The plant that purifies the water and puts it into the glass and aluminum containers almost certainly uses plastic or rubber tubing in its machinery. So you'd likely get some plastic particles transferred there as well. In the end, I'd be willing to bet that tap water has fewer micro plastics than water bottled in glass or aluminum.

Problem, of course, is that your municipality likely uses some form of metal piping to get water to your tap. Which, depending on what all that is, could mean elevated lead levels etc.

It's a tough problem.