*The following regulatory news article on iron is intended to be an overview of the report, legislation or proposal, and not a replacement for the actual guidance from the government. For the comprehensive data and all relevant information, please visit the linked source material within the article.
A new guideline technical document from Health Canada proposes to slightly lower the aesthetic objective level of iron in drinking water to minimize discoloration, complaints of bitter or metallic taste, and the presence of manganese.
Canada formed the initial iron guideline in 1978 at ≤ 0.3 mg/L, and is now proposing to lower it to ≤ 0.1 mg/L. The consultation period runs until November 28.
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Health Canada states that when the iron concentration is 0.3 mg/L, consumers may notice the flavour of ferrous iron and see rust and iron staining.
“This shows that a concentration of 0.3 mg/L is not low enough to minimize complaints about water colour and taste complaints or to improve consumer confidence in drinking water quality,” states Health Canada’s guideline technical document.
The new aesthetic objective proposal would also minimize excessive deposit buildup in the distribution system.
The technical document states that most well-operated and optimized treatment plants can achieve iron concentrations of 0.1 mg/L or less in the treated water, and this generally improves the removal of manganese. The level can be measurable by available analytical methods and achievable by commonly available technologies.
Iron can be lowered through aeration, chemical oxidation followed by filtration, coagulation, adsorption, membrane filtration, or coagulation followed by ultrafiltration. The most widely used technology that is effective for decreasing iron concentrations in drinking water is based on directly oxidizing dissolved Fe(II) to form Fe(III) particles.
“The particles are then removed by a physical process, such as clarification and granular media filtration or low pressure membrane filtration,” states Health Canada.
While there is no health-related guideline for iron, oral exposure to very high levels may cause adverse health effects, with gastrointestinal distress being the most sensitive endpoint, notes the technical document.
“Considering that iron levels can vary significantly in source water, within treatment plants, and especially in distribution systems, monitoring programs should be system-specific to enable utilities to have a good understanding of iron levels from source to tap,” Health Canada states.
The main sources of iron exposure for the Canadian general population are food and, to a lesser extent, drinking water.
From an aesthetic perspective, ferric iron present at high levels can be responsible for the often objectionable reddish-brown colour of water, according to the technical document. Some staining of plumbing fixtures and laundry may occur at iron concentrations above 0.05 ppm.
“Particulate iron, commonly called rust, occurs in tap water because of corrosion of iron pipes and is a common source of consumer complaints,” Health Canada states.
