Hippocrates (460 - 354 BC), the father of modern medicine wrote "whoever wishes to investigate medicine properly should ... consider the water that the inhabitants use ... for water contributes much to health.
The history of water treatment dates back to ancient times. The first constructed sources of drinking water were shallow wells scooped out in wet areas. As tools were developed, deeper wells were constructed such as the ancient Egyptian Joseph's well at Cairo dug to a depth of 297 feet in solid rock. It is two stories, the upper to a depth of 165 feet was 18 feet by 24 feet, and the lower was 132 feet and 9 feet by 15 feet. Water was raised in two lifts by means of buckets on endless chains.
Methods for improving the aesthetic qualities of drinking water were recorded as early as 4000 BC. In addition, there are references in Sanskrit dating back to 2000 BC that refer to boiling and filtering drinking water. Egyptians used alum for clarifying water in the 16th century BC and wick siphons to transfer water from one vessel to another to remove suspended contaminants in the 13th century BC.
These practices seem to indicate that the ancients made a connection between drinking water and health. However, these methods were used for individual homes rather than treating community water systems.
The first community water systems were constructed by Roman engineers to deliver 130 MGD through aqueducts from 343 BC to 225 AD. These aqueducts included settling basins at the headworks and pebble catchers along
the aqueduct.
The aqueducts supplied water to only the richest Romans' private taps. Their main function was to supply water to the fountains and reservoirs for the public and for the public baths. Venice utilized rainwater collection systems to channel water from the roofs and courtyards. The water passed through sand filters surrounding the reservoir.
Water treatment was not a concern and did not progress during the Middle Ages. It was not until the 18th century that there was renewed interest in water treatment. Several patents were issued for filtration devices in France and England; however these were for use in private households and on board ships. These filters consisted of charcoal, sponge and wool, much as was described by Hippocrates 2,200 years earlier.
The City of Paisley, Scotland is generally considered as being the first city providing treated water, in1804. It was built by John Gibb to serve his bleachery and the Town and included settling followed by filtration. Three years later this system had expanded to serve customers in Glasgow.
In 1855, Dr. John Snow proved that cholera was transmitted through drinking water by linking an outbreak of the disease in London to the infamous Broad Street well. In the late 1880's Louis Pasteur demonstrated that the
"animacules" described by Anton van Leeuvenhoeck 200 years earlier caused illness and could be transmitted through water. By the end of the 19th century most major municipal supplies in Europe had slow sand filtration.
The first filtration system in America was constructed to serve Richmond, Virginia, in 1832. It was not successful, but attempts to make it work were tried for several years. After the civil war (war of Northern aggression) several more attempts were made unsuccessfully.
Slow sand filters constructed in other American cities were also unsuccessful in providing satisfactory water. This was attributed to the sediments in streams in America being essentially different than those in Europe. However, after the civil war, slow sand filtration plants were constructed to improve aesthetic quality in many of the major cities across the U. S.
In 1895, Allen Hazen proved the effectiveness of filtration for removal of microorganisms. In Europe, ozonation was first used as a disinfectant in Nice, France. However, it was too complex and expensive for use in the United States. In 1908, Jersey City, New Jersey started the first continuous chlorination system in the United States. It was based on experience with chlorination in Great Britain where it sharply reduced typhoid deaths. This practice was used across the U.S. and resulted in the virtual elimination of waterborne illness. It succeeded in reducing the death rate from waterborne disease from 25 of 100,000 people annually to virtually none today. These early systems relied on hypochlorites of sodium and calcium. In 1913, liquid chlorine was first used for disinfection in Philadelphia. The chlorination process consisted of bubbling chlorine into the water stream directly from the tank. Leaks were common and costly.
The U.S. Public Health Service published the first federal standards for drinking water in 1914. They established a standard of 2 coliform per 100 ml. While they applied only to drinking water put aboard interstate carriers, many States adopted these standards to apply to all of the public water supplies in the State. The standards were revised in 1925, 1946, and 1962. The 1962 drinking water standards applied to substances and included an Appendix giving the background for the limit for each standard. Most were based on epidemiological evidence from the substances that occurred naturally.
With the advent of manufactured chemicals in the environment and improved analytical methods, concerns were raised about the safety of the drinking water based on the probability of producing cancer as well as long-term toxicity. For the first time, Congress gave a federal agency the ability to promulgate and enforce drinking water standards.
In more recent years, improvements have been made to the coagulation and settling processes. These include the use of polyelectrolytes to form denser and tougher floc, upflow clarification, tube settlers and plate settlers.
Filters have also been improved. Different types of underdrain systems allow filters to be built in many shapes and allow for a more choices in filter media. The filter media can be the traditional silica sand or anthracite. In addition, combinations of these with garnet sand and synthetic media allow for higher filter rates without turbidity breakthrough or loss in filter efficiency.
Ozone is being used more widely, not only for disinfection, but also for oxidation of iron and manganese. New technology for ozone generation developed in Indiana is being used in many States with great success. The new generation of ozone generators operates at lower temperatures and higher efficiency, eliminating the need for expensive materials and complex equipment.
Source: Indiana Department of Environment Management
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