Abstract: An apparatus, system and method for utilizing a source of liquid to rotate an output shaft and produce rotational torque that operates a machine to produce electricity, operate a pump or accomplish other work. Liquid from the supply of liquid flows into a flow chamber where the liquid is mixed with pressurized gas to form an aerated flow stream that flows upward in the flow chamber to lift the liquid to a position above a liquid-driven rotating mechanism, such as a water turbine or open impeller. The liquid is directed to the rotating mechanism by liquid discharge devices. Liquid passing through the rotating mechanism rotates the output shaft and then flows back into the supply of liquid. A supply of pressurized gas supplies the gas to the flow chamber. Gas discharge vents remove the gas from the aerated flow stream upstream of the liquid discharge devices.