This invention relates to a grit trap which is intended for use in removing grit from a flow of sewage. The grit trap is of the kind which includes a settlement chamber which has an inlet through which the flow of sewage can flow and an outlet from which treated sewage can flow. There is also provided a grit storage chamber which is disposed between the settlement chamber and in which in use the separated grit will collect, the settlement chamber having a mixing device for promoting a desired motion to the flow of sewage entering the settlement chamber. In accordance with the invention said mixing device comprises a disc 25 which is provided with a plurality of generally radially extending blades, said disc being located just above the upper end of the grit storage chamber.

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