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The application of Appropriate Technology

An Introduction to Slow Sand Filtration

The use of sand and gravel as filter media for water supplies can me split into three basic filter types: slow sand filters, rapid filters and roughing filters.

Apart from desalination and reverse osmosis, slow sand filters are perhaps the most effective single treatment for purifying drinking water supplies. They are use on a large scale as part of the water supply for large cities, as part of systems for small villages and on a much smaller scale they can be adapted for use in individual households.

Rapid sand filters are normally require a subsequent chlorination process and are thus of less use for small village supplies unless the raw (untreated) water supply is of a reliably high quality.

Roughing filters are used to reduce the turbidity of water supplied and often used as a pre-treatment before slow sand filtration.

This short document gives an introduction to these filtration methods.

You can read the whole document as a PDF file (7 mb)