associates LLC contracted with Applied Science Associates, Inc. (ASA) to 

perform an analysis to estimate the trajectories of oil spills and calculate probable estimates of 

area coverage and minimal travel time 1

. ASA developed a modeling tool, OILMAP, that was 

used to simulate these processes. In conjunction with another model, HYDROMAP, ASA was 

able to produce a model that allowed course grid resolution in the areas offshore the coasts of 

Massachusetts and Rhode Island and finer resolution in Nantucket Sound. A total of 100 

dielectric insulating oil spills were simulated with varying seasons and wind conditions. The 

simulations yielded the following area oiling results: 

• If a spill were to occur, there is >90% probability that oil will travel towards Cape Cod 

and Martha’s Vineyard; 

• The model results indicate the central and western area of the Cape Cod coast and the 

east/northeast coasts of Martha’s Vineyard are the most vulnerable; 

• The shortest times for each of the scenarios range from 4.8 to 11.3 hours. 

Rapid increases in fuel and production costs have forced US utilities to investigate many new 

alternative sources that were overlooked less than 10 years ago. Southeast New England and 

mid-Atlantic coastal zones have all the regional ingredients to become a global leader in offshore 

renewable power: strong offshore winds, a major project that is in the process of being permitted, 

multiple port facility access, a skilled workforce for labor and manufacturing, and a rich 

maritime tradition. Cape Wind’s model predictions have estimated the net energy production 

delivered to the regional power grid to be in the 1,600-1,800 GWh/year range. This annual 

electrical production rate is equal to power generated from 113 million tons per year heavy oil 

power plant or 570,000 tons per year coal power plant. Because its biological diversity is 

unique, protection of Nantucket Sound and future turbine powered coastal zones is important. 

The goals of this project were devised to provide a valuable source of information regarding the 
7 

installation and operation of wind-powered structures within the region. The information 

acquired from this study will help BOEMRE, USCG, and NOAA to safeguard our natural 

resources from possible spills involving dielectric insulating fluids and mineral oils along our 

nation’s coastlines. Results from this study will aide federal and state planning and management 

personnel when designing coastal use permits for future offshore wind generation systems. 

OBJECTIVE 

The objective of this research project was to provide a comprehensive study and analysis of the 

weathering behavior, dispersibility, and the window of opportunity for using short-term response 

options for removal of spilled dielectric fluid in the marine environment. The studies were 

conducted using MIDEL 7131(pentaerythriol fatty acis ester), a widely used dielectric fluid in 

European turbine power systems. The goals of the proposed project were achieved through a 

series of three (3) tasks: (1) a series of laboratory flask studies to determine weathering 

characteristic; (2) a laboratory flask study to measure the effects of long-term weathering and 

biodegradation on dielectric insulating fluid in the marine environment; (3) a series of field 

studies to accurately determine capabilities/limitations of conventional response tools for 

removal of dielectric fluids from the marine environment. In this study, biodegradation and 

bench top dispersibility studies were conducted at Louisiana State University’s (LSU) 

Department of Environmental Sciences (DES) Response and Chemical Assessment Team 

(RCAT) laboratory in Baton Rouge, Louisiana. Large-scale tank tests, using Corexit 9500, were 

conducted at the Ohmsett wave tank facility in Leonardo, New Jersey. 

STUDY APPROACH 

The inception of the Cape Wind Project has sparked much interest in the behavior and fate of 

dielectric insulating oil in the marine environment. In order to provide a comprehensive analysis 

of the possible fate and effects of spilled dielectric insulating oil, LSU and BOEMRE has 

conducted a collaborative one (1) year project to provide a detailed literature review and 

scientific information on the characteristics, weathering behavior, and window of opportunity for 

using short-term response options for removal of spilled dielectric fluids in the marine 

environment. The goals of this project were achieved through a series of laboratory and field-
8 

scale studies conducted at research facilities in Baton Rouge, Louisiana (LSU) and Leonardo, 

New Jersey (Ohmsett). The Ohmsett facilty is the only facility where full-scale oil spill response 

equipment testing, research, and training can be conducted in a marine environment with oil and 

fluids under controlled environmental conditions (waves, temperature, oil types). The facility 

provides an environmentally safe place to conduct objective testing and to develop devices and 

techniques for the control of oil and hazardous material spills. The facility is maintained and 

operated by the Bureau of Ocean Management, Regulation and Enforcement (BOEMRE) 

through a contract with MAR, Incorporated of Rockville, Maryland. The flask and 

bioremediation studies were conducted at LSU facilities, while the oleophilic skimmer tests and 

dispersant studies were carried out at the Ohmsett research facility. 

MATERIALS & METHODS 

Artificial Weathering of Dielectric Fluid 

MIDEL 7131 was artificially weathered in order to simulate evaporative losses typically 

encountered following a spill at sea. Typically, dispersants are applied to the oil during the 6-12 

hour window of opportunity following the initial spill. Approximately 500-ml of dielectric fluid 

was placed in a preweighed 1000-ml Pyrex beaker in a fume hood with a controlled air flow 

system and allowed to evaporate. The weight of the fluid and beaker were recorded at the start 

of the experiment. Triplicate density measurements were determined by weighing known 

volumes of fluid at the beginning and end of the experiment. Average initial density results were 

compared to published literature (M&I Material Ltd). Temperature (20-22°C) and air flow (~ 

0.8 m/sec) within the fume hood was monitored and recorded during the experiment. The 

artificial weathering process was concluded after 96 hours. This “weathered” dielectric fluid was 

used as the starting material for all the experiments. The weathered fluid was stored in multiple 

glass bottles in a secured refrigerator (4°C) prior to use. 

