Underground Treatment Of Airport Deicing Fluid 

Authors: 

Scott Wallace, P.E., President, Naturally Wallace Consulting 

Mark Liner, PE, Senior Engineer, Naturally Wallace Consulting 

Introduction

How bad was last winter? We all have different ways to answer that; but for airports, it 

can be measured by how much chemical was used to keep planes and pavement free of 

snow and ice. And, by that metric, the past two winters have been unusually severe for 

European airports. In the case of London Gatwick, chemical use jumped over five times 

compared to levels in the past decade. 

While keeping air flight safe, airports and airlines are also obliged to clean up after 

themselves and protect nearby streams and water bodies. And due to increasing 

chemical usage and looming regulations, some airports will need to invest in significant 

infrastructure upgrades to capture and treat stormwater contaminated with deicing fluid. 

 

In 2009, the United States Environmental Protection Agency proposed new Effluent 

Limitation Guidelines (ELGs) for airport deicing that would set a national standard for the 

capture and treatment of airport runoff. The regulations are in the process of being 

finalized and will be promulgated later this year. These new regulations are prompting 

airports to review existing and planned infrastructure to manage deicing activity. The 

costs can be high; the airport in Portland, Oregon recently completed a 100 million dollar 

project for the protection of neighboring water bodies. 

Other airports have turned to a relatively new approach that provides treatment of runoff 

in underground basins. Referred to as “aerated gravel beds”, these biological treatment 

systems are specifically tailored for winter operation and are being used in the United 

Kingdom, Canada, and the United States. Experience with the design, construction, and 

operation of these systems over the past five years has demonstrated the ability of the 

systems to work even during the recent spate of “bad” winters. 
The Cost of Compliance

The magnitude of the issue should not be dismissed. A gallon of the most commonly 

used deicing chemical, propylene glycol (PG) has roughly eight pounds of oxygen 

demand. To put that in some perspective, this is equivalent to the sewage generated by 

40 people in one day. Considering that over 200 gallons of PG can be used per airplane 

for deicing (equivalent to 8000 people), you can imagine how the numbers and impact 

on the environment begin to pile up. 

The problem is sizeable. No question about that. Each airport is unique in its climate, 

chemical usage, and stormwater storage capacity and there are different solutions 

depending on an airport’s particular circumstances. A recent project that provides a rule 

of thumb for treatment costs is the treatment system at Buffalo Niagara International 

Airport (BNIA). The treatment system at BNIA cost 7.82 million dollars and is designed 

at 10,000 pounds of BOD/d treatment or $782 per pound of BOD/d. Using eight pounds 

of BOD per gallon of glycol that equates to roughly $6,250 per gallon of glycol captured 

per day. Assuming that airports can only capture about 33 percent of the chemical used, 

the cost of a treatment system can be estimated at $2,000 per gallon of glycol used. 

With larger airports using over 20,000 gallons of glycol per day, the capital cost of 

treatment can be staggering. 

 
Three Treatment System Examples 

Buffalo Niagara International Airport (BNIA), New York 

With over eight feet of snow on average and 110 daily flights, BNIA joins the ranks of 

“big sprayers” when it comes to the amount of deicing fluid used each year and are 

required to treat stormwater prior to discharge to adjacent Cayuga Creek. 

To reduce sewerage costs and meet stormwater discharge limits, BNIA selected an onsite treatment option for management of spent aircraft deicing fluid (ADF). The system 

had to be low profile and fit within the airside of the airport. It also needed to be capable 

of handling seasonal fluctuations, be designed for low operation and maintenance, and 

be integrated into the existing stormwater management system. 

The airport constructed an aerated gravel bed treatment system in 2008-2009. A key 

criterion for the system was for it to be built adjacent to the edge of the object free area, 

400 feet from the centerline of the runway. No easy task. The contaminated stormwater 

is distributed into underground beds specifically designed to operate with no exposed 

water or other bird attractants. The finished project is at grade with no above ground 

structures that could present an airside hazard. The patented Forced Bed AerationTM 

system supplies air uniformly over the floor of the beds and that promotes biological 

degradation of glycol and other contaminants in the water. Development of the project 

was supported by a treatability study conducted in a walk-in refrigerator that established 

specific cold-weather removal rates for the airport’s ADF. 

“In the last year, the treatment system saved the airport $500,000 in operations cost”, 

noted Kim Minkel, Executive Director of the Niagara Frontier Transportation Authority 

(NFTA) during the opening remarks of the Snow Symposium held in Buffalo on April 18, 

2011. Online monitoring over the 2010-2011 deicing season indicated consistent 

treatment of 90 percent or more. 

