Comparative assessment of ion-exchange/reverse osmosis and ultrafiltration/reverse osmosis for seawater desalination: environmental, economic, and operational perspectives.

The urgent need for economically viable and environmentally friendly desalination technologies to address global water scarcity is underscored. This study compares ion-exchange reverse osmosis (IX-RO) and ultrafiltration reverse osmosis (UF-RO) systems, examining their environmental impacts, energy efficiency, cost-effectiveness, and operational stability. The IX-RO system reduced water hardness and ion concentrations by 83%, while the UF-RO system achieved over 99% removal of total dissolved solids. Energy consumption for desalinating 1 m³ of Caspian Sea water was 1.49 kWh for IX-RO and 1.3 kWh for UF-RO. UF-RO's impact on human health, ecosystems, and resources was 1.62, 3.06, and 3.31 times greater than that of IX-RO, respectively. CO₂ emissions were 192 kg CO₂/m³ for UF-RO and 81.93 kg CO₂/m³ for IX-RO. Over 68% of energy in both systems was from non-renewable resources, suggesting potential for utilizing Iran's solar and wave energy. The sensitivity analysis showed that citric acid had a significant environmental impact on UF-RO, while magnesium utilization had a notable impact on IX-RO. Water production costs were $0.06/m³ for IX-RO and $0.11/m³ for UF-RO. Over 20 years, the net present value was $172.8 million for IX-RO and $177.9 million for UF-RO, demonstrating their economic resilience. This study forms a basis for further research in the field.