Round-Robin Testing of a New EPA Solidifier Effectiveness Protocol

Abstract

ABSTRACT A new laboratory testing protocol for evaluating effectiveness of solidifiers in removing crude oil slicks on the water surface has been developed by the U.S. Environmental Protection Agency (EPA). Since an assessment of a testing protocol requires validation through an inter laboratory study with several independent research partners, a round-robin test was performed by five operators across two laboratories. The protocol was qualitatively and quantitatively evaluated to determine if it can satisfactorily differentiate product effectiveness, while still accounting for experimental and operational errors. Each operator evaluated the efficiency of six solidifier products with Arabian Light, Endicott and IFO 120 crude oils. All the experiments were carried out in triplicates and, additionally, an oil alone control sample was run for quality control purposes. The five operators were provided with all the supplies required to conduct the experiment and a detailed standard operating procedure. The results were collected and analyzed statistically to quantify repeatability and reproducibility. The average repeatability and reproducibility standard deviations were 5.1, 2.7, and 3.3% and 11.2, 10.1, and 13.1% for Arabian Light, Endicott and IFO, respectively. The within-operator error was ≤ 5% regardless of operator and oil type. Due to the difficulty and uncertainty associated with the separation of the solidified and un-solidified mass, the between-operator error was around 10%. The oil alone control had an average repeatability and reproducibility standard deviation of 4.8 and 6.1%, respectively. The variability among operators was also examined with h-statistics and the differences in operator means were found to be statistically insignificant. The variability is deemed acceptable for purposes of differentiating effective from ineffective solidifier products in the laboratory. The results from this round robin experiment will serve as an initial screening tool for the solidifier products in the market and will also help response teams determine the desirability and appropriateness of using a specific solidifier for oil spill remediation.