Mayfield Farm Refurbishment and Upgrade, Heathrow Airport, London 

The British Airports Authority (BAA) commissioned a reed bed treatment facility in 2001 

at Mayfield Farm to treat deicing runoff from Heathrow Airport. Due to expansion of 

airfield operations, the existing facility was upgraded in 2010 to provide a significant 
increase in treatment capacity. 

The upgrade of the treatment system included the addition of aeration equipment, a 

nutrient feed system, a reconfiguration of the existing reed beds, and related electrical 

and instrumentation work. The upgrade is divided amongst three major “unit processes” 

downstream of the main reservoir: a complete mix lagoon, partial mix lagoon, and the 

aerated gravel beds. During normal operations, flow is pumped from the main reservoir 

so as to flow in series through each unit process until discharge. 

The system upgrade allowed BAA to re-use its existing infrastructure therefore reducing 

the impacts of new build facilities. The re-engineering, including Forced Bed 

AerationTM, allowed Mayfield Farm to increase its treatment capacity from 770 pounds of 

BOD to a minimum of 7,700 pounds of BOD per day. 

Edmonton International Airport (EIA), Alberta 

Glycol contaminated stormwater at Edmonton International Airport stays frozen every 

winter until the spring thaw. At this point, glycol and other plane and pavement deicing 

compounds are washed away to a large collection pond. Water from the pond requires 

treatment prior to discharge to a nearby creek. The existing wetland system has been 

treating the flow for almost a decade, but with expansion of the airport, a major increase 

in overall treatment capacity was required. 
The system expansion is designed to provide over 1,500 pounds of BOD/d treatment 

capacity and is engineered to allow increased flow rates as the concentration of the BOD 

drops during spring melt. The upgrade includes reconfiguration of up to three of the 

existing treatment trains. The first cell of each train has been modified to a vertical flow 

configuration and incorporates Forced Bed AerationTM. The second cell in the train has 

been reconfigured as a surface flow wetland for polishing of the effluent. A nutrient feed 

system will also be included to allow addition of nutrient solution to match the level of 

organics in the influent. 

With addition of aeration and nutrients, the upgraded system can provide up to 10x more 

treatment in half the footprint of the old wetland system. The aeration and nutrient 

systems are designed so that levels can be adjusted based on influent concentrations. 

Converting to vertical flow removes the hydraulic constraints previously experienced with 

the old horizontal flow wetlands. A new lift station also provides substantially more 

flexibility with meeting the aberrant flows of spring melt. Finally, incorporation of a 

recycle system permits expedited start-up in the spring. 

In Closing

Under coming regulations, some cold climate airports will have to consider onsite 

treatment for ADF contaminated stormwater. The environmental impacts of not treating 

are significant and engineers will be challenged to develop systems that are cost 

effective. The evolution and use of aerated gravel beds for treatment of runoff is proving 

to be an effective solution for this unique problem. They offer the benefit of excellent 

treatment, low safety risk, and significant savings in operations costs. 
About the Authors 

Scott Wallace P.E., President, Naturally Wallace Consulting LLC, Stillwater, 

Minnesota 

Scott Wallace is a globally recognized leader in the design of ecological systems 

including constructed wetlands, decentralized wastewater systems, stream bank 

stabilization and control of nonpoint source pollution. The author of papers in numerous 

technical and environmental publications, Mr. Wallace is the co-author of Treatment 

Wetlands Second Edition, the definitive textbook on wetland treatment systems. 

Wallace and his team were awarded the 2009 Diamond Award for Engineering 

Excellence in Water Resources from the American Council of Engineering Companies

(ACEC) for his design of a natural treatment system to treat spent deicing fluid at Buffalo 

International Airport in Buffalo, New York. They also received the 2005 Grand Award for 

Engineering Excellence from (ACEC) for his design of a hydrocarbon remediation 

wetland for British Petroleum in Casper, Wyoming. 

Scott can be reached at scott.wallace@naturallywallace.com

Mark O. Liner, P.E., Senior Engineer, Naturally Wallace Consulting LLC, Stillwater, 

Minnesota 

Mr. Liner is a senior engineer with Naturally Wallace Consulting. Over his 20-year 

career, he has worked as a regulator at EPA headquarters, as a process and equipment 

supplier, as a design-build project manager, and as a consultant engineer for industrial 

clients. He has designed over 500 new and retrofit treatment systems across the world. 

He specializes in the design of onsite treatment systems for industrial facilities with an 

emphasis on airport deicing, mines, landfill leachate, and remediation. Mark as the 

Senior Design Engineer on the Buffalo Airport project. 

Mark can be reached at mark.liner@naturallywallace.com