A Town's Woodchip Bioreactor Reduces Nitrate Flow into Lake George

By Lake Champlain Sea Grant
February 16, 2022

In a study funded by Lake Champlain Sea Grant, the Town of Bolton, New York, demonstrated that woodchips can be used to reduce the release of cyanobacteria-causing nitrate into groundwater and a tributary that feeds Lake George. This demonstration project is believed to be the world’s first use of a woodchip bioreactor at a municipal wastewater treatment plant.

“Excess nutrient loading on Lake George threatens local biodiversity, ecology, and water quality and spans beyond the Lake George drainage basin into the Lake Champlain drainage basin,” said Dr. Kris Stepenuck, Associate Director of Lake Champlain Sea Grant. “What’s good for Lake George is good for Lake Champlain, and we are pleased to have provided the funding for this very important study.”

The Lake George Association (LGA), Lake George Waterkeeper, and the Town of Bolton conducted the 27-month monitoring study from 2019 to 2021. They found that the town’s woodchip bioreactor removed 38 percent of nitrate from the wastewater that flowed through it compared to zero removal of nitrate from the rest of the plant’s effluent stream.

Nitrate is a chemical compound present in organic waste that, when discharged to water in high quantities and over long periods of time, can result in human and ecosystem health problems and foster growth of harmful cyanobacteria blooms. The Bolton wastewater treatment plant, constructed in the late 1950s and early 1960s, lacks a modern-day denitrification stage. Newer treatment plants convert nitrate to nitrogen gas and release it harmlessly into the air.

The Bolton plant discharges nitrate as part of the effluent to sand infiltration beds where it enters the groundwater and sometimes resurfaces and flows into nearby tributaries. The woodchip bioreactor adds a wholly natural denitrification process to Bolton’s treatment capabilities.

“Over the past two years, 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,” said Lake George Waterkeeper Chris Navitsky, who conducted the study along with water quality scientist and LGA Science Advisor Dr. Jim Sutherland. “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.”

The demonstration project was so successful that the town applied for and recently received a New York State Water Quality Improvement Project grant 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.

Read the full story on the Lake George Association website: “Bolton’s Woodchip Bioreactor Working to Protect Lake George.”

View a January 2022 video presentation by Chris Navitsky and Kathy Suozzo, P.E. on the woodchip bioreactor project, part of the Lake Champlain Sea Grant Research Seminar Series, and read the December 2021 final report from the bioreactor study.