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The application of Appropriate Technology

Water Filtration

Documents about slow sand filtration and multi-stage filtration.

Slow sand filtration can be use from a very small household scale right up to filtering the water supplies for whole cities. It allows water to pass slowly through a sand bed where the majority of the purifying process happens in a naturally occurring bio-layer in the first few millimetres of sand.

Multi-stage filtration is a method for improving community water supply in rural and semi-urban areas. It uses a combination of coarse gravel filtration and slow sand filtration, with two or three separate stages in the cleaning of the water.

  • Articles:

    Surface Water Treatment By Roughing Filters

    Excellent manual on roughing filters by SANDEC, detailing water treatment alternatives applicable to rural water supplies and processes for solid matter separation. For further SANDEC publications, go here:http://www.eawag.ch. You can read the whole document as a PDF file (12.4 Mb)

    Horizontal Flow Roughing Filter

    Manual detailing how to estimate and design horizontal flow roughing filters. Among pre-treatment methods used before slow sandfilters (SSF), horizontal-flow roughing filters( HRF) have been found to be the most effective and appropriate for application in developing countries. This is because they are simple, require no mechanical parts, have low capital cost, can be operated […]

    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 […]

    Slow Sand Filtration

    By L. HUISMAN and W.E. WOOD. A WHO document from 1974 outlining the action, construction, operation and maintenance of slow sand filters. This is the standard text on the subject. (PDF Files) Contents & Preface (13 KB) Chapter 1 – Introduction (41 KB) Chapter 2 – Filtration of water supplies (1.2 MB) Chapter 3 – Theory of biological […]

    Life Water Slow Sand Filter

    Plans, construction guide and operation instructions for Life Water’s slow sand filter, suitable for a town of 1 or 2 thousand people. Lifewater is a water charity based in the USA. This document is available as 3 PDF files: Design (1 Mb) Construction (720 Kb) Operation & Maintenance (436 Kb)

    Biosand Filters

    The biosand filter is a modified form of the traditional slow sand filter in such a way that the filters can be built on a smaller scale and can be operated intermittently. These modifications make the biosand filter suitable for household or small group use. The biosand filter can be produced locally anywhere in the […]