Viruses in our water are infectious organisms which range in size from 10 to 25 nanometers, basically invisible to the human eye. Viruses are particles composed of an acidic nucleus surrounded by a protein shell. They depend totally on living cells and lack an independent metabolism. There are over 100 types of enteric viruses. Enteric viruses are the viruses which infect humans. Enteric viruses which are problematic in our drinking water are hepatitis A, Norwalk-type viruses, rotaviruses, adenoviruses, enteroviruses, and reoviruses. The test for coliform bacteria in a water supply is widely accepted as a barometer as to whether or not the water is safe to drink; therefore, tests for the above specific viruses are not usually conducted. The US EPA has established an MCL that states a 99.99% reduction or inactivation for viruses in water supplies. Major enteric viruses found in water and their diseases are shown below.
Enteroviruses: Polio, aseptic meningitis, and encephalitis Reoviruses: Upper respiratory and gastrointestinal illness Rotaviruses: Gastroenteritis Adenoviruses: Upper respiratory and gastrointestinal illness Hepatitis A: Infectious hepatitis Norwalk-type: Gastroenteritis
Virus Water Removal and Treatment – Chemical oxidation/disinfection is the preferred treatment to remove viruses from drinking water. Chlorine feed with 30 minute contact time for retention, followed by activated carbon filtration, is the most widely used treatment. Ozone or iodine may also be utilized as oxidizing agents. UV water purification or water distillation may also be used for the treatment of viruses.