The Concrete Biosand Water Filter

The concrete Biosand filter is an innovative version of the slow sand filter specifically designed for intermittent and/or household use. These filters are produced locally at the point of need using locally available materials and labor. So not only are we meeting the clean drinking water needs of the region, but providing much needed jobs and supporting the local economy.

The concrete Biosand filter is comprised of a concrete container (the approximate size of an office water cooler) with an inset plastic pipe, and filled with layers of sand and gravel. Contaminated water is poured into the top of the filter, where a diffuser plate distributes the water over the sand bed. The water travels through the sand bed, passes through multiple layers of gravel, and collects in the plastic pipe at the base of the filter. The clean water then exits the plastic piping for the user to collect.

The removal of waterborne pathogens and contaminants occurs in the Biosand filter due to a combination of biological degradation and mechanical filtration processes. The organic material present in the contaminated water is trapped at the surface of the sand bed, forming a biological layer, or “schmutzdecke”, to actively remove the pathogens and contaminants. The water produced by the Biosand filter process is odorless, tasteless, clear in color, and safe for human consumption.

Studies have shown the Biosand filter effectively removes more than 90% of bacteria and 100% of parasites. Although the filter does remove more than 90% of bacteria, which means the level is often below the infectious dose, it is recommended to use disinfection (UV, boiling, or chlorine) after filtering the water to eliminate all bacteria and virus matter.