Learn how these filters make contaminated water safe to drink

There is generally no shortage of water in the Cambodian villages where World Vision New Zealand is working.  It’s clean, safe-to-drink water which is hard to come by. 

Water in rivers, ponds and lakes can be polluted by animal and human waste.  Villages may not have a community source of safe water, or it may be a long walk away.  Clean water is expensive to buy and poor families may not be able to afford the fuel needed to boil water to make it safe.  In some areas where wells have been installed, the water can become poisoned and not fit for drinking, and/or the wells may be broken.

Biosand filters help solve some of these problems.  These are cheap, easy to install and maintain.   A water filter is much cheaper to install and easier to maintain than a well for example. 

The filters are an adaptation by a Canadian engineer of traditional sand filtration technology.  They can produce about 30 litres of clean, safe, odour free water an hour and remain effective for about 10 years.

Funding from World Vision supporters in New Zealand is providing biosand filters for school classrooms and villages in the 15 year, long-term development programmes we operate in Cambodia. 

The top few centimetres of sand trap the bulk of micro-organisms, which then accumulate and develop into a highly active food chain called a biological layer. 

This layer, which must remain partially wet, traps and feeds on the micro-organisms and contaminants in the dirty water which is poured into the top of the filter.

Further filtration occurs in the lower layers of sand and gravel, which removes contaminants that cause odour, cloudiness, and taste.