Put the Brakes on Biofilm

Feb. 24, 2016
Gerald R. Ford International Airport’s new $20 million water treatment facility keeps glycol from the river where it can create biofilm.

Did you know that naturally occurring bacteria use glycol as a food substance?

Or that in the average year Gerald R. Ford International Airport uses 93,400 gallons of polypropylene glycol to deice planes leaving the Grand Rapids, Mich., facility?

For years, the deicing fluid and stormwater runoff from this major airport emptied into the Trout Creek tributary of the Thornapple River. But environmental experts discovered the fluid was partially to blame for a biofilm that had developed on the surface of the water.

Those are the facts that led to a new $20 million water treatment facility aimed at keeping deicing chemicals from entering the Thornapple River. The Michigan Department of Environmental Quality (DEQ) had advised the airport to develop a new water treatment plan for the deicing fluid by fall of 2015; and the airport in the interest of being a good neighbor felt the new treatment system was a worthwhile investment that protected natural resources and citizens living nearby. The majority of the funding for the $20 million project came from the FAA, which put in approximately $17.8 million. The state office of aeronautics and the airport paid for the rest.

“Our goal is to first and foremost be a good neighbor to the communities that surround us. Our second goal is to do things that end up with a positive impact on the environment. The airport is going to be here for a long time,” says GFIA Executive Director Brian Ryks. “The centerpiece of our new stormwater management program is a natural treatment system that will significantly strengthen the airport’s environmental performance, protect and improve water quality in the Thornapple River, and help sustain the river system’s water quality, aquatic life and natural beauty.”

Biofilm Issues at Trout Creek

Gerald R. Ford International Airport, which served 2.3 million passengers in 2014, only uses propylene glycol-based aircraft deicing products. Although the EPA finds polypropylene glycol is highly biodegradable and environmentally preferred, it still presents two challenges — its fast biodegradation competes with some organisms for dissolved oxygen in the water and it provides a rich food source for naturally occurring algae, fungi and other aquatic organisms, allowing them to proliferate to nuisance levels under ideal conditions.

“Glycol is a food source for biofilms,” says Tom Ecklund, facilities director for the Kent County Department of Aeronautics which oversees the operation of the airport.

Though the presence of biofilms can create nuisance-type conditions that negatively impact aquatic insect habitat, fish habitat and dissolved oxygen levels, Ryks states that “previously, there was really nothing being done from a treatment standpoint as far as collecting the glycol or treating it.” He explains excess glycol flowed into a detention pond that would rise to a certain level then spill over into the tributary that flowed into the river on the airport’s north side.

But in early 2000, the DEQ received a complaint from neighbors living near the Trout Creek tributary after they noticed a smelly film in the water. The DEQ dispatched environmental experts to investigate and those experts “felt the biofilm was from the glycol used for aircraft deicing,” Ryks says.

The airport put best management practices into place immediately, among which were testing and monitoring of runoff and a collection process designed to pick up glycol from the aprons. “Basically what would happen is an aircraft would deice and then these large ‘vacuums’ would suck up as much of the glycol as possible,” Ryks says.

According to Ecklund, these changes enabled the airport to capture close to 30 percent of what had been flowing into the tributary. “However, there was still a fair amount of fluid going off in the general runoff,” says Ryks. “And that wasn’t acceptable.”

DEQ officials agreed, and its Water Resources Division reissued the airport’s National Pollutant Discharge Elimination System (NPDES) permit in August 2013, which authorized the discharge of stormwater associated with deicing activities with one caveat: The airport needed to construct a natural treatment system for stormwater or aircraft deicing fluids by 2015. Airport officials then teamed with the DEQ to analyze options to further mitigate the problem.

Turn a Negative Into Positive

Neighbors were up in arms, believing the glycol runoff resulted in the deaths of fish and other creek wildlife as well as emitted an unpleasant odor in the area. But airport officials took the negative situation with vast public outcry and turned it into a positive. “We turned to the community to come up with a solution,” says Ryks.

Their first step was to assemble a stakeholders’ advisory committee that consisted of community individuals, DEQ experts, airline representatives, airport staff and consultants to review available options and select one to move forward with. The airport then used social media to announce the meetings and publicly posted information on an area of its Website devoted to the project. “We wanted to be very transparent and open, and I think we were very successful with that,” says Ryks.

“There was quite a bit of press attention to the issue early on, but pulling together the stakeholders’ advisory committee really helped improve dialogue and reassured the community that this was going to be an open and transparent process moving forward,” Ryks said.

