ABSTRACT
Chemical disinfection is used to destroy or control the growth microorganisms present in water that would otherwise cause fouling, corrosion of equipment, or lead to diseases from microbial activity (Hooper in Lorch, 1987). Disinfection is not sterilisation; that is, not all microorganisms are destroyed. However, the number of microbes left after disinfection should allow safe human consumption of the disinfected material. Hence, stringent guidelines laid down by water authorities have to be followed. This also implies that the guidelines for water disinfection should be chalked out taking into consideration the assessment of various physical, chemical, and bacteriological parameters. Generally, every country as well as individual state has regulations to ensure good drinking water quality. These rules and guidelines are reviewed and updated from time to time considering the changing global environmental scenario, including the emergence of new pathogens and pollutants as well as the sources of water. Yet another important element of water disinfection guidelines is to ensure safe residuals of the chemical used for disinfection given the fact that disinfection by-products are very harmful to humankind. This implies that drinking water that is disinfected per norms need not be completely devoid of deleterious byproducts. Therefore, the use of chemical disinfection must be undertaken with care, as various limitations exist whereby products in water are sometimes unevenly distributed. In order to understand this, it is necessary to know some fundamentals about the theory of chemical disinfection.
