An outbreak of hydrocarbon pollution was detected at a refinery outlet. Around 7:30 am, the alarm sounded on the cooling water quality analyser dedicated to the turbo-alternator unit. Effluent discharge around the Berre Lagoon was subsequently halted. Technicians extracted a sample for analysis and patrolled the lagoon: they noticed the presence of very slight iridescence over some 100 m swept near the shore by the southern wind. A floating boom was set up at the sewer outfall to contain any new hydrocarbon release. Absorbent products along with pump trucks were deployed to clean the shore and skim the water surface in the polluted zone. The sewers were also scraped clean to eliminate all residual traces of hydrocarbon. The authorities were duly informed.

The polluted banks were cleaned in less than 48 hours. This incident was caused by a backflow of process water from an adjacent firm hooked up to the industrial water network used to cool the refinery’s turbo-alternator unit. This backflow was identified by means of chromatographic analyses.

Following this incident, the refinery operator decided to install both a check valve and disconnection device to prevent any backflow of process water from the other firm in order to protect the site’s industrial water networks.