Following the softening process, the pH is high and the water is _____ with excess caustic alkalinity.

In the context of water treatment, after the softening process, the presence of excess caustic alkalinity typically results in water that is supersaturated. This occurs because the softening process often involves the removal of hardness ions, such as calcium and magnesium, and may also involve the addition of alkaline substances, which can increase the water's pH.

When the pH is high, it indicates that the water has a significant concentration of hydroxide ions, particularly when caustic materials like sodium hydroxide are used. This can lead to conditions where certain minerals, such as calcium carbonate, may not only be present in solution but potentially begin to precipitate out as the conditions become favorable, depending on the specific chemical equilibria at play. However, the terminology of "supersaturation" conveys that the water holds more dissolved substances than it would under normal equilibrium conditions, indicating a state where the potential for precipitation exists because of the high alkalinity.

Consequently, the indication of excess caustic alkalinity alongside a high pH supports the understanding that the water is in a supersaturated state, which can lead to undesirable scaling or other operational challenges in treatment systems if not managed correctly.