Bioreactor that removes Imperial River pollutants earns statewide award

Chambers of wood chips and pea gravel underneath a downtown parking lot could be Bonita Springs’ best weapon to combat pollutants in the Imperial River.

And that innovative tool is getting an upgrade.

The bioreactor, hidden under a parking lot at Felts Avenue and Abernathy Street, stops hundreds of pounds of nitrates from reaching the river every year. Nitrates are linked to blue-green algal blooms, according to Florida Gulf Coast University experts.

The bioreactor was the first of its kind in the state when installed in 2015 at a cost of $450,000. Rainwater from the downtown area is funneled into the chambers before spilling into the Imperial River.

Last year, tests showed the chambers scrubbed nearly all nitrates from water, according to Greg Rawl, a hydrologist consultant hired by the city.

The system sucks about 130 pounds of nitrates per year from surface water before flowing into the river. New construction could make the bioreactor 70 times more efficient, Rawl said.

A Florida Department of Environmental Protection grant of $400,000 and city funding of $150,000 are expected to pay for a second phase which pipes water directly from the Imperial River through the bioreactor.

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The system would run 24 hours a day, 7 days a week instead of relying on rainwater to function.

“The water doesn’t have to stay in the system for a long time,” Assistant City Manager Matt Feeney said. It will trickle through like Britta filter.”

About 1,800 feet of piping will connect the Imperial River to the bioreactor situated off Old 41 Road. Directional drilling would be used to avoid tearing up roads and lawns to bury a pipe.

The finished project could remove up to 1,100 pounds of nitrates from the Imperial River per year, Feeney said.

Bioreactor’s importance in Florida

Bonita Springs earned this year’s Environmental Stewardship Award from the Florida League of Cities. The award “recognizes cities that are paving the way for innovation and excellence in municipal government,” League of Cities President Isaac Salver states in a news release.

City councilors have praised and supported the project, including the expansion, and accepted the League of Cities award.

“We’re on the map,” Mayor Peter Simmons said at an Aug. 19 public city council meeting. “I’ll point out with an asterisk ­— for that little town somewhere between Fort Myers and Naples, I think that little town is doing great things.”

The reward has only garnered interest of a bioreactor from other cities across the state, Feeney said.

“I think there’s people who see the potential value for a cost-effective tool in the toolkit,” he said.

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Collier County officials are already recognizing the value of a low-maintenance bioreactor. Collier County Commissioner Bill McDaniel recently toured the Bonita Springs system and he said in an interview later that he has considered how a bioreactor could be used to clean water leading to the Gordon River in Naples.

“I saw the positive results they’ve had so far,” McDaniel said. “It’s good to see them contract the land and then turn it into a parking lot to service the businesses downtown.”

The Golden Gate Main Canal, which stretches from Golden Gate Estates to Gordon River and Naples Bay, would be a prime candidate for bioreactor systems.

Bonita Springs uses Midwest idea to clean water

The idea to build a bioreactor to clean rainwater came from articles published by university professors in the Midwest, Feeney said.

Bioreactors have been studied in one form or another for nearly two decades, but not for cleaning rivers, said Matthew Helmers, director of the Iowa Nutrient Research Center at Iowa State University.

“They are primarily used in farm fields to treat agricultural drainage water from crop land with high nitrates from fertilizers,” Helmers aid.

There are about 50 such systems across Iowa with others scattered about the Midwest, mostly to cleanse fertilizer runoff on private farms. Iowa has no water pollutant standards for agriculture.

The thought of using bioreactors to cleanse river water hadn’t occurred to Helmers, he said, but the impressive results should remain.

“I can see this being very significant for water quality, absolutely,” he said.

A clean future for the Imperial River

In 2012, the Florida Department of Environmental Protection issued Bonita Springs a demand — stop nearly 10,000 pounds of nitrogen from flowing into the Imperial River every year. Tests showed the river had too much nitrogen pollutants in the water.

The city has until 2027 to hit the mark. City projects have cut the pollutants down to 6,000 pounds of nitrogen per year, according to city officials. If the bioreactor addition is built, it could remove another 1,000 pounds of nitrogen from draining into the Imperial River.

Normally, the South Florida Water Management District uses large swaths of wetlands to filter nitrogen from polluted water. Bonita’s parking lot system appears to do the same thing but in a much smaller space.

The testing of water is an overlooked aspect that could provide valuable data for the future of bioreactors, Feeney said. Computer models are needed to estimate how much pollutants will be scrubbed in an area of wetlands, and the actual number cannot be known, Feeney said.

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With a bioreactor, experts test the water upstream and downstream of the system and will know exactly how well the bioreactor is working and can adjust and improve future projects, Feeney said.

Thaddeus Mast is a south Lee County reporter for the Naples Daily News and The Banner. Support his work by subscribing to our local news organization. Find him on Twitter as @thaddeusmast.