A method for separating and recovering ultrafine particulate solid material from a suspension or slurry of the solid material and a hydrocarbon liquid by precipitation or flocculation of a heavy fraction of the hydrocarbon liquid with an effective amount of a precipitation or flocculation agent such that the precipitated heavy fraction encapsulates the particulate solid material. The system includes an upright vessel having an inlet for introducing oily water in a horizontal pattern. The first transfer electrodes are connected in a horizontal direction by an inter-pixel interconnection formed in the same layer.