Innovative bioreactor lowers wastewater nitrate release into Lake George

BOLTON | In what has been described as the world's first use of a woodchip bioreactor at a municipal wastewater treatment plant, the Town of Bolton has demonstrated that woodchips can be used to reduce the release of algae-causing nitrate into groundwater and a tributary that feeds Lake George. Funded by a Lake Champlain Sea Grant, a 27-month study conducted by the Lake George Association, Lake George Waterkeeper, and the Town of Bolton, found that the town's woodchip bioreactor removed 38 percent of nitrate from the wastewater that flowed through it compared to zero removal from the rest of the plant's effluent stream. Nitrate is a chemical compound present in organic waste that, when discharged into the water in high quantities and over long periods of time, can result in human and ecosystem health problems and foster the growth of algae, including harmful algal blooms (HABs). LIMITS OF OLDER PLANTS The Bolton plant was constructed in the late 1950s and early 1960s and, like other plants of that era, lacks the denitrification stage found in modern-day plants that converts nitrate to naturally occurring nitrogen gas and releases it harmlessly into the air. Instead, nitrate is discharged as part of the effluent into sand infiltration beds, where it enters the groundwater and sometimes resurfaces and flows into nearby tributaries. DENITRIFICATION PROCESS When wastewater is diverted from the treatment plant through the bioreactor—an underground cell, 20 feet wide and 100 feet long, filled with four feet of locally-sourced woodchips—bacteria in the water feed on carbon from the chips and take their oxygen from the nitrate, converting it to nitrogen gas. The process has been widely used in treating high-nitrate runoff from Midwestern agricultural lands for more than a decade. PROVEN EFFECTIVENESS The Bolton bioreactor was the brainchild of the town's consulting engineer, Kathy Suozzo, and was funded by a $50,000 grant from The FUND for Lake George (since merged with LGA). It was constructed by the town's treatment plant and public works staff, with volunteer assistance from local logging contractor Barry Kincaid, who supplied the woodchips. It began operation as a demonstration project in October 2018 and treated approximately 30 percent of the plant's total wastewater flow until being temporarily taken offline in June 2021 for maintenance and structural improvements. The demonstration project was so successful that the town applied for and received a New York State Water Quality Improvement Project grant of $246,000 for the construction of two additional bioreactors. It is expected that the three together will be capable of treating all of the town's wastewater flow, which ranges from 80,000 to 275,000 gallons per day depending on the time of year. "We were absolutely thrilled to partner with the LGA on this demonstration project and can't wait to expand and improve upon Bolton's world-leading use of this natural process to protect Lake George," said Bolton Supervisor Ron Conover. "I want to thank our treatment plant operators, Matt Coon and Justin Persons, for embracing and quickly becoming experts in this technology. The process may sound simple on the surface, but it requires a very careful balancing of a wide variety of complex factors to ensure that the bacteria are working to their optimum levels. Matt and Justin are doing a great job for our town and for our Lake." Lake George Waterkeeper Chris Navitsky, who conducted the study with water quality scientist and LGA Science Advisor Dr. Jim Sutherland, said, "Our study demonstrated conclusively that the woodchip bioreactor is an effective, affordable, and environmentally compatible nitrate-reduction tool for smaller municipal treatment plants like Bolton's that were constructed decades ago, prior to the advent of denitrification technology. We look forward to working with the town in the months ahead to further refine its processes for the long-term health of the Lake and the benefit of other communities who can learn from Bolton's success." GLOBAL IMPORT Dr. Jim Sutherland, principal researcher, said the research team is planning to write a peer-reviewed scientific journal manuscript to describe and share the project with other scientists. "This will be an extremely important publication that needs to be shared globally," he said. "We took a concept previously applied to agriculture and aquaculture and developed the first in-situ, real-time application that successfully reduces reactive nitrogen in wastewater from entering the aquatic ecosystem. Reactive nitrogen is a problem globally and this Lake George demonstration project has huge implications and potential application around the world."

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Innovative bioreactor lowers wastewater nitrate release into Lake George

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