What's a pollution control plant? (people who know only)?

Question

obviously has something to do with controlling pollution

but exactly what kind of pollution and what do they do?

Answer 1

Well, the term "Pollution Control Plant" usually refers to a wastewater treatment facility, with plant meaning a physical plant, not a botanical one.

However, there are many plants that do remove pollutants from the air.  NASA research has demonstrated the ability of a number of houseplants (including ivy and spider plants) to remove things like benzene, formaldehyde, and CO from the air.