Water is essential to life.
People in the industrialized world take clean water for granted. Not all countries, however, provide a clean source of water for their people, and as a result many illnesses occur. Keeping water free of contaminants is very difficult and costly. Water treatment facilities monitor for fecal contamination of their water by checking for the presence of bacteria that are normally found in feces. Water treatment plants test their water for the presence of E. coli very frequently.