Pollution
Humain
Environnement
Economique

In a chemical plant, aqueous effluent from the azo dye derivative production shop was released into the PETITE BAÏSE watercourse through the unpolluted water network (rainwater, cooling water, etc.) and onsite lagoon. The spill was estimated at 10 m³ or 130 kg of hydrazine hydrate, 70 kg of aminotriazole and 5.6 t of aminoguanidine formate.

The workshop was rendered safe and secure. To limit the impact of such a release, the operator confined much of the pollution to facility lagoons by reducing discharge flows into the environment (300 m³/h instead of 800) and moreover fed the PETITE BAÏSE with clean water (900 m³/h) in order to dilute the pollutant. Bleach was used to neutralise the hydrazine hydrate in the gutter. Lagoon emissions returned to normal after about 10 days. The operator issued a press release within 24 hours.

The accident occurred while restarting the workshop after a routine steam cleaning operation of batch production lines and building capacities to eliminate the accumulated crystals in finished products. Connection valves between the line connected to the steam network and the purge network remained open during re-start and were the cause of this accident. The steam injection device using pipes with purges was installed in 2004, replacing the previous system (which used flexible connections), deemed hazardous for plant technicians. This modification therefore had not been subjected to any rigorous change management, as required by the safety management system.

By not separating the manufacturing network from the unpolluted water, the steam cleaning system design was also suspect.

To reduce the likelihood of repeating this accident, steam injection lines were modified and technicians made aware of good practices.