Abstract: An apparatus for treating of sewage or waste water comprises an aggregate separator (30, 32, 34). The apparatus includes a waste water reservoir (12), a device (22) for circulating the waste water (16) in the reservoir (12), and a replenishing chamber (38) for the waste water containing the aggregate. The apparatus is characterized in that there is provided at least one settling tank (66) into which the waste water contained in the waste water reservoir (12) can be delivered through a conduit (64), and in that a further conduit (82, 90) is provided between the settling tank (66) and a concrete mixer (61).