Pollution
Humain
Environnement
Economique

At 19:45 hrs, 11 t of polychloro-acetone were released in a chemical factory due to a faulty piping connection for the filling of a reactor. Polychloroacetone was to be pumped from a tank to the reactor in order to start the production of 1,3-dichloroacetone. The pipe-line connecting the tank to the mixer had previously been connected during production tests to another piping system with a connection to the sewage water tank. This connection to the sewage water tank had not been dismantled because of tests carried out with pressurised water in another part of the unit. Despite the double check by employees of the pipelines connections before the start of the pumping, the faulty connection was not discovered (mainly because of the complexity of the piping system). Pumping was thus started and the control room followed only the 2 parameters : amount of incoming polychloro-acetone and level increase in the stirring vessel. No additional crosscheck between outflow of the tank and inflow of the stirrer had been considered necessary because of the low chosen flow-rate. Part of the polychloroacetone flow reached a sewage water tank and from there entered the organic sewage water channel of the sewage system and mixed with process water.

The on-line sewage monitoring system of the biological sewage treatment plant recognised the hazardous charge early and redirected the charge mixed with process water into a retention pond. Pumping was stopped and the on-site fire brigade abated the vapours with water curtains at the entry of the retention pond. The affected sewage water channel and retention pond was flushed and neutralized.

The plant operator took organisational measures to ensure that only pipes containing process water are connected to the sewage water tank.