Tessenderlo Eyloos

Modernization of a water electrolysis plant

In 2015, Belgian chemist Tessenderlo Group, which works in particular in the agricultural products and water treatment systems markets, decided to invest in its French plant in Loos, named Produits Chimiques de Loos (PC Loos). The project, called Eyloos, consisted in completely transforming the site’s electrolysis facilities, which were becoming obsolete. Tessenderlo called on Artelia to carry out the project.


Tessenderlo Group today operates in a variety of markets but maintains a strong presence in the agricultural products sector and in the supply of industrial solutions, particularly in the water sector. Active in many countries, it manufactures certain categories of chemical products in its own plants, notably the Loos plant in France. Anticipating a change in regulations, this former industrial site, a pioneer in the French chemical industry, had to completely overhaul its water electrolysis facilities, adopting membrane technology to replace the mercury cathode system used until then.

Artelia was responsible for the entire revamping project, which covered not only the electrolyzer itself, but also all associated installations (utilities, technical and electrical rooms, control room, etc.). Thanks to this operation, Tessenderlo Group now has a state-of-the-art facility capable of supplying 30,000 t/year of chlorine, compared with 18,000 t/year previously, as well as sodium hydroxide and almost 45,000 t/year of potassium hydroxide. This has enabled the Loos site to position itself as one of Europe’s leading manufacturers of coagulant products (based on chlorine and iron), used mainly for wastewater treatment and drinking water purification.