Rotary Pressure Exchangers for Brackish Water Desalination: A Comprehensive Review with Future Application Prospects for Al-Kharj, Saudi Arabia

Al-Kharj City is emerging as a major industrial and agricultural center in Saudi Arabia, where improving the energy efficiency and energy savings of brackish water reverse osmosis (BWRO) desalination is an important long-term objective for sustainable water management. Motivated by an ongoing research project focused on groundwater desalination in Al-Kharj, this review critically examines the development, performance, and application potential of rotary pressure exchangers (PXs), including isobaric devices such as PX®, XPR, FLEX™, iSave®, and SALINO® Pressure Center, for enhancing the energy efficiency of BWRO systems. The review covers operating principles, mathematical and computational modeling approaches, experimental investigations, and commercial technologies. Performance is evaluated using key indicators, including energy recovery efficiency, specific energy consumption (SEC), mixing rate, and leakage characteristics. The analysis shows that modern isobaric pressure exchangers consistently achieve hydraulic efficiencies exceeding 95%, while emerging low-pressure pressure exchangers (LPPXs) can reduce SEC by approximately 20–30% in brackish water desalination applications. However, increasing the recovery ratio in BWRO plants reduces the effectiveness of energy-recovery devices. Recent developments integrating pressure exchange, boosting, and pumping functions into compact modular units further enhance system reliability, operational flexibility, and lifecycle cost efficiency. By synthesizing current advances in rotary pressure exchanger technologies, this review provides a comprehensive technical foundation for selecting and implementing energy recovery devices in BWRO systems. In addition, a case study of one BWRO train at Prince Sattam bin Abdulaziz University in Al-Kharj demonstrates the practical potential of LPPX integration. The case study indicates that the proposed LPPX configuration can increase freshwater production by approximately 45% while reducing the SEC to approximately 80% of that of the baseline configuration without LPPX, demonstrating the potential of LPPX for improving the productivity and energy efficiency of existing BWRO systems.