Environmental self-monitoring tests conducted by a lead-acid battery manufacturer revealed that the lead concentration in the plant’s effluent was above the maximum limit. The cause was a build-up of lead deposits at the bottom and along the edges of the final settling pond. The operator had the pond dredged and the wastewater collection network cleaned. The cost was estimated at €7,200.

The incident was caused by multiple factors:

• failures on the pipe and equipment at the wastewater treatment plant (valves, lifting pump, excess foam that clogged flocculation);
• maintenance operations near the WWTP that affected the effluent collection and treatment system. These consequences had not been properly anticipated.
• the lack of casing of the wastewater network allowed lead to build up in the wastewater system.

Since this incident, the operator has created a form for tracking tasks and incidents at the WWTP. The pond is now to be cleaned out twice a year and the network encased to reduce the build-up of residues. Work affecting the WWTP is now scheduled during shutdowns of the site (August and December). The operator created a dashboard for monitoring the WWTP’s critical equipment and set up preventive maintenance for specific equipment. New equipments have been installed, such as an anti-foaming radar to solve the foaming issue that prevented flocculation.

A similar incident had already occurred at the site on 16 February 2015 (ARIA  46597).