In a simple and general definition, drinking water is water that is suitable for drinking. Therefore, drinking water should not contain parasites, pathogenic microbes and any harmful chemicals. The access of all human beings to safe drinking water is one of the rights recognized by the United Nations. Despite the fact that most of the earth is covered by water, it is not so easy to access suitable water for drinking because almost all the water in the oceans and seas is salty and not suitable for drinking. On the other hand, due to lack of hygiene and environmental pollution, many fresh water rivers and springs are also polluted and are unsuitable for drinking. Therefore, providing suitable drinking water for humans has become a big challenge in this era. Especially, with the ongoing climate changes, the dry areas of the world will increase and healthy water sources will become less and less.
