A comparative study on minimum and actual energy consumption for the treatment of desalination brine

Brine is a hyper-saline by-product that is produced in the desalination process. This by-product has an adverse environmental impact due to its high salinity and therefore its treatment is considered necessary. The minimum energy consumption (MEC) has been studied in seawater desalination, but not in brine treatment. In this regard, this research study introduces a mathematical model to calculate the MEC in the desalination brine treatment. Furthermore, the actual energy consumption (AEC) of the desalination technologies is presented. In this model, various parameters, such as the recovery rate, the salinity and the temperature of the feed brine, the purity of the freshwater produced and the dissolved salt nature, are considered. The analysis revealed that the MEC increases by increasing the recovery rate, the feed brine salinity, the feed brine temperature and the purity of the freshwater produced. On the other side, the MEC decreases by increasing the molar mass of the dissolved salt. The AEC is at least two times higher than the MEC due to irreversibility. Most membrane-based technologies are less energy-intensive than thermal-based technologies; however, they cannot currently treat significantly high-saline brine as do thermal-based technologies. Future advances in materials/system designs are expected to reduce the AECs.