Energy analysis of a laboratory process of water desalination by pervaporation and reverse osmosis

Fresh water is essential for life. More and more countries around the world are facing scarcity of drinking water, which affects over 50% of the global population. Due to human activity such as industrial development and the increasing greenhouse effect, the amount of drinking water is drastically decreasing. To address this issue, various methods of sea and brackish water desalination are used. In this study, an energy analysis (specific energy consumption, SEC) of two laboratory membrane processes, reverse osmosis (RO) and pervaporation (PV), was conducted. A model feed system saline water at 0.8, and 3.5% wt. NaCl was used. The efficiency and selectivity of membranes used in PV and RO were examined, and power of the devices was measured. The desalination processes were found to have a high retention factor (over 99%) for both PV and RO. For PV, the permeate fluxes were small but they increased with increasing feed flow rate, process temperature and salt content in the feed. The calculated SEC values for both laboratory processes ranged from 2 to 70 MWh/m3. Lowering the process temperature, which consumes 30 to 60% of the total energy used in the PV process, can be an important factor in reducing energy consumption.