Well Water Treatment for Bacteria

Owners of private wells hold responsibility for the purity of their well water. Most well water comes from groundwater at depths where bacteria are not usually present. However, bacteria can still enter a well through surface runoff water or because of damage to the well. Wells that are too shallow can also incur bacterial contamination.

Bacteria in Wells

Coliform bacteria and iron bacteria may cause problems in well water. Coliforms themselves are usually harmless, but their presence indicates possible contamination by pathogenic organisms. Homeowners should have a laboratory test their well water for total coliforms every one to two years. The EPA standard for drinking water mandates zero coliform colonies per 100 milliliters of water; the presence of any coliforms indicates a need for treatment. Iron bacteria show up as brown slime in wells and plumbing. They do not harm human health, but can cause odor, reddish water and corroded pipes.

Chlorination

Home chlorination systems use low concentrations of liquid or dry chlorine to kill off bacteria. Chlorine also leaves a residual in the water, ensuring bacteria cannot regrow. Because iron bacteria form thick layers of slime, homeowners may need to shock chlorinate a well to adequately remove an infestation. Shock chlorination involves leaving a strong solution of chlorine bleach and water in the well and pipes for at least 24 hours, then flushing the chlorine solution from the system.

Ultraviolet Disinfection

The ultraviolet light used in UV disinfection damages bacterial DNA, inactivating the bacteria and rendering them harmless. Homeowners can choose a Class A or Class B UV system; Class B systems are mainly effective against bacteria, while Class A systems also work for other types of microorganisms. Ultraviolet disinfection does not add any chemicals to the water; however, this also means no residual exists to maintain water purity after disinfection.

Ozonation

Ozonation systems convert oxygen to ozone, pump the ozone into the water, then remove unused ozone. Ozone is a stronger chemical disinfectant than chlorine, but it is also more expensive and more difficult to obtain. In addition, ozonation produces chemical byproducts, and scientists do not fully understand the effects of these byproducts.

Emergency Treatments

Flooding or damage to parts of the well may introduce bacterial contamination into a usually clean well water. Boiling and iodine serve as viable short-term treatment options for drinking and cooking water. Boiling water vigorously for two minutes kills most bacteria. Dissolving iodine tablets in the water is another possibility. To avoid contamination due to well damage, homeowners should regularly inspect well casings, seals and caps for cracks or other damage and repair any problems they find.

References

• Utah State University Cooperative Extension: Coliform Bacteria; Barbara Daniels, et al.; June 2005
• University of Arizona, Sustainability of Semi-arid Hydrology and Riparian Areas: Disinfection Methods
• Colorado State University Extension: Bacteria in Water Wells; R. Waskom, et al.; April 2009
• Wisconsin Department of Natural Resources: Iron Bacteria in Drinking Water

Resources

• University of Missouri Extension: Bacteria in Drinking Water; Wanda Eubank, et al.; April 1995