A BioSand Water Filter is a technological adaptation of the centuries old slow sand filtration process. David Manz designed the system and hold US patents. The system is intended for use in rural homes where naturally safe or treated water sources are not available.

BioSand Filters remove 95.0 to 99.0 percent of organic contaminants, including bacteria, viruses, protozoa, worms, and particles. Safe water

Drinking water

Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...

 produced by the filters is free of discoloration, odor, and unpleasant taste , and can be used for drinking, food preparation, personal hygiene, and sanitation. Most common home-based models can produce 20 to 60 l (42.3 to 126.8 ) of water per hour.

Filtration process

Most BioSand Filters are constructed from concrete or plastic. Gravel and sand are layered inside the filter with a PVC collection pipe situated at the base of the filter. Contaminated water from rain, surface, or ground sources is poured through the top of the filter and passes through a plate that diffuses the stream and blocks large contaminants (e.g. stones, large twigs, leaves).

The layer of sand must remain undisturbed by the flow of poured water. These conditions are achieved respectively by the installation of a diffusion plate on the top (reducing the impact of the poured water flow), filtration occurs in the lower layers of sand and gravel, which removes contaminants that cause odour, cloudiness, and taste. Then, filtered water comes through the PVC pipes.

Health benefits

A 2007 study conducted by the School of Public Health at the University of North Carolina at Chapel Hill

University of North Carolina at Chapel Hill

The University of North Carolina at Chapel Hill is a public research university located in Chapel Hill, North Carolina, United States...

indicates that BioSand Water Filters can reduce the incidence of diarrheal illness by up to 40 percent.

Maintenance

Over time, the top layers of sand may become clogged with material, causing flow rates to drop. A simple stirring or skimming of the top layer of sand is usually sufficient to restore optimal flow. Frequency of needed maintenance is dependent on the quality of the source water. Although longitudinal studies have not been completed, Samaritan's Purse reports that filters have remained in effective operation for over eight years.

External links

• Manz Water Info containing a number of detailed resources relating to construction and operation