MAKING WATER SOFT

This part is going to be almost exclusively from my Water Treatment Fundamentals book from the Water Quality Association, nearly word-for-word. THE ION EXCHANGE PRINCIPLE The idea of ion exchange is not new. Scientists have been aware of the principle for a long time. It has only been since the start of the present century, however, that the principle has been put to practical use. One area in which it has been highly effective has been in the treatment of water for removal of hardness minerals and certain other contaminates.

All recognized household water softening equipment now on the market makes use of the ion exchange principle. Equipment using this principle contains a bed of permanent bead-like or granular softening material through which the water flows. As the water travels through the bed of ion exchange material, the hardness minerals are removed, leaving the water soft and more satisfactory for household use. (info: The granules or particles of ion exchange material in a softener are referred to as the BED.)

The ion exchange material (usually resin beads or granules) consists of permanent insoluble anions, kept electrically neutral by replaceable sodium cations. Hard water contaminated with calcium and magnesium ions enters the exchange column or bed. As it flows through it, the magnesium and calcium cations in the water are drawn to the anions of the ion exchanger. The ion exchanger has a greater affinity for the calcium and magnesium ions than for the sodium ions. Therefore, the calcium and magnesium ions are absorbed, and a chemically equivalent number of sodium ions is released into the water. Thus, a water containing the ions of calcium bicarbonate when it enters, contains the ions of sodium bicarbonate as it leaves the ion exchanger bed. In brief, harmless sodium ions have replaced the trouble producing hardness ions.

Ion exchange occurs literally BILLIONS of times between the material in the exchange column and the minerals in the water as softening proceeds. In lesson #3 diagrams using the block technique illustrated a number of basic relationships. WATER SOFTENING Now when this calcium bicarbonate in solution flows through the exchange material in the softener, the chemical change which occurs is diagrammed below.

After a vast number of hardness ions in the water has become affixed to the softening material through the attraction of positive and negative charges, and most of the sodium ions have been released, the unit can NO LONGER SOFTEN the water. It has become temporarily exhausted. In actual practice, a small number of sodium ions remains in the softening material after the unit is exhausted. If no new chemical reaction is set into operation at this point, the incoming calcium bicarbonate ions flow untouched through the unit. RECHARGING OR REGENERATION Recharging or regeneration is necessary at this point. To do this, a reverse-ion-exchange-operation is now put into motion. In this REVERSE process, it is necessary to bombard the exchange material with the original type of cations in a concentrated solution. The affinity of the exchanger for the hardness ions is overcome by the use of a relatively strong solution of sodium ions. Generally, sodium chloride in a concentrated solution is used for this purpose. What occurs in all examples of ion exchange is a “swap”, or, BALANCED EXCHANGE of ions.

The calcium ions in the softening process are not destroyed. They have merely been replaced in the water by a chemically equivalent amount of sodium ions. The same type of balanced exchange occurs with whatever other hardness minerals that are removed from the water.

O.K., so that’s it directly out of the book itself. Obviously, I didn’t use the little block symbols, or Letter symbols, because it’s already confusing enough as it is. But you can understand now that water softening is little more than a method we found of attraction and repulsion to clear the water of hardness minerals before they get into our homes.

DAVE