Dispersants Bibliography

Abstract
A large number of chemical agents for treating oil spills have been promoted in the past 20 years. During the seventeen years of the life of the Environmental Emergencies Technology Division over 100 dispersants have been tested for toxicity and/or effectiveness. Only eight products still remain on the accepted list and only about 15 products are still being produced. The compendium on oil spill treating agents prepared for the American Petroleum Institute in 1972 lists 69 dispersants and 43 beach cleanup agents, most of which are also dispersants. Only two of these are current commercial products, but both are produced in different formulations. Over 50 biodegradation agents, including bacterial mixtures, enzymes, or fertilizers have been proposed and only five of these, all very recent inventions, remain on the market

Abstract
Laboratory effectiveness tests are described for four classes of spill-treating agents, solidifiers, demulsifying agents, surface-washing agents and dispersants. Many treating agents in these four categories have been tested for effectiveness and the results are presented here. Solidifiers or gelling agents solidify oil, requiring a large amount of agent to solidify oil-ranging between 16% by weight, to over 200%. Emulsion breakers prevent or reverse the formation of water-in-oil emulsions. A newly-developed effectiveness test shows that only one product is highly effective; however, many products will work, but require large amounts of spill-treating agent. Surfactant-containing materials are of two types, surface-washing agents and dispersants. Testing has shown that an agent that is a good dispersant is conversely a poor surface-washing agent, and vice versa. Tests of surface-washing agents show that only a few agents have effectiveness of 25-40%, where this effectiveness is the percentage of heavy oil removed from a test surface. Results using the 'swirling flask ' test for dispersant effectiveness are reported. Heavy oils show effectiveness values of about 1%, medium crudes of about 10%, light crude oils of about 30% and very light oils of about 90%

Abstract
Laboratory studies on dispersant effectiveness have been conducted to assess the effect of several variables and to determine the action mechanisms of dispersants. The variables examined were temperature, salinity, and dispersant quantity. Dispersant effectiveness was measured and correlated with the five oil bulk components, asphaltenes, aromatics, polar compounds, saturate compounds and waxes. The effect of water temperature variation is logarithmically correlated to dispersant effectiveness. The effect of salinity on typical commercial dispersant formulations is that effectiveness is at a peak when salinity is about 40 ‰ (parts per thousand) and falls to nearly zero as salinity decreases to 0. Effectiveness also falls to 0 as salinity rises from 40 to 80 parts per thousand. This behavior is explained by the necessity for a certain level of ionic strength to stabilize the surfactant between the oil droplet and the water. Dispersant quantity is found to be an important factor. Dispersant-to-oil ratios greater than 1:40 to 1:60 result in very low dispersant effectiveness. Effectiveness is logarithmic with respect to dispersant-to-oil ratio. Dispersion experiments were conducted to investigate the effect of oil composition. Dispersant effectiveness is positively and strongly correlated with the saturate concentration in the oil and is negatively correlated with aromatic, asphaltene and polar compound contents of the oil. Dispersant effectiveness is only weakly correlated with oil viscosity. Dispersant effectiveness is primarily limited to oil composition

Abstract
Laboratory effectiveness tests have been developed for four classes of spill treating agents: solidifiers, demulsifying agents, surface-washing agents, and dispersants. Many of the currently available treating agents in these four categories have been tested for effectiveness. These results are presented. Solidifiers or gelling agents change liquid oil to a solid. Tests show that these require a large amount of agent to solidify oil, ranging from 16 percent by weight to over 200 percent. Demoussifiers or emulsion breakers are used to prevent or reverse the formation of water-in-oil emulsions. A newly developed effectiveness test shows that only one product is highly effective. However, many products will work, but require large amount of spill treating agent. Surfactant-containing materials are of two types, surface-washing agents and dispersants. Testing has shown that an agent that is a good dispersant is conversely a poor surface-washing agent, and vice versa. Tests of surface washing agents show that only a few agents have effectiveness of 25 to 40 percent, where this effectiveness if defined as the percentage of oil removed from a test surface. Extensive work has been done on dispersant testing and comparison of laboratory tests. All laboratory tests will yield the same effectiveness value if the oil-to-water ratio is about 1:1,000 or greater, and if a settling time of 10 or more minutes is employed. Extensive results using the “swirling flask” test are reported. Heavy oils show effectiveness values of about 1 percent, medium crude of about 10 percent, light crude oils of about 30 percent, and very light oils of about 90 percent

