Iron In Water
It is no small wonder iron is often a concern with well water as it is the fourth most abundant element in the earth’s crust and the single most abundant heavy metal. It is not hazardous to health at levels most often found in drinking water, however as little as 0.3mg/l can stain laundry and fixtures and build up in plumbing.
The challenge is there is no one size fits all solution for dealing with iron in your water supply as iron manifests in several different forms – often at the same time. Additional variables effecting treatment decisions include overall water chemistry, flow rates, pressure and usage. Let’s discuss the most common types of iron and common treatment methods.
Ferrous or “clear water” iron comes out of the tap fully dissolved in the water and clear, but once exposed to oxygen it oxidizes and becomes the “rust” stains you see in toilets and other fixtures. The secret to removing this type of iron is to get it to oxidize completely so it can be filtered effectively before it reaches the house; otherwise it slips through conventional filtration. A water softener will generally remove up to 3 mg/L of iron, but iron must be clear water iron or it will damage the softener resin. Care must be taken if a softener is used to remove iron because it tends to foul the softener resin. A resin cleaning compound must be used regularly to protect the resin. The most common resin cleaning compounds contain sodium hydrosulfite or phosphoric acid. Some water softener salt contains a resin cleaner, however we do not recommend these products as they are more expensive and tend to “bridge” (harden into a solid mass that is difficult to remove from the tank without damaging equipment.) Higher iron concentrations require a different approach. Air injection introduces oxygen between the pump and pressure tank, oxidizing the iron in preparation for filtration. Extremely high iron levels may require additional equipment such as retention tanks and mixing devices. Please note that air injection does require certain parameters be met including adequate pressure and flow – and exceptionally low water temperatures and pH can be problematic. Likewise, if there is Anaerobic Bacteria present, introducing oxygen can create a breeding ground for it. (See below for more information on Anaerobic Bacteria.) Chlorination can also be used to oxidize ferrous iron, but a mechanical approach is generally preferable.
Ferric iron is commonly referred to as “red water” iron because of its rusty appearance. In reality it is simply clear water iron which has been oxidized, usually from dissolved oxygen present in the water supply. This type of iron is not dissolved in the water but instead
suspended in solution. These iron particles are not easily removed with conventional filtration either as filters clog quickly slowing down flow rates and must be changed frequently. Ferrous iron is almost always present as well and will slip right through. The go-to treatment for ferric iron is a custom built backwashable iron filter with our custom media blend. This requires adequate pressure, pH above 7 and regular regeneration.
Iron Bacteria (Anaerobic Bacteria)
Iron bacteria are a type of bacteria that feed on iron in water. As previously mentioned, iron is very common in the ground so is often present in well water. It is important to note that iron bacteria, while a nuisance, is not a health threat although it can make water unpleasant to drink. Iron bacteria manifests in slimy strands and films and musty odour. If your toilet tank is lined with slimy goo, you probably have iron bacteria. It can also colonize in the well casing and piping eventually reducing water flow. You will never get rid of it entirely, however regular shocking of the well will usually keep iron bacteria in check and is recommended at least spring and fall depending on the severity of the problem. Be aware, if there is significant buildup it may take two or three treatments before you have acceptable results. If shocking proves ineffective, anaerobic bacteria treatment systems are available.
Organic Iron & Tannins
Tannins are organic acids that are a by-product of nature’s processes and are produced as water passes through peaty soil and/or decaying vegetation. Organic iron occurs when iron combines with organic acid usually producing yellow or brown water, although it sometimes remains colourless. Organic iron is most frequently the product of shallow wells, river or lake supplied water or wells under the influence of groundwater. Organic iron and tannins cause staining of fixtures, china and fabrics as well as musty or earthy odour and unpleasant taste. Organic iron and tannins can be treated with a water softener or Manganese/Greensand filtration, but in both instances organics must be removed with activated carbon and other variables such as water pressure must be taken into consideration.
Colloidal iron does not occur as often as the other types, but is worth mentioning as it can come about as a side-effect of the treatment process itself. If using chlorine to oxidize iron, the appropriate dosage is essential as over-dosing with chlorine can cause the oxidized particles to fracture and become so small that they slip past the filter. This can also happen if water is run through an iron filter too quickly. If you are treating for iron and still notice staining it does not necessarily mean your system is not working. It may just need some fine tuning. Colloidal iron can also occur in chlorine-treated water supplied municipally by aging distribution systems.
Fracturing can happen with old cast iron or galvanized fittings and introduce colloidal iron into the water supply.
As you can see, iron can be a tricky problem and properly identifying the type of iron with which you are dealing is critical to applying the appropriate method of treatment. Finding a water treatment professional with experience in diagnosing “problem water” and applying suitable equipment is your first step in finding a solution to your concerns.