What are the most common Disinfection Technologies used to treat water?

Disinfection technologies kill or screen-out biological contaminants present in a water supply. Chlorination, microfiltration, ozone and ultraviolet light are the four major technologies used to disinfect water. Chlorination Chlorination consists of adding a concentration of the chemical chlorine or chloramines to a water supply. Generally, the chemical is fed directly into a well or retention tank so the concentration and contact time can be controlled. While in contact with the water, the oxidizing ability of the chemical “burns up” the organic contaminants in the water. Chlorine can effectively treat biological pathogens like coliform bacteria and legionella, though it is ineffective against hard-shelled cysts like those produced by Cryptosporidium and Giardia lamblia. Chlorination also treats for organically related taste, color and odor problems. Microfiltration Microfiltration utilizes a filter media with a pore size smaller than 0.2 microns to physically prevent biological contaminants from passing through. Ceramic water filters and solid block carbon filters are commonly used in the microfiltration process. Ceramic water filters have an advantage in that they can be cleaned and reused a number of times before they lose effectiveness. Solid block carbon filters usually have to be disposed of after each use. This media, however, provides additional treatment for a variety of additional health and aesthetic contaminants (see activated carbon section, above). Microfiltration is effective in treating a complete range of biological contaminants including hard-shelled cysts like Cryptosporidium. Ozone Ozone treatment, which oxidizes organic contaminants similar to the way chlorine does, is typically reserved for large-scale commercial and industrial applications. However, there has been a recent increase in the number of ozone units designed for use in single-family dwellings and businesses. After an ozone generator converts oxygen found in the air to O3, or ozone, the chemical is fed into a water supply where it effectively treats for pathogens like coliform bacteria and legionella. Like chlorine, however, it too is ineffective in treating hard-shelled cysts like Cryptosporidium or Giardia lambila. Ultraviolet Light (UV) Capitalizing on the power of natural light, ultraviolet light has effectively treated water since the beginning of time. Modern ultraviolet water filter systems use a UV bulb in a clear quartz or plexi-glass housing, around which flows the untreated water. The UV light destroys the genetic material of certain pathogens, making it impossible for the pollutants to reproduce. Using a ultraviolet water filter is effective in treating coliform bacteria and legionella, but is not effective in the treatment of hard-shelled cysts like Cryptosporidium and Giardia lamblia. Distillation Distillation produces high quality, treated water by heating the raw water until it turns to steam. The steam then travels through a condensation coil, where it is cooled and condensed back into liquid form that is held in a separate section. Typically, the contaminants present when the water is converted to steam remain in the boiler section, with the condensed water in the second section being substantially free of contaminants. Maintenance of a distillation unit usually involves cleaning out the build-up of contaminants on the boiler side of the unit. Distillation provides a high degree of effectiveness against a broad range of health contaminants. Typically, however, it is not effective in treating contaminants such as benzene and radon because they give off harmful vapors that move through the system with the steam. The energy requirement of distillation, coupled with a relatively long production time, typically limits distillation use to point-of-use drinking water applications in home and commercial markets. There are some distillation units that are tested and approved for the reduction of biological pathogens. Reverse Osmosis Reverse osmosis (RO) is a common treatment technology that produces high quality water. A reverse osmosis water filter system purifies water by first passing the water through a series of filters to remove large contaminants and harmful chemicals/pollutants, and then secondarily forcing the water through a special plastic membrane to remove the very small contaminants. Typical contaminant rejection rates range from 85 percent to 95 percent, and a gallon of highly treated water can usually be produced from two to four gallons of raw water, depending on the initial quality of the water. Maintenance involves the replacement of the RO membrane cartridge every two or three years, and the carbon filter cartridges six to 12 times per year. RO is effective in the reduction of a broad range of health and aesthetic contaminants, though it is typically not used for the reduction of biological pathogens. The process also typically incorporates an activated carbon water filter, which can provide additional protection against the volatile organic compounds (VOC's) not treated by the membrane itself. Home Page | FAQs | Glossary | Contact Us