Existence of earth and its natural resources

To understand the fundamental of water treatment we should know about its basic formations of how water gets polluted and contaminated. To understand this elements we have to know about water and its presence on our planet and how it is significant to all living beings.

Earth is the third planet from the sun and the only object in the universe known to harbor life. According to radiometric dating and other sources  of evidence, earth formed over 4.54 billion year ago. Earth's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of earth's surface is covered with water, mostly by oceans. The remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. As water covers 71% of the earth's surface, it is vital for all known forms of life. On earth 96.5% of the planet's crust water is found in seas and oceans, 1.7% in ground water, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, 0.001% in the air as vapor, clouds (formed of ice and liquid water suspended in air) and precipitation. Only 2.5% of this water is fresh water, and 98.8% of that water is in ice (excepting ice in clouds) and ground water, less than 0.3% of all fresh water is in rivers, lakes and atmosphere. A smaller amount of the earth's fresh (0.003%) is contained within biological bodies and manufactured products. A greater quantity of water is found in the earth's interior. Safe drinking water is essential to humans and other lifeforms even through it provides no calories or organic nutrients. Access to safe drinking water has improved over the last decades in almost every part of the world, but approximately 1 billion people still lack access to safe water and over 2.5 billion lack access to adequate sanitation.