Undershot overflow filter

摘要

A filter (10) for concentrating a fluid stream (72-74) containing particulate matter (74-76) or for filtering particulate material from a fluid stream, consists of a plurality of solid elements (a, b, c, d) in an array having gaps (g) between adjacent solid elements through which spill flow of the fluid passes. The fluid stream (72-74) and filter (10) are orientated with respect to each other such that the spill flow of fluid through adjacent gaps is bounded by a dividing streamline that terminates on a solid element intermediate adjacent gaps (g). The stream and filter elements are also arranged so that the incidence of the dividing streamline to the plane of the array is such that particulate matter larger than the gaps are deflected out of the spill flow between the gaps. To optimally maintain the incidence at least two chambers are located on the spill flow side of the filter. To further optimise the operation of the filter the one or more chambers each has spill flow controls sized and positioned to allow spill flow to exit each chamber so as to maintain the incidence. The filter may be used to concentrate sewage at locations where sewage overflow would otherwise occur.