If bacteria are found in your water (after verification testing and chlorine shocking) the water can be disinfected. The oldest form of disinfection is chlorination. This method of water purification has been in use for about a hundred years. However, if your water supply becomes contaminated, elimination of the source of contamination is the most permanent solution. Continuous chlorination to kill disease-causing (fecal) bacteria in a contaminated water source should be a temporary measure used only until you can develop a new, sanitary water supply. If fecal bacteria have contaminated a water supply there may also be an associated increase in nitrogen which can be a significant health threat to infants. Let’s be honest here, the most likely source of fecal bacteria is a nearby septic system now focus on the source of fecal contamination and think of the yuck factor. If disease-causing bacteria enter your water supply on a continuous basis, you must eliminate the source or construct a new water supply.
Chlorination is widely used because it readily controls bacteria which may enter your well during construction, repair, flooding or as a result of improper construction. Chlorination can be appropriately used to control nuisance organisms such as iron, slime and sulfate-reducing bacteria. Iron bacteria feed on the iron in the water. They may appear as a slimy, dark-red mass in the toilet tank but microscopic examination is needed to confirm their presence. Iron bacteria colonies may break loose from the inside of pipes and flow through faucets to cause stains in laundry, plumbing fixtures, etc. Though thorough shock chlorination of the well and water system may destroy all iron bacteria colonies within the house; iron bacteria that has penetrated the water-bearing formation will be difficult to eliminate and will likely re-infest the system. In this situation you will need to repeat chlorination treatment periodically or install a continuous disinfection system.
Other nuisance organisms that chlorination can eliminate include sulfate-reducing bacteria which produce a rotten-egg odor. Nuisance bacteria do not cause disease. Proper chlorination will kill these bacteria. Finally, large amounts of iron can be removed from water by adding chlorine to oxidize the clear soluble iron into the filterable reddish insoluble form. Chlorine helps remove manganese and hydrogen sulfide in the same way. In these instances a chlorination system would be installed with a filtration system, the chlorinator first. Chlorination does have drawbacks; it will not remove nitrates from water despite the implied or direct claims of some water treatment firms. Adding chlorine may prevent nitrates from being reduced to the toxic nitrite form; however, nitrates are not removed from water by chlorination.
Chlorine in water is not poisonous to humans or animals. However, if the concentration is great enough the water will have an unpleasant taste and or smell. Some people object to the smell and/or taste of extremely small concentrations of chlorine. In those cases an activated carbon or charcoal filter may be used to remove the chlorine from the drinking water. Chlorination can also produce disinfection by products which are carcinogenic. Trihalomethanes (THMs) are organic chemicals that may form when chlorine is used to treat water supplies that contain humic compounds which are associated with decomposition of organic materials such as leaves, grass, wood or animal wastes. Lifetime consumption of water supplies with THMs at a level greater than 0.10 milligrams per liter is considered by the Environmental Protection Agency to be a potential cause of cancer. THMs can be removed from drinking water through use of an activated carbon filter.
Other methods of disinfecting water include boiling, distilling, treating with ultraviolet light and treating with ozone. Treatment with ultraviolet light and ozonation are replacing chlorination in may water treatment plants and is becoming more popular for home use. Water must be filtered before treatment with UV light. So, unlike chlorination systems, the filtration system is installed ahead of the UV treatment system. The typical single home UV system is a complete unit that includes a filtration cartridges and can be purchased as a whole house unit or an under the sink kitchen installation. UV, like distillation, disinfects water without adding chemicals. It does not create new chemical complexes, nor does it change the taste or odor of the water, and does not remove any beneficial minerals in the water. Ultraviolet devices are most effective when the water has already been partially treated, many units use filtration-sometimes both sediment and a carbon filter to clean the water prior to passing it through the UV light, which results in both disinfected and cleaner tasting water.