Aircraft de-icing/anti-icing fluid (ADAF)-laden wastewater: Evaluation and recommendations for its treatment and regulation
Smith-Cunningham, Sandra L.
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Airports that operate in cold climates are required by the FAA to de-ice aircraft and runways. The most common method involves the use of glycol-based aircraft de-icing/anti-icing fluids (ADAF). The majority of these fluids contain either propylene or ethylene glycol that act as freezing point depressants, along with additives such as corrosion control inhibitors, surfactants, and wetting agents. Historically, the runoff of spent fluids from aircraft and pavement de-icing/anti-icing operations has been difficult to manage, resulting in significant discharges to surface waters on both a national and global level. Currently, best-practice treatment of airport storm water containing ADAF is geared for glycol-rich wastewaters, with the treatment efficiency being measured by reduction of BOD and nutrient levels in the effluent. The objective of the thesis was to assess whether the traditional parameters (BOD, COD, and pH) most frequently used to monitor the treatment and release of airport stormwater effluent containing de-icing fluids were adequate indicators of the effluent quality. Current literature was used to evaluate the chemistry, environmental fates, persistence in the environment, and toxicity of two classes of compounds, glycols and benzotriazoles. Glycols were shown to be readily degraded in the environment and relatively non-toxic. Benzotriazoles were shown to be resistant to degradation, persistent, and toxic in the environment. The fate of both of these types of compounds was then evaluated in best practice treatment methods for airport stormwater. Glycols were shown to be effectively treated and benzotriazoles were projected to be recalcitrant. The research supports the hypothesis that using BOD, COD, and pH as measures of suitability of return to the environment for treated stormwater containing spent ADAF is inadequate. New additives and more sophisticated ADAFs affect the toxicity of the effluent and require treatment processes that effectively treat all of the constituents of the fluid.