Waterborne diseases such as typhoid, cholera, dysentery, amebiasis, salmonellosis, shigellosis, and hepatitis A are still estimated to be responsible for the deaths of millions of people globally. In that context, the United Nations General Assembly has declared 1981-1990 as the International Drinking Water Supply and Sanitation Decade (WHO, 1984).
Current drinking water disinfection practices internationally provides the means to control most pathogenic bacteria, viruses, helminths, and protozoa responsible for the major waterborne diseases. Some outbreaks still occur oweing to continuing problems involving consumption of untreated water, errors of insufficient or interrupted disinfection, failures to maintain adequate levels of residual disinfectant in potable water distribution systems, and/or breaches in the systems. Most outbreaks in recent years have been caused by viruses and protozoan cysts that are generally more resistant to disinfection than are pathogenic bacteria, the primary targets of concern in past decades.