Iron bacteria

Iron bacteria in water

Iron bacteria are naturally occurring microorganisms appearing as a slimy reddish-brown stain or substance in waterways. Iron bacteria live in streams, lakes, canals, and rivers and generally grow in slow-moving water with high amounts of iron. They're commonly found in streams fed by groundwater and around stormwater outlets. Iron bacteria feed on iron and have been present in natural waterways for millions of years.

When the bacteria feed on iron they may leave a slimy rust-coloured deposit suspended in the waterway. While the bacteria may seem unsightly, iron bacteria are not known to pose an environmental or human health risk. If you live near a waterway you may notice this condition worsens after heavy rainfall or during extended dry periods. This is a result of iron-rich soils leaching into the waterways.

Iron bacteria formation

Iron occurs naturally in the soil and leaches out into waterways during rainfall events and extended dry periods. When oxygen, water, and iron mix together they can create the right conditions for iron bacteria to bloom. Iron bacteria needs to oxidise (change their compound structure) to fulfil their energy requirements. This involves changing ferrous iron (Fe2+) into ferric iron (Fe3+). This process makes the iron insoluble and produces the rust-coloured slimy deposit you may have noticed.

Iron bacteria appearance

Iron bacteria

Iron bacteria are typically rust-coloured, slimy and have an oily or film appearance on the water's surface. This film can be distinguished from oil by taking a stick and running it through the film. If the film breaks apart it's likely to be iron bacteria. If it quickly pulls back together and adheres to the stick it's likely to be oil. Council officers use simple test kits for quick identification of the presence of iron and take water samples for further analysis under the microscope.

Report iron bacteria

It's important to remember that iron bacteria are not harmful to our health, nor do they adversely affect our waterways.

If you see iron bacteria and would like it checked, contact us by: