The process of electro deposition of heavy metals on bodies of different materials (for instance on non metallic objects to improve their look, their mechanical resistance and other physical properties) generates effluents contaminated by residues of valuable metal salts whose disposal is difficult and expensive. After several months of on site pilot testing it was possible to draw optimised flow schemes and to define the type of membrane more suitable to the recovery of metal salts from highly acidic solutions (pH close to 1) and to the production of high quality, reusable industrial water. The paper describes the various steps of the testing program, the comparison of mathematical models and results of plant operation, the optimised flow diagram of different applications (recovery of copper from the cleaning baths in a copper electro deposition plant, recovery of nickel sulphate and chloride from the cleaning baths in the electro deposition of nickel) and the operating costs and physical features of industrial plants.