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Improving the Quality of Water Through Disinfection


To Remove Doubt, Test It Out! See also issues relating to swimming pools

Disinfection is necessary to destroy pathogenic (disease-producing) bacteria and other harmful organisms that may be present in water. Methods of disinfection include chlorination, distillation, ultraviolet treatment, ozonation, and iodine or bromine feed.

Chlorination - for more detail see issues relating to swimming pools

Chlorine is effective against bacteria and requires short to moderate contact time. It is readily available in several forms and it and its effect is easily tested. High chlorine concentrations have objectionable tastes and odors, and even low concentrations react with some organic compounds to form strong, unpleasant tastes and odors. Trihalomethanes, by-products produced when chlorine reacts with humic and fulvic organic compounds present in natural waters, have potential adverse health effects.

Inorganic materials such as dissolved iron and manganese are oxidized by chlorine and converted to insoluble forms. Chlorine reacts with organic matter usually breaking it down into simpler substances.


Ultraviolet light (UV) disinfection units are effective at destroying bacteria and viruses. UV disinfects water without adding chemicals. It does not create new chemical complexes, nor does it change the taste or odor of the water and it does not remove any minerals in the water.


Ozone generators are used in some systems to produce small quantities of ozone gas, which is a very strong oxidizing agent and is effective in killing bacteria with even brief exposure times. Ozone is also effective in oxidizing organic matter, iron, and manganese. The use of ozone does not form trihalomethanes, as can chlorine. It produces no tastes or odors in the water. Ozone is unstable and has a very short life, so it must be generated at the point of use. Ozone is hazardous to health when breathed.

Bromine and Iodine Feed

for more detail see issues relating to swimming pools

Both iodination and bromination have been proven effective in controlling most disease-producing bacteria, even with relatively short contact time. These methods have been used successfully for disinfection of swimming pools, but bromine is not recommended for drinking water. Iodine disinfection is not recommended for long-term or routine drinking water supply application. There is some evidence that iodine intakes of as little as 0.5 milligrams per day might have resulted in hyperthyroidism, thyroiditis, or increased rates of thyroid carcinomas.

Prepared by Trevor Croll,

42 Pearse Street, Keperra, Queensland Australia, 4054.
Phone 61 7 3855 1115