Manganese (Mn) is a chemical element found naturally in minerals from rocks, often in combination with iron. It is found abundantly in many common grains and vegetables and is essential to human nutrition.

On Hornby Island, manganese and iron may be present in well water. Common issues with manganese and iron in groundwater include rusty-orange, brown or black staining that can often be seen on clothes, fixtures, sinks, tubs, water-using appliances and toilets.

How does it get into the groundwater?

Fractured bedrock (shales, sandstones, conglomerates and older volcanic rocks) is rich in manganese silicates. Rainwater infiltrates fractures in bedrock and dissolves manganese along its flowpath.

Glacial tills deposited by retreating glaciers naturally contain manganese rich minerals sediments that weather over time and release into the groundwater.
Low oxygen conditions (e.g., deeper stagnant zones) in groundwater can mobilize manganese.

Slow recharge and localized areas of organic material in glacial tills or overlying soils (from vegetation or former wetlands) can mobilize manganese.

Well depth may influence manganese levels. Deeper wells are likely to tap into older, low oxygen water. Shallow wells may show less manganese if they interact more with surface water.

What are the health effects?

Health Canada has set guidelines for manganese:

• Aesthetic Objective (AO) – 500 µg/L (tasting and staining)

• Health-based Maximum Acceptable Concentration (MAC) – 120 µg/L (based on protection of infants)

Studies have shown manganese at high levels can affect learning and behaviour of young children. If the manganese levels in your well are higher than 120 µg/L, this could pose a risk, especially for infants if the water is used to prepare formulas.

For adults and older children, short-term exposure to higher levels of manganese is unlikely to cause negative health impacts. Data indicates that the human body can recover from certain adverse effects of overexposure to manganese if the exposure is stopped and the body can clear the excess.

Is there manganese in well water on Hornby?

Two different studies on Hornby showed that 11.3% of 115 (Allen and Matsuo, 2002) and 15.3% of 59 (Cox, 2019) well water samples collected were greater than 120 µg/L manganese.

Where can I get my well water tested for manganese?

Island Health recommends that private wells should have a chemical and physical analysis (which will include manganese) every 3-5 years or after major maintenance, flooding of water quality changes.

The closest accredited laboratory for Hornby residents is the Bureau Veritas laboratory in Courtenay. Costs for a chemical and physical analysis is approximately $500. A total metals scan which includes manganese, iron and hardness costs ~$200.

How do I remove the manganese from my water?

To effectively treat manganese, a whole-house or point-of-use water treatment system can be used. Whole-house systems, like greensand filters or reverse osmosis systems, treat the water entering your home, while point-of-use systems, like reverse osmosis at the tap, target specific water sources.

The following manganese concentrations are a general guide for manganese removal:

• <300 µg/L – water softener (ion exchange),
• 300-1500+ µg/L – oxidation (common oxidants – aeration, chlorine, potassium permanganate, ozone – convert soluble Mn+2 to insoluble MnO2) plus filtration (greensand filters, birm filters, or manganese dioxide media) – best for most cases, and
• >1500 µg/L – pre-oxidation plus advance filter

The following are not effective alone to remove manganese: carbon filters, boiling water (may concentrate it) and UV disinfection.

Where can I get help?

The following are some of the local water treatment suppliers that can help with manganese removal (as of August, 2025):

• Van Isle Water Services (Victoria, BC)
• Filterco Water Treatment Ltd. (Nanaimo area)
• Aqua North Water System Ltd. (North Vancouver Island)
• Excalibur Water Systems (Parksville)
• Vortech Plumbing and Filtration (Duncan/Cowichan)

There are also off the shelf whole water filter devices to allow for comparisons in price and capacity but it’s important to check, shipping, installation and warranty terms for BC. A few examples are:

• PRO+AQUA PRO‑WELL‑1E Whole‑House Well Water Filter (~$1000) – Chemical‑free catalytic media; removes iron, manganese, sulfur, heavy metals.
• Waterdrop 2‑Stage Whole‑House Iron & Manganese Filter (~$250) – Double manganese sand media; tested to remove ~99.7% of manganese; high flow rate (15 GPM), NSF‑certified.
• Clack WS1 Air‑Over‑Media Iron/Manganese Filter (~$1,500) – Premium catalytic media with air injection; ideal for higher manganese or hydrogen sulfide levels.
• Fleck 2510AIO Katalox‑Light Iron/Manganese Filter (~$1,400) – Chemical‑free
• Katalox‑Light media on a Fleck control valve; high flow, ideal for moderate to heavy manganese.

Any treatment system installed must be properly operated and regularly maintained to be effective.