Nexus - 0207 - New Times Magazine-pages

Page Content (OCR)

100 YEARS OF WATER CHLORINATION was initiated at Adrian Michigan, though it was not until 1908 that chlorination was introduced on a large scale at the then huge Boonton Reservoir waterworks in Jersey City, New Jersey. By World War II, the practice of chlorination was widely established in the United States.' filtration, though the more common practice now is to apply chlorine both before and after filtration. The idea is that prechlorination serves to reduce the accumulation in filters of biological material such as algae. Postchlorination is alleged to minimise the number and variety of bacteria which would otherwise enter the distribution system. Chlorine also combines with ammonia and organic nitrogen compounds forming chloroamine. When ammonia is combined with chlorine, a slower acting disinfectant results which has been found to be beneficial in the suppression of iron-fixing or slime-forming types of bacterial growths. The process of water chlorination involves a relatively straightforward chemical process. Chlorine is one of the most reactive elements in nature and is found in a free form only in volcanic gas. Even a small amount of chlorine will dissolve in water, some of it combining with water to form hypochlorous acid and hypochlorite ion. Chlorination of water is achieved by adding chlorine gas directly to the water or by adding the chemicals calcium hypochlorite or sodium hypochlorite. In these latter forms chlorine is known as ‘free available chlorine’ and has effective germicidal powers because of its ability to combine with or oxidize classes or organic compounds essential to life. Chlorination is not employed as a substitute for other forms of water treatment; on the contrary the effectiveness of the process to some extent depends upon other treatments such as filtration. Being a very reactive element, chlorine will readily react with many other substances which may be found in water. If a range of these substances are present in the water even in minimal quantities, they may create a chlorine demand which significantly reduces the available chlorine for germicidal purposes. Consequently, chlorination is usually accompanied by filtration to reduce the presence of substances which may create excessive chlorine demand. One theory of how chlorine works suggests that there is a physiochemical reaction between chlorine and the structural proteins of the bacterial microbes, thus causing the disintegration of their cell walls. Another popular theory holds that the process of disinfection works by inhibiting a key enzymatic process which oxidizes the glucose of the cell; the bacterial cells die, that is to say, because the chlorine destroys the oxidation process upon which the cells Been al Chlorine is notorious for its pungent and disagreeable odour. The human olfactory sense is capable of detecting only a few parts of chlorine per million in the atmosphere, and a concentration of only 50 to 60 parts per million can cause serious illness within one-half hour to one hour. Being a toxic substance, it is capable of causing major congestion of lung tissue and even death if breathed in sufficient quantities. depend. Chlorine was originally added to the water just prior to The odour and taste of chlorinated water may be produced by the presence of excess chlorine or strangely, it may also occur if insufficient chlorine has been added. In the latter case the characteristic odours and taste are produced when chlorine reacts with organic matter such as algae in the water. When stronger chlorine levels are used, the organic matter in the water is destroyed completely, and the result is water which is virtually odour free. From the fact that water odour is minimal it would thus be misleading to conclude that chlorine levels are low and vice versa. THE POTENTIAL HEALTH RISKS FROM CHLORINATED WATER It is amazing to think that a very reactive and poisonous chemical could be deliberately added to public drinking water without an extensive study of the possible harmful health effects being carried out beforehand. Yet with chlorination, this appears to have been the case. In 1951, Dr. W.J. Llewellyn wrote to the editor of the Journal of the American Medical Association: NEXUS¢*27 APRIL-MAY 1992 What studies have been made to determine the