ST. PETERSBURG — Distrust and frustration are mounting on both sides of the bay over plans by the city of Tampa to produce up to 50 million gallons a day of drinking water from treated wastewater by pumping it into the Floridan aquifer.

St. Petersburg City Council member Darden Rice said a push by Mayor Bob Buckhorn to get the project approved has more to do with the departing mayor's legacy than it does with the best interests of her city.

Tampa is seeking approval to proceed with the $350 million project from the regional water authority, Tampa Bay Water.

"We're getting the shaft," Rice said Tuesday during an editorial board meeting at the Tampa Bay Times. She said Tampa isn't sharing all the possible costs and risks associated with converting wastewater to drinking water and that more time is needed to vet the project.

In October, the Tampa Bay Water board — made up of three elected officials each from Pasco, Pinellas and Hillsborough counties — voted to delay approval of a project sometimes referred to as toilet to tap.

Buckhorn said Tuesday that Rice, a member of the Tampa Bay Water board, is "wrong on all counts."

"For somebody who is known as being an environmentalist, we're all a little surprised at her unreasonableness on this," Buckhorn said. "We've been at this since 2013. It's been fleshed out. It's going to allow the partners to have even more water, it will drought-proof the city of Tampa permanently and it's the wave of the future."

Tampa has provided its studies and documents to anyone who has asked, said Tampa Water Director Chuck Weber. Further delays might risk millions of dollars in Southwest Florida Water Management District funds to help build the necessary infrastructure.

The 50 million gallons of highly treated wastewater now is dumped into Tampa Bay.

Rice pointed to two August studies that show costs may increase above the project's estimated $350 million price tag. By 2027, the approximately 50 million gallons a day now flowing into Tampa Bay from the Howard F. Curren treatment plant on Hookers Point would be pumped into the aquifer to further clean it before being added to Tampa Bay Water's system.

Still unanswered, she said, is whether Tampa Bay Water will be left on the hook financially if any problems arise. Adding to the distrust, she said, are recent discussions that officials with the Southwest Florida Water Management District had with Polk County — not a member of Tampa Bay Water — about purchasing some of Tampa's proposed new supply.

Rice said she believes Tampa's ultimate goal may be to leave Tampa Bay Water altogether, leaving water-scarce St. Petersburg in the lurch.

"If I understand why Tampa wanted this project, we could know how to negotiate," Rice said. "It hasn't been very clear. If what they want is to get out of Tampa Bay Water, let's just say so and let's negotiate it."

Buckhorn, who leaves office in May at the end of his two-term limit, said Tampa will never step away from the water authority and any assertion it would is a "bald-faced lie."

"We don't understand the paranoia. There is no plot," Buckhorn said Tuesday, approached before a regularly scheduled lunch with St. Petersburg Mayor Rick Kriseman and Clearwater Mayor George Cretekos.

Clearwater, which is not a member of Tampa Bay Water, is also pursuing a toilet-to-tap project but recently slowed down on it because costs have risen and technology has changed, Cretekos said.

During her meeting with the Times editorial board, Rice said she has Kriseman's full support. Outside the lunch Tuesday, Kriseman said he supported the vote by the Tampa Bay Water board to delay approval of Tampa's project but still hopes for a solution.

"I've also said to her, 'I'd love to see us get to a place where it's a win-win for everybody," Kriseman said.

He said he has concerns about Tampa Bay Water, created 20 years ago to end the so-called water wars that had divided local governments, coming unraveled over new intergovernmental disputes like this one.

"I'm a believer that there's always a way to find a solution," Kriseman said.

Buckhorn has made the project his biggest remaining priority.

Rice has requested a Dec. 17 board workshop on the Tampa project, and Buckhorn said he has no problem with this. But regardless of what happens there, he intends to bring the plan to a vote at the board's meeting in February.

He needs to win two votes among four board members — Pasco County Commissioners Kathryn Starkey and Ron Oakley and Pinellas County Commissioners Pat Gerard and Dave Eggers.

"This is exactly where we need to be," Buckhorn said, "doing good by the environment, using a product over and over again, replenishing the aquifer and sharing the wealth."

Contact Charlie Frago at cfrago@tampabay.com. Follow @charliefrago