Abstract
Laboratory effectiveness test results are presented for four classes of spill-treating agents: solidifiers, demulsifying agents, surface-washing agents and dispersants. Solidifiers or gelling agents required large amounts of agents to solidify oil - ranging by weight from 16% to over 200%. For demulsifiers, an effectiveness test showed that only one product was highly effective, although many products would work, but required large amounts of spill-treating agent. Surfactant-containing materials were comprised of two types, surface-washing agents and dispersants. Testing showed that an agent that was a good dispersant was a poor surface-washing agent, and vice versa. Tests of surface-washing agents showed that only a few agents had effectiveness of 25 to 40%, with effectiveness expressed as the percentage of oil removed from a test surface. The 'swirling flask' test for dispersant effectiveness was used. Heavy oils showed effectiveness values of about 1%, medium crudes of about 10%, light crude oils of about 30% and very light oils of about 90%

Abstract
A study of the relationship of dispersant effectiveness and mixing energy was performed. Energy was varied by changing the rotational speed of a specially designed apparatus. The effects of dispersant type and oil type were also measured. The stability of the resulting emulsions was gauged by measuring the amount of oil that remained in the water column over time. The findings are that each oil-dispersant combination shows a unique threshold or onset of dispersion. The effectiveness goes up linearly with energy, expressed as flask rotational speed. Natural dispersion was also measured and shows behavior similar to that of chemical dispersion, except that the thresholds occur at a higher energy and effectiveness rises more slowly with increasing energy. Effectiveness (defined as the percentage of oil in the water column) rises rapidly to 80 to 90 percent with increasing energy for light oils treated with chemical dispersants. Heavier oils will disperse, but to lesser effectiveness values

Abstract
Studies on the formation of emulsions were summarized, and analytical methods used to determine the final results of the emulsion breaking process were evaluated. These include visual appearance, viscosity, zero-shear-rate viscosity, elasticity, water content, and conductivity. All but the latter two are useful for determining the stability of an emulsion. The development of four new tests was reviewed. These test the effectiveness of emulsion breakers in open and closed systems and emulsion preventers in open and closed systems. Results of testing on commercial products are presented

Abstract
Effectiveness, a key issue of using dispersants, is affected by many interrelated factors. The principal factors involved are the oil composition, dispersant formulation, sea surface turbulence and dispersant quantity. Oil composition is a very strong determinant. Current dispersant formulation effectiveness correlates strongly with the amount of saturate component in the oil. The other components of the oil, the asphaltenes, resins or polars and aromatic fractions show a negative correlation with the dispersant effectiveness. Viscosity is also a predictor of dispersant effectiveness and may have an effect because it is in turn determined by oil composition. Dispersant composition is significant and interacts with oil composition. Dispersants show high effectiveness at HLB values near 10. Sea turbulence strongly affects dispersant effectiveness. Effectiveness rises with increasing turbulence to a maximum value. Effectiveness for current commercial dispersants is gaussian around a peak salinity value. Peak effectiveness is achieved at very high dispersant quantities - at a ratio of 1:5, dispersant-to-oil volume. Dispersant effectiveness for those oils tested and under the conditions measured, is approximately logarithmic with dispersant quantity and will reach about 50% of its peak value at a dispersant to oil ratio of about 1:20 and near zero at a ratio of about 1:50

Abstract
The effects of varying the rotational speed (energy), settling time and shaking time were measured on the laboratory dispersant test; the swirling flask test. Dispersant effectiveness onset between 100 and 150 rpm, indicating a threshold process for dispersion. The dispersant effectiveness increased slowly after the onset with increasing rotational speed. The settling time changes effectiveness very much between 5 and 80 min. Change was especially rapid at 5 min. The amount of shaking time did not change the effectiveness significantly. This is also indicative of a threshold dispersion process

Abstract
Authors report on the use of a modified chromatographic method for measuring dispersant effectiveness on various crude oils in the laboratory. For this investigation, ASMB, Federated, Pitas Point, South Louisiana, Thevenard, Udang, Bunker C, Hondo, Santa Clara, Jet Fuel, Diesel, and North Slope oils were used. Results indicate that the modified method increased accuracy of dispersant effectiveness for very light and very heavy ends of the oil spectrum

