Abstract: The invention relates to an apparatus for cleaning sewage, having a housing (1) of substantially rectangular outline which is formed in the manner of a transportable container, wherein a plurality of compartments (C1, C2, C3, C4) are provided one behind the other along a longitudinal direction of the outline, wherein a first compartment (C1) contains at least two treatment basins (B1, B2, B3, B4) and an adjoining, second compartment (C2) contains a tank (7) with a lamellar separator (8) and a clarifying basin (9) arranged one after the other downstream of it. In order to improve the cleaning efficiency, it is proposed according to the invention that the clarifying basin (9) be arranged between the lamellar separator (8) and the first compartment (C1).