Pollution
Humain
Environnement
Economique

Effluent from a sugar refinery overflowed the site’s sump pit for both rainwater and process water, at which point the wastewater pooled and subsequently polluted the OEUF stream, causing fish to die. The ONEMA Agency for Aquatic Environments was duly informed.

This sump pit spill was due to shutting down the pumping system following a refinery-wide electricity outage triggered by boiler malfunction. At restart, the remote control for all electrical devices (pumps and their control mechanisms, alarm rotating light) short-circuited when switching from the power mains to the alternators. Despite bringing the electric generating sets online, the remote control short circuit prevented the pump from restarting and the sump pit’s high level alarm light remained without power. Since the alarm fault could not be relayed, the spill went unnoticed until the work shift at 8 the next morning. The on-duty electrician switched the remote control circuit breaker back on and the pump restarted.

The next day, the refinery operator replaced both the remote control circuit breaker and the float on the pit’s very high level emergency alarm. On 31 October, he decided to relay alarm faults to the control room, which was permanently manned; instructions were given to control room managers about processing this type of fault. A pump unit was rented the very next week to discharge effluent that had remained pooled for transfer to the site’s lagoon basins.

During a break in the 2013 production calendar, the operator planned on consolidating the pumping system by installing a backup pit lift pump along with an immersed backup lift bottle jack, making for 2 new pumps to back up the current ones, plus a new safety level detector (for the pit’s very high level) and a second bottle level radar (total capital investment: €31,564). Faults were relayed to the fire station located at the permanently manned refinery entrance. The operator scheduled other studies to improve electrical installation reliability, in particular by connecting the inverter network to the new remote control set-up, since the inverter itself was backed up by the electric generating set. This operation was intended to make the remote control more robust to electricity outages, the source of this accident. Installation monitoring was also enhanced, notably by adding rounds so as to verify lift station operability. Analyses performed on river water samples displayed that the November results were in fact identical to those of previous years.