Iron-oxidizing bacteria in the floodplains of Congaree National Park.
Karen Jackson, ©2020, Clemson University
“There’s orange water coming up through the ground!” said the homeowner who called me last week, wondering what kind of contaminant had made its way into her yard. If you’ve ever come across this orange-tinted water in a stream or seeping up from the ground, you may have been alarmed too! Not only does the water appear “orange” or “rusty”, but it can also have a “fluffy” appearance. Not to worry, this is nothing more than iron-oxidizing bacteria. These bacteria are not harmful and occur naturally in streams, lakes, and ditches. They are most commonly found in streams or seeps fed by groundwater rich with iron. Even though they’re not harmful to humans or aquatic organisms, they may cause some odor and taste issues if found in well water.
The rusty colored water produced is just a sign of the bacteria trying to make a living, turning ferrous iron (Fe2+) into ferric iron (Fe3+) to produce energy. The change from ferrous to ferric iron makes the iron insoluble, which produces a fuzzy or slimy texture. This often happens when previously anoxic (low oxygen) water in the soil comes in contact with atmospheric oxygen. In fact, this process only needs 0.3 ppm of dissolved oxygen to take place! The bacteria will begin to increase rapidly as more iron becomes available.
Iron in the soil has come in contact with iron-oxidizing bacteria and water to produce a “rusty” color.
Karen Jackson, ©2020, Clemson University
Another sign of this bacteria is the presence of an oily sheen on the water’s surface. To distinguish bacteria from petroleum products, use a stick to mix the water. If the oily sheen shatters like glass, it’s a natural byproduct of bacterial decomposition. If it swirls together and refuses to separate, it’s a petroleum product.
If you have additional questions on this subject or anything else relating to our water resources, please reach out to the Clemson Extension Water Resources Team! Also, check out HGIC 1879 Protecting Headwater Streams to learn more about our freshwater systems’ importance.
