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4 EPA survey in 2006. The reduced oxygen demand by acetate- Approved airside urea, calcium magnesium acetate, sodium and formate-based deicers compared with urea is evident in formate, and sodium acetate products must meet SAE AMS Table 1, as reported as chemical oxygen demand. Testing for 1431C, Compound, Solid Runway and Taxiway Deicing/ chemical oxygen demand is faster than standard BOD tests Anti-icing. Airside urea must also meet the military specifica- and indicates the theoretical maximum oxygen that would be tion MIL SPEC DOD-U-10866D, Urea-Technical ("Airport consumed; BOD is related more to biological decomposition. Winter Safety and Operations" n.d.). In addition, more costly PDPs must be justified and programmed into operating bud- Third, materials compatibility between PDPs and the air- gets. The costs associated with both aircraft and airfield main- craft and airfield infrastructure is yet another objective. Field tenance and alleviating the environmental impacts of PDPs reports suggest that the use of modern PDPs, including alkali must be balanced in decision making for deicing and anti-icing acetate and alkali formate products on aprons, runways, and operations. Alternative PDPs may also pose new challenges taxiways may result in the need for more frequent mainte- related to rules of practice and training. nance and inspection for various aircraft and airfield infra- structure. Such PDPs have recently been reported to corrode The previously mentioned multiple dimensions of this or degrade cadmium or aluminum components and carbon complex problem define the context of this synthesis. There carbon (C/C) composite brakes of aircraft. Often mixed with are no simple solutions to the competing, and sometimes corrosion inhibitors, KAc and KF were reported to degrade conflicting, objectives of aircraft safety, environmental reg- insulation in aircraft electrical systems. Existing research has ulatory compliance, materials compatibility, and operational indicated that KAc and KF may cause accelerated structural implementation viability. degradation of C/C composite aircraft brakes as a result of the catalytic oxidation by the potassium cation, which may ACRP has two airfield deicing research projects underway result in reduced brake life and introduce the possibility of at this time: ACRP Project 02-01, Alternative Aircraft and brake failure during aborted take-off. KF was found to cause Airfield Deicing and Anti-Icing Formulations with Reduced corrosion to landing gear and associated wiring of some Aquatic Toxicity and Biochemical Oxygen Demand, which Boeing airplane models. Other examples of damage poten- responds to the voiced need for new formulations of aircraft tially associated with the use of PDPs include reports of cor- and airfield deicers that combine safety, performance, and rosion in landing gear joints, electrical wire bundle degrada- materials compatibility with environmental stewardship and tion, corrosion of runway lighting fixtures, and damage to cost-effectiveness. The identification of new formulations will airfield pavements. Airfield pavement damage has been ob- be based primarily on reduced toxicity and BOD5 and evalu- served in both asphalt and concrete runways. Evidence of the ated based on their performance, efficiency, material compat- former is more widely reported in European airports; how- ibility, and environmental, operational, and safety impacts. ever, laboratory tests worldwide have shown emulsification of Airports of all sizes and operational levels are reporting in- asphalt and the disruption of asphalt-aggregate bonds. Exten- creased difficulty in balancing environmental concerns dur- sive laboratory testing of concrete pavement has shown an ing their operations (General Accounting Office 2000). ACRP increase in alkalisilica reactivity and the need for improved Project 02-02, Managing Runoff from Aircraft and Airfield standardized tests for aggregate selection and mix design. Deicing and Anti-Icing Operations, will provide an array of planning guidelines with best management practices useful Finally, operational implementation viability is another con- for the implementation of site-specific solutions for the col- straint for airports and airlines to consider. The FAA prescribes lection of deicer runoff while still maintaining safe aviation. a list of chemicals that are approved for the snow and ice con- These guidelines can provide sound technical information in trol of airfield pavements, which limits options of chemicals support of the ongoing effort by the EPA to establish effluent being used as PDPs. The approval of PDPs by the FAA advi- guidelines for discharges of deicing runoff. sory circular ("Airport Winter Safety and Operations" n.d.) is currently based on two specifications of the SAE through Aero- To avoid duplication, this synthesis strictly limits this space Material Specifications (AMS). Approved glycol- and report to how airports chemically treat their airfield pave- potassium-acetate-based fluids must meet SAE AMS 1435B, ments to mitigate snow and ice, and chemicals used; reviews Fluid, Generic Deicing/Anti-icing, Runways and Taxiways. damage reported to aircraft components and airfield infra- structure in association with the use of traditional or modern TABLE 1 PDPs; and identifies critical knowledge gaps on these sub- CHEMICAL OXYGEN DEMAND FOR RUNWAY DEICERS jects. Such information is expected to provide a holistic view of airfield pavement deicing and anti-icing operations and COD COD assist in the design of new deicer formulations. Deicers [g(O2)/kg dry deicer] (kg/10 hectare surface) Potassium Formate 190 285 Potassium Acetate 653 1,134 METHODOLOGY Urea 2,133 5,365 This synthesis was primarily based on a critical review of lit- Adapted from Sava (2007). erature and a formal survey with follow-up interviews.