There are heavy metals in synthetic vitamin and mineral supplements. Those products would easily be banned from application to any farm or garden regardless of the organicity of the application. No way could they be recycled in a compost operation. But they do find their way into human sewage simply from the use in vitamins. Of course there are plating plants and chip manufacturers who might leak some metals into the sewer.
You should check it out for the Houston product, but I know that San Antonio monitors heavy metals coming into the treatment plants. If the waters test out of limits, they move upstream toward likely offenders and test again. They will find the culprits and fine the living sewage out of them and continue to fine them until the pollution stops.
For example, the notorious Coca Cola Bottling Plant was dumping evil expired and non-conforming product into the sewer. The excess sugar in the water was fouling the bio-filters in place at the treatment plants. Coke was fined $1,000 per day plus fees until they solved that horrendous problem. $1,000/day for sugar
I wonder what the charge was for serious metals. Coke paid it for awhile but then found out that they could "dump" the waste into compost piles and recycle it completely. 