Valorisation of SWRO brines in a remote island through a circular approach: Techno-economic analysis and perspectives

Nowadays, small remote islands rely heavily on desalination technologies to overcome freshwater scarcity. Unfortunately, these technologies are accompanied by the production of brines which can affect the receiving water bodies i.e., the aquatic ecosystem. Yet, it is extremely appealing how such brines constitute an abundant source of valuable raw materials (such as magnesium). In this work, a novel hybrid system is introduced to capture the value of seawater reverse osmosis (SWRO) brines produced in the minor Sicilian island of Pantelleria. The “Minimal Liquid Discharge” (MLD) process consists of: (i) Nanofiltration NF (separation of bivalent from monovalent ions), (ii) Mg Reactive Crystallizer MRC (selective recovery of magnesium and calcium), (iii) Multi-Effect Distillation MED (freshwater production) and (iv) NaCl Thermal Crystallizer NTC (sodium chloride recovery). The economic and environmental performances of the process have been evaluated by implementing and integrating the techno-economic models of each unit in a simulation platform called RCE (Remote Component Environment). Results revealed important economic benefits in comparison to conventional brine disposal methods. In addition, the proposed MLD chain turned out to be an attractive alternative for the production of high purity minerals/salts, achieving lower selling prices than the current market price.