Access to clean drinking water is taken for granted in most countries across the world. However, in many third world countries clean drinking water is not always available. Many people, especially children, suffer from diseases contracted from drinking water infected with salmonella, E-coli bacteria and many other forms of bacteria. Drinking impure water can be fatal and at best cause severe diarrhoea. Diarrhoea dehydrates the body and often the sufferer drinks more contaminated water in an attempt to replace the water his/her body has lost.

A basic water filter can purify ‘dirty’ water making much safer to drink. The filter is based on simple technology and one example is shown below. It is composed of quite common materials and is relatively easy to put together. Technology does not always need to be complex or computer controlled to be effective and useful.

The ‘dirty’ water is poured into the top of a tank which contains layers of sand, charcoal and gravel. As the water sinks through the various layers the bacteria and dirt are removed. The clean water flows through a hose/pipe into a ‘clean’ water storage tank. The water is now safe to drink. This is simple technology helping people live safer and longer lives.

QUESTION:
1. Draw a simplified diagram representing the purification system seen above. Label the various parts and explain how the filter works.

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