Where does it come from / what causes it?
Iron ochre is found in soils with high concentrations of iron. There are two processes that can result in the creation of iron ochre. First, iron ochre can be caused by a chemical reaction between water, air, and soil with a high iron concentration. In other words, when ferrous soil migrates with water toward a drain, the contact of air with this solution creates an iron hydroxide sludge.
Secondly, iron ochre can be the result of a biological process caused by the presence of ferrobacteria. Also known as siderobacteria, when these bacteria get into the water table, they produce a gelatinous mass as the iron oxidizes upon contact with air.
What are the risks associated with iron ochre
Since ferrous ochre is not something that a normal person would want to consume, the risks associated with it are mostly related to property rather than human health.
On the other hand, slime deposits may appear in the stormwater pond or in ditches. In addition, these reddish deposits can also accumulate on concrete slabs in basements and give off an unpleasant sulfur-like odour. Secondly, problems related to agricultural drains can appear and, as a result, runoff water no longer channels away from the buildings and seeps into the foundations at the junction of the walls. Finally, iron ochre can clog backwater valves, which can cause significant water ponding.
How to remedy the iron ochre problem
Since the presence of iron ochre comes mainly from the soils surrounding a building, the best way to solve a problem related to the iron ochre is during the construction of the building or by making major modifications to the land, floor or structure of the building.
However, if the problem is downstream of your water treatment system, there are a few options that can be performed. Generally speaking, a chemical disinfection step using chlorine or one of its derivatives will kill the ferrobacteria that cause iron ochre. On the other hand, if your pipes are clogged, you will have to clean them manually.