BIOSAND WATER FILTER

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What is a BioSand Water Filter?

The BioSand Water Filter is an award-winning Canadian water filtration technology developed by Dr. David Manz, a former University of Calgary professor. BioSand Water Filters are an adaptation of slow-sand filtration, designed for use at the household level. The filter removes water-borne bacteria, viruses, protozoa, and other organisms that cause diseases such as cholera, typhoid fever, and amoebic dysentery. The filter also strains out the particles and organic matter that cause cloudiness, unpleasant taste, colour, and odour.

Filters can be built on location with local materials. The exterior is made of concrete, with gravel and sand layered inside. Rain, surface, or ground water is poured through the top and filtered as it passes through the layers of sand and gravel. The sand filters 1 liter of water per minute, enough to providean entire family with sufficient water for their daily drinking, cooking, cleaning, and hygiene needs.

BioSand Water Filters are a technological adaptation of the centuries old slow sand filtration process. While implementations exist in many different sizes and varieties, the most common design 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% of organic contaminants, including bacteria, viruses, protozoa, worms, and particles. Safe water 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 between 20 and 60 litres of water per hour

History

The BioSand Water Filter (BSF) was developed by Dr. David Manz, while a professor and researcher at the University of Calgary, in Calgary, Alberta. BSF development began in 1990 and has continued, involving numerous individuals and organizations that actively develop and deploy the technology. While several commercial and community-scale implementations exist, the largest use of BSF technology has been in the humanitarian arena. The relief organization Samaritan's Purse has installed 70,000 filters world-wide and has recently embarked on an initiative, called Turn on the Tap to install at least 65,000 more filters by 2010. The first large scale production of plastic biosand water filters was begun in 2007 by International Aid Inc.; some 300,000 units are scheduled for worldwide distribution by 2010, 61,000 of which are planned for Honduras.

Filtration Process

Most BioSand Filters are constructed from concrete, though a new patented light weight plastic model has been tested and is being distributed by HydrAid^TM for both humanitarian and commercial purposes. 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 top few centimeters of the sand trap the bulk of micro-organisms, which accumulate and develop into a highly active food chain, called the Biological Layer or Schmutzdeke. The biological layer, which must remain partially wet, traps and feeds on the micro-organisms and contaminants in the water. Further filtration occurs in the lower layers of sand and gravel, which removes contaminants that cause odour, cloudiness, and taste.

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 ten years.