ST. PETERSBURG — Days after 58 million gallons of mostly treated wastewater spilled out of the Northwest sewerage plant on the west side of the city, Mayor Rick Kriseman kept mum.

He did not inform the City Council. His public works administrator, Claude Tankersley, did not mention the spill while briefing the council Sept. 8. The mayor's staff finally confirmed the spill Monday — five days after the wastewater stopped flowing.

The city posted warning signs in the Azalea neighborhood right next to the plant. But Kriseman did not alert residents about the massive spill, even as the wastewater surged across 22nd Avenue N and ended up in their yards.

The city had to tell the state about the spill. But the mayor said Thursday that he didn't need to tell anyone in his city because what gushed out of the Northwest plant wasn't dangerous.

"They didn't need to be notified because it wasn't sewage; it was clean,'' Kriseman said.

Two weeks since Hurricane Hermine drenched the city, the tens of millions of gallons of sewage that St. Petersburg dumped and how transparent city officials have been about that dumping dominated the conversation Thursday at City Hall.

The city's official estimate of how much partly treated sewage it discharged into Tampa Bay once again grew: City officials told the state that anywhere from 78 million to 93 million gallons were discharged between Aug. 31 and Sept. 9. The previous estimate was 70 million.

St. Petersburg has now released up to 151 million gallons of waste. That pushed the total estimate of what the area's utilities have dumped into its streets and waterways to 253 million gallons.

A four-minute video of Kriseman addressing the sewage crisis was posted to YouTube on Wednesday. But the mayor did not mention the Northwest plant release or the latest estimate of just how much waste the city dumped. And the city didn't send an announcement to the media or disclose the information on social media.

City tests showed very low levels of fecal coliform in the wastewater as it left the Northwest plant on Sept. 1. Unsafe levels were initially found in nearby Jungle Lake, but the mayor said that was probably animal feces and bird droppings.

The wastewater had been treated but bypassed the final stage of filtration, Tankersley said. It was classified as "reject" water for that reason, although city officials maintain it met state standards for reclaimed water.

Reject water is normally water that doesn't meet those standards and is stored in tanks until it can be run back through the plant and treated again. Very high flows of sewage during the storm forced the overflow, officials said. But they said those high flows did not affect the treatment of the sewage.

The exact amount of sewage released by St. Petersburg into the bay from a pipe flowing out of the Albert Whitted wastewater treatment plan may never be known. City officials said a broken flow meter is to blame. That meter has since been repaired. Closing that plant in 2015 worsened the city's sewage woes.

As the sewage estimates continue to rise, residents are getting angry, City Council member Jim Kennedy said at Thursday's meeting.

"They expect better," Kennedy said. "The way we are presenting information doesn't assist in credibility."

Kennedy asked the city staff to prepare another sewage briefing for next week's meeting on Thursday. He said council members need to be kept informed.

Most of the Northwest plant's spill ended up in the stormwater system and, eventually, in Boca Ciega Bay. Initial tests at the southern and northern parts of Boca Ciega Bay showed elevated levels of fecal coliform, Kriseman said, but the city doesn't believe that was related to the spill.

"I trust my scientists," Kriseman said. "I would notify residents if there was any public health risk. There was not."

City Council member Charlie Gerdes disagreed, and he said so do the residents in Azalea, which he represents.

Gerdes said he was shocked by the amount of sewage that overflowed from the Northwest plant. He also couldn't understand why Tankersley never mentioned the spill when briefing the City Council last week.

Why not tell residents what happened, Gerdes said, and let them know that the wastewater that was released into their neighborhood wasn't dangerous?

"I'm struck by the difference of perspective," Gerdes said. "We shouldn't be focused on the technicalities of 'Do we have to notify the public?'

"We should be focused on transparency."

In August 2015, an overflow of 15 million gallons of "reject water" at the city's Southwest Plant sparked an outrage at Eckerd College and surrounding communities. Part of the anger was that the city didn't notify residents of that spill either until City Council member Steve Kornell raised the issue weeks later.

And St. Petersburg's official estimate of spilled sewage could continue to grow, and officials still doesn't know how much overflowed from more than 40 manholes around the city.

The state Department of Environmental Protection is preparing a consent order that would outline a plan requiring the city to fix its beleaguered system or face fines. That order hasn't been issued yet, DEP officials said, but should be finalized soon.

Contact Charlie Frago at cfrago@tampabay.com or (727) 893-8459. Follow @CharlieFrago.