Water-treatment concepts underlying those used today were developed in Europe during the 1700s. An outbreak of cholera in London was linked to a sewage-contaminated drinking water well in 1854. John Snow was credited with this finding. At the point in which the United States began using chlorine to disinfect drinking water (1908), Europe was also using chlorine but exploring the possibility of employing ozone to treat drinking water. The U.S. Public Health Service developed the first drinking-water regulations in the United States in 1914. The U.S. Environmental Protection Agency (EPA) later assumed responsibility for this task when it was established in 1970. The Safe Drinking Water Act (SDWA) became law in 1974, and was significantly revised in 1986 and 1996. The revisions reflected improvements in analytical methods to detect contaminants at lower levels and improvements in automated monitoring used to evaluate treatment plant performance. The revisions also started to address the need to balance immediate (acute) risks versus long-term (chronic) risks. The need to disinfect water to kill pathogens to protect against acute illnesses, versus the formation of disinfection by-products and their chronic health effects is an example of this risk balance.
The United States has continued to examine water treatment practices in Europe, particularly water-quality standards established by the World Health Organization (WHO). Although there are some philosophical differences between the United States and Europe relating to the treatment of the distribution system and its operations, the United States has benefited from the European experience. One such philosophical difference is that the European water treatment community does not see the maintenance of a disinfectant residual to the end of the distribution system as a necessary public health protection measure. The United States drinking water community sees this as an important step to protect customers and the water system from bacteriological regrowth or recontamination. As the United States entered the twenty-first century, researchers were collaborating with scientists around the world to continuously improve water quality and treatment, and openly share their research findings.
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