Slow sand filters are used in water purification for treating raw water to produce a potable product. They are typically 1 to 2 metres deep, can be rectangular or cylindrical in cross section and are used primarily to treat surface water. The length and breadth of the tanks are determined by the flow rate desired by the filters, which typically ha...
Found on
http://en.wikipedia.org/wiki/Slow_sand_filter
(from the article `aquarium`) ...be rapidly removed or transformed because it is harmful even at very low concentrations. In the aquarium the bacteria that convert ammonia to ... Two types of sand filter are in use: slow and rapid. Slow filters require much more surface area than rapid filters and are difficult to clean. Most ... [2 ...
Found on
http://www.britannica.com/eb/a-z/s/110
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