Abstract
Authors report on a modified GC method for measuring dispersant effectiveness in the laboratory. The method resulted in improved accuracy of determining effectiveness, which showed dispersants having lower effectiveness on lighter oils and higher effectiveness on heavier oils than previously found in laboratory tests

Abstract
Laboratory effectiveness tests have been developed for four classes of oil spill treating agents: solidifiers, demulsifying agents, surface-washing agents and dispersants. Several treating agent products in these four categories have been tested for effectiveness. The aquatic toxicity of these agents is an important factor and has been measured for many products. These results are presented. Solidifiers or gelling agents solidify oil. Test results show that solidifiers require between 16% and 200% of agent by weight compared to the oil. De-emulsifying agents or emulsion breakers prevent the formation of or break water-in-oil emulsions. Surfactant-containing materials are of two types, surface-washing agents and dispersants. Testing has shown that effectiveness is orthogonal for these two types of treating agents. Tests of surface washing agents show that only a few agents have effectiveness of 25 to 55%, where this is defined as the percentage of oil removed from a test surface. Dispersant effectiveness results using the "swirling flask" test are reported. Heavy oils show effectiveness value of about 1%, medium crudes of about 10%, light crude oils of about 30% and very light oils of about 90%

Abstract
Dispersant effectiveness tests are reviewed. Studies have been conducted of the variances among several standard regulatory tests. Three main causes of differences have been identified, oil-to-water ratio, settling time and energy. Energy can be partially compensated for in high energy tests by correcting for natural dispersion. With this correction and with high oil-to-water ratios and a settling time of at least 10 minutes, five apparatuses yield very similar results for a variety of oils and dispersants. Recent studies into the energy variation of dispersant tests show that the energy level varies in many apparatuses. The repeatability of energy levels in apparatus is largely responsible for the variation in dispersant effectiveness values in certain apparatus. Studies of analytical procedures show that traditional extraction and analysis methods cause a bias to results. Methods to overcome these difficulties are presented

Abstract
Female F. grandis were intubated with a single dose of one of a number of Aroclor formulations with and without fuel oil. The PCB with fuel oil and fuel oil alone caused considerable inhibition of fin regeneration from 14 days onwards. In further experiments the oil dispersant BP 1100X was given singly and in combination with Aroclor 1268 and fuel oil. BP 1100X with fuel oil inhibited fin regeneration for the first 21 days. Some differences were seen according to the time of year at which the experiment was carried out. Aroclor 1268 with fuel oil in the autumn resulted in stimulation rather than the inhibition of regeneration seen in spring. The results highlight the complexity of problems with compounds that interact and the seasonal differences in the effects observed

Abstract
Modern oil spill dispersant formulations are concentrated blends of surface active agents (surfactants) in a solvent carrier system. The surfactants are effective for lowering the interfacial tension of the oil slick and promoting and stabilizing oil-in-water dispersions. The solvent system has 2 key functions: 1) reduce viscosity of the surfactant blend to allow efficient dispersant application, and 2) promote mixing and diffusion of the surfactant blend into the oil film. A more detailed description than previously given in the literature is proposed to explain the mechanism of chemical dispersion and illustrate how the surfactant is delivered by the solvent to the oil-water interface. Laboratory data are presented which demonstrate the variability in dispersing effectiveness due to different solvent composition, particularly for viscous and emulsified test oils with viscosities up to 20,500 mPa·s. Other advantages of improved solvent components can include reduced evaporative losses during spraying, lower marine toxicity and reduced protective equipment requirements. Through this improved understanding of the role of the solvent, dispersants which are more effective over a wider range of oil types are being developed

Abstract
Recent data with modern demulsifying oil spill dispersant (Corexit 9500) challenge old viscosity limits for the window of opportunity for dispersant use on viscous oils and emulsions. The demulsification capability of the dispersant to reverse and significantly reduce the viscosity of emulsified oil was demonstrated. This demulsification effect is a prelude to dispersion of the oil. In addition, high effectiveness was demonstrated on no. 6 fuel oil fractions with viscosities over 40,000 cP, well beyond previous indicated limits

