Biological sand filters (BSFs) are home-scale water filtration systems based on the ancient practice of filtering water through sand. The sand filtration process is complemented by a newer process of also filtering the water through a biological layer. The BSF has 5 distinct zones: inlet reservoir zone, standing water zone, biological zone, non-biological zone (sand), and gravel.

Pathogens and suspended solids are removed through a series of biological and mechanical processes that take place in the bio-layer and the sand layer. These processes include:
• Mechanical filtering through the sand layer of the filter
• Predation: pathogens are consumed by other microorganisms in the bio-layer
• Adsorption: Pathogens become attached to each other, suspended solids in the water, and the sand grains
• Natural death: Pathogens finish their life cycle or die off because of lack of oxygen and food in the sand layer

According to the globally recognized Canadian NGO Center for Affordable Water and Sanitation Technology (CAWST), BSFs are capable of removing 99% of harmful pathogens.


Like all of Bareebos’ work, the BSF project is conducted through a participatory process with the families that we work with. Additionally, Bareebo’s families are involved in all phases of the project from the filter manufacturing process, through installation as well as the proper maintenance and daiily usage of the filters.

The BSFs are manufactured at Bareebo’s own facility. The construction team has attended numerous CAWST-sponsored manufacturing workshops.

Outcomes and Outputs

Since installing our first BSF in 2010, Bareebo has worked with over 564 families (2,847 human beings) in Banan District. We have increased their access to safe water and improved their knowledge of home water treatment and storage via Bareebo’s intensive training program that accompanies all of our community development (CD) projects.

Indeed, 84% of participants in Bareebo’s CD program state that the BSF project is the best project for their families. Additionally, the participants consistently report that the health of their families has improved dramatically since taking part in the project. Aside from the obvious benefits of an improved quality of life through better health, there are also less obvious benefits:

  • Decreased money spent on health care and thus more money available to invest in education, in businesses and in purchasing higher quality food etc.
  • Potential to reduce the need to borrow money to cover medical expenses
  • Fewer days of missed school for children and work for adults
  • The ability to take part in more physical activities, both for pleasure and work, to name but a few benefits


In short, drinking clean, safe and good tasting water makes life better, especially for people who have rarely or never had these opportunities.

  • Biosand Filter
    Training about, sanitation hygiene and water safety for the BSF project