| In order to ensure aircraft safety during winter conditions, glycol-based deicing and anti-icing fluids are employed prior to takeoff. These products can exert a severe impact on the environment if allowed to go untreated. The present study is related to the treatment of glycol-contaminated wastewaters by the activated sludge process.;The results from the field show that despite the increases in influent organic matter during the deicing season, there were very little changes in effluent values of organic matter. Furthermore, influent concentrations of deicing fluid between 10 and 30 mg/L were reduced to trace amounts (i.e. below 5 mg/L) throughout the deicing season. However, as witnessed by the high sludge volume index during the deicing season, the presence of deicing fluid creates settling problems in the clarifier.;The laboratory batch experiments indicate optimal substrate removal rates at biomass concentrations of 1000 mg/L and 2000 mg/L. Very low biomass levels lead to inhibition whereas a high biomass level of 3000 mg/L is unnecessary since the food to microorganism ratio is such that only a fraction of the biomass participates in the degradation reaction. With regards to deicing fluid concentration, organic matter removal rates tend to increase as the deicing fluid is increased. However, at the highest level of deicing fluid, certain inhibitory effects are present. As expected, higher temperatures produce much higher removal rates with the ethylene glycol substrate showing less variation with temperature than the other organic compounds present in the wastewater.;With regards to the mechanism of removal, the results showed very little adsorption of organic matter onto the biomass within the first hour of contact. In addition, the total organic matter removal (TOC and COD) followed first order kinetics with respect to substrate concentration.;The specific objectives of the research were to: (1) determine the effects of process parameters such as biomass concentration, deicing fluid concentration and temperature on the biodegradation kinetics. (2) determine the mechanism of deicing fluid removal and model the reaction rates. (3) determine the effects of microbial changes on the treatment process. (4) evaluate the advantages of a sequencing batch reactor for the treatment of deicing wastes. (5) corroborate our laboratory results with field data from an operating wastewater facility treating deicing wastes.;Lastly, sequencing batch reactor operation allowed for much higher removal rates as the microbial population is acclimatized to the substrate with increasing cycles. With regards to the microbial population, the Biolog results showed that there was a decrease in the variety of compounds that could be degraded as the biomass was exposed to the deicing fluid. Furthermore, most population changes occurred at the very beginning of the deicing season and in the first half of the SBR experiments. |
