At Sarah’s Pond, New Technology Is Making For Cleaner Water

ORLEANS – On a raw Tuesday morning in late March, Judith Bruce leads a reporter to the back of a residential property abutting Sarah’s Pond. Housed in a shed is an oxygenation system that the Orleans Pond Coalition, of which Bruce is a volunteer, has been testing to help improve the pond’s water quality.

The coalition’s three-year pilot of the oxygen saturation technology, or OST, has yielded positive results. Now the nonprofit is ready to test the system further to see how it holds up in the long term, this time with private homeowners at the helm.

While the coalition will continue to fund and assist in monitoring of the pond — Bruce estimates she’ll be going out monthly this season to monitor — maintenance and custody of the technology is being transferred over to two property owners on the pond representing the Pleasant Bay Narrows Trust, as well as the Orleans Conservation Trust.

“There’s probably going to be a dollar lease agreement,” she said.

The OST system produces highly concentrated oxygen that helps phosphorus at the pond’s bottom better bind to iron, thereby reducing the potential for harmful algal blooms. Two pipes connected to the oxygen concentrator housed on shore run out to the middle of the pond. The first brings water from the pond into the concentrator, which treats it and returns it through the other pipe.

While Bruce talks from the shore, two staffers with SOLitude Lake Management, the firm contracted to do maintenance on the system, busy themselves with data sensors in the pond that correspond with the oxygen concentrator. The sensors are attached to chains that measure the oxygen in the water at different depths.

“It continually reads the oxygen,” Bruce said. “So the machine comes on when the oxygen falls below a certain level. When the oxygen builds to the level we want, it shuts down. It doesn’t have to run 24 hours a day.”

The coalition’s efforts to treat Sarah’s Pond began in 2018, when it started testing the effects of a different system called a “nanobubbler” in improving water quality. But the system failed to achieve the expected results.

In 2021, money that the coalition raised and put toward the nanobubbler pilot was transferred over to the current OST system,which showed better results. Bruce described the pond’s water at the start of the pilot as “murky,” but she said there’s been a marked improvement in the water quality.

“The biggest difference is in clarity and algae suppression,” she said. “That’s the big thing, because we’ve basically suppressed the nutrients.”

Paul Gantzer, founder of Gantzer Water Solutions Engineering, developed the OST technology the coalition is using on Sarah’s Pond. Gantzer works with small groups and private homeowners on projects all over the U.S. Some employ the technology to be able to use their local waters recreationally. In another case in Madison, Wisc., the technology was used to restore a cold-water fish habitat.

Gantzer said the origins of OST date back to the 1970s, but his company has worked to advance the technology to make it more applicable to smaller projects such as the one in Orleans.

“Because up until a couple of years ago, this type of technology was only for big applications,” he said when reached by phone last week, “We’re talking multi-million dollar projects.”

While other waterways in Orleans are impacted by nutrients from stormwater runoff and septic systems, Bruce said there are no “external factors” impacting Sarah’s Pond, which is private.

“You’ve got no septic inputs,” she said. “You’ve got no fertilizers. You’ve got no stormwater runoff. The only nutrients that this pond gets are the leaves that fall from the sky and the trees and the regeneration.”

But long before it was a pond, the land was used for sheep farming, a practice that Gantzer said has had long-lasting implications for the pond’s health. Even today, he said, the phosphorus deposited through the farming remains “the driving force that sustains algal blooms” in the pond.

“So if we maintain oxygen levels, phosphorus stays bound to iron, and we kind of start to bury that historical phosphorus loading and resetting the pond so we don’t have all these harmful algal blooms,” he said.

The OST system will again run at the pond from April through October. At the time of the March meeting with Bruce, preseason maintenance was being done on the system, including cleaning headers that are used to bring water in and out of the pond.

The coalition has two oxygen concentrators in rotation that also need regular maintenance, Bruce said. One will be used at the start of the season before being switched out in July to undergo mid-season maintenance. The second system will similarly be swapped out for maintenance at the end of the season, she said.

Gantzer said while the technology has been proven to work reliably, there’s still some routine monitoring needed to ensure things are running as they should.

“Normally what we request homeowners to do is ‘Hey, every once in a while as you walk past it, just take a visual. Be my security guard and observe and report.’”

In his summary of oxygenation efforts at the pond from 2023, Dr. Ken Wagner, who has been working with the coalition on the project, said that OST “has demonstrated its ability to enhance conditions in Sarah’s Pond.” But he also said a system for “rapid response” to problems that might occur with the technology is needed for it to “maintain successful operation.”

“If this machine goes down for five days before it can be up and running, you’ve lost the pond for the summer, and you’re not getting it back,” Bruce said. “Because once it starts blooming, it’s a cycle that just keeps going.”

Having the Pleasant Bay Narrows Trust and the Orleans Conservation Trust step in to take over maintenance of the technology ensures that the gains made in cleaning Sarah’s Pond won’t be lost, Bruce said, noting that the town isn’t likely to invest resources in the private waterway.

“I think it will appeal more to private property owners around smaller ponds,” she said of the technology. “The town is not going to take on the remediation of ponds that don’t have public beaches and public access.”

But in talking with Gantzer, Bruce said the coalition is hopeful that with regular upkeep, the OST system can be employed for 10 to 20 years, a period long enough to potentially make some long-lasting improvements to the pond’s water quality.

“They seem to be very committed to it, so I’m hoping it will continue to run,” she said.

Email Ryan Bray at ryan@capecodchronicle.com