This presentation describes the Topsoe WSA technology and why it was chosen by the Buenaventura group for their plant at Procesadora Industrial Rio Seco S.A. plant located near Huaral which is about 100 km from Lima in Peru. At this site, magnesium sulfates are produced and a waste stream containing among others H2S has to be cleaned before it is sent to the atmosphere. This gas stream is treated in the WSA plant, and at the same time solid sulfur is burned, whereas 98.0 wt% sulfuric acid is produced by both feed materials for consumption at the site at a capacity of 60 MTPD. The installation of the plant at site, the precommissioning and commissioning of the WSA plant as well as the first experience of operation also are described