Glycol Removal Made Simple

Stormwater treatment plant using bacteria to eat up deicing fluids.


The Ohio Environmental Protection Agency’s instructions to Akron-Canton (OH) Airport were simple: meet the stormwater discharge limits by fall 2007. Fortunately for CAK, certain kinds of bacteria find propylene glycol delicious. Following the example set by Albany International Airport, the only other airport in the United States with a similar treatment system, CAK’s new deicing system is cleaning up the water, producing methane, and being good for the Akron environment.

“Quite frankly, the easiest way would have been to meter it out to the sanitary system,” says Rick McQueen, assistant director at CAK. “But our local sanitary system couldn’t handle the load.”

“Once we determined that, we had to go back to the drawing board and find out what other technologies were available.”

So CAK hired Reynolds, Smith and Hills, a national consulting firm, for a deicing management study. Based on the most cost-effective options, CAK decided to stop allowing deicing at the gate and instead build three deicing pads to minimize the effluent collection area.

Deciding how to clean the collected effluent led to weighing more options.

“We looked at membrane bioreactors, we looked at the anaerobic fluidized bed reactors (AFBR) — which is the system we went with — and we also looked at ultra filtration reverse osmosis,” explains Brad Wente, PE and senior aviation engineer at Reynolds, Smith and Hills. “There are pros and cons to each.”

Ultimately, CAK went with AFBR, securing two Airport Improvement Program grants of $5 million each, for a total of $10 million, to cover the cost of the new deicing pads as well as the treatment center.

HOW IT WORKS
Tim Arendt, a principal at Gresham, Smith and Partners who worked on the Akron project, says there are two bioreactors to the system, each approximately 30 feet tall, that contain activated carbon — which looks similar to coffee grounds.

“The idea is to grow bacterial films on these particles,” Arendt says. “Then these bacteria, once they come in contact with the water containing the deicing chemicals, use the chemicals as food to grow and multiply and do all of the things that bacteria do.”

“In the process, they ultimately change the chemicals to carbon dioxide, water, methane, and more [bacteria]. So the water is then clean and can be discharged to the stream.”

The methane is captured and used to heat the effluent to a temperature most palatable to the bacteria. The bacteria, Arendt notes, are not the disease-causing variety. “Most sewage treatment plants also use bacteria,” Arendt says.

AFRB does require some maintenance. Arendt says CAK hired two operators for the system, both of whom worked in the airport’s maintenance and deicing operations and expressed interest.

Ongoing maintenance issues unique to the system, Arendt says, deal primarily with supplying adequate nutrients required for the bacteria to thrive.
A computer system helps measure the bioreactors and ensures the right balance for the bacterial environment. The concentration of glycol percentages versus stormwater are also measured and adjusted.

“The bacteria are happier if you can feed them the same amount of stuff all the time,” Arendt says. “If they get overfed and then starve it’s not really conducive to the operations. There are a lot of analogies to human beings here.”

THE ALBANY EXAMPLE
A deciding factor on what treatment system to go with at CAK was seeing the treatment plant at Albany.

Comments McQueen at Akron, “They gave us a tour and a lot of information on their technology and how it works. We decided that that would be a very good alternative for us.”

Albany airport environmental planner Steve Iachetta says airport representatives from as far away as Tokyo and Copenhagen have come to tour the treatment plant since it opened nearly ten years ago. Located on a tributary to a drinking water supply, ALB has plenty of experience.

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