At the outset of the century, waterborne diseases like typhoid fever and cholera were scourges across America. Typhoid alone killed more than 150 per 100,000 people annually. (Wilbur Wright was one.) Dysentery and diarrhea - the most common waterborne diseases - were the third largest cause of death in the nation. Given the conditions of streets and waterways, it is not hard to understand how these diseases spread so widely.
In 1900, it was common practice to dispose of garbage and raw sewage by dumping it into streets, alleys and waterways. Industrial waste was also dumped into the nation's waterways. Few municipalities treated wastewater, because it was widely believed that running water purified itself. Cisterns, which held a family's water supply, were breeding grounds for the mosquitoes that carried yellow fever. Indoor plumbing was rare. In rural areas, outhouses were common place, along with wells. Pumping water for cooking was an early morning chore for most families. In urban areas, an average tenement housed two thousand people, but not one bathtub. To promote cleanliness, most large cities built public baths - the only place a person could wash his entire body.
At the beginning of the 20th century, the main goal was to eliminate deadly waterborne diseases by purifying drinking water. A second goal was to build distribution systems that would bring clean water to rural areas as well as urban. A century of engineering dramatically and significantly reduced death rates from waterborne diseases. In addition, engineers developed innovative water supply and distribution systems that now bring water to areas where it is most needed - whether arid, rural, or urban. All of these efforts have led to an increase in life expectancy, a reduction in infant mortality and morbidity, and improvements in the environmental quality of life around the world.
Disinfection with chlorine was underway in 1908 in Chicago and Jersey City and by 1910 was being used in several major U.S. and Canadian cities. By 1913 there were significant decreases in typhoid, and by 1918 over 1000 cities treating 3 billion gallons of water a day were enjoying the increased health benefits of chlorine disinfection. As a result, the major water-borne diseases ceased to exist in the United States by World War II.
Early in the century, engineers developed techniques to treat municipal and industrial waste water that included chemical coagulation, better sedimentation, and sand filtration. As new chemicals and other pollutants find their way into the water system, new ways to treat water are continually being developed. They include methods such as carbon absorption, enhanced coagulation, membrane filtration, alternative disinfection (ultraviolet, ozone, chlorine dioxide) and others. Microorganism systems reduce nitrogen, phosphorous, heavy metal concentration, eliminate sludge and offensive odors, and return water to its clear, clean, and healthy state.
Engineers have also developed sensitive and accurate instrumentation that can analyze water for carcinogens at parts per trillion levels. As a result, the EPA has greatly lowered the levels of allowable chemicals in wastewater.
Safeguarding the public water system means continually monitoring waterborne diseases caused by disinfection by-products and protozoan pathogens, carried by animals. Engineers have radically improved the filtration process at water treatment plants to successfully elimate these dangers to human health. They continue to revolutionize water treatment by developing numerous state-of-the-art technolgies.
An adequate supply of water often depends on the building of dams, reservoirs, and aqueducts. Today, storage and distribution systems enable semi-arid and arid regions to store water for later use during periods of high precipitation. They have also enabled people to move from large cities to suburban communities and helped those dependent on wells.
Milestones along the way include the Hoover Dam, which regulates the flow of the Colorado River. Completed in 1935, it provided work during the Depression and a range of benefits, including electricity for more than 1.3 million people, and irrigation for 1.5 million acres of land in the United States and Mexico. The 726-foot high structure was the highest in the world by 300 feet at the time.
The 242-mile Colorado River Aqueduct made the large-scale population and economic growth of southern California possible in 1933-39. Clean potable water piped from sources miles away led to the development of such large cities as Las Vegas, Nevada and suburban areas around Chicago and Los Angeles.
The Aswan Dam on the Nile River transformed Egypt into a self-sustaining agricultural economy by providing irrigation for more than one million acres of arid land and more than 2,100 megawatts of hydroelectric power.
In 1998 the Los Vaqueros aqueduct, forty miles east of San Francisco, began providing more than 400,000 residents and 28 industrial consumers with safe drinking water. Before the reservoir and dam, people endured drinking water with an exceedingly high salt-content.
Quantity and quality are the ongoing challenges for engineers. The World Bank estimates that currently more than a billion people — 1/6 of the world's population — do not have access to an adequate supply of water, and of those that do, access is often limited in time or quality. It is estimated that in the year 2000, millions of people in developing countries will die due to the lack of safe drinking water. Another concern for the future is the increase in global desertification. The world's drylands already make up about 40 percent of Earth's land surface. Expansion can lead to loss of farmlands, mass migrations, loss of economic activities, and disaster for many.
The transfer of engineering knowledge to ensure safe water supplies through the collection, treatment and distribution of surface, ground and wastewater is imperative for the continued economic growth and development of nations in the 21st century.
