Energy efficiency of single-pass electrodialysis and nanofiltration/reverse osmosis for brackish water desalination: An experimental comparison

Brackish water desalination is a key solution for addressing the growing demand for drinking water in areas with limited access to freshwater resources. In this experimental study, reverse osmosis (RO), nanofiltration (NF), and single-pass electrodialysis (SPED) autonomous small-scale systems were investigated for brackish water desalination based on salt removal, specific energy consumption (SEC), and thermodynamic energy efficiency. With a production capacity of 40–180 L/h at a common recovery of 30 %, RO could achieve permeate salinities <1000 mg/L at feed salinities up to 12 g/L, whereas NF and SPED were limited to 10 and 6 g/L, respectively. Under typical operation, defined here by 10 % recovery for a single NF/RO module and 50 % for a SPED system, permeate quality with salinity below 1000 mg/L could be achieved at ≤17.5 g/L for RO, and ≤ 15 g/L for NF and SPED. When operating at comparable recovery (30 %), SPED demonstrated lower SEC (0.7–1.4 Wh/L) than NF (1.8–3.2 Wh/L) and RO (2.4–3.7 Wh/L) across the investigated salinities 1–12 g/L. However, operating NF/RO at 10 % doubled the SEC due to reduced permeate production, while SPED maintained a stable SEC under 50 % recovery. For brackish water up to 12 g/L salinity, SPED showed higher energy efficiency than NF and RO when comparing experimental SEC with the minimum energy for desalination. These findings highlight the potential of SPED for low-to-moderate salinity brackish water, the suitability of NF/RO for stricter water quality, and the need for optimized recovery or hybrid processes to balance energy use and performance. • SPED and NF/RO systems were compared for brackish water desalination • Reducing the recovery of NF/RO from 30 to 10 % improved permeate quality and SEC • At 50 % recovery, SPED achieved <1 g/L permeate TDS for salinities up to 15 g/L • RO at 10 % recovery achieved <1 g/L permeate TDS for salinities up to 17.5 g/L • SPED was overall more energy efficient compared to NF/RO