Water is a naturally occurring resource in the world. There are more than 326 million trillion gallons of water on Earth. Less than 3% of this water is fresh water (naturally existing) and of that amount, more than two thirds is locked up in ice caps and glaciers. With so much water around, it seems like there is enough to see us through for millions of years but we have poorly managed it and it has turned out to be a scarce source, with many domestic agricultural such as irrigation that involves tapping from river tributaries, lakes which has led to water volume reduction and drying up. Lake Chad and the Nile are good examples.

Humans have further reduced the availability of clean water through openly defecating, disposing solid wastes (industrial, mineral) and waste water into the water bodies. This accounts for the death of many people, more so the children who die from water borne diseases such as diarrhea, typhoid, cholera and Hepatitis A.

The UN Sustainability Development Goal 6 is to ensure access to water and sanitation for all. In the Sub-Saharan Africa, some of the common sources of clean drinking water are bore holes, springs( mostly in rural areas) and tap water(mostly in the urban areas). The population growth is high so, with time the facilities cannot serve the people well. The springs can also easily be contaminated more so if the water is close to the surface. There are also slums which in most cases are found close to urban areas, have illiterate people in big numbers, people who may be in areas with no access to clean water or people who don't feel the need to use clean water for their health.

Here are some purifying designs for the developing world that I came across:

1. Life Straw: A Cigar-Shaped tube packed straw that purifies water from potential pathogens like Cholera, Typhoid. It is an inexpensive way to deliver portable water to those in need.

2. Water Purifying Bicycle: Introduced by the Japan?s Nippon Company also known as Cyclocean, a water purifying bike initially designed for use in remote villages and disaster zones. It uses kinetic energy to purify water gotten from nearby water bodies.

3. Life Sack: Designed by Jung UK Park, Myeong Hoon Lee and Dae Youl Lee. It can purify water and also work as a container for grains and other food substances. When filled with water, it can kill micro-organisms using UV-A radiation from the sun.

4. Pure Water Bottle Filters with UV Rays: This device by Timothy Whitehead is capable of filtering soiled water in two minutes, using micron-sized water filters and a wind up UV light system. The combination removes upto 99% of impurities.

These four purifying designs help in killing germs. It should also be noted  that salt from sea water and toxic chemical such as mercury and cannot be removed by these methods so, there is a need to test for the chemicals in the water bodies in order to get the best results.

References

http://wwf.panda.org/about_our_earth/teacher_resources/webfieldtrips/water/

http://water.org/water-crisis/water-sanitation-facts/

http://inhabitat.com/6-water-purifying-devices-for-clean-drinking-water-in-the-developing-world/