US Patent 7909992 Separation apparatus

A separation apparatus comprising, a series of compartments for holding particulate separation material, arranged so as to allow fluid to flow through the compartments in a primary direction from a first compartment in the series to a last compartment in the series, feed means for directing a flow of the fluid into the first of the series of compartments in the primary direction, barrier means for preventing flow of particulate separation material between compartments in the primary direction, and a pumping assembly arranged to pump a mixture of the particulate separation material and the fluid from the first compartment into a recovery stage.