Liquid-liquid solvent extraction process consists of dispersion of one phase into another in the form of fine drops and allowing the solute of interest to migrate from one phase into the other. Subsequently, it is essential to separate the two phases for further processing. In this regard, it is critical to continuously monitor the interface of two liquid phases as entrainment of one phase with another will lead to severe issues in downstream equipment and processes to follow. In this regard, an ultrasonic (UT) based online interface tracking device is developed which can detect the top layer of liquid-liquid interface (30% TBP/DD and water containing trace amounts of uranium) as well as estimate its dispersion thickness. This has been achieved using a single minimally invasive sensor. A novel signal-processing algorithm is developed to denoise and extract meaningful parameters for this estimation from the reflected and highly scattered/attenuated UT signal. The paper reports development of a mathematical model of the algorithm, experimental setup, and validation of the proposed system in a batch gravity settler.