Swirling Flask Test Research Articles

Comparative Laboratory-Scale Testing of Dispersant Effectiveness of 23 Crude Oils Using Four Different Testing Protocols*

A controlled laboratory study was conducted to measure the dispersion effectiveness of Corexit 9500 on 23 different crude oils. This study was a part of a larger project initiated by the Bureau of Safety and Environmental Enforcement (BSEE) testing 20 oils to compare the predictive value of laboratory dispersant effectiveness tests with their larger scale test conducted at Ohmsett, BSEE’s national oil spill response test facility located in Leonardo, NJ. The test used in this study was the Baffled Flask Test (BFT), which is planned for adoption as EPA’s official testing protocol for listing commercial dispersant products on the National Contingency Plan Product Schedule, replacing the current Swirling Flask Test (SFT) [1]. In addition, the results of 3 additional oils, the 2 used in the SFT and BFT as currently written plus another reference oil, are presented. The temperature used for the tests was 15°C, to match the temperature used at Ohmsett. The dispersion effectiveness ranged from 3.4% to 93%. The BFT is a laboratory test with results that are inversely correlated with oil viscosity and therefore has predictive value in the decision to use a dispersant in the event of a spill.

The role of dispersants’ dynamic interfacial tension in effective crude oil spill dispersion

The dispersion effectiveness of dispersants containing Tween 80, Span 80, and dioctyl sodium sulfosuccinate (DOSS) was characterized using a modified Swirling Flask test, and was correlated with both initial and dynamic interfacial tension produced by those dispersants at an oil–water interface. Compositional trends in effectiveness were shown to be governed by: (1) initial oil–water interfacial tension observed upon dispersant–oil–saltwater contact; (2) rate of increase (or decrease) from the initial interfacial tension as DOSS was rapidly lost to the aqueous phase; and (3) gradually slowing kinetics of dispersant adsorption to the oil–water interface as Span 80 concentration was increased, which ultimately diminished dispersion effectiveness considerably even as dynamic interfacial tension remained <10−3mN/m. It is proposed that this third phenomenon results not only from the hydrophobicity of Span 80, but also from the dependence of mixed Tween–Span–DOSS reverse micelles’ stability in crude oil on dispersant composition.

Determining the dispersibility of South Louisiana crude oil by eight oil dispersant products listed on the NCP Product Schedule

We recently conducted a laboratory study to measure the dispersion effectiveness of eight dispersants currently listed on the National Contingency Plan Product Schedule. Results are useful in determining how many commercial dispersant products would have been effective for use on South Louisiana crude oil in the Deepwater Horizon oil spill. The test used was a modification of the Baffled Flask Test (BFT), which is being proposed to replace the current Swirling Flask Test (SFT). The modifications of the BFT in this study included use of one oil rather than two, increasing replication from 4 runs to 6, and testing at two temperatures, 5°C and 25°C. Results indicated that temperature was not as critical a variable as the literature suggested, likely because of the low viscosity and light weight of the SLC. Of the eight dispersants tested, only three gave satisfactory results in the laboratory flasks at both temperatures.

ASSESSING DISPERSANT EFFECTIVENESS FOR HEAVY FUEL OILS USING SMALL-SCALE LABORATORY TESTS

ABSTRACT Four bench-scale dispersant tests were used to evaluate three dispersants, Corexit 9500, Superdispersant 25 and Agma Super-concentrate DR 379 with an IFO (Intermediate Fuel Oil) 180 and an IFO 380. Dispersant effectiveness was assessed using the Swirling Flask Test (SFT) and Baffled Flask Test (BFT) developed by the U.S, Environmental Protection Agency (EPA), the Exxon Dispersant Effectiveness Test (EXDET) developed by ExxonMobil, and the Warren Spring Laboratory (WSL) test utilized in the United Kingdom. This study allows comparisons among the small-scale laboratory tests and provides a basis to compare dispersant effectiveness data with findings from at-sea field trials and wave basin studies conducted with the same dispersants and oils. No single dispersant preformed with the highest effectiveness under all test methods, but the data demonstrate that viscous oils such as IFO 380s could be dispersed under the right conditions. The results show that laboratory tests with greater mixing energy yield the highest estimates of dispersant effectiveness.