SFT and BFT Experiments 

A series of bench-scale laboratory studies were performed to determine the dispersibility of 

dielectric fluid in the marine environment. Past research has determined the swirling flask 

dispersant effectiveness test (SFT), baffled flask dispersant effectiveness test (BFT), and Warren 
9 

Springs Laboratory test (WSLT) to be the most effective tests for determining product 

dispersibility. Table 1 gives an overview of the sample treatments and analytical determinations 

performed during the laboratory flask dispersibility studies. 

Table 1. Dispersant Study Sampling and Analysis Matrix 

Treatment 

No. of samples at sampling 

temperature 

Total No. of analytical determinations

40°F 72°F GC/MS Gravimetric 

Control 4 4 8 8 

Corexit 9500 

DOR=10 4 4 8 8 

DOR=20 4 4 8 8 

Corexit 9527 

DOR=10 4 4 8 8 

DOR=20 4 4 8 8 

Salinity = 30-32 PPT 

DOR = Dispersant to oil ratio 

Materials 

Two differently designed flasks were utilized for the SFT and BFT experiments. Modified 150-

ml glass Erlenmyer flasks with open top were used in all swirling flask tests. A side spout was 

added to the swirling flasks to enable sampling of the water without disturbance of resurfacing 

oil. The baffled flask tests used modified 150-ml baffled trypsinizing flasks with screw caps at 

the top and a glass stopcock near the bottom of the flasks. An orbital shaker (Lab-Line 

Instruments Inc, Melrose Park, IL) with variable speed controls (40-400rpm) and an orbital 

motion of 1 in. was used to provide agitation in the test flasks. A Brinkmann Eppindorf repeater 

pipetor (Fischer Scientific, Pittsburg, PA) capable of accurately dispensing 5 μl of dispersant and 

100 μl of oil was used with the flask studies. Glassware used in the tests consisted of a 250-ml 

graduated cylinder, 125-ml separatory funnel with Teflon stopcock, Pasteur pipettes, and 50-

1000 μl gas tight syringes. Natural sea water was collected from Grand Isle, Louisiana 
10 

(salinity=33 ppt) and used in all SFT and BFT. A dielectric fluid sample, MIDEL 7131 (M&I 

Material Ltd), was provided by BOEMRE. The physical and chemical properties for MIDEL 

7131 are shown in Table 2. 

A 250-ml separatory funnel was used to determine the efficacy of the dispersant in the Warren 

Spring Laboratory Test. A Burrell Wrist Action Shaker, model 75 (Burrell Scientific, 

Pittsburgh, PA) was used to agitate MIDEL 7131 and water mixture during testing. Additional 

glassware used in the Warren Spring Laboratory tests consisted of a 250-ml graduated cylinder, 

100-ml separatory funnel with Teflon stopcock, Pasteur pipettes, 5-ml glass syringe, and 50-

1000 μl gas tight syringes. Natural sea water was collected from Grand Isle, Louisiana 

(salinity=33 ppt). 

Table 2.MIDEL 7131 Properties 

Physical State: Organic liquid

Odor: Faintly sweet

Melting Point/Freezing Point: -57°C

Boiling Point: >300°C

Flash Point (Closed Cup): 260°C

Flammability: Non flammable

Vapour Pressure at 20°C: <0.01 Pa

Relative Density at 20°C: 970 Kg/m3

Water Solubility: <1 mg/L

Partition Coefficient, log Kow : >6.74

Auto-ignition Temperature: No auto-ignition expected

Viscosity at 40°C: 28 mm2/sec

Methods 

SFT and BFT Dispersant Effectiveness Tests: 

The weathered MIDEL 7131 and dispersant solutions were premixed at a volumetric ratio of 

1:10 and 1:20 (SFT and BFT tests) in a 40-ml amber vial and mixed vigorously prior to each 

tests. A 100 μl volume of MIDEL 7131 or MIDEL 7131 -dispersant mixture was dispensed 

using Eppendorf repeating pipette onto the surface of 120-ml natural seawater in either the side 

spout flasks (SFT) or baffled trypsinizing flasks (BFT). For each sample, four (4) replicates 
11 

were prepared. The flasks were then placed on the orbital shaker and mixed for 20 minutes at a 

rotational speed of 200 rpm. After 20 minutes, the orbital was turned off and the flasks were 

place on the laboratory bench and allowed to remain stationary for an additional 10 minutes. 

Following the equilibration time period, approximately 2-3 ml of water sample was drained from 

the individual side spout or stopcock flasks and discarded. A 30-ml volume of water sample was 

then drained from the flasks into a 50-ml volumetric cylinder. The 30-ml water sample was then 

transferred to a 125-ml separatory funnel and extracted three (3) times with 5-ml hexane aliquots 

and drained through a sodium sulfate funnel (H2O removal) into a 40-ml amber vial. The extract 

was then adjusted to a final volume of 25-ml and stored in a 4°C refrigerator until the time of 

analysis. Natural seawater blanks were prepared with each batch of SFT or BFT treatment 

samples tested. The preparation and extraction of the seawater blanks followed the same 

experimental protocol as the SFT and BFT treatments, but lacked addition of MIDEL 7131 or 

dispersant. The seawater blanks were used to correct for potential error from existing 

contaminates in the seawater sample before reagents are added. All experimental treatments 

were conducted in a temperature controlled room at the desired temperature (40 and 70°F ± 1°F). 

For each sample, four (4) replicates were prepared. Gravimetric analysis was not performed on 

the SFT and BFT due to small volume of MIDEL 7131 spiked. 

