WHAT ROCK ARE YOU LIVING ON? (Part 3 of a Series)

WHAT ROCK DO YOU LIVE ON?
(Part 3 of a Series)
By Frank Waksmunski
The Times News, © 2004

Thursday, May 27, 2004

What does geology have to do with pH of water?  What is pH anyway?

Geology plays a large role in the characteristics of our groundwater. When we have a standard water test done, one of the results reported is pH.

Let’s start with pH.

Here goes a little chemistry.  We know water as “H2O.” Another way to write it is H-O-H.  Pure water is mostly H-O-H, with a small amount ionized into H+ (hydrogen ion) and OH- (hydroxide ion.)  You’ll notice that these ions have electrical charges, positive or negative.  When the amount of H+ is equal to the amount of OH-, the water is said to be neutral, and the pH is 7.0

pH is usually measured with a meter, on a scale of 0 to 14. Acidic water has a low pH (0-6.9) and alkaline water has a high pH (7.1-14).

The pH scale requires some explanation.  A one-unit change is a ten-fold change in the amount of H+ concentration.  Water with a pH of 6.0 has ten times the amount of H+ than pure water with pH 7.0; pH 6.9 has twice the amount of pure water.

Acidic water has many more H+ ions than OH- ions.  The opposite is true for basic water.

When acids dissolve in water, they produce hydrogen ions (H+). The pH tells us how much H+ is in the water.  It does not tell us what the acid is, or how much acid is present. The water could contain a small amount of a strong acid or a large amount of a weak acid.  These acids can be found in nature or be man-made.

pH is a general water quality indicator, which means it is only a clue to water quality rather than the answer to a specific question. Knowing your water’s pH can give you a rough idea of what might be in your water.

The Environmental Protection Agency does not regulate pH in drinking water, and has set a Secondary Maximum Contaminant Level (SMCL) of 6.5 to 8.5.  For all practical purposes, a range of 6.5 to 8.0 is desired to prevent health and aesthetic problems.

Most of the groundwater in Carbon County will not have a pH above 7.5. Unfortunately, there is ample groundwater with a pH of less than 6.5.

I drink Coca-Cola, which has a pH less than 3 and it doesn’t hurt me. So what’s the big deal about pH?

You might be surprised how geology and Coke are connected. The answer will appear in the forth and final part of this geology series. We will then move on to well drilling.