Grant funds in action: New tech helps small towns tackle water pollution problems

Bolton’s wastewater treatment upgrade includes a wood chip bioreactor, keeping pollution runoff out of Lake George

By Zachary Matson

A yeasty odor of brewery waste emanates from an indispensable pipe in Bolton on a sunny March day. Flush a toilet or dump beer-making discard in this lakefront hamlet and eventually it finds its way to that pipe.

The town of Bolton’s treatment plant, installed in the 1960s, is permitted to handle an average of 300,000 gallons of wastewater a day, which from time to time bursts out of the pipe and into a large open-air holding tank—a fountain of sewage and the first stop at the plant. 

The aging plant’s system enables bacteria to break down the wastewater’s high levels of ammonia into nitrates, but for decades there was no process to take care of the nitrates, which flow through the rest of the treatment plant, seep into groundwater, enter nearby streams and end up in Lake George. Excessive levels of nitrates can lead to development of harmful algal blooms. 

Addressing a similar problem, the village of Lake George built a new $24 million plant that opened in 2022, relying on denitrification technology built into modern treatment plants.

Bolton received a $1 million Department of Environmental Conservation (DEC) grant in 2018, in part to test a novel approach, sending the plant’s final flow through a 100-foot-long, 25-foot-wide, 4-foot-deep trench packed with wood chips, called a wood chip bioreactor. Deprived of oxygen, bacteria in the carbon-rich detritus break off oxygen molecules from the nitrates, producing a less harmful stew of carbon dioxide, nitrogen and water. Monitoring research by Lake George Waterkeeper Chris Navitsky indicated a 38% reduction in nitrates exiting Bolton’s wood chip bioreactor when it operated from 2019 to 2021. 

A second DEC grant in 2022, this one for $246,000, will enable the town to reconstruct and expand the plant’s bioreactor capacity. Construction is expected later this year. 

“It’s green, it’s passive and it works,” said Kathy Suozzo, Bolton’s town engineer.

The approach was modeled off methods used by large farms in the Midwest, where high-nitrate runoff from fertilized fields is treated in similar wood chip-filled trenches. The model, which had never been used in the region and possibly in any municipal operation, could be replicated by other small treatment plants based on older technology. 

Town Supervisor Ron Conover and plant operator Matt Coon joined the Bolton highway crew and a local contractor to build the demonstration plot that went into use in October 2019. About 115,000 gallons a day was sent through the bioreactor. 

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Navitsky examined nitrate levels in Stewart Brook upstream and downstream of the plant. The stream flows into Bolton Bay, one of Lake George’s bays most impacted by algae growth. The difference with and without the bioreactor was clear, Navitsky said.

“After the bioreactor was taken down, you could actually see the nitrates go back up in Stewart Brook,” he said. “Clearly there was a water quality benefit to the streams as well as Lake George.”

Learning from the first grant, the new bioreactors will be covered more completely, to choke off even more oxygen, and the town will use a larger woodchip to limit breakdown. A second or third trench will enable the town to increase capacity during busy summer months and continue to treat flows if one needs maintenance. The bioreactor, though, is still a stopgap before the full plant overhaul that Bolton will eventually need to pursue, officials said.

Coon, who operates the plant, became a part-time chemist during the demonstration project, collecting monitoring data and fine-tuning how the system functioned. 

“The whole thing was basically a science experiment,” Coon said.