The Department of Natural Resources says the city's current system does not meet state regulations.
Construction for the new plant would mean a 25 to 30 percent increase in customer water bills.
The city's Public Works Department says it's strictly an environmental issue.
"This is the information we've got. This project is going to happen. We don't have a choice in the matter. It's something that's been handed to the city but we just want to do it in a manner with the least amount of impact as possible," C.E. Goodall, Maryville Public Works Director said.
Maryville will be able to utilize existing lagoons, one for storm water overflow and one for sludge storage.
Without them, Goodall says the new project would cost an additional $3 million.
If voters approve the bond, the water/sewer bill increase would begin in late summer or early fall of 2013.
Goodall says the project needs to be finished by July 2015, or the city will face fines.