Energetic, economic and environmental assessment of zero liquid discharge (ZLD) brackish water and seawater desalination systems

Abstract

The discharge of brine (saline wastewater) from brackish water and seawater desalination plants poses a major threat to the natural environment. This research study presents an energetic, economic and environmental assessment of zero liquid discharge (ZLD) desalination systems in the Eastern Mediterranean. Two scenarios are considered: (i) ZLD brackish water and (ii) ZLD seawater systems, both aimed at producing saleable freshwater and mixed solid salt. Results showed that the energy consumption in scenario 1 (9.48 kWh/m3) is 2.38 times lower than in scenario 2 (22.55 kWh/m3) due to the 7 times lower feed salinity. The differentiation in energy demands is also translated to costs since scenario 2 (US$1.04/m3) is 1.24 times more expensive than scenario 1 (US$0.84/m3). Both scenarios are 3.18 times cheaper than the disposal method of the evaporation pond, while they are in the same cost range as the land application and deep-well injection. Whether only freshwater is sold or both freshwater and mixed solid salt are sold, both scenarios are profitable as the profit ranges from US$215.05/day to US$302.55/day. Concerning CO2 emissions, scenario 1 (5.91–6.45 kg CO2/m3) has lower values than scenario 2 (14.05–15.33 kg CO2/m3) as the energy demanded in scenario 1 is significantly lower.