Metropolitan Water District of

          Salt Lake & Sandy

Pretreatment

The intake process removes all the larger debris found in the water.  Once the larger debris has been removed, the chemical treatment starts.

Sometimes stream water has a fishy or earthy smell and taste. Would you like that smell coming from the your tap water?  I didn't think so!  In order to remove these smells, we add a chemical called potassium permanganate.  Chemists often write this using the chemical formula of KMnO₄.  This

chemical breaks the chemical bonds of the molecules that cause odors.

Think of an odor molecule as a really big piece of paper (let's say the size of a soccer field).  It would be difficult to find a garbage can large enough to throw away paper that size.  However you could first to cut it into smaller pieces and then throw it away quite easily.  This is what we are doing with the potassium permanganate.  We are making the large organic molecules smaller so they are easier to remove.  This process of breaking chemical bonds is called oxidization.

One thing you will notice about potassium permanganate is its color - PINK. When we add it to the water the water will also turn a light pink color.  The pink color of the permanganate changes to a brown color as the permanganate is used in the oxidization process.  The brown color comes from very fine suspended manganese dioxide (MnO₂), a

by-product of the oxidization of potassium permanganate.