Warren Spring Laboratory Effectiveness Tests: 

The experimental treatments were conducted in a temperature controlled room at the desired 

temperature (40 and 70°F ± 1°F). For each sample, four (4) replicates were prepared. The 

unstoppered separatory funnel was placed on the wrist action shaker and clamped securely. 

Approximately 250-ml of natural seawater was added to the separatory funnel. Using the 5-ml 

glass syringe, a 5.0 ml aliquot of MIDEL 7131 was added to the surface of the natural seawater. 

After one (1) minute, a specific amount of dispersant (DOR= 1:10 or 1:20) was evenly 

distributed to the surface of the separatory funnel. The control treatments were spiked with 

MIDEL 7131 only. The stopper was securely fastened to the separatory funnel and the entire 

apparatus was allowed to stand for 2.5 minutes. The separatory funnels were then mechanically 

shaken for approximately 2 minutes and allowed to stand for 1 minute. The stopcock was 

opened and 50 ml of water was drained into a graduated cylinder. The 50-ml water sample was 

then transferred to a 125-ml separatory funnel and extracted three (3) times with 20 ml hexane 
12 

aliquots and drained through a sodium sulfate funnel into a 100-ml volumetric flask. The 

graduated cylinder was rinsed with 20 ml of hexane and rinsate was passed through the sodium 

sulfate funnel into the flask. The sodium sulfate funnel was thoroughly washed with hexane and 

then the volumetric flask was filled to the mark with hexane. The flask was then stoppered and 

shaken well. The preparation and extraction of the seawater blanks followed the same 

experimental protocol as the MIDEL 7131 -dispersant treatments, but lacked addition of MIDEL 

7131 or dispersant. 

Gravimetric Analysis: 

Gravimetric analysis is the initial method to evaluate the effectiveness of an oil or 

bioremediation agent for oil spill response. The disappearance of oil and significant decreases in 

total oil residue weight versus a control is a strong indicator of materials biodegradability. 

Gravimetric analysis was performed by taking 15 ml from the final extract and placing in a preweighed 40-ml glass vial. The vial was placed beneath a purified nitrogen stream and allowed to 

evaporate to dryness. The residual weight of the MIDEL 7131 was measured three (3) times and 

recorded. 

Bioremediation Study 

This bioremediation effectiveness testing protocol (CFR, 1999) was designed to determine oils 

ability to naturally biodegrade by quantifying changes in the oil composition resulting from 

biodegradation. The protocol determines changes in the materials composition through the use 

of GC/MS, gravimetric and microbial enumeration determination. The sample preparation 

procedure extracts the oils into hexane and the analytical method uses a high resolution GC/MS 

and gravimetric analysis to determine the overall biodegradability of the test oil. Microbial 

enumerations are performed at each sampling period using a microtiter Most Probable Number 

(MPN) determination. The bioremediation protocol consists of an experimental shaker flask 

setup with a specific set of microbiological and chemical analyses that are performed on 

individual oil or product samples. Treatments typically include a control, nutrient, and product 

samples. An EPA National Contingency Plan (NCP) approved product, Oil Spill Eater II (Oil 

Spill Eater International, Corp.), was include in the experimental design. Bioremediation testing 
13 

on Oil Spill Eater II (OSE II) has proven it to be effective at degrading highly-saturated crude 

oils in the laboratory. The following test flasks (labeled with unique identifiers) were prepared 

and set up on an orbital shaker at day 0 to reflect the following treatment: 

Table 3. Bioremediation Study Sampling and Analysis Matrix 

Treatment 

No. of samples at sampling times Total No. of analytical determinations 

Day 0 Day 7 Day 28 Microbial 

Counts 

GC/MS Gravimetric 

Control 3 3 3 9 9 9 

Nutrient 3 3 3 9 9 9 

Product* 3 3 3 9 9 9 

Control = Oil + Seawater 

Nutrient = Oil + Seawater + Nutrients 

Product = Oil + Seawater + Nutrients + Product 

*A NCP approved product, OSE II 

A detailed description of the test procedure can be found in the Code of Federal Register Title 

40, Chapter 1 Part 300. 

Materials 

The bioremediation studies used 250-ml Erlenmeyer flasks to determine MIDEL 7131’s ability 

to degrade in the marine environment. An orbital shaker (Lab-Line Instruments Inc, Melrose 

Park, IL) with variable speed controls (40-400rpm) and an orbital motion of 1 in. was used to 

provide agitation in the test flasks. A Mettler model PM600 balance (Mettler-Toledo, Inc., 

Columbus, OH) was used to determine mass of material accurate to 0.01 mg. A Brinkmann 

Eppindorf repeater pipetor (Fischer Scientific, Pittsburg, PA) capable of accurately dispense 

material during the preparation of culture media and nutrient solutions. Glassware used in the 

tests consisted of a 250-ml graduated cylinder, 125-ml separatory funnel with Teflon stopcock, 

Pasteur pipettes, and 50-1000 ul gas tight syringes. Natural sea water was collected from Grand 

Isle, Louisiana (salinity=33 ppt) and used in all SFT and BFT. A dielectric fluid sample, MIDEL 

7131 (M&I Material Ltd), was provided by BOEMRE. The MIDEL 7131 used during the 

bioremediation study was prepared as described in the Artificial Weathering of Dielectric Fluid 

section of this report. 
14 

An Agilent Technologies-7890A gas chromatograph (GC) interfaced to an Agilent Technologies 

5975 Inert XL mass selective detector (MSD) operated in electron ionization mode (70eV) with 

helium as a carrier gas was used determine MIDEL 7131 concentrations in analytical standards 

and samples. An Agilent Technologies 7683B series injector was used to inject the standard and 

samples extracts. The MSD scanned the mass range (50-550 amu) every 3 seconds. The GC 

oven contained a HP-5MS (30 m, 0.25 mm i.d., 0.25 μm film thickness) and was programmed to 

ramp in temperature from 60°C (1.5 min.) to 280°C at 20°C min-1, and then at 4°C min-1 to 300° 

(52.5 min.). 

