Editor’s note, October 2026: No floating wetland has been built on Waquoit Bay, Popponesset Bay or Santuit Pond since this meeting. Mashpee and the Mashpee Wampanoag Tribe chose an alum treatment for Santuit Pond, starting in fall 2026. Barnstable’s two-season floating wetland test in Long Pond took up only a few grams of phosphorus, and the Cape Cod Commission still lists floating wetlands as a pilot technology. Dr. Todd’s cost estimates below assume nitrogen removal rates far higher than published studies have measured, including tests in brackish tidal water, cold coastal lagoons and a review of 169 studies.
CPWB’s 2021 Annual Meeting on Wednesday evening, August 25, met at the Boathouse at the Waquoit Bay Reserve, with about 35 more people joining online. Our guest was biologist John Todd, inventor of the Eco-Machine and president of Ocean Arks International, who since the 1980s has built systems that use sunlight, plants and thousands of other living things to clean wastewater.
Todd began close to home. In the mid-1980s Harwich was dumping septage into pits at its landfill, a few feet above the town’s drinking water. His first Eco-Machine, a string of clear-sided tanks seeded with life from more than a dozen wild places, treated that waste to drinking water standards for heavy metals and earned an award from the US EPA. He went on to a greenhouse system in South Burlington, Vermont, that removed nitrogen as well in January as in August; floating systems in the sewage canals of Fuzhou, China, where fish thrived in water that had held almost no life; and a floating system at a poultry plant in Berlin, Maryland, that cut the plant’s electricity use by 74 percent.
Then he turned to our watershed. For Santuit Pond, which has had toxic blue-green algae blooms, he proposed a floating “restorer” at about $3 million, along with adding finely ground rock minerals to the streams and replanting stream banks to keep the water shaded and cool as the climate warms. For Popponesset Bay he sketched about eight acres of floating restorers spread across its smaller bays, at about $13 million. For Waquoit Bay he estimated about $20 million, paid off over 30 years like a treatment plant, and said that works out to less than $10 per pound of nitrogen removed, against sewer estimates as high as $150.
In the question period, members asked how floating marshes would hold up in storms, how much upkeep they need and what the Bay would look like with them in place. The systems are built from the same materials as offshore salmon farms and depend far less on machinery than a treatment plant does. From shore, Todd said, they would look like floating marshes. The plants are harvested to take nutrients out of the water, and he chooses plants people want so the harvest can help pay for the upkeep. The hardest part, he said, is money: the first projects may need private backing because public officials see an untried approach as too risky, and he has been working to raise funds to underwrite a few.
CPWB president Matthew C. Patrick noted that Waquoit Bay is among the last of Falmouth’s bays in the town’s sewer plans and asked why the Bay should keep declining for the 20 or 30 years until sewers arrive. He suggested that watershed residents could form a cooperative and tax themselves to pay for an Eco-Machine, which would take several votes over a couple of years, and floated starting smaller, with a pilot on one of the rivers that feed the Bay.
What it means for the Bay
Sewers for the Waquoit Bay side of Falmouth were more than a decade away, and Patrick reminded the room of the fish kills after heavy rains in the early 2000s. Todd’s talk put a price on a different kind of interim fix: a living system that pulls nitrogen out of the water itself. He was clear that it works alongside better septic systems, not in place of them.
CPWB updates
After the meeting, CPWB’s Wetlanders committee studied floating wetlands and proposed the Moonakis River as a pilot site. That work grew into the Moonakis River Restoration Study and its 2023 plan. The Mashpee Enterprise also covered the meeting; read our summary of its story.
Thank you to John Todd, to the Waquoit Bay Reserve for hosting us, and to everyone who came in person and online. A bigger membership gives Waquoit Bay a louder voice. Become a member.
Drafted with AI assistance from CPWB's notes.
