Potable Water
Potable water is simply drinking water, water that is of sufficiently high quality so that it can be consumed or used in food preparation or cleaning without risking the health of those using the water.
In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard even though only a very small proportion is actually consumed or used in food preparation (often as little as 5%). We think nothing of watering the garden or washing the car with water that is clean and safe to drink.
In many parts of the world, drinking water contains diseases or unacceptable levels of dissolved contaminants or solids in suspension. This water is not safe to drink, especially for children. Even washing in this contanimated washing has health implications.
One difficulty for many families in using water of this unacceptable quality, even in cooking, is that it can lead to widespread acute and chronic illness and is a major cause of death in many countries, especially amongst children.
One way to make the water safe is by boiling it. But many societies around the world simply do not have the means or the fuel to boil the water. They would also need to store the clean, boiled water in a way that keeps it safe to use, but many societies are too poor or lack the resources to do this safely!
Water quality and contaminants
The most common contamination of raw water sources is from human sewage and in particular human faecal pathogens and parasites.
In 2006, waterborne diseases were estimated to cause 1.8 million deaths each year while about 1.1 billion people lacked proper drinking water.
According to the U.N. children's agency UNICEF, polluted water and lack of basic sanitation claim the lives of over 1.5 million children every year, mostly from water-borne diseases. "Despite commendable progress," says UNICEF executive director Ann Veneman, "an estimated 425 million children under 18 still do not have access to an improved water supply, and over 980 million do not have access to adequate sanitation."
It is clear that people in the developing world need to have access to good quality water in sufficient quantity, water purification technology and availability and distribution systems for water. In many parts of the world the only sources of water are from small streams often directly contaminated by sewage. Even using wells does not eliminate the risk of contamination.
Most water requires some type of treatment before use, even water from deep wells or springs. The extent of treatment depends on the source of the water. Appropriate technology options in water treatment include both community-scale and household-scale point-of-use (POU) designs.
The most reliable way to kill microbial pathogenic agents is to heat water to a rolling boil but this requires abundant sources of fuel and is very onerous on the households especially where it is difficult to store boiled water in sterile conditions. Other techniques, such as varying forms of filtration, chemical disinfection, and exposure to ultraviolet radiation (including solar UV) have been demonstrated in an array of randomized control trials to significantly reduce levels of water-borne disease among users in low-income countries.
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