A liquid filtering apparatus is placed in a vessel having a bed of filtration material, the bed comprising at least two different sizes of filter media wherein the filtration material is stratified using upper and lower spaced apart inverted cones so that the unfiltered liquid first contacts coarse grained...http://www.google.com.au/patents/US8152998?utm_source=gb-gplus-sharePatent US8152998 - Screenless granular media filters and methods of use
