Purification plant
A purification plant, as the name implied, was a factory that made substances purer. One such example was the dolamide purification plant on Ultima Thule. 

In 2369, Kira Nerys alleged that the plant on Ultima Thule refined dolomite to weapons-grade during the Bajoran Occupation, and that it was likely still capable of doing so in 2369. She used these suspicions as justification to delay the Valerian transport Sherval Dass request for docking at Deep Space 9, contrary to Benjamin Sisko's orders. ()

Architecture