Many rural areas in the developing countries, in particular Africa and Asia, suffer from lack of clean water and sanitation. Poverty makes the situation extremely severe for large population what regards accessibility but also affordability. There exist simple, economic and Effective systems for water purification, e.g. biosand, that can remove the solid particulates and disease-causing micro-organisms from contaminated water. Slow sand filters contain very fine sand and usually function without pre-treatment and chemical additives such as flocculation and chlorination.
Harmful bacteria, parasites and other micro-organisms are greatly reduced through the so-called “bio-film”, a biologically active layer in top layers of the sand that gets created and destroys most pathogens “disease-causing organisms” as they can not survive there. The pathogens get consumed by micro-organisms in the bio-film as they are trapped in and on the sand surface; other filtration mechanisms support the quality improvement.