What makes water do what it does?
Water is the universal solvent. It dissolves a little of everything it contacts. The water that we use in our homes and buildings has traveled a distance, possibly underground, possibly on the surface, and certainly through some plumbing systems. This travel gives it plenty of opportunity to dissolve minerals and contaminants. The water itself provides a great vehicle for carrying the dissolved minerals on its way.
The less "stuff" present in water, the more likely it is to dissolve minerals. A measure of the "stuff" in water is Total Dissolved Solids, or TDS. Lower TDS water is hungry to reach equilibrium, which it does by dissolving minerals present. The lower the TDS, the more aggressive, or likely to dissolve minerals, the water is. For example, when de-ionized water is used in a medical or manufacturing process, it must be piped through special plastic plumbing as it is too corrosive for copper.
The relative acidity of water is measured by pH. The lower the pH of the water (increased acidity), the more likely it is to dissolve minerals. In New Hampshire our rain water, which is the main source of recharge for our groundwater, is acidic. It then travels through soils which have been impacted by years of pine forests, which are acidic. And it then travels through ground which does not have large calcium deposits. Calcium is a great buffer of acidity and is present as limestone or marble in many parts of the country. While we have some calcium in New Hampshire, in most regions it is not enough to offset the acidity of the water.
Finally, much of our water comes from bedrock wells. In a true bedrock well the water is in contact with granite. Very little of this granite dissolves into the water. However, some of the trace elements in the granite are very quick to dissolve into our low TDS, low pH water. Therefore we end up with elements such as iron, manganese, arsenic and fluoride dissolving into the water. Then, we run this still acidic water through copper plumbing and the water dissolves some of the copper.
When dissolved into the water, these trace elements are not visible. Some may be present in enough quantity to cause a taste in the water, but many give no symptoms of their presence. The water user becomes aware of their presence when the water comes in contact with air, heat or bleach which will oxidize the dissolved minerals. Once oxidized, some elements take on a color, often creating a very tenacious stain. Iron shows up as a rust color, manganese will stain beige to black, copper leaves a blue-green residue and calcium precipitates as a white crust. Some elements such as arsenic or fluoride are present in such trace amounts that they still are not visible when precipitated and only lab testing can verify their presence or absence.
Water treatment systems are available that can remove these trace elements before they have a chance to stain, cause a taste or affect the healthfulness of the water.
Christine Peach Fletcher is president of Secondwind Environmental.
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|Author:||Fletcher, Christine Peach|
|Publication:||New Hampshire Business Review|
|Article Type:||Brief Article|
|Date:||Nov 17, 2000|
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