 

Methods 

Nutrient and Bioremediation Agent Preparation: 

A mineral nutrient solution was added to designated treatments to prevent nutrient-limitation 

within treatments. The initial stock salt and mineral solutions were prepared, pH adjusted, and 

autoclaved as specified in EPA 40 CFR Pt. 300, App. C. The final concentrate solution was 

prepared by adding designated volume of solutions to non-sterile natural seawater and made up 

to a 1000-ml volume immediately prior to testing. The bioremediation agent, OSE II, was 

prepared as specified on the package labeling. 

Bioremediation Study Setup: 

The test flasks were prepared and set up on a gyratory shaker at day 0 according to the 

experimental design displayed in table 4. Approximately 100 ml of natural seawater was poured 

into the individual flasks, followed by the addition of 0.5 g (515 μl) MIDEL 7131. Care was 

taken to minimize splashing oil on sides of glassware and preventing microbial contamination. 

The flasks were shaken at 200 rpm at 20oC until removed for sampling at the designated time. 

The control and treatment (nutrient and product flasks) were sampled three (3) times over a 28-

day period. The entire flask was sacrificed for analysis; a 0.5-ml aliquot was removed from each 

flask for the microbiological analysis and the remainder of each flask was used for the chemical 

analysis. 
15 

The viability of the hydrocarbon degrading microbial cultures was determined at each sampling 

time using a microtitter MPN determination. This is used as an indicator of the relative change 

of the biomass. The test method relies on monitoring growth response as an indication of 

healthy or enhanced microbial activity as compared to the control treatment. After 0, 7, and 28 

days of incubating on the rotary shaker, a 0.5-ml aliquot was removed from each flask for the 

microbial analysis. Detailed information relating to the preparation of media and microbial 

enumeration is located in 40 CFR Ch. I, PT. 300, App. C. 

After 0, 7, and 28 days of incubating and rotating on the orbital shaker, the appropriate flasks 

were sacrificed for chemical analysis. Following removal of microbial sample, the entire 

contents of the flasks were transferred to a 250-ml separatory funnel. The treatment flask was 

thoroughly rinsed with a 50-ml aliquot of DCM and rinsate poured into the appropriate 

separatory funnel. A 100-μl aliquot of surrogate standard (2,000 μg/ml d10-phenanthrene and 

5α-androstane solution) was added to each flask. The 250-ml separatory funnel was capped and 

gently shaken for approximately three (3) minutes and placed on a ring stand. The water/solvent 

mixture was allowed to stand for 15 minutes or until the water/solvent phase separated. The first 

10 ml of DCM extract was drained into a 20-ml vial and retained for gravimetric analysis. The 

remaining DCM extracted was drained through a sodium sulfate drying funnel into a 250-ml flat 

bottom flask. The flask containing the DCM extract was placed on a Rotovapor R-114 

concentrator unit (Buchi Corporation, New Castle, DE) and concentrated to a volume of 

approximately 10 ml. The DCM extract was exchanged to hexane with the addition of 

approximately 30 ml of pesticide grade hexane. The hexane exchanged extract was concentrated 

to a volume of approximately 5 ml and removed from the Rotovapor unit. The hexane extract 

was transferred to a 15-ml micro-extraction thimble. The flat bottomed flask was rinsed with 

approximately 10 ml hexane and rinsate transferred to the micro-extraction thimble. A 3-ball 

micro Snyder column was attached to the thimble and the apparatus was placed in a hot water 

bath. The hexane extract was concentrated to a volume less than 0.5 ml and immediately 

removed from the water bath. The extract was drawn into a Pasteur pipette and rinsed along 

sides of extraction thimble. The final volume was adjusted to 1.0 ml and extract was transferred 

to a 2.0-ml autosampler vial. A 10-μl aliquot of internal standard (1000 μg/ml d8-naphthalene, 
16 

d10-acenaphthene, d12-chrysene, and d12-perylene solution) was spiked into extract and vial 

was immediately capped and stored in 4oC refrigerator until analysis. 

The gravimetric analysis was performed by taking a 10-ml aliquot removed prior to the final 

GC/MS extraction procedure and placing in a 20-ml pre-weighed vial. The vial was placed 

beneath a steady stream of purified nitrogen and extract was concentrated to dryness. The 

residue was weighed three (3) times and weight was recorded in log book. Results from the 

gravimetric analyses of the MIDEL 7131 with bioremediation agent, MIDEL 7131 with nutrient, 

and MIDEL 7131 control were statistically compared at respective times to determine if 

advisable to continue GC/MS analyses. 

