Effluents were accidentally discharged in an industrial laundry. Resulting from clothes washing operations, these effluents were collected at a lift station comprising 2 pumps and supplying the facility’s treatment plant.
On the day of the accident around 11 am, one of the 2 pumps malfunctioned and effluent reached the upper levels of the detection systems. The second pump, which should have been automatically activated, did not start up and the industrial water remained blocked inside the pump station, pushing the effluent towards a leak channel and causing fish mortality (500 kg) over an 800-m stretch.
At 3:45 pm, the maintenance manager arrived at the treatment plant to perform daily biomass verification on the activated sludge basin (involving sedimentation control in a specimen). No effluent was entering into the buffer tank, which was not abnormal since production had been stopped. Around 4 pm, the manager received a call from the neighbouring company, informing him of dead fish in the channel; he responded by checking operations at both the plant and lift station, observing that the effluent level in the lift station was very high and neither pump was operating. Untreated effluent was diverted into the channel by the station’s overflow outlet. The maintenance manager then manually started up pump no. 1 and, in conjunction with the production manager and a maintenance crew member, remarked that a piece of clothing had obstructed pump no. 2. He disassembled the second pump and placed it back into service. Pump no. 1 should have started up automatically, but the maintenance manager determined that the automatic order transmission link controlling this pump was inoperable, and this assessment was confirmed by the subcontractor called to the scene; although the level switches had detected high (and then very high) levels, no electrical contact allowed pump no. 1 to turn on. The volume of untreated effluent discharged into the natural environment was evaluated at 154 m³; the products used inside the company consisted of sodium bisulphite, hydrogen peroxide, soda lye, acetic acid and oxalic acid. A specialised subcontractor was assigned to reprogram a new automated command for controlling pump no. 1; moreover, the lift station’s overflow outlet was definitively closed and the level switches were replaced. An official Prefecture notification was issued on 3rd March, 2005.