Iron Related Bacteria in Cooling Towers

Aug 23, 2016

Iron related bacteria (IRB) can present itself in many different forms within cooling tower systems. Typically, iron bacteria are introduced to the system through the building’s makeup water supply or through airborne contaminants. Once they manifest themselves in the piping or cooling tower, they are determined to stay. “Iron Bacteria” are capable of withdrawing iron from its aquatic environment and depositing it in the form of Fe(OH)3 (hydrated ferric hydroxide) or in its extracellular secretions. The brown/reddish slime byproduct of the iron bacteria is almost always found on the distribution pans, in the sump and on the ends of the cooling tower. If you were to draw your name in the slime layer and come back a few days later, it would be filled in completely by the extracellular secretion.

As previously mentioned, iron bacteria are tenacious and are extremely hard to get rid of. The slime layer of the iron bacteria often sloughs off and forms deposits that affect the industrial process. Also, the conditions they promote also provide the perfect environment for sulfur-reducing bacteria to thrive. As the sulfur-reducing bacteria multiply in the anaerobic conditions underneath the iron related bacteria they begin to form corrosion nodules in the piping. This presents an entire new problem to the system.


Chardon Laboratories has a proven process to mitigate an iron related bacteria issue in a cooling tower system or closed loop system. This differs from the typical biocide program of a water treatment company and is necessary because the current program is not effective. A typical biocide program could be described as mowing the lawn. The grass is still there, but is trimmed back. In the case of a cooling tower, there are small amounts of bacteria still present in the bulk water after the majority is eliminated by the biocide. In the case of iron bacteria, the lawn needs scorched. Three different chemicals are used for the procedure and it may take multiple doses to eradicate the iron related bacteria. Please contact Chardon Laboratories for the solution to your IRB problem.

IRB slime layer peeling away during chemical cleaning process.
IRB slime layer peeling away during chemical cleaning process.
Cooling Tower distribution pans following Chardon’s IRB eradication process.