Abstract: A filtration system utilizes a heater 40 and a heat exchange subsystem for elevating the temperature of a feed stream to a membrane filtration unit 12. Upstream from the unit 12, a solids-liquid stream is divided into two streams 32, 33 that pass through respective heat exchangers 22, 28 wherein heat from the concentrate stream 44 and the permeate stream 34 is transferred to the solids-liquid stream before entering the membrane filtration unit 12. Flow regulators are provided to equalize the flow rates of the streams passing through the heat exchangers. The invention lowers the viscosity of the feed stream resulting in the benefits of increased filtration capacity and extended membrane life.