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An iron-oxidizing bacteria causes the rusty stain. You may find it ponding in low spots on your lawn and oozing from the ground after heavy rain during the summer. During the winter, a high water table can push it to the surface, where it can show for several days.
These bacteria are naturally occurring microorganisms that can be found in iron-rich environments. They use iron as an energy source, and in the process, they oxidize it, forming rust.
The rusty-colored discharge is typically harmless to humans and the environment and leads to aesthetic staining on sidewalks and driveways.
There are a number of different species of iron-oxidizing bacteria; most have long names and are sometimes hard to pronounce…if you’d like to give it a try, the most common include:
- Gallionella ferrugine
- Leptothrix ochracea
- Sphaerotilus natans
- Thiobacillus ferrooxidans
These bacteria often form “biofilms” on various surfaces, including metal, concrete, and plastic. Biofilms are communities of microorganisms that are embedded in a slimy matrix. Take care. The condition can lead to a slip hazard on hard surfaces like concrete.
You can remove it using a power washer or a brush and a strong cleaning solution. Try WD-40 and a stiff brush. Follow it with a soap cleaning. Let dry and repeat as needed.
You may also seal the concrete surface to prevent the bacteria from returning.
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