Promoting circular economy in the chemical sector: Innovative process for the recovery of minerals and water from industrial saline effluents

Process industries generate high amounts of waste effluents and most of them present high salinity. Management of these streams has a high environmental impact and an elevated cost related to the discharge of these streams to be treated in a wastewater treatment plant. The project Zero Brine aims to apply Circular Economy to redesign the value and supply chains of minerals and water by developing an innovative process to recover these resources from saline effluents. This approach will eliminate wastewater discharge, reducing operational costs and minimising environmental impact of industrial operations thorough brines. This new process is based on: a) a first Nanofiltration process using tailor-made membranes produced by regenerating end-of-life reverse osmosis (RO) elements from desalination plants whose fate was a landfill; b) treatment of the concentrate stream produced in the first stage by eutectic freeze crystallization to achieve Zero liquid Discharge. In order to avoid scaling problems during nanofiltration, a pre-treatment was also defined. End-of-life membranes were regenerated by means of simple chemical processes and they were divided into two types regarding their regeneration degree derived by permeability and rejection of salts. They were able to achieve a suitable quality of water, equivalent to the current quality in the industry, and it could be reused in the production process and to achieve a high saline concentrate to be treated by crystallization. To demonstrate the technical and economic feasibility of this innovative process, a pilot plant was installed in a silica industry. Both types of regenerated membranes will be tested at pilot-scale for six months and evaluated on their rejection and recovery. First results demonstrate good membrane performance, obtaining permeability and rejection comply with the limits established for their reuse at industry level. In addition, high water recovery is obtained and consequently a concentrated stream able to feed crystallization process.