Pollution
Humain
Environnement
Economique

On Sunday, 20 m³ of a chelated iron-EDDHAS complex polluted the BRENNE River following an operational incident in one of the workshops at a chemical plant manufacturing basic organic products. A closed-loop iron complex filtration phase started up at 5 am inside the unattended Z30 workshop, as the assigned technician was working in another workshop. The 20 m³ of solution escaped from the filter and wound up spilling into the shop’s wastewater network, then onto the treatment plant’s (600-m³) homogenization basins and ultimately the 3,000-m³ biological basin before discharge into the river. Analyses confirmed a significant pollution event on the watercourse with readings considerably above established thresholds: 5 times the authorised COD level (1,826 mg/l vs. 350 mg/l), 3 times the nitrogen level (99.7 vs. 32 mg/l), and 53 times the iron level (265 vs. 5 mg/l). The subsequent investigation revealed that the wastewater network valve for the Z30 workshop had not been closed while the premises were unattended; closure of this shutoff valve on 2nd February proved impossible since it had become loosened from its support. The Classified Facilities Inspectorate recalled the need to regularly control the reliability of shutoff valves. The homogenisation and biological basins would not have been polluted had the 25th November 1998 Prefectural decree been respected: in particular, this decree stipulated that any process water capable of being accidentally polluted was to be channelled via a buffer tank for verification before flowing to the treatment plant. Early pollution detection would have allowed piping the polluted water to the 3,000-m³ backup basin. A similar pollution outbreak, but of lesser magnitude, had already occurred on 11th March 2002 in the adjoining Z40 workshop. The inspectors’ visit exposed negligence in the way installations were being run. Inspectors recorded their findings and requested that the operator submit: operating procedures for the manufacturing and use of this chelated complex, the installation monitoring procedure for workshops, and the technical and organizational measures anticipated in order to avoid similar incidents from occurring. A notification order was proposed to the Prefect to ensure compliance with the maximum annual quantity of water extracted from 2 boreholes, as set per adopted prescriptions.

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