He describes some public meetings as “a little tense” but stresses tensions subsided as the community received the message that the airport planned to get public approval for any remedy. Officials used these meetings to present the facts and educate the public on what the system would be designed to do, how it would operate and the results they expected it to achieve. “It took a lot of education — it can be a complicated issue — but once we got to the preferred solution, things were much improved,” he says.

Members of the community commended the airport for its openness in what was at times an “ugly” situation. “As a member of the stakeholder committee I am happy with the final product that was debated, designed, engineered and built by the team,” said Erv Gambee, president of the Thornapple River Watershed Council in an airport press release. “I look forward to seeing positive test results at the confluence of the discard and the Thornapple as well as the restoration of Trout Creek as time moves on.”

The airport was also recognized by the Airports Council International, North America (ACI-NA) for its efforts. The association honored Gerald R. Ford International Airport for its stormwater/glycol treatment project with an ACI-NA Environmental Achievement Award for Outreach, Education and Community Involvement.

Lead the Sustainable Way

The new system, completed in September, is the first system of its kind constructed at an airport in Michigan. Similar systems are being used successfully at airports in Buffalo, Montreal, Toronto and Washington Dulles. The system is designed to create a favorable environment for bacteria and other micro-organisms to establish and consume the residual aircraft deicing fluids in the stormwater before it is discharged to the Thornapple River. The stormwater treatment system enhances the quality of the natural environment with an innovative design for collecting and treating propylene glycol, and managing stormwater. The green design uses gravity, vegetated beds and natural organisms to treat the stormwater with essentially no power consumption or residual waste, reports Ecklund.

The new treatment system will bypass the Trout Creek tributary and reroute runoff directly into the Thornapple River and will include a natural treatment system that consists of treatment cells that the runoff travels through before reaching the river. The vertical system includes a top layer of dry vegetation, followed by two layers of sand, and then by two layers of gravel.

“We wanted to change the ultimate end runoff point from this small tributary to the larger river,” says Ryks. “It’s better for the stormwater to be going into the river which has a much greater volume of water than the smaller tributary. That was the real issue — the runoff was going into a smaller water source, and the way glycol is dissolved it was using up the oxygen in the water. When you put it into a much larger water source, that’s not going to happen.”

That being said, not much of the glycol runoff should make it to the river after treatment. “The basin will act as a sediment trap and also act as a trash removal facility,” Ecklund says.“The flow will leave the basin, and the basin is designed to control the flow into the first set of cells. The flow will go through the first set of cells and receive treatment. It will then be discharged into the second set of cells where that treatment process will be duplicated. It will then go into a third stage of treatment, which is basically a riprap channel, to add some oxygen into the flow, which is important to improve quality.”

Ecklund said the bacteria that feed on glycol would use the material as a food source during this process. “The natural bacteria in the soil will break down the glycol into a carbon food source,” he says.

The wastewater glycol treatment system is 100 feet lower than the airport, adds Ecklund, who notes this is important because the water is brought to it through gravity eliminating the need for a pumping system.

Part of the project also included adding a pipeline at the apron areas to ensure that all commercial aircraft deicing runoff flowed directly toward the treatment system. “Previous to that some of it was flowing in one direction and some of it was flowing in another direction,” Ryks says.

Project Deemed a Success

Though this is the first winter the system has been in place — and it’s been a particularly mild winter thus far, Ecklund says the system is exceeding expectations.

Eventually the airport hoped the treatment facility would effectively remove up to 80 percent of the glycol in stormwater runoff. Ecklund explains they expected the system wouldn’t work at that capacity immediately and would require a few tweaks before it did. However, after just one winter event, testing showed the system was already removing 75 percent.

“We were extremely happy with the results and expect to attain higher than 80 percent removal with some fine-tuning,” Ecklund says.

Before 2000, an estimated 65 percent of the glycol used at the airport made it to the tributary. Once the airport began vacuuming up and recycling glycol, that amount dropped 36 percent. Now that the project is complete, less than 7 percent will make it to the river. “It may even be lower than that with the system performing as well as it is,” says Ryks.

GFIA’s stormwater management will ensure the stormwater reaching the Thornapple River will be well within the state of Michigan’s water quality protection standards, and provide significant improvement in the Thornapple River. “We commend the airport on their actions to better the quality of storm water discharged from their facility, and completing such a large challenging project on time,” says William Creal, Michigan DEQ Director of Water Resources Division. “This was a difficult situation that Kent County showed quality leadership on, and took action to put a positive solution in place. We look forward to working with the airport and observing the treatment system in action.”