Water Treatment: Keeping It Pure
Katsioloudis, Petros J., The Technology Teacher
The availability of water has dictated the location and survival of civilizations through the ages. Nearly 1.1 billion people around the world lack access to potable drinking water sources, and 2.2 million die from basic hygiene-related disease, an issue that can easily be justified as the most important environmental problem of all (World Health Organization, 2007). The majority of these deaths are wholly preventable through effective improvements in water, sanitation, and hygiene. The United States remains strongly committed to providing sale drinking water for all of its citizens (Environmental Protection Agency (EPA, 2005)).
The national goal for sanitary drinking water has been to provide water that meets all health-based standards to 95% of the population served by public drinking water supplies by 2005 (EPA, 1999). In 2002, the level of compliance with these health-based issues was 94% (EPA, 2003). However, conventional piped water systems using effective treatment to deliver safe water to households may be decades away in much of the developing world. This leaves the majority of the poorest people in the world with the task of collecting water outside the home, then treating and storing it themselves (Sobsey, 2002). Even though water is essential for human life and its quantity and quality ate equally imperative, natural waters are in most cases not aesthetically or hygienically appropriate to be consumed, thus calling for some means of treatment. Appearance, taste, and odor are useful indicators for the quality of drinking water, but the critical suitability factor in terms of public health is determined by microbiological, physical, chemical, and radiological characteristics. As far as is known, the first instance of filtration as a means of water treatment dates from 1804, when John Gibb designed and built an experimental slow-sand filter for his bleachery in Paisley, Scotland, and sold the surplus treated water to the public at a halfpenny per gallon (Baker, 1949). In 1855 the first mechanical filters were installed in the U.S. (Baker, 1949). Since then a number of modifications and improvements have been introduced and have attained varying degrees of popularity. Table i describes a number of the most common water-treatment methods. A variety of technologies for water treatment exist; some are based on historical water treatment techniques. However, there is new research that has found effective reduction of waterborne pathogens using innovative technologies (Lantagne, 2007).
According to the Public Health Service (PHS), (2005) the federal regulation of drinking water quality began in 1914, when standards were set for the bacteriological quality of drinking water (PHS, 2005). The standards, however, applied only to water systems that provided drinking water to interstate carriers such as ships and trains, and only applied to contaminants capable of causing contagious disease. Upon revision in 1925, 1946, and 1962, PHS revised the standards to regulate 28 substances, establishing the most comprehensive federal drinking water standards in existence before the Safe Drinking Water Act of 1974.
With minor modifications, all 50 U.S states adopted the Public Health Service standards either as regulations or as guidelines for all of the public water systems in their jurisdictions. However, the aesthetic problems, pathogens, and chemicals identified by the Public Health Service in the late 1960s were not the only drinking water quality concerns, since industrial and agricultural advances and the creation of new man-made chemicals also had negative impacts on the environment and public health.
The main sources of drinking water are often polluted by industrial and municipal chemicals (Gevod et al., 2003). While filtration was a fairly effective treatment method for reducing turbidity, disinfectants such as chlorine played the largest role in reducing the number of waterborne disease outbreaks in the early 1900s. …