Cheap water filters fight disease and slash fuel use

A Rocha International

Water is the staff of life – and also the single biggest source of risk of both disease and death in the developing world. It’s estimated that 80% of disease in the developing world is caused by contaminated water or poor sanitation.


When rich world standards of water infrastructure are not available, what can be done? As Christian environmental charity A Rocha has proved, a great deal can be achieved at minimal expense.


Instead of large-scale, expensive water treatment plants, A Rocha has shared plans for a neighbourhood biosand water filter. This equipment is so simple that it can be constructed by many communities with minimal materials and the right-know how.


The filter is a container about 1m tall. Untreated water is fed into the top and first hits a diffuser, a metal plate which protects the sand underneath. The top layer of sand is about 2cm deep and quickly becomes its own community of bio-organisms. These feed on organic matter in the water and eat many of the potentially dangerous pathogens.



Easy to make: A plan for a biosand waterfilter Picture: CAWST (Centre for Affordable Water and Sanitation Technology)


A further, deeper layer of specially selected filtration sand filters out solid particles and more of the pathogens. Underneath this is a layer of fine separation gravel which stops the sand from being carried deeper. On the bottom of the filter container is a final layer of drainage gravel, which in its turn stops the separation gravel from being carried away.


A tube takes the filtered water from the bottom of the container by force of gravity to a tap near the top of the filter, where it can be captured in a separate storage container.


This simple device is made from concrete and removes about 97% of bacteria and 90% of viruses from untreated water. A Rocha has helped to install 500 biosand filters in the Namungoona slum in the Ugandan capital Kampala. It has not simply delivered the filters but is teaching members of the community how too make them, so that the initiative is self-sustaining.


This simple device is made from concrete and removes about 97% of bacteria and 90% of viruses

Communities using biosand filters report far less diarrhoea and other water-borne illnesses.


As well as the health improvement, there is also a benefit to the environment. Water that is safe to drink does not have to be boiled, using precious fuel: it is estimated that each biosand filter saves 15 days of boiling, equal to about 70,000 trees cut down for fuel each year.


A Rocha, a Christian charity, operates around the world: in Africa alone, it has projects in Kenya, Uganda, South Africa and Ghana. Its first field centre was in Portugal, hence its name is Portuguese, meaning A Rock. Its other activities in Africa include teaching Farming God’s Way. A Rocha has also been promoting other low cost technologies such as basket cookers and charcoal briquette-making, which radically reduce both the environmental impact and the cost of cooking food.

A Rocha UgandaHow to make a basket cooker, by charity Practical ActionGuide to making a bio-sand filter