St. Pete says its stormwater capacity can handle big storms

Update, Thursday 13 July 2017:  The day after announcing its largest wastewater treatment plant was prepared for another major rain event, the City of St. Petersburg had an overflow of about 50,000 gallons of “mostly treated” wastewater during a heavy rain event Wednesday night. The city says no water was lost from the plant property; it seeped into the ground at the Southwest Water Reclamation Facility. In an email statement, St. Pete’s public works administrator Claude Tankersley said nearly two inches of rain in one hour doubled the flows to 42 million gallons a day. But on Tuesday, the city gave reporters a fact sheet that says the plant has a treatment capacity of 50 million gallons a day “NOW.” The city blames construction-related changes that took half of a chlorine contact chamber out of service for expansion.

The City of St. Petersburg says it already has built enough wastewater treatment infrastructure that it could successfully withstand a rain event like one two summers ago that caused the city to dump millions of gallons of stormwater during Tropical Storm Colin. In addition, the city expects that by the end of next month it will add enough capacity to prevent a spill if hit by a storm the size of last summer’s Hermine, in which it dumped 151 million gallons.

On Tuesday morning at the city’s Southwest Water Reclamation facility near Eckerd College, public works administrator Claude Tankersley said the additional capacity comes from new filters and a new injection well.

Listen:

“Every day that new injection well gives us an additional 20 million gallons of disposal of reclaimed water. But, we’ve gotta treat that water to the reclaimed quality. The component that helps us do that are these new filters that you see here.

“Last year, when we unfortunately were not able to treat to full reclaimed quality, it was because we did not have enough filtration capacity. We are doubling the filtration capacity at our two plants in Northwest and Southwest. What you see here is one of those new filters.

“Back in May, this plant and our system had the capacity of treating 112 million gallons per day and storing 8 million gallons in one day. Now, we have the capacity of treating 122 million gallons a day and we have a storage capacity of 20 million gallons. By the end of this summer, we will be able to handle a treatment of 175 million gallons per day with storage of 20 million gallons. Last year, our peak day during Hermine, we saw at peak flow, 145 to 150 million gallons. So, this process of increasing our capacity allows us to handle another Hermine-style storm.”

The city has approved spending $60 million on wastewater improvements by April 2019 and a total of $304 million through 2021.

Tankersley explained to WMNF News how one of the new filters works.

Listen:

“This is brand new and it is a filter. It’s one of the last processes in the treatment process. It filters out anything that is remaining in the water from the previous processes. It uses a very very fine membrane that’ll filter out any dissolved solids or any suspended solids to make sure that it meets our permitted requirements.”

Does that take [the wastewater] from “partially-treated” to “completely-treated” or is there another step after that?

“There’s one more step and that’s chlorination. So, once the water goes through this filter it’ll go to our disinfection area and be chlorinated and then it’s done.”

Would it go from this step to the injection well if there’s an emergency only?

“That’s correct. So, once it goes through the chlorination, it is now considered “reclaimed water” and normally we ship that out to our customers. But, during a storm, people are not watering their lawns. And so, therefore, we have to get rid of the water somehow. So, during a storm we would get rid of that water through a deep-well injection.”

And does that connect to the drinking water aquifer at all?

“It does not. No. It goes down to an aquifer that is the same salinity as the Gulf or the Bay and it is designated for this kind of disposal of reclaimed water. … 1,000-feet [deep].”

St. Petersburg Mayor Rick Kriseman has faced criticism about the stormwater discharges from his main rival standing in the way of reelection, former mayor Rick Baker. But he says with the new improvements the city will be ready for all but the most devastating storm events.

“We’re gonna do everything that we can to prepare our city for what we anticipate to be the worst-case scenario. But, having said that, we could get rains that are far worse than anything we could have ever dreamt of. We could get hit by a Category 5 [hurricane]. You know, when something like that happens, there’s not gonna to be a whole lot that we can do. And you have to balance trying to build what your expectations are and what you expect to be the worst-case vs. something that’s way beyond that that just sits idle forever.

“And so that’s what we tried to do. We tried to build a system to what we expect our expectations are of what the future holds for us. I think any politician who promises you there will never ever be another spill is really lying to you, because they cannot guarantee that. All we can guarantee is that we’re gonna do everything we can to build for what our expectations of the future are.”

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