Iron derived from groundwater delivered via irrigation systems and home watering methods can produce unsightly rust stains on concrete sidewalks and driveways, sides of homes and buildings, or landscaping materials. When iron -bearing water is mixed with tea, coffee or alcoholic beverages, the mixture turns black. It can ruin the flavor as well. When iron stains are found, the water should be tested to measure the amount and type of iron. Types of Iron in Water Inorganic iron exists in water in two oxidation states, +2, or ferrous, and +3, or ferric : Iron in the +3 state is commonly known in water treatment as red water iron: Water containing oxidized, ferric, iron compounds is filled with reddish rust particles that are visible in the water when first drawn from the tap. Iron in the +2 state is commonly known in water treatment as clear water iron: Water is clear when first drawn from the tap. However, after coming in contact with the air, the ferrous iron oxidizes to ferric, “rusts”, forming red or reddish-brown particles in the water; a gelatinous precipitate. It is commonly found in well water supplies throughout the United States Red water iron causes less of a metallic taste than clear water iron, but the taste of both are objectionable. Colloidal iron: Very small particles of oxidized, ferric, iron are suspended in the water (less than 0.1 micron). Typically, they are combined with and bound to other substances. Colloidal iron can form when water comes in contact with iron-bearing rock in the presence of decaying vegetation. It may be present in shallow wells or surface water supplies. It is sel dom found in deep well supplies. Iron bacteria are living organisms that feed on iron in the water and on iron in wells, piping and tanks. They build slime in toilet flush tanks and can clog pipes, pumps, water heaters and appliances. This can lead to a decrease in water pressure. Bad tastes and odors in the water supply are often common with the presence of iron bacteria. Larger clumps of iron bacteria can cause discoloration of the water.
Ferric Iron Ferric (Fe3+) iron starts out as dissolved ferrous (Fe2+) iron until it contact oxygen. In a distribution system this often happens when water containing ferrous iron is poured into a glass from a tap. The water takes on a reddish/brownish color and flakes (precipitate) of ferric iron begin to form and settle to the bottom of the glass.
Tannins Water containing tannins can vary in color from a dark brown, indicating a higher tannin concentration, to a weak yellow, indicating a lower tannin concentration.
Color of water with tannins ranging from a high to low concentration, side view.
Color of water with tannins ranging from a high to low concentration, top view.
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