Abstract: A filtration apparatus in which a rotating filter element is concentrically mounted in a hollow conical of cylindrical chamber. The filter element consists of a support and a membrane mounted on the support. Fluid enters the chamber through an inlet port and concentrate leaves the chamber through an outlet port. Filtrate drains through the membrane and support to a channel in the centre of the filter element. Filtration relies upon cross-flow of the fluid across the surface of the rotating filter element. This reduces the tendency of solids in the fluid to block pores of the membrane, thereby maintaining high flux and minimising the requirement for cleaning of the filter.