TLDR - They are not allowed to dump it in the rivers so they make us pay to drink it.

Chemical Byproducts have to be disposed of safely.  So you must ingest it.

Ask ai.

Fluoride in Aluminum Production
Based on the search results, fluoride is indeed a byproduct of aluminum production. Here’s a summary:

The Aluminum Company of America (ALCOA) acquired a plant that produced sodium fluoride, which was later sold (last sale in 1952). This indicates that fluoride was a byproduct of their aluminum smelting process.
The electrolytic reduction of aluminum oxide (alumina) in cryolite produces a molten fluoride material, which is used to dissolve the alumina. This process involves fluoride as a participating chemical.
Phosphate rock processing for fertilizer production also generates fluoride as a byproduct, which is then used to fortify water supplies.
Industrial processes such as aluminum smelting, fertilizer production, and iron ore manufacturing can all produce fluoride as an unwanted byproduct.
In summary, fluoride is a byproduct of:

Aluminum smelting, particularly in the electrolytic reduction process.
Phosphate rock processing for fertilizer production.
Iron ore manufacturing.
These byproducts are often sold or utilized in other industries, such as water fluoridation, rather than being considered waste.

https://fluoridealert.org/news/toxic-waste-in-water-fluoride/