Life cycle assessment and techno-economic evaluation of alternatives for the treatment of wastewater in a chrome-plating industry

Abstract The chrome plating industry originates wastewater containing hazardous pollutants as hexavalent chromium. In this work, two alternatives for the treatment of the wastewater streams generated in a Spanish chrome-plating plant are studied from environmental and techno-economic perspectives. Both scenarios include the operations needed to obtain a chromate material and the further treatment of the produced wastewater. In the base scenario, the wastewater rich in Cr(VI) is treated through a sequential reduction – precipitation - settling process. In the alternative scenario the treatment of the wastewater consists of ionic exchange and photocatalytic process, which allows reducing Cr(VI) content by the use of solar light. Life Cycle Assessment (LCA) was applied to both scenarios in order to determine the most important impacts. For that purpose, data provided by a chrome-plating plant, experimental data obtained in the laboratory and results of process simulation were used to build up the inventory data. Obtained results show that the main impact in the base scenario is the disposal of the solid sludge, obtained as waste, due to intensive energy consumption. Regarding the alternative scenario, the use of chemicals is the main contributor to environmental impacts. By comparing both scenarios, the alternative one presents a clear improvement of the environmental performance, reducing about 85% the environmental damage. Finally, techno-economic evaluation results reveal that the cost of the alternative process per unit of treated water is about 15% higher than in the case of the conventional treatment.