Oil Spill Dispersant Effectiveness Protocol. I: Impact of Operational Variables

The current U.S. Environmental Protection Agency protocol for testing the effectiveness of dispersants, the swirling flask test, has been found to give widely varying results in the hands of different testing laboratories. The sources of the ambiguities in the test were determined by considering several options in a rigorous systematic fashion. Options considered were variability among three operators and the variability and limitations of three analytical instruments in establishing a calibration curve for oil/dispersant mixtures. Other options included flask type, impact of operational variables (rotational speed, mixing time, settling time, and oil:dispersant ratio), development of a revised procedure for dispersant effectiveness, reproducibility and repeatability of the revised procedure, and development of selection criteria for screening of dispersants. A redesign of the test flask, which is characterized by having baffles with a stopcock at the bottom for sample collection, was deemed necessary to accomplish reproducibility within operator and between operators. The results indicated that the baffled flask provided a total coefficient of variation (variations within operator and between operators) less than 11% compared to above 100% in some cases for the swirling flask.

Oil Spill Dispersant Effectiveness Protocol. II: Performance of Revised Protocol

The current U.S. Environmental Protection Agency (EPA) protocol for testing the effectiveness of dispersants for use in treating oil spills on the open water, the swirling flask test (SFT), has been found to give widely varying results in the hands of different testing laboratories. Part I addressed the sources of the ambiguities in the EPA SFT and the development of a new test referred to as the baffled flask test (BFT). In this part of the series, further experiments were conducted for estimating the repeatability of three operators in determining the effectiveness of 18 dispersants by both the EPA SFT and the BFT methods. Overall statistical analysis of the results indicated that the coefficient of variation by the BFT was only 7.8% compared to 21.9% for the EPA SFT. The mean percent effectiveness of the EPA SFT was only 19.7% as compared to 64.6% for the BFT. Proposed selection criteria for screening of dispersants for listing on the National Contingency Plan Product Schedule have been developed.

Determining Dispersant Efefctiveness Data for a Suite of Environmental Conditions

ABSTRACT Chemical dispersants are used in oil spill response operations to enhance the dispersion of oil slicks at sea as small oil droplets in the water column. 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 (ER03S) model (http://www.epa.gov/athens/research/projects/erosl). 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 useful or practical approach for including dispersants in a model. The main objective 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. These data are intended to give an indication of the amount of dispersal of these oils under certain environmental conditions. Recently, the US EPA developed an improved dispersant testing protocol, called the baffled flask test (BFT) which was a refinement of the swirling flask test. Use of this protocol was the basis of the experiments conducted in this study. 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. The three oils that were tested were South Louisiana Crude Oil, Alaska North Slope Crude, and Number 2 fuel oil. Two dispersants that scored effectiveness above 85% by the BFT were selected for this study. A factorial experimental design was conducted for each of the three oils for four factors: volatilization, dispersant type, temperature and flask speed. Each of the four factors were studied at three levels except for the dispersant factor where only two dispersants were considered. Statistical analysis of the experimental data were performed separately for the three oils. Analysis of variance was conducted to determine which factors, or set of factors, were related to the percent effectiveness. Empirical relationships between the amount of oil dispersed and the variables studied were developed.

The Baffled Flask Test for Dispersant Effectiveness: A Round Robin Evaluation of Reproducibility and Repeatability

After two previous investigations demonstrated that the baffled flask test was an effective and reproducible method for screening the effectiveness of dispersant products in the laboratory, the US Environmental Protection Agency decided that before the new protocol could be considered for replacement of the swirling flask test, it would have to be subjected to an interlaboratory round robin investigation. This paper describes how the round robin evaluation was carried out and presents repeatability and reproducibility calculations that demonstrate the superiority of the new method over previous methods. Probabilities for passing various threshold levels of effectiveness values were computed, and the results will be used by the Agency to develop final pass–fail decision rules for dispersant manufacturers wishing to have their products listed on the national contingency plan product schedule.

