An Introduction to Drinking Water Treatment

Water treatment has been used since the beginning of recorded history. Early methods were simple like heating, filtration through gravel and sand, and boiling. In the mid-nineteenth century water disinfection with chlorine was discovered, and the importance of water disinfection to check the spread of waterborne diseases was recognized. This led to rapid growth of drinking water treatment for public water supplies.

During the last quarter of the 20^th century, health concerns of the public (and of regulatory bodies) expanded to include water pollution caused by industrial and biological waste, and organic chemicals, rather than just concern with waterborne disease. Due to new requirements instituted by regulatory bodies, such as the U.S. Safe Drinking Water Act, water treatment plants were developed according to the specific requirements, and the water treatment processes were improved to make water more suitable for the desired purposes such as drinking water, industrial use, and other applications. The aim of all the processes of water treatment is to remove the contaminants present in the water, or adequately reduce their concentration.

The modern technique of drinking water treatment is based on a multiple barrier approach involving the disciplines of science, engineering, biology, and chemistry in order to introduce barriers in the water path to block water contaminants and ensure suitable water quality reaching consumers. The initial barrier is protection of the water sources from contamination, by restrictive discharge of waste to the water sources, utilizing better water contamination recognition techniques. The water contaminants are reduced or the concentration minimized by numerous treatment and disinfection methods, and the solids are separated by settling and filtration methods, including the removal of bacteria, viruses, nutrients, and some minerals like iron and sulphur. The treated water is also protected during distribution after treatment by allowing residual disinfectants in the treated water to destroy the remaining bacterial contamination.

Environmental water quality concerns the water quality of lake

s, rivers, and oceans. Their regulations are established by taking into account the factors of environmental state, ecosystems, and the desired use of the water. The quality of water is examined to determine the presence of contaminants, including organic and inorganic compounds, and bacteria, to ensure that the quality of water is in accordance with the federal and state standards. Testing is conducted at varying schedules according to the requirement, and at several sites on the water systems. Water quality for uses other than drinking is also important, such as agriculture, fisheries, industry, and, if not taken seriously, may be a potential health hazard. Measurements related to water quality are pH, temperature, dissolved oxygen, and many others. Since the water quality measurements are expensive, and of serious concern for the community, these are normally conducted by the government bodies, though some local volunteer programs are also available for a general evaluation. Waterborne diseases can be controlled by the efficient implementation of water treatment programs, including monitoring of the water quality.

1. US Environmental Protection Agency: The History of Drinking Water Treatment.

2. Hall, E.L, and Dietrich, A.M., A Brief History of Drinking Water, Rhode Island Water Resources Board

3. Bengtson, H.H., Design of Small Water Systems, An online, continuing education course for Professional Engineers