Iron Removal

Iron in water can cause red-orange stains to appear and affects the taste of food and beverages if left in during the production process. Water should be tested to determine the amount and type of iron you have (oxidized, soluble, colloidal, bacteria, or organic-bound, see below) to then ensure the correct method of iron removal is put in place.

Envirogen supply an extensive and comprehensive rangeof Iron Removal Plants from 0.9 m³/hr – 14.5 m³/hrfor use across a variety of applications. Iron is a natural substance typically found in water. Filtration plants are used when a relatively high concentration of inorganic iron is present. They are similar in appearance and size to water softeners but contain beds of media that have oxidising capabilities.

The Process:

This type of iron is usually found in a surface water supply. This is water that contains red particles when first drawn from the tap. The easiest way to remove this type of iron is by a fine mechanical filter. A cartridge-type filter is usually not a good solution due to the rapid plugging of the element. Another method of removal is by dosing a chemical into the water to cause the small particles of iron to clump together. It will then fall to the bottom of a holding tank where it can be removed by means of a pump or flushing to drain etc.

Soluble iron is called “clear water” iron. After being drawn from its source and making contact with the air, the iron oxidizes (rusts), forming reddish brown particles in the water. Depending on the amount of iron in the water, there are several ways of dealing this problem, one possible action is a combination of base-exchange, softening and filtration. Another possible solution is an iron removal system that regenerates with chlorine or potassium permanganate. You can also feed chemicals to oxidize the iron, followed by filtering it with a mechanical filter. You can sometimes hide the effects of soluble iron by adding chemicals that, in effect, coat the iron in the water and prevent it from reaching oxygen and oxidizing.

Colloidal iron is very small particles of oxidized iron suspended in the water. They are usually bound together with other substances. They resist clustering together due to the static electrical charge they carry. Because these particles are so small, when looked at in a clear glass this iron looks more like a colour, rather than particles. There are two popular treatments for colloidal iron: feed chlorine to oxidize the organic away from the iron. This will allow clustering to occur. Another way is to feed polymers that attract the static charge on the particles, forming larger clumps of matter that is filterable.

Iron bacteria are living organisms that feed on the iron found in the water, pipes, fittings, etc. They may create a heavy bacterial film along the water flow path. Occasionally, these slimy growths may break free, causing extremely discolored water. In severe cases it can pass to the point of use, even blocking fixtures or fittings. Initial signs of bacteria iron can cause a reddish or green film to build up in tanks etc. This type of iron problem can be hard to eliminate. Normally these types of bacteria are removed by cleaning/sanitising, usually by chlorination. It may be necessary to dose with chlorine continuously to prevent re-growth. Filtration alone is not an effective way to solve this problem.

Organic Bound:
When iron combines with tannins and other organics, complex compounds are formed that cannot be removed by ion exchange or oxidizing filters. This iron is often mistaken for colloidal iron. In these cases tests to identify the organics  etc should be carried out. If they are present, it is most likely combined with the iron. Low-level amounts can be removed by using carbon filtration. This absorbs the complex compounds. Regular replacement of the carbon bed is essential when it becomes totally saturated. Higher amounts may well require dosing with chlorine. This will oxidize the organics causing them to break apart from the iron allowing both to precipitate out into filterable particles.

PH and its effects on iron:
The pH (potential Hydrogen) of a water source plays a very important role in understanding the way that the iron can convert from a ferrous (dissolved) state to a ferric (un-dissolved) state. The higher the pH level, the faster iron can convert.

We supply a range of Iron removal filters.  Click here to download a datasheet.

Envirogen Water Technologies