In a chemical plant, 35 kg of 1.2-dichloroethane was discharged into the ROMANCHE river then the DRAC river for 2 hours via the wastewater. The incident was detected by the permanent analyser located on the plant’s discharge structure. The flux from the stripping column in question was diverted towards the retention basin 5 minutes later and an instantaneous sample of the site’s effluents was collected. Its analysis revealed a 14.1 mg/l content of 1.2-dichloroethane. The record of the stripping column’s operating parameters showed that the pollution peak lasted 45 min and therefore concerned 35 kg of dichloroethane. According to calculations modelling the dispersion of the pollutant in the natural environment after the accident, the concentration of dichloroethane in the environment was much lower than its CE(l)50 and had no visible environmental impact. Measurements taken in the area surrounding the retention basin showed no emission of volatile organic compounds.

The malfunction of a level measurement on a settling tank used for separating water from the 1.2-dichloroethane in the DCE workshop caused the accident. Modification of the density of the aqueous phase, due to a change in its sodium concentration, distorted the level measurement and caused the level of dichloroethane to rise and overflow towards the stripping unit. This unit was unable to treat the entire flux, which caused a discharge towards the site’s water collection system. To reduce the likelihood of such an accident from happening again, a study was carried out on the stripping column to determine whether it was possible to rapidly detect an influx of 1.2-dichloroethane using a temperature sensor.