The application of closed circuit reverse osmosis for inland groundwater desalination in Malta with an emphasis on brine discharge

Abstract

Water scarcity is an escalating issue worldwide, particularly in arid regions such as the Mediterranean. In Malta, a country heavily dependent on groundwater and desalination, the inland treatment of brackish water for agricultural and industrial use presents a growing environmental and logistical challenge of brine disposal. Current legislation prohibits brine discharge into both the sewer network and groundwater. This study explores the application of Closed Circuit Reverse Osmosis (CCRO), a high-recovery, semi-batch desalination process, as a potential solution to reduce brine volumes and increase freshwater recovery from brackish groundwater sources. The project assesses the water quality from various inland areas in Malta, models the CCRO system performance using WAVE software, and compares energy consumption, brine production, and feasibility of different brine disposal options, including transport to the discharge point, pipeline installation, and the use of evaporation ponds. Results indicate that CCRO achieves substantially higher recovery rates (81-90%) than conventional RO (56-70%), leading to significant reductions in brine volume and pretreatment chemical use, with only marginal increases in specific energy consumption. Scenario analyses further demonstrate that lower concentrate volumes under CCRO considerably decrease the costs associated with trucking, pipeline infrastructure, and land area required for evaporation ponds. This positions CCRO as a promising alternative for inland desalination in Malta, offering both technical and economic advantages that can ease the constraints of brine disposal. This study highlights the potential of CCRO to support sustainable water resource management in Malta and serves as a model for similar water-stressed, inland regions.