Patent ID: 8123941

Claim:
A sand filter apparatus for treating water, the apparatus including a filter retention vessel having an outlet from which filtrate can be supplied, a floor, a pair of opposed side walls extending from major sides of the floor and a pair of end walls extending from minor sides of the floor; an inlet arrangement in fluid communication with the filter retention vessel and connectable to a supply of water to be treated; a filter interposed between the inlet arrangement and the outlet and spanning the floor so that a width of the filter is a distance between the side walls, the filter including two layers of aggregate, being one of a granite-bases aggregate and a calcium carbonate-based aggregate, and a layer of sand interposed between the two layers of aggregate, one of the two layers of aggregate being a lower aggregate layer positioned on the floor and the other of the two layers of aggregate being an upper aggregate layer positioned on a top of the layer of sand, the sand being at least one of granite-based sand and substantially pure silica sand and a mixture of granite-based sand and substantially pure silica sand, and the upper aggregate layer having an intermediate sub-layer with an aggregate size of between approximately 20 mm and 25 mm, a top sub-layer with an aggregate size of between approximately 3 mm and 10 mm and a lower sub-layer with an aggregate size of between 3 mm and 10 mm; and a distribution arrangement that is connected to the inlet arrangement and that is configured to distribute waste water from the inlet to the filter, the distribution arrangement being positioned in the upper aggregate layer and configured so that waste water is distributed substantially evenly into the upper aggregate layer.