A liquid treatment system using gas flotation to separate suspended matter from liquid influent, including a flotation tank into which the liquid influent is fed through an inlet, an outlet conduit through which treated effluent is fed from the flotation tank, a separation conduit for feeding liquid to a bubble release point, means for pressurising the liquid in the separation conduit and dissolving gas in the pressurised liquid, wherein an energy recovery device is used for reducing pressure of the liquid before the bubble release point such that gas bubbles are released into the flotation tank for floating said suspended matter to a surface of the liquid in the tank, and wherein the energy recovery device supplies energy obtained through said pressure reduction of the liquid.