The biosand filter is an intermittent-flow slow sand filter, designed to produce safe drinking water without the use of chemicals. The mechanisms within the filter include both mechanical and biological processes. Mechanical processes include straining, adhesion and adsorption within the sand, whereas biological processes include predation by other organisms, die-off and inactivation and competition for food.
As micro-organisms such as bacteria, viruses and parasites travel through the sand, they are subject to both of these removal mechanisms. Over time, a biological zone gradually develops within the top layers the sand, the most dense/active part being the top few centimetres of sand – the origins of this biological population being the raw water fed into the filter. These micro-organisms form part of an active food chain that consumes pathogens (disease-causing organisms) as they are trapped in and on the sand surface, and in so doing the pathogens are removed and safe drinking water is produced.
BioSandFilter.org is a resource website linking efforts by field practitioners and academics doing research on the biosand filter. It gives filter and mould instructions for those who want to make their own. Equally, for those that require it, moulds can be bought by BushProof, the Madagascar-based company that owns BioSandFilter.org. In addition, a number of consultancy and training services are available aimed at helping organizations start up their own biosand filter projects.
All sand filter products are supplied through BushProof, a humanitarian company registered in Madagascar.
Publicly available: yes
Countries where available: Worldwide
Price range (USD): Contact supplier for quote
Offered or can be licensed for local manufacture: Yes