By John Cardiff
When there is a reddish-brown tint to the colour of water, a distinct metallic taste, foul smell, or visible sediment or discolouration, there could be a chance that iron might be found in the drinking water. Iron itself isn’t a direct harm to human health, but it can help organisms to grow.
On Dec. 27, Health Canada, in collaboration with the Federal-Provincial-Territorial Committee on drinking water, published an updated aesthetic objective (AO) for total iron in Canadian drinking water. The new objective of less than or equal to 0.1 mg/L is intended to improve confidence in Canadian drinking water and minimize discoloured water events due to iron. Health Canada also notes that when both iron and manganese (Mn) are present, the removal of iron generally improves the removal of Mn and thus will reduce the health risks associated with this metal. The previous guideline for iron in Canadian drinking water was less than or equal to 0.3 mg/L.
For municipal water treatment systems, the new objective will also help ensure that disinfectant residual is maintained throughout distribution and improve consumer confidence in drinking water quality. In Canada, iron has an aesthetic objective in drinking water but not a maximum acceptable concentration.
Food is the main source of iron for Canadians and drinking water accounts for less than 10 per cent of our total daily iron intake. As such, nonheme iron (iron that is primarily found in plant-based foods) in drinking water is not expected to cause significant systemic health effects in healthy individuals but can cause laundry and fixture staining, biofilm growth in pipes and water systems, bad or metallic taste in drinking water, and plumbing issues. An upper level (UL) of 45 mg per day for total intake of iron for adults (14 and over) and 40 mg per day for children (13 and younger) has been established by Health Canada.
Treatment options
Before choosing a treatment method, it is essential to determine the type of iron present in the water. The most common forms of iron found in drinking water are ferric oxides and hydroxides, and ferrous iron. Ferric oxides and hydroxides can’t be dissolved and are commonly called red water iron because discolouration is visible from the faucet. Ferrous iron is commonly called clear water iron and is clear from the faucet but eventually oxidizes causing particulates to settle to the bottom of a glass.
It’s important to choose water treatment systems that have been certified by an accredited certification body as meeting the appropriate NSF International Standard/American National Standards Institute (NSF/ANSI) for drinking water treatment units. Certification ensures that materials in the system adhere to material safety standards and include performance requirements that specify the removal that must be achieved for specific contaminants. NSF/ANSI Standard 42, Drinking Water Treatment Units—Aesthetic Effects, is applicable for iron removal from drinking water. For a drinking water system to be certified to Standard 42 for iron removal, it must be capable of reducing an average influent concentration to a maximum final concentration of 0.3 mg/L, according to NSF International.
When purchasing equipment, look for these certification organizations that are accredited in Canada: CSA Group, International Association of Plumbing and Mechanical Officials (IAPMO), NSF International, Water Quality Association (WQA), UL LLC, Bureau de Normalization du Québec, and ALS Laboratories.
Selecting the most effective treatment system for iron removal depends on a variety of factors, including the concentration and form of iron, the water composition, and the presence of other contaminants like manganese, sulphide or ammonia. When selecting a system, consider the total iron in the water using this formula: Total iron = Iron ppm x one plus manganese ppm x two.
Point-of-entry filtration systems
Whole home air oxidization filters are a popular and reliable choice for homeowners because they don’t involve ongoing use of chemicals. They use air to convert dissolved iron into a solid form and then remove it through filtration. These types of filters are designed to treat water with high iron levels.
Before selecting a system, consider whether a two-tank or single-tank air oxidization filter is best for the application. Two-tank systems, one tank for air and a second tank for media have higher iron removal capacities and are more efficient than single-tank systems because they require less frequent regeneration. Single tank systems are ideal solutions for water with lower iron content and smaller spaces.
Birm (a catalytic filtration media) promotes iron oxidation and is used when dissolved oxygen is present. It is a low-maintenance option but requires the right water chemistry for optimal performance.
Greensand filters can also be used for residential iron removal. These systems have a filter medium with a manganese oxide coating that adsorbs and then oxidizes dissolved iron. Often called manganese greensand filters, they require significant maintenance, including frequent regeneration with an oxidant and regular backwashing to remove oxidized iron particles. When not operated or maintained properly, greensand filters can release manganese into the tap water. It is important to note that potassium permanganate is a Class A precursor and controlled substance by Health Canada and that regulatory updates have introduced more stringent requirements regarding its distribution.
for homeowners because they don’t involve ongoing use of chemicals.
Another POE filtration option is a conventional water softener. While designed specifically to remove hardness, ion exchange water softeners can also remove moderate levels of ferrous iron. It is important to keep in mind that softener resin is selective towards hardness cations (calcium and magnesium) so the harder the water is, the less effective the softener will be at removing iron. When installing a water softener that will also reduce iron, inform the homeowner that the iron will shorten the life of the softening resin causing more frequent replacements.
Regular use of a resin cleaner is recommended in these applications. For extreme problem water applications, chemical injection systems may be recommended to treat exceptionally high levels of manganese, tannins, or hydrogen sulphide in combination with iron.
Point-of-use filtration systems
Reverse osmosis (RO) drinking water treatment systems are best suited to applications where there are concerns about other contaminants in the drinking water and very low levels of iron. While RO technology has been proven effective at removing low levels of iron at the tap, it is important to consider the service, maintenance, and cost implications of using it for this purpose. Over the course of several years, a point-of-entry iron filter may be a more affordable option, even if the upfront cost is higher.
Prior to installation, water testing and system sizing are required. Properly sizing an iron filter requires you to know the service flow rate, well pump output, the oxidation demands of the water and that the well is capable of providing the volume of water needed for backwash and rinse. Asking your equipment manufacturer to recommend the right system and size based on the water test results and application parameters is the best way to ensure the system performs as expected.
To ensure long-term performance, regular maintenance is required for all iron filters. When installing iron filters, review the maintenance requirements with the homeowners or set up a service call schedule.
Selecting the right treatment system to remove iron is crucial for maintaining water quality, protecting plumbing systems, and enhancing overall water taste and usability. Helping your customers invest in a certified system and then adhere to a strict maintenance schedule will provide long-term benefits for households relying on private wells.