Just downstream of Temple Terrace, the city of Tampa launched a two-year pilot program at the end of March to test how ultrasonic technology will reduce algae growth in the Hillsborough River Reservoir, the city’s primary source of drinking water.
This could potentially lower Tampa’s operating costs incurred when managing algae impacts.
This time of year, the city of Tampa is usually fighting off all kinds of different algae strains in the reservoir with people on boats applying chemicals, called algaecides, up and down the river.
But John Ring, Tampa's water production manager, said two ultrasonic buoys, powered by solar panels, have been installed. Within a 500-foot radius of each, the sound waves will prevent algae from rising to the surface and get the sunlight it needs to grow.
"For lack of a better word to describe it, we play them a song. And once they get used to that song, that population sinks and another algae population comes up and takes its place. Well, then we start playing them a different song. And we keep basically shocking them.”John Ring, Tampa water manager
“The sound waves disrupt the algae’s buoyancy, their ability to float, because they need to rise up into the water column to the surface where they start collecting sunlight and undergo photosynthesis," Ring said. "And that's when they begin to proliferate and grow and the ultrasonic will disrupt that process of them rising to the surface, and then they'll sink down. And from there, they will die off. It's not 100%, but it has a detrimental effect.”
"For lack of a better word to describe it, we play them a song. And once they get used to that song, that population sinks and another algae population comes up and takes its place. Well, then we start playing them a different song. And we keep basically shocking them.”
The technology is currently being used in 20 countries worldwide, including several cities across the United States, according to the city’s press release. Studies have shown that the buoys are non-invasive and will not harm fish, plants, zooplankton, and insects.
“This technology came out of Europe, and they had performed some studies early on with fish and this actually was used within fisheries to keep the algae under control in closed loop and they saw no detrimental effects to fish, shrimp and wildlife at this point,” Ring said.
The Tampa Water Department hopes to one day completely replace algaecides with these buoys, which would save the city between $150,000 and $200,000 a year, according to Ring.
Not only is the technology environmentally friendly and cost effective, but he said it also will reduce the odor the algae could add to the drinking water supply.
"When you start approaching maybe four micrograms per liter, some people can start detecting it … and you’ll taste and smell musty and give it a kind of a fishy smell to it," Ring said.
Although they have treatment methods inside the plant to oxidize that smell and taste that algae can create, he said an overwhelming amount of algae can still get through.
This project is being funded by a $115,254 grant from the Florida Department of Environmental Protection. Over the course of a couple years, the city will collect data during the 3- to 4-month periods when algae activity is typically high on the river.
Observations will include comparing the parts of the reservoir where algaecides have been applied with the perimeter around the two buoys.
Ring said that after the two cycles, the city will submit a report to the DEP.
“I would hope if we see some positive results on this even before two years, I would think we would start exploring expanding these buoys so we could better protect our intake area from algae,” Ring said.
But implementing more buoys will not increase Tampa residents’ water bills due to the high return on investment, according to Ring.
