A filter module comprises a body of wound layers of sheet material, the body having inner and outer peripheral surfaces, a winding axis and a passage extending along the axis and in fluid communication with the inner peripheral surface, the sheet material having openings forming two channel types extending from the inner to the outer peripheral surfaces, a first channel type open at the outer peripheral surface and closed adjacent to the inner peripheral surface, a second channel type open at the inner peripheral surface, in fluid communication with the passage and closed adjacent to the outer peripheral surface, the two channel types separated from each other by sheet material, one channel types being inlet channels communicating with a fluid inlet, the other channel types being outlet channels communicating with a fluid outlet, wherein the surface of at least one channel type supports a precoat.