Water is a fundamental human need. Each person on Earth requires at least 20 to 50 liters of clean, safe water a day for drinking, cooking, and simply keeping themselves clean.

Polluted water isn’t just dirty—it’s deadly. Some 1.8 million people die every year of diarrheal diseases like cholera. Tens of millions of others are seriously sickened by a host of water-related ailments—many of which are easily preventable.

The United Nations considers universal access to clean water a basic human right, and an essential step towards improving living standards worldwide. Water-poor communities are typically economically poor as well, their residents trapped in an ongoing cycle of poverty.

Education suffers when sick children miss school. Economic opportunities are routinely lost to the impacts of rampant illness and the time-consuming processes of acquiring water where it is not readily available. Children and women bear the brunt of these burdens.

Water is obviously essential for hydration and for food production—but sanitation is an equally important, and complementary, use of water. A lack of proper sanitation services not only breeds disease, it can rob people of their basic human dignity.

The World Health Organization (WHO) and various national agencies have drinking water quality standards that specify the acceptable microbial, chemical, and radiological characteristics of safe drinking water.

Excessive amounts of microbes or chemicals derived from human and animal wastes, agricultural runoff, industrial chemicals, and even natural pollutants, make some water unsafe to drink and cause water-related diseases. If water sources are not protected or are unexpectedly contaminated for any reason, the quality of drinking water suffers.

Contamination can occur at the source of the water both at the surface and in the ground. Once the water is in the distribution system, there are additional opportunities for drinking water to be contaminated. If pipes are not successfully protected from contaminants, the quality of drinking water suffers. Improper storage can also result in unsafe drinking water.

Source: https://www.koshland-science-museum.org/water/new/en/Overview/Why-is-Safe-Water-Essential.html