A review of approaches to direct reverse osmosis membrane recycling: a technical, economic and environmental assessment

Background and Objective: Global market growth of reverse osmosis (RO) has led to an increase in annual disposal of membrane wastes. Therefore, evaluation of membrane waste management strategies is important to reduce their adverse environmental impacts. Due to the widespread domestic RO membrane market and their economic considerations, this study aims at investigation the direct recycling methods of RO membranes to extend their life cycles. Materials and Methods: Academic search engines and citation databases such Scopus and PubMed was used to retrieve relevant papers. Selected documents were analyzed and compared in three aspects of technical, economic and environmental issues.  Results: Direct recycling of RO is performed with fouling removal and degradation of polyamide layer (PA) using oxidizing agents like KMnO4 and NaOCl. The degradation rate of the PA layer is controlled by optimizing the oxidant concentration during the oxidation process. Factors such as the type of membrane used, its storage conditions, the operating units’ conditions and the final expected product will determine the required concentration-time values. Strategies to reduce these values are very important from an economic and environmental point of view. Decreasing the concentration of oxidizing agent reduces the chlorinated and halogenated compounds emitted from the oxidizing unit which subsequently lessen their harmful environmental impacts and reduces the energy consumption required for treatment. Conclusion:  The conversion of RO membranes to porous filters is technically possible by optimizing the conditions. In addition, the proper choice of RO membrane and final product type lead to economic and environmental productivity.