Florida Drinking Water Operator "B" Practice Test

What occurs when iron in the ferric (solid) form is applied to an ion exchange softening unit?

1. The unit will act as a filter

2. The iron will dissolve in the water

3. The unit will malfunction

4. The unit will produce more hardness

The correct answer is: The unit will act as a filter

When iron in the ferric (solid) form is applied to an ion exchange softening unit, the unit will primarily act as a filter for the iron particles. In this process, the solid ferric iron can be captured in the resin bed of the ion exchange system, which is designed to remove certain cations, such as calcium and magnesium, to soften water. Although the resin bed is primarily intended to exchange hardness minerals, the presence of solid ferric iron can lead to physical filtration effects, wherein the particles are trapped by the resin media. This does not enhance the softening capabilities of the unit, but rather causes it to perform filtering actions for the suspended iron particles present in the water. Other potential processes, such as the iron dissolving in water or a malfunction of the unit, would typically not be expected to occur with solid ferric iron, as it is not soluble under normal operational conditions in a water softening system. Additionally, the assertion that the unit would produce more hardness does not align with the fundamental purpose of an ion exchange softening unit, which aims to reduce hardness rather than increase it.