Abstract
Significant effort continues to be directed at improving, and ultimately correlating, laboratory and field testing of dispersant effectiveness on oil spills at sea. This technology, which is complicated by the formation of water-in-oil emulsions, was recently advanced as part of the successful 1997 AEA North Sea field trial with Alaska North Slope crude oil and Corexit 9500 dispersant. Prior to the field trial, standardized and slightly modified laboratory test methods were used to better simulate field conditions and predict dispersant performance. Simplified field tests for emulsion stability and dispersibility were also carried out to provide a qualitative linkage between the laboratory and field results. The field trial effectiveness data obtained after two days weathering at sea confirmed the extended "window of opportunity" for this demulsifying dispersant, as the oil dispersed rapidly and completely after treatment. For the first time, a direct comparison of laboratory effectiveness test data could also be made with an extensive set of field data on highly weathered emulsified oil. It was concluded that an extended-time MNS test provided the closest match with field observations on the performance of the demulsifying dispersant. Recommendations for future laboratory and field tests are proposed to further advance the technology

Abstract
This paper describes the role of dispersants in oil spill response, the benefits of use versus natural dispersion of oil, and the evolution of dispersants from environmentally toxic and haphazardly applied to modern, safer formulas and application techniques that have very small environmental impact. The Sea Empress spill is highlighted as evidence of the evolution of dispersants and their beneficial use in specific cases

Abstract
In this study, Corexit 9500 was tested on heavy bunker fuel oil (IFO-38) and analyzed using the SINTEF methodology. Dispersability evaluations were undertaken on the oil, covering a wide range of properties found in different laboratory effectiveness procedures (MNS, WSL, IFP, EXDET). Finally, a meso-scale flume test was run to confirm the laboratory methodology. Viscosity, influenced by sea temperatures and weathering, was an important factor in the dispersability of the heavy oil. Time after spill, especially after 24 h, slowed the dispersion process, and required higher dispersant treatment rates

Abstract
Chemical beach cleaners can facilitate cleanups of oiled shorelines by improving the efficiency of washing with water. The improvement is a result of reduced adhesion of the oil coating, which makes it easier to remove from shoreline surfaces, thereby reducing washing time and lowering the temperature of the wash water needed to clean a given area. The criteria established for use of chemical beach cleaners in the Exxon Valdez spill cleanup included demonstrating enhanced cleaning with low levels of toxicity to marine biota and with minimal oil dispersion. Since no commercially available products satisfactorily met the criteria for use in Alaska, a new product, Corexit 9580, was specifically developed in response to this need. This paper describes the successful development of this chemical, including both laboratory testing and field testing in Prince William Sound

Abstract
A critical need currently exists for standard laboratory procedures for evaluating demulsifiers over the range of applications encountered in oil spill response. The procedures should be flexible enough to generate emulsions that are representative of those encountered at various time during a spill situation, and the applications should cover emulsion inhibition, breaking emulsion slicks at sea, and breaking recovered emulsions. Two laboratory test procedures are proposed. The procedures have different mixing energy and treating conditions, but each has the desirable feature of utilizing the same apparatus to generate the emulsion and to test the demulsifer. One procedure, called the wrist-action shaker emulsion test (WRASET), utilizes a standard laboratory apparatus, and is applicable for emulsion inhibition and for simulating at-sea application of demulsifers. A second procedure, called the rotating flask emulsion test (ROFLET), can also be used for a range of applications and is applicable for treating emulsions during oil recovery operations. Data from each of the two laboratory emulsion tests are used to demonstrate their features and to provide guidance on their use. An important implication of this work is that laboratory tests currently used to evaluate the effectiveness of dispersants to break up emulsions at sea need to be modified to provide time for the emulsions to be first broken by the dispersant

Abstract
A simple test, using embryos of the grass shrimp Palaemonetes pugio, was employed to determine the toxicity of two commercial oil dispersants (Corexit 7664 and Corexit 9527) and toxicity of the water soluble fraction of Number 2 fuel oil (WSFoil) prepared with and without the addition of the dispersants. Tests revealed P. pugio embryos were similar to previously measured life stages in their sensitivity to WSFoil prepared without dispersants. They were approximately ten times more sensitive to water soluble fractions of dispersed oil, which may have been due to the increases in total hydrocarbons (measured analytically). Both temperature and salinity of the sea water affected toxicity of WSF prepared with dispersants, the most obvious effect being earlier onset of mortalities at higher temperatures. Differences observed in the onset of mortalities with WSF prepared with and without dispersants implicated egg-casing permeability as a factor in toxicity. The shrimp embryo toxicity test, described here for the first time, exhibited highly significant results, outstanding reproducibility and virtually 100% response within a narrow time interval

