Understanding Tannins in Drinking Water

Understanding Tannins in Drinking Water

Tannins are a group of organic substances that naturally occur in various plants – including trees, shrubs, and herbs. Tannins give a characteristic brownish or yellowish hue to water and can cause a bitter or pungent taste. A great example of Tannins in water is when you add a tea bag to a glass of water, the discoloration of the water from the tea bag is caused by Tannins.

Causes of Tannins in Water.

Tannins are typically found in shallow wells, swampy or marshy areas, coastal areas, and peaty areas. Tannins enter water through:  

1. Decomposing Vegetation: When leaves, wood, and other plant materials decompose, tannins are released and can leach into groundwater and surface water sources.
2. Areas rich in organic material: Wetlands like Peat bogs, swamps, and marshes are significant contributors to tannins in water.
3. Runoff: Rainwater running over decaying plant matter can carry tannins into streams, rivers, lakes, and wells.

Health effects of Tannins in Drinking Water.

While tannins are generally not harmful to human health, they can affect water quality in several ways:

1. Color: Tannins can cause water to have a yellow, brown, or tea-like color. This
discoloration can be unappealing and may stain laundry and fixtures.
2. Unpleasant Taste: Tannins can cause a tangy or bitter taste.
3. Bad Odor: The presence of Tannins can make the water have an earthy or musty odor.

Detection and Testing.

Due to the color, taste, and odor Tannins produce, it is easy to detect. You should always do testing to confirm since Iron can cause some of the same symptoms.

1. Overnight glass test: Fill a clear glass with water and let it sit overnight. If the water remains the same color, tannins are likely the cause. If the discoloration moves to the bottom of the glass, the color is most likely caused by Iron or Manganese. This test is not guaranteed and should be followed up with lab testing.
2. Lab Testing: Sending water samples to certified laboratories offers confirmation and more precise contaminant levels.

Removing Tannins from Water and prevention.

By managing plant growth around water sources and maintaining wetlands to reduce Tannin runoff we can reduce Tannin contamination. Several methods can effectively remove Tannins from drinking water:

1. Activated Carbon can remove very low levels of Tannins by absorption on their surface.
2. Ion Exchange can remove high levels of Tannins by exchanging Tannin Ions with chloride or Hydroxide Ions. In certain situations, this can be used in the same vessel as the softener resin.
3. Reverse Osmosis can remove high levels of Tannins resorting in high-quality water.

Tannins in drinking water are primarily an aesthetic concern rather than a health hazard. Understanding their sources, effects, and removal methods can help ensure water quality remains high. Regular water testing and appropriate water treatment solutions can effectively manage and reduce tannin contamination resulting in clear, palatable drinking water.

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