A method for treating metallurgical residues issuing from electric steelwork dust, ESD, containing mainly iron and zinc in the form of zinc oxide and zinc ferrites, and metallurgical residues issuing from blast furnace sludge, BFS, containing mainly iron and zinc in the form of zinc oxide, characterised in that it comprises performing the succession of following steps: Step A - acid attack of a first quantity of ESD for dissolving the iron and zinc oxides and breaking down the ferrites, - filtration giving a cake and a filtrate, - adding to the filtrate a second quantity of the ESD in order to partially neutralise it and cause the dissolution of the zinc oxides and break down the ferrites of this second quantity of ESD, - carburising of the filtrate in order to remove the metals other than zinc and iron, - precipitation of the iron by increasing the pH and separation in order to obtain a cake, - obtaining an acid solution of zinc. Step B - desalination of the BFS by washing with water, - basic attack of the cake in order to obtain firstly a basic solution containing zinc and a cake containing iron, - carburising of the solution so as to obtain a cake containing the metals other than zinc and a solution containing zinc, - treatment of the solution by electrolysis in order to obtain zinc powder. Step C - introduction of the acid solution of zinc issuing from the acid attack of the ESD of step A in the BFS of the basic treatment of step B, upstream of the basic attack of the cake, in order to obtain a precipitate of iron sulphate, - association of the iron precipitated during the increase in pH after the acid attack of the ESD and of the iron after the basic attack of the BFS, - association of the products issuing from the carburising after the acid attack of the ESD and after the basic attack of the BFS. Step A - acid attack of a first quantity of ESD for dissolving the iron and zinc oxides and breaking down the ferrites, - filtration giving a cake and a filtrate, - adding to the filtrate a second quantity of the ESD in order to partially neutralise it and cause the dissolution of the zinc oxides and break down the ferrites of this second quantity of ESD, - carburising of the filtrate in order to remove the metals other than zinc and iron, - precipitation of the iron by increasing the pH and separation in order to obtain a cake, - obtaining an acid solution of zinc. - acid attack of a first quantity of ESD for dissolving the iron and zinc oxides and breaking down the ferrites, - filtration giving a cake and a filtrate, - adding to the filtrate a second quantity of the ESD in order to partially neutralise it and cause the dissolution of the zinc oxides and break down the ferrites of this second quantity of ESD, - carburising of the filtrate in order to remove the metals other than zinc and iron, - precipitation of the iron by increasing the pH and separation in order to obtain a cake, - obtaining an acid solution of zinc. Step B - desalination of the BFS by washing with water, - basic attack of the cake in order to obtain firstly a basic solution containing zinc and a cake containing iron, - carburising of the solution so as to obtain a cake containing the metals other than zinc and a solution containing zinc, - treatment of the solution by electrolysis in order to obtain zinc powder. - desalination of the BFS by washing with water, - basic attack of the cake in order to obtain firstly a basic solution containing zinc and a cake containing iron, - carburising of the solution so as to obtain a cake containing the metals other than zinc and a solution containing zinc, - treatment of the solution by electrolysis in order to obtain zinc powder. Step C - introduction of the acid solution of zinc issuing from the acid attack of the ESD of step A in the BFS of the basic treatment of step B, upstream of the basic attack of the cake, in order to obtain a precipitate of iron sulphate, - association of the iron precipitated during the increase in pH after the acid attack of the ESD and of the iron after the basic attack of the BFS, - association of the products issuing from the carburising after the acid attack of the ESD and after the basic attack of the BFS. - introduction of the acid solution of zinc issuing from the acid attack of the ESD of step A in the BFS of the basic treatment of step B, upstream of the basic attack of the cake, in order to obtain a precipitate of iron sulphate, - association of the iron precipitated during the increase in pH after the acid attack of the ESD and of the iron after the basic attack of the BFS, - association of the products issuing from the carburising after the acid attack of the ESD and after the basic attack of the BFS.