"two to four million gallons of water per day"
So that's 7.5 to 15 million liters of pure, drinkable water that is made toxic and, apparently, gets purified before being returned to "the water supply".
I damn well hope so.
Now, if the water is being taken from the dam, used, then purified again and returned to the dam, where is the issue ?
Actually, shouldn't this whole thing be a closed loop, only topping up to compensate for evaporation ?
The plant should have a 20 million liter reservoir, with water being constantly used, purified, stored and used again.
Not doing that is a clear sign that used water cannot be purified to the level they need to use it again, meaning it's likely not water that goes back to the dam, nor is it water you'd want to drink.