MIDEL 7131 Standard Calibration Preparation: 

The dielectric fluid calibration standards used during this study (dispersibility and 

bioremediation tests) were prepared according to the methodology used in previously published 

methods (U.S. EPA, 1996). For all GC/MS analysis, standard solutions of dielectric fluid were 

prepared with MIDEL 7131 neat sample. A dielectric fluid with dispersant calibration standard 

was not prepared due to the GC/MS system’s ability to separate and differentiate the DIF and 

dispersant components. A stock solution of MIDEL 7131 stock solution was prepared by adding 

2.5-ml of weathered dielectric fluid into a 25-ml class A volumetric flask and filling to volume 

with pesticide grade dichloromethane (Mallinckrodt, St. Louis, MO). Specific volumes of 260, 

130, 52, 26, 13, and 3.0 μl of weathered MIDEL 7131 stock solution were added to 30-ml of 

natural seawater in a separatory funnel and extracted three (3) times with 5-ml of 

dichloromethane (DCM) and passed through a sodium sulfate funnel to remove water. The 

combined final extract volume was adjusted to 50-ml and transferred to two (2) amber 40-ml 

glass vials for storage in a 4°C refrigerator. The dielectric fluid standard solution and MIDEL 

7131 plus dispersant standard solution final concentrations are displayed in Table 4. 
17 

Table 4. MIDEL 7131 Standard Solutions* 

Volume of stock 

solution added to 

seawater (μl) 

Total amount of 

MIDEL 7131 in 

standard (mg) 

Final extract 

volume (ml) 

Final MIDEL 7131 

concentration 

(μg/ml) 

260 25 50 500 

130 12.5 50 250 

52 5 50 100 

26 2.5 50 50 

13 1.25 50 25 

3 0.31 50 5 

* Assuming an oil density of 0.97 g/ml and an extraction efficiency of 100% for MIDEL 7131 

from the natural seawater. 

Sample Analysis: 

The GC/MS system was calibrated and operated using a modified EPA method 8270. A fivepoint MIDEL 7131 calibration standard curve was prepared by analyzing 5, 25, 50, 100, 250, and 

500 μg ml-1 concentration levels on the GC/MS system. At the beginning of each analysis 

period, the MS system was tuned using PFTBA to verify the system’s stability and sensitivity. 

Once the initial calibration was established, a daily calibration standard (250 μg/ml) was 

analyzed prior to analyzing instrument blanks and unknown treatment extracts. All standard, 

blank, and sample treatment extracts were injected using a volume of 1 ul with injector in 

splitless mode. If required, samples extracts were diluted with hexane so extract concentrations 

were within the GC/MS calibration range. 

Ohmsett MIDEL 7131 Field Study 

The MIDEL 7131 field study consisted of a week-long series of tests at Ohmsett, the National 

Oil Spill Response Research and Renewable Energy Test Facility, located in Leonardo, New 

Jersey. The primary goal of the study was to determine the dispersibility of DIF using 

COREXIT® 9500 and determine the capabilities and limitations of common response tools, 

namely oleophilic skimmers. Full-scale dispersant testing was conducted in Ohmsett’s main test 
18 

tank and mechanical recovery testing was performed on the deck of the main tank using three (3) 

types of oleophilic skimmers: a drumskimmer, a disc skimmer, and a rope-mop skimmer. 

Oleophilic Skimmer Testing 

The mechanical recovery testing followed the test protocol outlined in the American Society for 

Testing and Materials (ASTM) F 2709-08 – Standard Test Method for Determining Nameplate 

Recovery Rate of Stationary Oil Skimmer Systems. The MIDEL 7131 DIF used during the 

oleophilic testing was dyed red to increase visibility while making measurements. In addition to 

MIDEl 7131, two (2) comparison oils (Hydrocal lube oil and diesel) were tested during the 

mechanical recovery portion of the test. The objective of the mechanical recovery testing was to 

quantify the Oil Recovery Rate (ORR) and Recovery Efficiency (RE) for each of the three (3) 

test oils using each of the drum skimmers. A detailed description of the mechanical recovery 

tests can be found in Appendix A of this report. 

Wave Tank Dispersant Effectiveness Testing 

The second phase of the Ohmsett field study was a full-scale dispersant study, conducted in the 

main test tank. Effectiveness of the dispersant tests was determined by physically measuring 

floating DIF on the water surface. In addition to physical measurements, a LISST 100 particle 

size analyzer was utilized to confirm the presence of DIF in the water column and to characterize 

the oil drop distribution. Prior to the dispersant tests, a control run was performed without the 

application of COREXIT® 9500 to the slick. Natural dispersion was observed and the DIF that 

remained on the surface of the wave tank after 30 minutes was corralled, collected, dewatered, 

and quantified. During the two (2) dispersant tests, COREXIT® 9500 dispersant was applied to 

the DIF slick at a dispersant-to-oil ratio (DOR) of 1:20. Following application of dispersant to 

entire DIF slick, the main bridge of wave tank was brought to a stop, then run back in the 

direction of the slick so the LISST 100 could record oil droplet size and in-water oil 

concentration. A detailed description of the wave tank and dispersant tests can be found in 

Appendix B of this report. 
19 

RESULTS AND DISCUSSION 

Figures 1 and 2 show the GC/MS results obtained for the SFT, BFT, and SWLT tests at 4° and 

22°C. It can be seen that dispersant effectiveness was significantly lower for both Corexit 9500 

and Corexit 9527 at the lower test temperature. The average dispersion of MIDEL 7131 controls 

ranged from 0.054 to 3.00 % for all tests. Corexit 9500 exhibited a higher average dispersant 

effectiveness over Corexit 9527 for all flask tests. At 4°C, the SFT did not achieve greater than 

21.1% effectiveness. The BFT and WSLT were comparable in effectiveness, ranging from 35.3 

to 45.8% dispersant effectiveness at 4°C. At 22°C, the SFT never achieved greater than 45.7% 

effectiveness. Once again, the BFT and WSLT were comparable in effectiveness, ranging from 

71.8 to 84.7% dispersant effectiveness at 22°C. Due to the large amounts of MIDEL 7131 used 

for testing, gravimetric analyses were performed on the WSLT. The WSLT gravimetric results 

(Tables A7-A8) were comparable to GC/MS results at both temperatures. All tests results 

indicated there was slightly higher dispersant effectiveness when MIDEL 7131 was dispersed at 

DOR 1:20, compared to DOR 1:10. Tabular results from the dispersant effectiveness tests can 

be viewed in Appendix A, tables A1-A8. 

