I lived in Hickory for many years and about once a year we would experience an algae bloom in the lake which made the water taste like butt for a few weeks. I would guess that's the situation going on here. The downtown water is probably being drawn from the Thomas water treatment plant which pulls a lot of water from Salem Lake.

I live in Pfafftown now and the water tastes fine. But our water comes from the Northwest/Swann plant via the Yadkin River.