Partial roasting is an efficient technology for de-arsenifying As-containing Cu-concentrates, where As is contained typically in enargite (Cu3AsS4) and tennantite (Cu12As4S12). The operation of the Codelco DMH roaster train (roaster, gas cleaning, acid plant, and effluent treatment plant), supplied by Metso, at >100% load is discussed. Chemical transformations lead to a de-arsenified chalcopyrite (CuFeS2)/bornite (Cu5FeS4) roaster calcine to be fed to a Cu-smelter upon blending with high S-grade feed. The typical calcine As-content is <0.3 wt% and the S-grade is approx. 20 wt% for a concentrate S-feed grade of 35 wt%. The fluid-dynamics of the roaster rely on entraining the bulk of the calcine and maintaining a SiO2 rich bed. Thereby, calcine residence time is limited, hence pointing to rapid arsenic removal rates. Calcium arsenite (practiced at Codelco DMH) or calcium arsenate stabilization is questionable. Scorodite (FeAsO4*2H2O) is accepted as one of the most stable As-compounds. The weak acid stream (15 g/L As, as HAsO2) produced within the wet gas cleaning section of the roaster train can be used to produce scorodite. Opportunity lies in clean scorodite processes exhibiting an As content of 25–30 wt% in the residue to be disposed. In addition, added stability can be achieved through scorodite encapsulation with use of aluminum gel.