Abstract: A separator assembly comprises a vertical vessel including a fluid inlet for receiving a fluid including a gas, at least two liquids, and solids, at least two liquid outlets for discharging the liquids, a gas outlet at an upper end thereof for discharging gas, and a solids outlet at a lower end thereof for discharging solids. A baffle plate extends across the vessel, and cooperates with the vessel to define an upper section and a lower section, and has a first conduit extending downwardly so that liquids and solids may flow into the lower section, and a second conduit extending upwardly so that gases may flow from the lower section to the upper section. A backpressure valve is in fluid communication with the gas outlet and is configured to discharge gas while maintaining a selected level of pressure inside the vessel.