Development of a Rational Oil Spill Dispersant Effectiveness Protocol

ABSTRACT Chemical dispersants are used in oil spill response operations to enhance the dispersion of oil slicks at sea as small oil droplets in the water column. To be considered for use, the dispersants must be listed in the National Contingency Plan (NCP) Product Schedule. Since 1994, dispersants were required to pass an effectiveness test known as the Swirling Flask Test (SFT), which is described in Appendix C of 40 CFR 300. Listing of a dispersant on the NCP Product Schedule is contingent on the dispersant being at least 45% effective in dispersing South Louisiana crude (SLC) and Prudhoe Bay crude (PBC) oils as measured and calculated by the test. Shortly after adopting the SFT, the U.S. Environmental Protection Agency (EPA) began to receive complaints that the test was too rigorous and few dispersants that were previously listed on the NCP Product Schedule could achieve the 45% effectiveness criterion. Additionally, the SFT has been found to give widely varying results in the hands of different testing laboratories. A redesign of the test flask, which is characterized as being baffled with a stopcock at the bottom for undisturbed sample collection, is considered to be necessary to accomplish reproducibility within operators and between operators. This paper presents the development of a revised procedure for dispersant effectiveness testing, called the Baffled Flask Test (BFT), and reports the reproducibility of the revised procedure by three independent operators. It also details the development of pass/fail selection criteria. Experimental results are presented comparing the repeatability of the SFT and BFT methods with three operators determining the effectiveness of 18 dispersants on SLC and PBC oils. Statistical analysis of the results indicated that the overall mean effectiveness of the SFT for all 18 dispersants was only 19.7% compared to 64.6% by the BFT and the coefficient of variation for the SFT was 21.9% versus only 7.8% for the BFT.

Round-Robin Testing of a New EPA Dispersant Effectiveness Protocol

ABSTRACT The current U.S. Environmental Protection Agency (EPA) protocol for testing the effectiveness of dispersants, the Swirling Flask Test (SFT), has been found to give widely varying results in the hands of different testing laboratories. A redesign of the testing flask by eliminating the side arm, incorporating baffles in the wall of the flask, and adding a stopcock at the bottom has been adopted to improve reproducibility in the hands of different operators. The new procedure is called the Baffled Flask Test (BFT). Similar to the original SFT, the test is relatively simple, requires minimum equipment, and involves a total time span of about 2.5 hours for testing four replicates on one of the two crude oils. Before EPA can adopt the BFT as the official protocol replacing the SFT, the newly developed test must undergo independent testing in the hands of commercial laboratories. Thus, to demonstrate its repeatability and reproducibility to support its adoption as the new EPA testing protocol, a round-robin test was conducted during the spring 2000 with eight independent laboratories. The participating laboratories were provided with all the supplies needed to conduct the BFT: baffled flasks, South Louisiana and Prudhoe Bay crude oils, six dispersant products, and the artificial seawater formulation used in the protocol. The laboratories were given specific, detailed instructions on how to conduct the tests for the dispersants, including all necessary quality assurance procedures. Results were reported back to EPA and the results were analyzed statistically to quantify repeatability and reproducibility. The paper discusses the data and presents the analysis showing the method's reproducibility.

Research Leading To Revisions In Epa's Dispersant Effectiveness Protocol

ABSTRACT The current EPA protocol for testing the effectiveness of dispersants in the laboratory—the Swirling Flask Test—is fraught with difficulties because it has been found to give widely varying results in the hands of different testing laboratories. The objective of this study is to develop an understanding of the factors most responsible for this lack of reproducibility. Once that objective has been accomplished, the protocol will be modified to achieve better reproducibility in the hands of multiple laboratories. To accomplish the objective, fractional factorial experiments were conducted to determine which factors have the greatest impact on the variance of the method. Such factors as oil type, mixing speed, settling time, dispersant type, flask type, and operator were evaluated systematically and in a statistically rigorous manner. In addition, since the calibration curve used for analyzing the oil concentration dispersed in the seawater solution may also be a major source of variability, a systematic evaluation of the way such measurements are made was conducted (such as comparing various types of instruments and evaluating the variance due to operator vs. that due to the instrument per se). Instruments evaluated were the spectrophotometer, diode array detector, and gas Chromatograph with a flame ionization detector. Results from these experiments to date have indicated that the factors most responsible for the lack of reproducibility of the method are mixing speed, settling time, and the type of flask in which the test is conducted. This has led to a redesign of the flask used in the test, which is characterized as being baffled and having a stopcock located at the bottom of the flask to prevent remixing of the dispersed oil mixture when transferring to the extraction vessel. The paper discusses the design of the new flask and the important experiments leading to the refinement of the protocol to reflect a more accurate simulation of mixing and dispersion in the open sea.

