Europac is a paper, cardboard, and packaging company with mills in Spain, France, and Portugal. The French site near Rouen specializes in corrugated cardboard and has a production of more than 300’000 tons per year. In the cardboard production process, Sulzer pumps and agitators are widely used.
The mill has its own biological wastewater treatment plant with a total capacity of 350’000 population equivalent. Once treated, the water is recycled in the mill or restored to the natural environment. The WWTP has been modernized regularly during the past years.
The effluents from the paper mill contain a high amount of organic matter. In the wastewater treatment plant, the effluents go through an anaerobic tower reactor prior to being aerobically treated in an activated sludge process. The aeration of the wastewater is done in successive basins — first in a circular tank with external bottom jet aerators and then in a rectangular lagoon with surface aerators. With the increase of the WWTP capacity, the oxygenation of both basins, especially the first one, had become insufficient. Therefore, Europac decided to upgrade the aeration performance of the existing installation with minimum capital expenditure in 2014.