The $2 million water treatment facility was welcomed with a ribbon cutting ceremony Thursday.
Officials say the plant will help the city better serve its residents' needs.
"Consistent with Governor Barbour's vision of Katrina recovery not just being about rebuilding, but about rebuilding stronger, then we initiated this project with the city of Union," said MDA's Lee Youngblood. "What you have here is a much more modern, much more high-capacity, much better water treatment plant than they had in the past."
The plant was paid for entirely with money from the Hurricane Katrina Disaster Recovery Fund, through the Mississippi Development Authority. The facility took about a year to build.