DEGRADATION AND TOXICITY OF ADDITIVES TO AIRCRAFT DE-ICING FLUIDS; THE EFFECT OF DISCHARGE OF SUCH FLUIDS TO MUNICIPAL WASTEWATER TREATMENT PLANTS

Experiments were performed to study the degradation of three additives to aircraft de-icing fluids in aerobic and anoxic bioreactors for wastewater treatment, as well as in an anaerobic digestion. These three additives were fatty alcohol ethoxylate, benzotriazole and sodium petroleum sulphonate. Chronic toxicity tests were performed for benzotriazole and sodium petroleum sulphonate. The results from the degradation of fatty alcohol ethoxylate and benzotriazole are confirmed in a full-scale plant.Fatty alcohol ethoxylate is very toxic, but readily biodegradable in biological wastewater treatment plants. Benzotriazole is toxic, hydrophilic, and not biodegradable in such plants. Sodium petroleum sulphonate is rather hydrophobic and slowly biodegradable. Approximately 10 % of the substance may be degraded during biological wastewater treatment.The present use of de-icing fluids as an external carbon source at Gardermoen wastewater treatment plant will not exceed the limits given by the environmental risk assessments for the additives.