Calcium, Magnesium and Iron Minerals in Ground Water
As groundwater makes its way through the earth’s crust it reacts with various gases and minerals (including Calcium, Magnesium and Iron). The water dissolves these minerals until it reaches a point of balance or equilibrium where no more minerals can be dissolved.
These minerals and gases make up the chemical character of the groundwater. The quality of the groundwater therefore varies greatly from one location to another and is influenced by the available minerals, sediments and gases in the Earth’s crust though which the water flows.
For example, water that flows through pores and fractures in rocks typically has a higher mineral content than water not exposed to the same environment. This explains why water derived from deeper sources is highly mineralized.
Dissolved minerals can be measured in several different units or measures. The most common unit of measure for minerals is in parts per million (ppm) of a given weight. One ppm is equal to the weight of one part of the dissolved mineral contained in one million parts by weight of the solution.
Hardness as magnesium and calcium carbonates
The majority of hardness in most water is due to calcium and magnesium carbonates. These calcium and magnesium carbonates contribute to the formation of scale in boilers, water heaters, and pipes. Hardness that can be eliminated through boiling is called carbonate or “temporary” hardness. Any hardness that cannot be removed by boiling is called noncarbonate or “permanent” hardness.
Hardness is easily identified in water by the larger amount of soap or detergent needed to make a lasting lather. As hardness increases, the need for more soap to rises sharply, and an unpleasant curd is formed. Water hardness is one of the most important factors to be considered when preparing a water supply for use in residential and commercial applications.
Corrosiveness
Corrosive water is any water that attacks metal. Corrosion from water often results in “red water” caused by solution of iron. Corrosion is not the only contributor to red water. If water has enough iron in solution form may give the appearance of being red when exposed to air. Acids and strong bases, together with high pH support the electrochemical process that causes the decay of water pipes, steam boilers, and water-heating equipment.
Manganese
Manganese is dissolved from certain rocks and soils. It’s not as common as iron but has many of the same unpleasant features as iron. In its oxidized form manganese creates dark brown or black stains. Large amounts of manganese are frequently related to high iron content and acidic water.
Calcium and magnesium
Calcium (Ca) and magnesium (Mg) are dissolved from almost all solids and rocks, but particularly from limestone, dolomite, and gypsum. Magnesium is found in large measures in sea water. Calcium and magnesium are the primary cause of the development of scale in boilers, water heaters, and pipes. The presence of calcium and magnesium greatly affect the value of water for public and industrial uses.
Iron
Iron (Fe) is also exceedingly common and dissolved from virtually all rocks and soils. Water with a low pH is usually corrosive and may dissolve iron in undesirable quantities from pipe, pumps, and other equipment. More than 1 ppm to 2 ppm of soluble iron in surface water is a typical sign that acid wastes from mine drainage or other contaminated sources is present. More than 0.3 ppm of iron will stain laundry and utensils with a red-brown colouring. In larger quantities iron causes a nasty taste in food processing or when used in beverages, ice manufacturing, brewing, and other processes and may promote the growth of iron bacteria under slight oxidizing conditions and typical groundwater temperatures.
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