Propylene Glycol Deicer Biodegradation Kinetics: Anaerobic Complete-Mix Stirred Tank Reactors, Filter, and Fluidized Bed

Propylene glycol-based aircraft deicing fluid (ADF) is sprayed on aircraft during cold weather to remove ice and snow or prevent ice formation. A large fraction of the fluid typically falls to the pavement where it mixes with stormwater. Since airport stormwater containing ADF can exert a high biochemical oxygen demand, biological treatment may be required. The objective of this study was to determine and compare the rates of ADF chemical oxygen demand (COD) removal in anaerobic complete-mix stirred tank reactors (CMSTRs), anaerobic filters (AFs), and anaerobic fluidized bed reactors (FBRs) treating acidified and nonacidified propylene glycol ADF at temperatures between 35 and 11(degree)C. The AF and FBRs were initially operated in a continuous-flow mode. Subsequently, kinetic data were collected when the reactors were operated in batch mode. Maximum specific removal rates of 0.93, 0.30, and 0.045 g COD per g volatile solids per day were determined at temperatures of 35, 24, and 11(degree)C, respectively. The rates of acidified and nonacidified ADF COD removal were not significantly different. An Arrhenius equation temperature correction coefficient (theta) of 1.11 was determined. The most significant increase in overall COD removal rates (mg COD/L-day) were a result of biomass immobilization and increased biomass concentration in AFs and FBRs. Final COD concentration in the CMSTR were chronically high (circa 700 mg/L), and did not decline after five additional days of batch reaction time, whereas no chronically high final COD concentrations were observed in AFs and FBRs.