Bio Sand Filter

The Bio-Sand filter is a traditional slow sand water filter, it is specifically designed for intermittent use. Slow sand filtration has been used for centuries. The filter can be produced locally anywhere in the world because it is built using materials that are readily available. It is simply a concrete container, enclosing layers of sand and gravel whose purpose is to eliminate sediments, pathogens and other impurities from the water

How a Biosand Filter works?

Water is poured into the top of the filter as needed, where a diffuser plate placed above the sand bed dissipates the initial force of the water. Traveling slowly through the sand bed, the water then passes through several layers of gravel and collects in a pipe at the base of the filter. At this point, the water is propelled through plastic piping encased in the concrete exterior, and out of the filter, for the user to collect.

How does a Biosand Filter remove contaminants?

As with all slow sand filters, the removal of pathogens occurs in the BioSand filter due to a combination of biological and mechanical processes.

When water is poured into the top of the filter, the organic material it is carrying is trapped at the surface of the fine sand, forming a biological layer.

Over a period of one to three weeks, micro-organisms colonize the Biological layer, where organic food and oxygen derived from the water abounds.

Four processes remove pathogens and other contaminants in this filter:

  • Predation
  • Natural Death
  • Absorption
  • Mechanical Trapping

How effective is a Biosand Filter?


  • More than 90% of fecal coliform
  • 100% of protozoa and helminths
  • 50-90% of organic and inorganic toxicants
  • 95-99% of zinc, copper, cadmium and lead
  • < 67% of iron and manganese
  • <47% of arsenic
  • all suspended sediments