Pollution
Humain
Environnement
Economique

An accidental spill of ditertiobutyl polysulphide (mercaptan sulphur product) occurred at around 7:50 a.m. in a hazardous waste treatment centre. The incident occurred when an odorous liquid waste injection line leading to the rotary kiln on one of the incineration lines was being cleared. One litre of waste was dumped into the retention basin provided for this purpose. A cleaning operation was immediately performed and all the cleaning and recovery waste (bucket) was incinerated.

Despite the immediate intervention of the crews on duty, the smell was perceptible beyond the site’s limits. The accident troubled 60 people at a neighbouring logistics company. At the waste treatment site, six people suffered from headaches and vomiting and 38 others were inconvenienced. Only one person was transported to the hospital by firefighters.

The waste involved was sulphur washing water from a company producing additives containing sulphur, packaged in 1000-litre pressurisable containers. The waste is injected into the rotary kiln by a nitrogen-based transport system. The waste is conveyed by fixed hoses and pipes. After positioning the liquid waste container and pressurising the nitrogen, the technicians noticed a significant loss of output in the line, indicating that a clog had formed. The clog was located in the flexible hose used to connect the pressurisable container to the installation’s fixed piping. In order to unclog the flexible hose, the operator made a nitrogen branch connection and pressurised the piping in the direction of the container (6 bar). Since this operation did not work, decompression (towards the kiln) was carried out at the nitrogen branch connection, downstream from the clog. As the section between the clog and the branch connection valve was under pressure, the decompression caused splashing where the incident originated.

The cleaning method used by the facility operator in the event of a persistent hose clog thus involves a risk of venting the waste during transfer from the hose to the recovery bucket and uncontrolled splashing.

The operator did not have a formal unclogging procedure. Only oral instructions were provided, even though unclogging operations were being performed at least once a day.

Following the accident, the operator:

  • drafted a procedure in the form of a checklist to unclog lines;
  • included the provision of an absorbent media before initiating unclogging operations;
  • designed a decompression system to collect drips without the risk of projection.