On 13 December, issues were found on a water sample taken the day before at the outlet of a sugar refinery’s wastewater treatment plant (WWTP). The water’s appearance was unusual and the values measured (pH of 5.5 and COD > 10,000 mg/l) were above the limits set by prefectoral order. At 8:30 a.m., a leak was found on an old pipe at the bottom of the stormwater pond towards the venturi tube used to discharge treated water to the municipal WWTP. Discharges from the sugar refinery’s WWTP were immediately stopped and the municipal WWTP was notified. At 10:30 a.m., an inflatable pipe plug was placed in the venturi tube at the outlet of the sugar refinery’s WWTP to keep the water in the stormwater pond. At the same time, a submersible pump was set up to recirculate the discharge, forcing the plant to operate at partial capacity.

The refinery and the municipal WWTP worked together to manage the discharge until 17 December in order to lower the level in the stormwater pond with negatively impacting the municipal WWTP.

The old pipe, which was no longer being used and blocked by a solid seal, had been eaten away by the acidity of the water in the stormwater pond. This particularly acidic water came from storage tanks containing fermented sugar juice. This juice had to be drained due to yellow vest protests that lasted for two weeks. 

The operator plans to implement the following measures:

• repair the stormwater pond and inlet/outlet network for 2020–2021;
• improve preventive inspections of the thicknesses of the inlet/outlet pipes in all the WWTP’s ponds (review of the frequencies and thoroughness of the inspections);
• order inflatable pipe plugs, which proved to be effective.