Abstract
The use of dispersants to control marine oil spills is common practice in many areas throughout the world. In the United States, the use of dispersants has been discouraged up to this time by federal regulations. A Task Force was appointed by the American Petroleum Institute to make recommendations on the utilization of dispersants based on studies of current information on dispersants and mechanical recovery equipment. The use of dispersants should be encouraged where it is justified. The Task Force believes that the use of dispersants can at times be the most effective and biologically sound method of controlling offshore oil spills. For this reason, we would like to see the National Contingency Plan revised so that the responsible On-Scene Coordinator (OSC) has more authority over the use of dispersants. The OSC should be able to decide to use dispersants to control offshore oil spills that threaten to move into sensitive environmental or commercial areas. If the plan is revised, then oil spill cleanup organizations would be encouraged to have stocks of low toxicity dispersants, and suitable spraying systems

Abstract
New formulations of dispersant products are less toxic and more effective than ever before. These new products, coupled with more detailed application techniques, have brought about safer and more cost-effective use of these substances. Dispersants, as well as surface collecting agents, biological additives, and a new miscellaneous category of products that includes gelling agents, elastomers, solidifying agents, and polymers can be used alone or in combination for more effective oil spill cleanup. New testing protocols being developed by the U.S. Environmental Protection Agency and new product developments during the past three years are discussed. The National Contingency Plan Subpart H Product Schedule, the number of products on the schedule, what it means for a product to be listed on this schedule, and how to get a product listed on the schedule also are described

Abstract
Work is in progress by ASTM Subcommittee F20.13 on Treatment on a series of guidelines covering the use of dispersants in nonsaline environments. These environments include freshwater ponds, lakes, and streams, as well as land. The guidelines are to be patterned after those produced by an earlier task group of the same committee covering saline environments. This paper describes what has been accomplished thus far. Participation by those interested, whether an ASTM member or not, is welcomed

Abstract
A marine oil-degrading population grown at 8°C showed a selective sensitivity regarding utilization of compounds in Prudhoe Bay oil in the presence of the dispersant Corexit 9527. The response was dependent on the nitrogen and phosphate levels of the medium and on the concentration of dispersant used. In the presence of a nitrogen-phosphate solution and a Corexit 9527-crude oil substrate, degradation of the n-alkanes of the saturate fraction was temporarily retarded in proportion to the concentration of Corexit 9527 present. This retardation was overcome with extended incubation time. In the absence of nitrogen-phosphate supplementation, the effect of Corexit 9527 was pronounced, retarding n-alkane degradation even with extended incubation time. Corexit 9527 had less effect on the degradation of the aromatic fraction and may indeed be stimulatory in the case of select compounds. The development and testing of dispersants containing nitrogen and phosphate is recommended

Abstract
Samples from a previous study observing the effects of Corexit 9527 on microbial degradation of aromatics and saturates in crude oil were reanalyzed by capillary gas chromotography with a sulfur-specific detector. The results shown an inhibitory effect on degradation of sulfur heterocycles (such as benzothiophenes and dibenzothiophenes), dependent upon dispersant concentration and nutrient supplementation

Abstract
Capillary gas chromatography (CGC) and C14-radiometric techniques were used to investigate the effects of 15 oil dispersants on microbial degradation of Norman Wells crude oil. Other biochemical processes, including phosphatase, methane production, and both aerobic and anaerobic nitrogen fixation, were studied with selected dispersants. Several dispersants showed no inhibitory effects on microbial biodegradation under laboratory conditions. Other dispersants were found to be toxic or inhibited degradation. Phosphatase activity was stimulated by two of the four dispersants tested in the presence of crude oil. All four dispersants stimulated phosphatase activity when no oil was present. Three dispersants stimulated aerobic N2 fixation. However, anaerobic stimulation occurred when dispersants were present in high concentrations. Only one dispersant stimulated methane production in anaerobic sediments

Abstract
In laboratory studies, the effects associated with water-to-air transfer of anionic detergents sprayed on oil slicks were investigated. Dissolved anionic detergents increased the production of marine aerosol. Detergents concentrated and enriched up to 100 times their concentration with respect to seawater. Additionally, mm-thick oil slicks reduced the amount of spray and also the amount of surfactant transferred to aerosol state. Detergent concentrations and type of oil was thought to affect the amount transferred to aerosol