Water treatment with sand between aggregate layers, and distribution of water evenly at inlet

摘要

A sand filter apparatus (10) for treating water includes a filter retention vessel (16) having an outlet (18) from which filtrate can be supplied. An inlet arrangement (not shown fully) is in fluid communication with the filter retention vessel and is connectable to a supply of waste water. A filter is interposed between the inlet arrangement and the outlet. The filter includes two layers of aggregate (12) and a layer of sand (26) interposed between the two layers of aggregate. The sand is at least one of, or a mixture of, granite-based sand and substantially pure silica based sand. A distribution system (not shown) is connected to the inlet arrangement so that waste water from the inlet to the filter is distributed substantially evenly into the upper aggregate layer.