Pollution
Humain
Environnement
Economique

At around 10:00 a.m., the operator of a cheese factory noticed that the infiltration basin of its wastewater treatment plant was overflowing, resulting in a portion of the factory’s raw effluent being discharged directly to the River Colombine. The first- and third-level lifting pumps were not operating. The maintenance personnel arrived at 10:30 a.m. and found a problem with the first-level tilt float switch. The switch was replaced and the WWTP was back online at 11:00 a.m. The next day, the gendarmes were called in for suspected river pollution. They discovered about 20 kg of dead fish. The whitish discharge extended over 1.5 km. Firefighters laid a containment boom on the water. Abstraction by the neighbouring town and the summer conditions had lowered the river’s level, concentrating the amount of effluent in the water. The operator did not notify the inspection authorities for classified facilities until 7 August.

The first-level tilt float switch had an estimated service life of 18 months. In addition, first- and third-level tilt float switches often malfunction. The inspection authorities asked the operator to find a solution to this. The operator must also clear the river of branches so that it can flow unhindered. Until a permanent solution is found, the operator must provide the inspection authorities with the flow analyses and parameters measured on the raw effluent leaving the plant each week.

The operator has developed the following action plan:

  • preventive maintenance and annual replacement of the tilt float switches;
  • modify the PLC program so that an alarm is sent to the 24-hour telephone number;
  • train its employees once the PLC’s program has been modified;
  • distribute the list of persons/emergency services to be contacted in the event of an incident;
  • remove branches from the river.

In addition to these actions, the inspection suggested to the operator that it clean the raw waste disposal well once a year and clean all the tilt float switches once a week to ensure optimal performance.