A modified swirling flask efficacy test for oil spill dispersants

The state of California has recently implemented the Swirling Flask Test (SFT) as the standard method for evaluating the comparative effectiveness of oil spill cleanup agents on petroleum products transported through state waters. Use of this ‘standard ruler’ will provide an aid in spill response decision-making. This implementation has involved modifications undertaken to address problems encountered with the existing SFT procedure as specified by the U.S. Environmental Protection Agency (EPA). These modifications involve the actual laboratory procedures, chemical analysis, and data reduction techniques. Primary differences between the California (CAL) and EPA SFT techniques include use of a closed test vessel, chemical analysis by gas chromatography (GC) and correction for dispersant contribution when estimating effectiveness. These new procedures have been used to evaluate the relative efficacy of two surfactant-based dispersants, Corexits® 9500 and 9527, with Prudhoe Bay crude oil.

The effect of energy, settling time and shaking time on the swirling flask dispersant apparatus

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.

EVALUATION OF THREE OIL SPILL LABORATORY DISPERSANT EFFECTIVENESS TESTS

ABSTRACT Chemical dispersants can be used to reduce the interfacial tension of floating oil slicks so that the oils disperse more rapidly into the water column and thus pose less of a threat to shorelines, birds, and marine mammals. The laboratory test currently specified in federal regulations to measure dispersant effectiveness is not especially easy or inexpensive, and generates a rather large quantity of oily waste water. This paper describes the results of an effort by the U.S. Environmental Protection Agency (EPA) to identify a more suitable laboratory dispersant effectiveness test. EPA evaluated three laboratory methods: the Revised Standard Dispersant Effectiveness Test currently used (and required by regulation) in the United States, the swirling flask test (developed by Environment Canada), and the IFP-dilution test (used in France and other European countries). Six test oils and three dispersants were evaluated; dispersants were applied to the oil at an average 1:10 ratio (dispersant to oil) for each of the three laboratory methods. Screening efforts were used to focus on the most appropriate oil/dispersant combination for detailed study. A screening criterion was established that required a combination that gave at least 20 percent effectiveness results. The selected combination turned out to be Prudhoe Bay crude oil (an EPA-American Petroleum Institute Standard Reference Oil) and the dispersant Corexit 9527. This combination was also most likely to be encountered in U. S. coastal waters. The EPA evaluation concluded that the three tests gave similar precision results, but that the swirling flask test was fastest, cheapest, simplest, and required least operator skill. Further, EPA is considering conducting the dispersant effectiveness test itself, rather than having data submitted by a dispersant manufacturer, and establishing an acceptability criterion (45 percent efficiency) which would have to be met before a dispersant could be placed on the Product Schedule of the National Contingency Plan (NCP). Also under consideration by EPA is a sequential testing procedure for a dispersant being placed on the schedule, whereby successful effectiveness testing would be required before toxicity testing would begin.

LABORATORY STUDIES ON THE CHEMICAL AND NATURAL DISPERSABILITY OF OIL

ABSTRACT We have reviewed the laboratory testing of the chemical and natural dispersion of oil, noting the weaknesses of the Mackay test and comparing it to other methods. Results of both chemical and natural dispersion tests show that anomalous test results are produced in the Mackay apparatus at 0° C. This is attributed to preferential viscous shearing when the oil viscosity is 30 to 200 centistokes (cs). A new test uses a small swirling flask. Dispersant effectiveness results for ten oils from the Mackay, Labofina, and swirling flask tests were compared and the correlation found to be low. Results from the new swirling flask test correlate well with physical property data, especially viscosity. Each laboratory test produces somewhat unique results, and no way has yet been found to determine which test most accurately represents reality.