A rotary filter is disclosed, comprising filtering cells rotating in a circular movement, including a fixed collector portion comprising at least two compartments each having arc-shaped upward opening and a central separator chamber, including a downward opening communicating the separator chamber with each of said compartments, said downward opening being arranged at a level lower than said upward opening of each of the compartments, the downward opening of the central separator chamber and the upward opening of each compartment of the collector portion partly overlapping in vertical projection.