Comparative techno-economic and environmental analysis of minimal liquid discharge (MLD) and zero liquid discharge (ZLD) desalination systems for seawater brine treatment and valorization

Abstract

Brine from desalination plants has become an environmental issue as the global desalination capacity is increasing. This study presents a techno-economic & environmental analysis of minimal liquid discharge (MLD) and zero liquid discharge (ZLD) systems in the Eastern Mediterranean. In particular, two cases are considered: (i) an MLD system incorporating reverse osmosis (RO) and forward osmosis (FO), and (ii) a ZLD system incorporating RO, FO, brine concentrator (BC) and brine crystallizer (BCr). The results indicated that the energy (6.74 kWh/m3) and cost demands (US$0.72/m3) in case 1 are lower than in case 2, with energy consumption of 10.36 kWh/m3 and cost demands of US$0.79/m3 due to two additional thermal-based technologies. MLD and ZLD systems are both comparable in cost to subsurface water sources; thus, they can be a valuable alternative to subsurface water. Furthermore, both cases are lucrative from the selling of fresh water (from US$195.33/day to US$228.4/day), while the ZLD system is even more lucrative when solid salt is also sold, increasing the profit in case 2 from US$228.4/day to US$247.44/day (8% increase). Overall, the proposed desalination brine treatment systems boost the circular economy and could have significant economic potential in the Eastern Mediterranean and elsewhere.