Sand filters are the oldest and most basic form of water filtration and originally consisted of large volumes of sand through which water simply percolated. Modern systems however now include various media layers which allows much more efficient filtration in smaller vessels. Multi-media sand filters normally consist of three media layers (ie. support base gravel, micro screened sand and anthracite) and are a very economical means of primary filtration to remove the bulk of suspended solids. They are particularly efficient on surface waters for the removal of grit, sediment, turbidity and organic matter but also widely used on oxidised iron ('rust') and other precipitated contaminants such as manganese or scale particles. Multi-media filters are periodically backwashed (either automatically or manually) by simply reversing the flow and this flushes to waste the accumulated sediment and also regrades the filter media layers. Operation and maintenance is extremely simple. After initial set-up, the system is virtually self sustaining. With the Performa Head, back-flushing and clearing of trapped contaminates occurs automatically.
Sand filters are used to remove suspended solids from water and wastewater. Because they have one layer of filter media, sand filters remove only relatively large solids (normally in the range of 40 micron and larger). The effective size of each granule of sand typically varies from 0.35mm - 1.2mm. Larger granules yield coarser filtration. Finer granules yield finer filtration.
Sand filters are typically used for:
Irrigation water Storm water Cooling water Swimming pool water Water in fountains and other water features
Removing suspended solids smaller than 40 microns requires filters with either two or three layers of filter media. These are referred to as dual-media filters or multi-media filters. When sized properly and with the correct configuration of filter media, these filters can remove suspended solids as small as 5 micron. Units are skid-mounted, factory assembled, wired, and tested, and delivered ready for installation. Piping, valves, filter media, pressure gauges and accessories are included with filter systems. Solar power, media air scour, and rinse cycle are available as options. Filter systems are engineered to require little maintenance. A separate source of water supply or a pump for backwash are seldom needed. Dual and Multi-media filters are typically used for: Industrial process water Waste water Potable (drinking) water. The size of each filter, the number of filters required, and the type of filter media used depend upon: how small a solid needs to be removed, how dirty the water is, how the water will be used once it is filtered, and the source of backwash water needed to clean the filters
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