In situ Measurement of Oil Slick Thickness in Open Water Environments

During an oil spill response, one of the parameters impacting the choice and management of the applied cleaning technique is the thickness of the floating oil. Studies have shown that technologies to accurately measure oil thickness in real-time under open water operational conditions are not commercially available. Aiming to enhance the efficiency of the currently used cleanup processes, we present the development of a capacitive-based measurement device that can measure the thickness of various types of floating oil. The presented device measures the capacitance of the oil/water/air that it contacts and uses this data to estimate the locations of the oil-air and oil-water interfaces. Determining the interfaces location provides the data necessary to calculate the thickness of the oil layer. This sensor can operate in open water environments while being dragged through waves, and does not require any calibration against different types of oil or water. In addition, the device is equipped with specialized software- and hardware-based mechanisms to mitigate the fouling problem caused by highly-viscous oils. The sensor is designed to be vertically mounted to a skimmer, boom, or floating buoy and provide thickness readings (up to 50 cm) remotely, A second configuration allows a user to measure readings directly from a handheld unit (up to 10 cm). To assess the performance of the sensor, extensive testing of the initial prototype was performed at Ohmsett facility. The experimental results demonstrated high sensor accuracy in most of the test cases. Based on the testing results, several improvements were identified and are currently being implemented to enhance the performance of the sensor while working under harsh dynamic-liquid conditions.