Techno-economic assessment of minimal liquid discharge (MLD) treatment systems for saline wastewater (brine) management and treatment

Abstract

The management and treatment of brine (saline wastewater) are of great importance, as its discharge to the environment poses a significant threat. A new strategy called minimal liquid discharge (MLD) appears to be a promising and more cost-effective option than zero liquid discharge (ZLD) as it uses only membrane-based technologies, leading to up to 95 % freshwater recovery. This research study introduces and presents for the first time a techno-economic assessment of five MLD treatment schemes that can be implemented in the brine treatment. The technologies included are reverse osmosis (RO), high-pressure RO, forward osmosis (FO), osmotically assisted RO (OARO), and membrane distillation (MD). Results showed that the MLD schemes costs ranged from US$0.79/m3 to US$1.36/m3, while the freshwater recovery ranged from 78 % to 89 %. In schemes 2 and 5, the implementation of MD substantially increased the energy consumption (>20 kW h/m3), however, these schemes were more economical (<US$1/m3) than the other 3 schemes. If the produced freshwater is sold, then the profit from the MLD treatment can reach up to US$2.21/m3. Furthermore, the costs of MLD schemes are at the same level as the subsurface water supplies, so MLD schemes can be valuable in countries relying on subsurface water sources.