Kinetics of anaerobic degradation of glycol-based Type I aircraft deicing fluids

The kinetics of anaerobic degradation of glycol-based Type I aircraft deicing fluids (ADFs) were characterized using suspended-growth fill-and-draw reactors. Both Type I ADFs tested showed near-complete anaerobic degradability. First-order degradation rate constants of 3.5 d^-1 for the propylene glycol-based Type I ADF and 5.2 d^-1 for the ethylene glycol-based Type I ADF were obtained through continuous-culture means under mesophilic conditions (35 °C). Fill-and-draw operation at lower temperatures affected anaerobic degradability only minimally down to 25 °C but substantially below 25 °C. High Type I ADF feed concentrations substantially affected degradability. Batch testing of fill-and-draw reactors resulted in first-order degradation rate constants of 1.9 d^-1 for propylene glycol-based Type I ADF and 3.5 d^-1 for ethylene glycol-based Type I ADF.