54-Use of Chemical Disinfectants in Drinking Water - Need for Cautious Approach

Abstract

Disinfection process typically carries out the control of pathogenic organisms in drinking water. It is generally felt that once the disinfectant is added to drinking water, it is safe to consume the same. However, this is not true under all situations. It is not only the addition of disinfectant in drinking water, but also the side effects in terms of the formation of by-products and the spatio-temporal scheduling of the disinfectant, that is equally important from the public health point of view. Generally, the means of disinfection are: physical agents, radiation and chemicals. Physical methods of disinfection are unsuitable for the mass bulk of supply to be treated in a water treatment plant. Radiation methods also find limited usage such as in private treatments and for small supply schemes. The biggest limitation with the physical and radiation methods is their inability to leave any residual. The consumers use both/either of the methods, if they doubt the safety of water reaching their taps. Chemical disinfectants find the maximum usage all over the world because of easy availability and long-term effects. In chemical methods, oxidizing chemicals such as chlorine and its compounds, ozone, bromine, iodine, potassium permanganate, etc. are used. Chemical disinfection can also be practiced by addition of acids or bases resulting in the pH values below approximately 3 and above approximately 11 so as to create intolerable toxicity levels for pathogens. Pathogens do not long survive in such waters because of increased ionic strength and osmotic pressure, which are suggested to be responsible for the destruction of cells. However, the chemical disinfectants have their own limitations due to which there is need for adopting a cautious approach while choosing the same for drinking water. The present study discusses the safety of chemical disinfection by assessing the toxicological effects and by-products formation of various disinfectants. Subsequently, it suggests the methods to control the Disinfectant-By-Product (DBP) formation, and their removal/ reduction to permissible limits.