Unsafe water and unsanitary conditions are a significant contributor to health issues worldwide. But for many rural people in developing countries, collecting water from less than ideal sources is an aspect of daily life. In rural villages, the expense and logistics of a central water system makes large scale solutions infeasible. But there is a natural and simple processes to transform tainted undrinkable water into safe and usable water; a biosand water filter designed especially for home use. Biosand filters delivers a 95% reduction of e-coli. Occurrence of diarrhea is cut in half when communities start using biosand filters. There are no moving parts, so the device is very durable for rural lifestyle. It does not need a constant stream of water feeding it, just daily refilling. They can also filter up to a liter per minute at max flow rate.
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Biosand filters achieve a minimal design, with maximum filtration results. At the top there is a diffuser basin which slows the rate that water falls into the sand. Filtration begins in the sand below. Gravity pulls water through the layers of sand, rock. 4 separate filtration functions work together to remove organic material, bacteria, parasites, and viruses. The first few centimeters of sand catch the majority of organic material. This layer becomes an active ecosystem that works to feed off subsequent organic material that filters through the system. As water and material work their way deeper into the sand filter, additional organisms become trapped in the sand particles. This is known as mechanical trapping. There is also an element of static electricity that works to bind the sand to organisms that are moving through the system. This is call adsorption. As water continues deeper into the sand filter, the lack of light or food results in the last filtration process for any remaining organisms; natural death. As water finishes through the filtration cycle, the increased pressure at the bottom of the BSF forces water up and out a spout for collection.
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