Disinfection technologies kill or screen out biological pathogens present in a water supply. The four major technologies used to disinfect water are described below.
MICROFILTRATION: a filter media is used with a pore size typically smaller than 0.2 microns. This physically prevents biological pathogens from passing through the filter. Ceramics and solid block carbon are commonly used to provide microfiltration. Ceramic filters have an advantage in that they can often be cleaned and reused a number of times before they lose effectiveness. Carbon block media usually has to be disposed of after each use. Also, ceramic filters typically have smaller pore sizes than carbon block and can therefore effectively filter a wider range of biological pathogens such as Escherischia coli (E. coli).
ULTRAVIOLET LIGHT: water flows in a clear quartz or plexiglas housing and is treated with ultraviolet light. The UV light destroys the genetic material of pathogens which effectively neutralizes them by preventing them from reproducing. Just recently has research shown that UV light, at a specific wavelength, is effective for the treatment of hard-shelled cysts like Cryptosporidium and Giardia lamblia
CHLORINATION: chlorine is added to the water supply where it oxidizes the organic contaminants and some inorganic contaminants in water. Chlorine can effectively treat biological pathogens such as bacteria. Chlorine however, has several limitations. It is ineffective against hard-shelled cysts like Cryptosporidium and Giardia lamblia. In fact, these cysts can survive up to 24 hours in concentrated bleach. Chlorine compounds typically have objectionable tastes and odors. They can also react with organic compounds to produce new halogenated organics that not only have unpleasant tastes and odors but also potential adverse health effects.
OZONE: just like chlorine, ozone oxidizes organic contaminants and is relatively more effective than chlorine as an inorganic oxidizer. Ozone is effective in treating biological pathogens like bacteria. It is also effective against hard-shelled cysts like Cryptosporidium and Giardia lamblia when high concentrations and contact times are used. Ozone does not produce any taste or odor in the water, it will only add oxygen to water. It is however, unstable and has a very short life.
