There has never been a recorded problem involving the contamination of brine in water softeners.
The reason is that:
● brine kills germs and viruses
● the water softener is rinsed thoroughly
● any bacteria left would be of the low HPC variety, which are harmless
Should a major contamination occur in a stagnant water softener it would create a strong smell that would be extremely difficult to drink. If consumed in large quantities, it may cause gastroenteritis.