It can be observed in figure 3 that the overall MIDEL 7131 biodegradation rate is higher for 

product + nutrient than nutrient alone. The seawater control treatments averaged a 9.47% 

decrease over the 28 day test period. The nutrient and nutrient + product treatments averaged 

50.0% and 78.0% MIDEL 7131 concentration decreases, respectively. In general, it was 

observed that the numbers of oil degrading bacteria increased with time in the MIDEL 7131 

contaminated treatments. The increase in bacteria populations was more pronounced in both the 

nutrient and nutrient + product treatments. Figure 4 shows the increase in bacteria numbers for 

the three (3) different tests treatments (control, nutrient, nutrient + product). The curves within 

figure 4 are representative of the growth phases (exponential, stationary, and death) observed in 

bacteria growth kinetic studies. The bioremediation study results for MIDEL 7131 were slightly 

lower than those advertised by the manufacturer (89% at 28 days). The increase in 

manufacturer’s biodegradation results was due to use of enriched microbial inoculum during 

testing. Tabular results from the bioremediation tests can be viewed in Appendix A, tables A9-

A13. 
20 

Figure 1. Avg. Dispersant Effectiveness for SFT, BFT, and SWLT Tests at 4oC (GC/MS)

Figure 2. Avg. Dispersant Effectiveness for SFT, BFT, and SWLT Tests at 22oC (GC/MS) 

0

10

20

30

40

50

60

70

80

90

100

Control 9500 (DOR 1:10) 9500 (DOR 1:20) 9527 (DOR 1:10) 9527 (DOR 1:20)

Effectiveness (%)

Dispersant

SFT BFT SWLT

0

10

20

30

40

50

60

70

80

90

100

Control 9500 (DOR 1:10) 9500 (DOR 1:20) 9527 (DOR 1:10) 9527 (DOR 1:20)

Effectiveness (%)

Dispersant

SFT BFT SWLT
21 

Figure 3. Average MIDEL 7131 Concentration for Bioremediation Tests (GC/MS) 

Figure 4. Average Bacterial Count for Bioremediation Tests (MPN) 

0

1000

2000

3000

4000

5000

6000

Day 0 Day 7 Day 28

Conc. (ppm)

Control Nutrient Product

0.E+00

1.E+05

2.E+05

3.E+05

4.E+05

5.E+05

6.E+05

7.E+05

8.E+05

9.E+05

1.E+06

Day 0 Day 7 Day 28

Bacteria (cells/ml)

Control Nutrient Product
22 

Tables 5 and 6 show the results obtained for the Ohmsett field tests. The skimmer tests were 

performed in a steel-framed fabric tank on the deck of Ohmsett’s main test tank as per the ASTM 

F 2709-08 test protocol. The skimmer tests (see table 5) employed two (2) reference oils (diesel 

and hydrocal) that bracketed the lower and upper viscosity range of the test oil. The disc 

skimmer exhibited the highest ORR for MIDEL 7131 at 6.4 gpm. The rope and drum skimmer 

had an ORR of 1.7 and 5.0 gpm, respectively. Results from the Ohmsett dispersant efficiency 

tests are shown in table 6. The control run indicated that MIDEL 7131 has a natural dispersant 

rate of approximately 25%. MIDEL 7131 dispersant run #1 and #2 had a dispersant efficiency 

rating of 100 and 99%, respectively. A complete summary of the Ohmsett field study is located 

in Appendix B. 

Table 5. Oil Recovery Rate (ORR) for Ohmsett Skimmer Tests 

   ORR (gpm)

Skimmer Diesel Midel 7131 Hydrocal

Rope Mop 0.5 1.7 2.6

Drum 0.7 5.0 10.2

Disc 1.0 6.4 8.3

Table 6. MIDEL 7131 Dispersant Efficiency Rate for Ohmsett Wave Tank Tests 

Treatment Released (gallons) Recovered (gallons) Dispersant Efficiency

Rate (%)

Control 23.5 17.5 25

Run #1 25.0 0.00 100

Run #2 25.5 0.25 99
23 

CONCLUSION 

The SFT gave very poor results with dispersant effectiveness less than 21% and 46% at a 

temperature of 4° and 22°C, respectively. For the BFT and WSLT, the dispersant effectiveness 

achieved was significantly higher for MIDEL 7131. The increase in DOR also resulted in a 

considerably increase in dispersant effectiveness. The bioremediation study results indicated that 

MIDEL 7131 is highly biodegradable and addition of microbial inoculum significantly enhances 

the fluid’s biodegradation kinetics. The Ohmsett field study showed that MIDEL 7131 could be 

effectively removed from the water’s surface using a disc skimmer recovery system. The wave 

tank study reinforced the results from the flask dispersant effectiveness studies, concluding that 

MIDEL 7131 is nearly 100% dispersible in the marine environment at the tested conditions. 

