Beneficiation of saline effluents from seawater desalination plants: Fostering the zero liquid discharge (ZLD) approach - A techno-economic evaluation

Abstract

Zero liquid discharge (ZLD) and the utilization of saline effluents (brine) for resource recovery have recently attracted interest. A major environmental threat is the discharge of brine from seawater desalination plants. This research study presents two different ZLD systems to utilize brine by recovering not only freshwater, but also solid salts with commercial value. Two ZLD systems are considered in this techno-economic assessment: (a) system 1, which produces both freshwater and mixed solid salt, and (b) system 2, which produces freshwater, mixed solid salt, and pure solid salt (NaCl). The results showed that in terms of specific energy consumption (SEC) and freshwater cost, system 2 was costlier than system 1. In particular, system 2 (31.81kWh/m3) had a 1.4 times higher SEC than system 1 (22.55kWh/m3) as well as system 2 (US$1.37/m3) had a 1.32 times higher freshwater cost than system 1 (US$1.04/m3). Nonetheless, system 2 was 1.52 times more profitable than system 1 as pure NaCl production increased revenue significantly. Moreover, systems 1 and 2 were even profitable exclusively from the selling of freshwater. Overall, the results showed that both ZLD systems are promising options for sustainable brine management and utilization that follow the circular economy model.