Five Years Later: What’s Happened with the Lake George Woodchip Bioreactor?

Lake George, situated within the Lake Champlain basin, is one of the cleanest lakes in the United States and is the largest lake wholly within New York State’s Adirondack Park, the largest state park in the lower 48. Lake George is rated a Class-AA Special water body, which means it is drinking water for surrounding municipalities.

Like all lakes, it suffers from nutrient-rich runoff from neighboring towns and developed land, including nitrogen. These nutrients feed harmful algal blooms and cyanobacteria. Like infrastructure across the country, the wastewater treatment plant that treats water flowing into Lake George from Bolton Landing, NY was built in the 1950s and lacks important treatment processes that need a modern upgrade. Specifically, the treatment plant’s effluent is discharged into infiltration beds on the plant’s property, then eventually enters the groundwater before subsequently ending up in Lake George through surface water.

In 2018, the town of Bolton constructed an experimental woodchip bioreactor to better treat the municipal wastewater. In 2019, LCSG funded a 27-month monitoring study conducted by the Lake George Association, Lake George Waterkeeper, and the Town of Bolton to monitor the bioreactor’s impact on the wastewater plant’s effluent and subsequently Lake George’s water quality. Primarily used for tile drainage in agriculture on Midwest farms, this project was the first of its kind to adapt the woodchip bioreactor technology for municipal wastewater.

So, how does it work?

When effluent flows into the underground bioreactor, it contains a high concentration of nitrates. Naturally present bacteria living on woodchips in the bioreactor seek oxygen from nitrate molecules in order to survive. This bacteria absorbs oxygen from the nitrate molecules, then releases only nitrogen gas, which ‘cleans’ the effluent water. When the treated water exits the bioreactor, it contains less nitrates than when it entered – nitrates that would otherwise end up negatively impacting Lake George’s water quality. Watch this animation to see how this process works.

The 2019 study found that the town’s woodchip bioreactor removed 38% of nitrate from the wastewater that flowed through it, compared to zero removal of nitrate from the rest of the plant’s effluent stream, a very promising finding. The team published a journal article in 2022 highlighting the potential implication of this research for other small wastewater treatment plants.

“The results from the woodchip bioreactor demonstration project were very encouraging for the reduction of nutrient loading, which has been negatively impacting Bolton Bay and Lake George,” said Lake George Waterkeeper Chris Navitsky. “This was an amazing collaboration between municipal, consulting, funding and environmental partners with significant environmental benefits.”

The bioreactor is no longer in operation but due to consistent monitoring by the Lake George Association and the Lake George Waterkeeper, and researchers can confirm the nitrate concentrations have increased since the bioreactor was removed. In fact, the demonstration project was so successful that the town received a New York State Water Quality Improvement Project grant of $246,000 for the construction of two new woodchip bioreactors to be built in 2026. After learning from the first application, the project leads will change a few technical aspects to make the bioreactor more efficient. Changes include improved woodchip specifications to reduce degradation over time, the inclusion of a separate primary chamber to collect suspended solids, and improved membrane installation to improve anoxic conditions.

“There are many rural communities with antiquated and inadequate wastewater treatment processes that are impacting surface waters and are in need of upgrades,” said Lake George Waterkeeper Chris Navitsky. “The success of the Town of Bolton’s woodchip bioreactor demonstration is exciting because it is cost effective, sustainable and can be mimicked implemented with limited system redesign across the country.”