Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
1-1 SECTION 1 INTRODUCTION The Airport Cooperative Research Program (ACRP) has sponsored research on environmental characteristics of aircraft and pavement deicers and anti-icers focusing primarily on biochemical oxygen demand (BOD) and aquatic toxicity of formulated products and individual chemical components of formulations. This report presents a background of issues leading to this research, objectives of this document, and a description of the efforts and findings of this research. Except when the distinction among products is necessary for clarity, âdeicerâ will refer to aircraft-deicing fluids (ADFs), aircraft anti-icing fluids (AAFs), and pavement-deicing materials (PDMs) generally. The efforts of this project have included the following: ⢠A review of regulations and specifications related to the performance and environmental characteristics of deicer formulations ⢠A review of issues related to the impact that deicers have on aquatic systems and causes of those impacts ⢠Laboratory testing of current-use deicers to establish benchmark values for aquatic toxicity, BOD, and chemical oxygen demand (COD) ⢠A review of deicer formulations under development and their relevant performance- and environmental-related characteristics ⢠A review of operational and infrastructure considerations ⢠A synopsis of current analytical methods used in environmental characterization of airport deicing runoff ⢠A toxicity-based investigation of current-use deicers to determine components responsible for toxicity and identify component classes to focus a search for alternative components ⢠Identification of gaps in knowledge and data pertaining to the above topics Background The aviation industry faces a formidable combination of tasks in ensuring the safety of winter flight operations, which includes removing ice and snow from aircraft surfaces, preventing ice and snow from accumulating on aircraft surfaces before takeoff, maintaining ice- and snow-free taxiways and runways, maintaining flight schedules, and minimizing the environmental impact of aircraft and airfield deicer and anti-icer formulations through deicer-runoff management programs. The industry has made steady progress over the past two decades in collecting and containing deicing runoff; however, it is recognized that
1-2 complete containment of spent deicing and anti-icing fluids is impractical without a significant financial burden. A potentially more practical approach to reducing the environmental impacts of deicers is in reducing BOD and the potential toxic impact of components in the products and, by extension, in discharges to the environment. Deicer manufacturers have made progress to reduce these impacts in formulations within recent years, but BOD and aquatic toxicity in deicing runoff entering receiving waters continues to be a concern. Freezing -point depressants (FPDs) in ADFs and AAFs are typically propylene glycol (PG), ethylene glycol (EG), or, rarely, diethylene glycol. ADFs and AAFs also contain water and various additives, collectively referred to as the âadditive package,â which enhance the fluidsâ performance. Classes of chemicals in additive packages include corrosion inhibitors, surfactants, thickeners, dyes, flame retardants, defoamers, and pH buffers. Although it is recognized that the primary source of BOD in a deicer is the FPD, the source of toxicity is not as clear. Aquatic toxicity in aircraft deicers has been reported to be associated with components of the additive packages (Pillard, 1995), but additive package components are proprietary and considered to be trade secrets. Only two classes of additives that contribute to toxicity have been identified in the literature: Benzotriazoles are corrosion inhibitors that contribute to toxicity in some deicers (Cancilla et al., 1997), and alkylphenol ethoxylates (APEs) are a class of surfactants that contribute to toxicity in some deicers (Corsi et al., 2003). In addition, APEs have the potential to produce degradation products that are considered endocrine disruptors (Servos, 1999). Recent research evaluating component toxicity in ADF and AAF has determined that benzotriazoles and APE are not present in all formulations and account for only a portion of toxicity in deicers where they are present (Corsi et al., 2006a). It appears that the remaining unexplained aquatic toxicity in deicers is due to other proprietary additive components, explaining the need for this project. The situation with airfield PDMs is similar but not as well defined. The primary FPDs in available PDMs are the glycols, plus urea, and potassium and sodium salts of acetate and formate. All of these chemicals represent significant sources of BOD. The composition of PDM additive packages and their potential contribution to toxicity are poorly understood. Objectives The purpose of this document is to present results of an extensive review of information on environmental characteristics, operational and infrastructure issues, and BOD and toxicity testing results. Specific objectives are as follows: ⢠Define the state of the art with respect to aquatic toxicity and BOD of aircraft and pavement deicers in use at airports in the United States ⢠Describe issues related to fate and transport of deicers through review of currently available information ⢠Identify the components of deicers that are responsible for aquatic toxicity and BOD
1-3 Report Structure This report is structured to be generally consistent with the work tasks described in the ACRP 02-01 Amplified Research Plan, dated November 15, 2006: ⢠Section 2 presents the results of a review of relevant literature and other appropriate data sources. ⢠Section 3 presents the methods and results used to characterize deicer formulations and components that contribute toxicity and BOD.
