Contaminant of the Week: Iron Bacteria

Iron bacteria are organisms that consume iron to survive. In the process, they oxidize available iron that produces iron deposits (rust) and a red or brown slime called a “biofilm.” Though the organisms are not harmful to humans,they can exacerbate an already troublesome iron issue in water.

Indications of iron bacteria activity include water with a red or yellow color, slime on the inner walls of the toilet tank, and/or odors that resemble fuel oil, cucumber or sewage. If iron activity is expected, an iron home testing kit can confirm your observations.

Iron bacteria testing kit from Hach.

Iron bacteria test kit from Hach.

These organisms naturally occur in shallow soils and groundwater, and may be introduced into a well or water system when it is constructed or repaired. Iron bacteria issues are treated by shocking the well with chlorine on a regular basis and/or installing a chlorinator. An ozone or hydrogen peroxide system with a contact tank can also be installed to kill the iron bacteria by oxidizing the iron prior to an automatic iron filtration system.

Stenner-45MHP-chlorinator. See for product details.

Stenner-45MHP-chlorinator. See the Clean Water Store website for product details.

Iron is considered a secondary or aesthetic contaminant. It is an essential mineral for human health in small concentrations. Iron deficiencies in the body can lead to conditions such as anemia. Though ingesting low quantities of iron from drinking water is not directly associated with adverse health effects, trace impurities and microorganisms that are absorbed by iron solids may still pose significant health concerns.

In a well, iron bacteria can colonize allowing pathogenic (harmful) organisms to thrive off the iron supply in the water. Eliminating the bacteria is more difficult if iron is not removed from the well water.

The effects associated with iron contamination can be grouped into two categories: Aesthetic Effects and Physical Effects

Aesthetic effects include undesirable tastes or stains. Iron in quantities greater than 0.3 milligrams per liter (mg/L) in drinking water can cause an unpleasant metallic taste and rusty color. Taste is a useful indicator of water quality. However, taste-free water is not necessarily the safest to drink. Taste can be a useful indicator of the effectiveness of water softening or reverse osmosis systems post-treatment. Elevated levels of iron in drinking water can also stain laundry and household appliances with a rusty color. Discolored water is one of the most frequent consumer complaints about drinking water.

Rust stains around a drain.

Rust stains around a drain.

Physical effects may include damages to water equipment and reduced effectiveness of treatment intended for other contaminants. This may cause additional costs to operate water systems. Corrosion and staining related to corrosion not only affect the aesthetic quality of water, but may also result in distribution system problems. Among other things, corrosion of distribution system pipes can produce sediment or loose deposits that block water flow.

Corroded iron pipe.

Corroded pipe.

For more information about other well water contaminants, visit the Clean Water Store Water Problems tab. You can also follow us on Facebook and Pinterest. Stay tuned for future Contaminants of the Week on the Well Water Test Kit Company blog!

About the Author Gerry Bulfin

Need help with your well water? I have been assisting homeowners, small communities and businesses improve their well water quality since 1989. Please email me at if you have a question about water testing, test kits or well water systems in general. Gerry Bulfin CWS-IV Master Water Specialist WQA Certified Licensed California Water Treatment Contractor