Abstract: A hydro-dynamic separator incorporating a solids interceptor (21) upstream of the overflow (19) for intercepting solid matter above a predetermined size entrained in liquid flowing towards the overflow (19), the solids interceptor (21) comprising: (a) a wall (51) terminating in an upper edge (51a) which constitutes a weir in the flow path of liquid flowing to the overflow (19); (b) a barrier (53), extending from the said wall (51) towards a solids collection region (55), said barrier (53) comprising a plurality of openings (69) to permit flow of liquid therethrough but to retain solids, the upper surface of the barrier (53) being disposed such that solids retained on the barrier (53) are washed across the surface by the flow of liquid towards the solids collection region (55); and (c) a liquid collection region (59) beneath the barrier (53) for collecting liquid flowing through the openings (69) in the barrier (53), said liquid collection region (59) being in fluid communication with the overflow (19) of the