However, further evaluation of MIDEL 7131’s bioremediation kinetics and breakdown products 

need to be conducted. Additional research is required for the detection of spilled dielectric fluids 

in the marine environment. Due to lack of color and fluorescence, detection and monitoring of 

MIDEL 7131 would be difficult under normal sea conditions. 
24 

LITERATURE CITED 

1 Kelly K, Swanson C, Isaji T, Whittier N, Subbayya S. 2006. Simulation of oil spills from the 

Cape Wind energy project electric service platform in Nantucket Sound. Applied Science 

Associates, Inc. Report # 05-128. 

2 Caroline MB, Jayaula FK, Doran PT, Priscu JC, Welch KA. 2009. Composition and 

biodegradation of a synthetic oil spilled on the perennial ice cover of Lake Fryxell, Antartica. 

Environ. Sci. Technol. 43: 2708-2713. 

3 Al-darbi MM, Saeed NO, Islam MR. 2005. Biodegradation of natural oils in seawater. Energy 

Services 27: 19-34. 

4 Aluyor EO, Obahiagbon KO, Ori-jesu M. 2009. Biodegradation of vegetable oils: a review. 

Sci. Res. Essay 4: 543-548. 

5 Amund OO. 1996. Utilization and degradation of an ester-based synthetic lubricant by 

Acinetobacter lwoffi. Biodegradation 7: 91-95. 

6 Eisentraegar A, Schmidt M, Murrenhoff H, Dott W, Hahn S. 2002. Biodegradability testing of 

synthetic ester lubricants-effects of additives and usage. Chemosphere 48: 89-96. 

7 Reddy CM. 2004. Oil in our coastal back yard. Oceanus 43: 30-35. 

8 Irwin RJ, VanMouwerik M, Stevens L, Seese MD, Basham W. 1997. Environmental 

contaminants encyclopedia. National Parks Service, Water Resources Division, Fort Collins, 

Colorado. 
25 

APPENDIX A 

LABORATORY FLASK STUDY 
26 

Table A1. SFT - Dispersant Effectiveness Test at 4°C (GC/MS) 

Dispersant DOR

% Effectiveness of the replicate samples   Average %

Effectiveness

Coeff. Of

R1 R2 R3 R4 Variation

Control  ‐  0.048 0.053 0.055 0.061 0.054 9.91

Corexit®9500 1:10 20.3 22.6 22.1 19.1 21.0 7.70

Corexit®9500 1:20 18.9 19.7 23.9 21.8 21.1 10.7

Corexit®9527 1:10 16.2 15.3 17.2 14.5 15.8 7.36

Corexit®9527 1:20 14.3 13.6 16.4 14.9 14.8 8.05

Table A2. SFT - Dispersant Effectiveness Test at 22°C (GC/MS) 

Dispersant DOR

% Effectiveness of the replicate samples   Average %

Effectiveness

Coeff. of

R1 R2 R3 R4 Variation

Control  ‐  0.066 0.073 0.081 0.074 0.074 8.35

Corexit®9500 1:10 48.1 49.6 39.7 45.2 45.7 9.57

Corexit®9500 1:20 43.1 48.2 40.3 49.3 45.2 9.40

Corexit®9527 1:10 36.2 31.1 32.6 33.8 33.4 6.45

Corexit®9527 1:20 35.7 35.1 30.8 34.1 33.9 6.44

Table A3. BFT - Dispersant Effectiveness Test at 4°C (GC/MS) 

Dispersant DOR

% Effectiveness of the replicate samples   Average %

Effectiveness

Coeff. Of

R1 R2 R3 R4 Variation

Control  ‐  1.12 1.24 1.16 0.951 1.12 10.9

Corexit®9500 1:10 40.1 38.3 35.1 36.4 37.5 5.84

Corexit®9500 1:20 39.4 41.5 38.7 42.5 40.5 4.38

Corexit®9527 1:10 35.5 34.3 39.6 37.1 36.6 6.26

Corexit®9527 1:20 38.0 31.4 36.3 39.5 36.3 9.69
27 

Table A4. BFT - Dispersant Effectiveness Test at 22°C (GC/MS) 

Dispersant DOR

% Effectiveness of the replicate samples   Average %

Effectiveness

Coeff. of

R1 R2 R3 R4 Variation

Control  ‐  2.98 2.84 3.41 2.75 3.00 9.76

Corexit®9500 1:10 80.1 83.5 89.2 84.1 84.2 4.46

Corexit®9500 1:20 83.1 86.4 89.1 80.2 84.7 4.58

Corexit®9527 1:10 70.2 75.6 69.4 80.5 73.9 7.00

Corexit®9527 1:20 72.8 71.6 76.7 70.1 72.8 3.88

Table A5. WSLT - Dispersant Effectiveness Test at 4°C (GC/MS) 

Dispersant DOR

% Effectiveness of the replicate samples   Average %

Effectiveness

Coeff. of

R1 R2 R3 R4 Variation

Control  ‐  0.895 1.13 1.20 0.973 1.05 13.3

Corexit®9500 1:10 41.2 40.5 39.2 35.4 39.1 6.62

Corexit®9500 1:20 46.3 45.5 47.0 44.4 45.8 2.44

Corexit®9527 1:10 38.5 35.1 33.3 34.2 35.3 6.44

Corexit®9527 1:20 38.1 38.5 31.2 33.4 35.3 10.1

Table A6. WSLT - Dispersant Effectiveness Test at 22°C (GC/MS) 

Dispersant DOR

% Effectiveness of the replicate samples   Average %

Effectiveness

Coeff. of

R1 R2 R3 R4 Variation

Control  ‐  0.067 0.058 0.070 0.072 0.067 9.27

Corexit®9500 1:10 78.2 76.2 80.1 70.1 76.2 5.69

Corexit®9500 1:20 81.2 75.6 85.4 83.1 81.3 5.15

Corexit®9527 1:10 69.5 72.1 75.2 70.2 71.8 3.55

Corexit®9527 1:20 70.4 75.5 77.2 70.9 73.5 4.58
28 

Table A7. WSLT - Dispersant Effectiveness Test at 4°C (Gravimetric) 

