An apparatus and method for separating a mixed flow into a higher-density component and a lower-density component is provided. The apparatus may include a casing having a fluid entrance assembly, a fluid outlet assembly, and a drain. The apparatus may also include a plurality of rotary separators disposed in the casing. Each of the plurality of rotary separators may include an inlet in fluid communication with the fluid entrance assembly, a discharge in fluid communication with the fluid outlet assembly, and an outlet passage in communication with the drain. At least one of the plurality of rotary separators may include a stationary housing and a rotatable drum disposed at least partially in the stationary housing. The stationary housing may define a slot at least partially providing the outlet passage, and the rotatable drum may be configured to centrifuge the mixed flow.