Slow-Sand Filters

Rwanda has a nine-month rainy season that provides a great deal of rainwater that can be harvested. But the dry season is very challenging for people whose main source of water is a nearby river or pond, which are often very polluted.

The slow-sand filter was developed in England over 150 years ago as a way to fight the cholera epidemics that swept through London on a regular basis. Modern slow-sand filters rely upon the same principles, and have been proven just as effective when smaller and used sporadically throughout the day.

The smaller version 20 Liters uses is referred to as a point-of-use filter, meaning that instead of the water purification being at the center of the community, it is performed where the water will be used and hopefully just consumed in the household.

The sand in the filter does two things: it strains out the larger particles like sediment, parasites and amebas, and then it acts as a home for bacteria. When the sand is fully colonized by bacteria, which happens after about three weeks, the colonized bacteria are capable of destroying 90 to 95% of the bacteria in the water poured through it.

The technology and materials used are all found in Rwanda, and the construction requires no electricity. Each household is taught how and required to take part in building the filter they will depend on, empowering them to be self-sufficient and address their own needs. There is minimal upkeep required and no recurring costs. It’s a great solution to a terrible problem, but there are two critical elements that are always needed. Your voice and your donation.

Slow-Sand Filters

Effective, economical solutions for filtering contaminated water and making it drinkable. In fact, slow-sand filters cost only $140 for parts and installation, and serve up to 4 families for 10 years. Units are installed in one home, but 3 or 4 households share the filter.

how it works video