Abstract: A surface-based separation assembly for use in separating fluid. The surface-based separation assembly includes a gas-liquid separator configured to receive a fluid stream, and configured to separate the fluid stream into a gas stream and a mixed stream of at least two liquids. A liquid-liquid separator is in flow communication with the gas-liquid separator. The liquid-liquid separator is configured to receive the mixed stream from the gas-liquid separator, and is configured to separate the mixed stream into a first liquid stream and a second liquid stream. The assembly further includes a rotatable shaft including a first portion extending through the gas-liquid separator, and a second portion extending through the liquid-liquid separator. The rotatable shaft is configured to induce actuation of the gas-liquid separator and the liquid-liquid separator.