Implementation of low-pressure pressure exchanger (LPPX) on two-stage reverse osmosis (RO) system: Energetic and environmental impacts in a large-scale water reuse facility

Abstract

As global water shortages intensify due to climate change, treated sewage effluent reuse has emerged as a sustainable alternative for industrial water supply. While reverse osmosis is the primary treatment technology, energy efficiency in high-recovery operations has been limited by constraints of efficient energy recovery devices. This study evaluates the implementation of recently developed low-pressure pressure exchangers (LPPX) in large-scale water reuse facilities. The assessment analyzed energy, environmental, and economic viability under varying feed water temperature (8.4–28.9 °C), water quality (Total dissolved solids: 500–1500 mg/L), and process recovery rates (75–85 %). A case study was conducted on a facility with a production capacity of 90,000 m3/day to evaluate the performance and economic impact of LPPX implementation. The results indicate that implementing LPPX can reduce specific energy consumption by up to 26.4 %, corresponding to a reduction of approximately 1725 tCO2eq per year. A sensitivity analysis of carbon credit prices revealed significant differences in capital-to-saving ratio (CSR) across different markets. Regions with high carbon credit prices, such as the EU, had shorter CSR (6.74 years for six trains), whereas Korea's current low carbon prices resulted in longer CSR (8.05 years for six trains). This study provides comprehensive insights into LPPX implementation in water reuse facilities while considering both operational performance and economic viability under varying carbon pricing scenarios.