A feasibility study of ultrafiltration/reverse osmosis (UF/RO)-based wastewater treatment and reuse in the metal finishing industry

Abstract Conventional treatment of wastewater from the metal finishing industry is generally based on physical-chemical treatment. Although the effluents from this can be discharged directly there is an increasing interest in industrial wastewater reuse. This requires further wastewater treatment. Here we studied the technical and economic feasibilities of adding an ultrafiltration process as a pre-treatment for removing dissolved and colloidal contaminants >0.4 μm, and to eliminate membrane fouling before a final reverse osmosis process resulting in permeate that would meet reuse criteria. The results show that the ultrafiltration–reverse osmosis treatment removed between 91.3% and 99.8% of the contaminants from the effluent, such as metal elements, organic, and inorganic compounds. Contaminants such as suspended solids, nickel, ammonium nitrogen, sulphate nitrogen, chemical oxygen demand, and biochemical oxygen demand were completely removed, the concentrations in the permeate being under the detection limits, thus the quality of the ultrafiltration–reverse osmosis process met the reuse criteria. This demonstrates the technological feasibility of wastewater reuse during electro-plating processes and the pre-treatment of powder coating processes. An economic feasibility analysis was performed based on a reuse capacity for 30,000 m 3 per year of treated water for two selected production lines at the Gorenje facility at Velenje, Slovenia. Specifically, the current water costs (including the operational costs of wastewater treatment, potable water use for industrial process and pre-treatment, and taxes) were compared with the investment required to implement the ultrafiltration–reverse osmosis processes. Based on the presented scientific results, the analysis shows that there is a potential for implementing this process within the metal finishing industry.