That water profile is typical of a lime-softening treatment process. Lime is added to bring the pH to about 11 and that causes the excess calcium and magnesium to precipitate out of the water. Some Ca and Mg still remains due to its solubility, but most of it is settled out. The clear water is then taken off the sediment. The acid addition is necessary to bring the pH back down within drinking water standards after treatment.
I am a little surprised to hear that the utility is using phosphoric acid for the neutralization since its typically more costly than hydrochloric or sulfuric acid. Maybe they got a good deal or they have some other concern they need to address.
You've got good water there. Enjoy.
Martin Brungard, P.E., D.WRE