Airport environmental managers know that the Environmental Protection Agency has been collecting data on the levels of deicing glycols and other contaminants in airport stormwater, and that mandatory stormwater management plans, and perhaps even prescriptive discharge limits, are on the horizon. The same managers also recognize that the airport is ultimately responsible for controlling discharge of pollutants to the environment. While airport stormwater runoff is particularly hard to treat using conventional means because it is cold, intermittent, and high-volume over short periods, an innovative approach using aerated gravel beds is proving to be an effective treatment for such contaminated stormwater.

These sub-surface flow (SSF) wetlands are insulated, aerated, and specifically engineered to remove glycol. In addition, they are easy to operate, requiring only minimal attention from airport staff, and their construction and operations and maintenance (O&M) costs are only a fraction of those of alternative conventional stormwater treatment facilities (less than 50 percent). A new facility of this sort is in its final design stages for Buffalo Niagara International Airport (BNIA).

Airports in cold weather areas use glycol-based aircraft deicing fluids (ADFs) for removing ice and snow from aircraft surfaces during winter and under frost conditions. Relatively concentrated, glycol-rich, spent ADFs (concentrate) may be collected from around the deicing pads; yet, significant parts of the spent ADFs at every airport end up in stormwater sewers and ditches, where they may be channeled into nearby streams.

The management of glycols varies from airport to airport. At some, sophisticated deicing pads and vacuum trucks are used to ensure the collection of up to as much as 65 percent of the glycols used. At others, little or none of the concentrate is recovered, and excess glycols and surface deicing chemicals are simply allowed to flow, drip, or blow into nearby sewers, ditches, and grassed areas.

Focusing on the Problem
Early emphasis for airport glycol management focused on the concentrate stream and ignored that portion of the spent ADF that entered stormwater systems. There are options for the off-site management of the glycol-rich concentrate.

In some cases, that which is vacuumed up or otherwise collected at deicing pads is sent to local municipal wastewater treatment plants. However, this option can be expensive and may be risky, as increasingly municipalities local to airports are reducing or eliminating taking such materials.

Alternatively, on- or off-site recycling or treatment plants such as anaerobic digesters, reverse osmosis plants, and distillation units can be used to manage the concentrate if there is a market for the recovered material. However, these concentrate management options usually also produce byproduct streams (sludges, residual water, gases/odors) that must in turn be managed, and they require extensive and expensive operations and maintenance by airport or contract staff.