For some 200,000 years when man was nomadic, having safe water wasn't a problem. We'd walk from one source to another and water our animals as well. Then, if it began to smell, we'd move on before we were infected with any diseases. Then, about 10,000 years ago, we moved into permanent settlements and many of today's aliments began to surface as pathogens transmitted by contaminated water became a very serious health risk and guaranteeing pure water for people became a prerequisite for successful urbanization and state formation.
The difficulty in these times was getting, retaining, and removing enough water for humans and cattle. The earliest settlements from about 8000 to 7000 B.C. were located near springs and other bodies of water. From about 3000 B.C. in Egypt, stone rain water channels and wells have been discovered and in Pakistan and Crete, toilets dating from the second millennium B.C. have been discovered.
Urbanization in Europe occurred between 500 B.C. and 500 A.D. around the Mediterranean and the quality of the water was examined by the senses (taste and smell) as well as the appearance and temperature to determine if it was healthy for people and animals. The ancient Greeks and Romans were also quite aware of the dangers of water coming from the hills and mountains where mining was practices. We also know that settling tanks, sieves, filters, and the boiling of water were methods used by the Greeks and Romans to purify their water. The boiling of water was recommended by the medial authors of that period but was unfeasible since extensive use of firewood and other combustibles would sooner or later have become a scarce resource.
After the fall of the Roman Empire, water supply and sewage systems experienced fundamental changes in Europe. Medieval cities, castles, and monasteries had their own wells, fountains, or cisterns. With towns usually building a few modest latrines for the inhabitants that were inadequate for the size of the population and the poor sanitation caused epidemics throughout medieval towns in Europe.
Sanitation in towns around Europe was one of the great achievements of the 19th century an during the period, the role of water in transmission important diseases - cholera, dysentery, typhoid, and diarrhea - was realized. The final proof came when the microbes, especially cholera, causing these diseases were discovered serving as justification for the sanitary movement around the world.
Sensory evaluation of water quality was complemented with chemical and microbiological examination and during the 19th and 20th centuries, the filtering and chlorination of towns' water supplies was introduced. The discovery of microbes and the introduction of efficient ways of treating large amounts of water paved the way to an era in which public health problems caused by polluted water seemed to belong to history and the developing world.
However, in the late 20th century, the biological hazards transmitted by water emerged in the post-modern Western world. Anxiety about chemical and radioactive environmental hazards and their impacts on human health mounted in the 1960's and the overall amount of known biological and chemical health hazards transmitted by water increased manifold during the last half of the 20th century.
Today, around 10,000 people die every day due to diseases like dysentery, cholera, and various diarrheal diseases caused by a lack of safe water and adequate sanitation. Yet, since most of those who die are children and elderly, whose death is considered "natural" , or people who are more or less marginalized in their societies (e.g. refugees, the poor) or living outside areas that are important for the global economy, mortality due to these waterborne diseases is too often considered unavoidable.
More than just a commodity, water is an economic and social good. This places responsibility for its management and oversight in the public sphere. Balancing of water use priorities, water quantity, and water quality is of high importance for the future and while water supply will continue to have the highest priority, water quality issues will be even more important. At the same time, it is more important to use water wisely and avoid wastage. In a global context, water pollution control and sanitation are probably the biggest challenges - removing wastewater from communities, industries, and agriculture in many parts of the world.
Recently, there have been a huge variety of development paths and solutions in urban water supply and sanitation. Local conditions, traditions, and people have to be in the core decision making when future solutions are considered. However, since water sources for every city have their own unique location and quality and each city has its own unique physical, social, and administrative morphology, solutions of one city may not work for another.