Dispersant DOR

% Effectiveness of the replicate samples   Average %

Effectiveness

Coeff. Of

R1 R2 R3 R4 Variation

Control  ‐  1.44 1.59 1.48 1.86 1.59 11.9

Corexit®9500 1:10 43.5 49.1 43.1 38.5 43.6 9.97

Corexit®9500 1:20 36.9 47.3 50.1 46.7 45.3 12.7

Corexit®9527 1:10 46.8 36.9 35.4 37.1 39.1 13.4

Corexit®9527 1:20 40.5 41.1 34.5 36.4 38.1 8.38

Table A8. WSLT - Dispersant Effectiveness Test at 22°C (Gravimetric) 

Dispersant DOR

% Effectiveness of the replicate samples   Average %

Effectiveness

Coeff. Of

R1 R2 R3 R4 Variation

Control  ‐  2.64 2.78 2.43 3.33 2.80 13.8

Corexit®9500 1:10 90.1 77.9 81.4 65.2 78.7 13.1

Corexit®9500 1:20 84.2 80.4 88.9 84.7 84.6 4.11

Corexit®9527 1:10 83.4 73.8 67.8 74.6 74.9 8.58

Corexit®9527 1:20 85.1 78.2 80.2 71.9 78.9 6.93
29 

Table A9. Bioremediation Study Average DIF concentration 

Treatment Day 0 Day 7 Day 28

Conc. (ppm) % Loss Conc. (ppm) % Loss Conc. (ppm) % Loss

Control 4941 – 4837 2.12 4473 9.47

Nutrient 4966 – 3749 24.5 2497 50.0

Product   4957 – 3068 38.1 1090 78.0

Table A10. Bioremediation Study Analytical Results (GC/MS) 

Day 0

Treatment Concentration (ppm) Std.

Deviation

Coeff. of

R1 R2 R3 Average Variation

Control 4914 4978 4932 4941 33.0 0.67

Nutrient 4978 4936 4985 4966 26.5 0.53

Product   4975 4925 4971 4957 27.8 0.56

Day 7

Treatment Concentration (ppm) Std.

Deviation

Coeff. of

R1 R2 R3 Average Variation

Control 4735 4880 4895 4837 88.4 1.83

Nutrient 3655 3849 3742 3749 97.2 2.59

Product   2910 3238 3056 3068 164.3 5.36

Day 28

Treatment Concentration (ppm) Std.

Deviation

Coeff. of

R1 R2 R3 Average Variation

Control 4401 4793 4226 4473 290.3 6.49

Nutrient 2621 2548 2322 2497 155.9 6.24

Product   991 1251 1028 1090 140.7 12.90
30 

Table A11. Bioremediation Study Average Bacteria Count (MPN) 

Treatment Average Bacteria (cells/ml)

Day 0 Day 7 Day 28

Control 7505 207674 310925

Nutrient 10263 638881 534675

Product   11747 923247 782218

Table A12. Bioremediation Study Microbiology Results (MPN) 

Day 0

Treatment

Concentration (ppm) Std.

Deviation

Coeff. of

R1 R2 R3 Average Variation

Control 8072 7129 7313 7505 499.9 6.66

Nutrient 9549 10791 10450 10263 641.7 6.25

Product   11440 12100 11701 11747 332.4 2.83

Day 7

Treatment

Concentration (ppm) Std.

Deviation

Coeff. of

R1 R2 R3 Average Variation

Control 200588 190109 232325 207674 21982.0 10.58

Nutrient 619463 633015 664165 638881 22921.1 3.59

Product   923838 954929 890974 923247 31981.6 3.46

Day 28

Treatment

Concentration (ppm) Std.

Deviation

Coeff. of

R1 R2 R3 Average Variation

Control 332387 301056 299333 310925 18606.3 5.98

Nutrient 526512 565516 511996 534675 27678.0 5.18

Product   764660 796774 785221 782218 16266.2 2.08

 
31 

Table A13. Bioremediation Tests Average Mass Decrease 

Treatment Avg. Mass Decrease (%)

Day 0 Day 7 Day 28

Control – 6.33 10.0

Nutrient – 14.7 52.3

Product   – 17.7 67.7

Table A14. Bioremediation Study Gravimetric Results 

Day  0

Treatment Weight (g) Std.

Deviation

Coeff. of

R1 R2 R3 Average Variation

Control 0.10 0.10 0.10 0.10 0.000 0.00

Nutrient 0.10 0.10 0.10 0.10 0.000 0.00

Product   0.10 0.10 0.11 0.10 0.006 5.59

Day  7

Treatment Weight (g) Std.

Deviation

Coeff. of

R1 R2 R3 Average Variation

Control 0.091 0.096 0.094 0.09 0.003 2.69

Nutrient 0.091 0.086 0.079 0.09 0.006 7.06

Product   0.081 0.085 0.089 0.09 0.004 4.71

Day  28

Treatment Weight (g) Std.

Deviation

Coeff. of

R1 R2 R3 Average Variation

Control 0.087 0.095 0.088 0.09 0.004 4.84

Nutrient 0.044 0.048 0.051 0.05 0.004 7.4

Product   0.029 0.034 0.037 0.03 0.004 12.12
32 

APPENDIX B 

OHMSETT SKIMMER & WAVE TANK STUDY