Propylene glycol (PG) is a main component in several commercial formulations of aircraft deicing fluids (ADF). Their use is a source of soil pollution along airport runways. Even though PG is biodegradable by soil bacteria, seasonal overloads can give rise to occasional groundwater contamination. A prevention strategy could be the enhancement of biodegradation rate in the unsaturated zone. The effect of addition of nutrients on the kinetics of PG degradation has been studied in soil slurries. In the absence of added nutrients, the aerobic removal kinetics is zero-order in PG concentration over the range 0.05-1 g/L. There is no biomass growth and PG degradation occurs by maintenance metabolism at constant rate depending on the initial concentration of PG-degraders. In the presence of ammonia as a nitrogen source, biomass exponential growth allows a faster aerobic PG degradation. Biomass growth can be detected by the apparent change in PG removal kinetics.
