Valorization of surface-water RO brines via Assisted-Reverse Electrodialysis for minerals recovery: Performance analysis and scale-up perspectives

Abstract

Reverse osmosis (RO) processes have been recently identified as mostly capable of quantitative removal of salts and contaminants from saline and surface waters, though posing the problem of a concentrated brine to be disposed of and a produced permeate too low in minerals, thus requiring a sometimes expensive remineralization step. In the present paper, Assisted-Reverse Electrodialysis (A-RED) has been proposed for the remineralization of surface-water RO permeate by recovering minerals from its brine. A purposely developed and validated model has been adopted to carry out a parametric analysis for design and optimization of an industrial-scale plant. The techno-economic analysis underlined that full permeate remineralization can be achieved with minimum specific energy consumption of 0.08 kWh m−3, while a minimum remineralization cost of 2.2 c€ m−3 was found applying a permeate by-pass and feed & bleed scheme to (i) increase the plant remineralization capacity and (ii) maintain a stack inlet conductivity above 100–160 μS cm−1 (starting from a permeate ~10 μS cm−1). Compared to current post-treatment techniques, results appear very promising thanks to the reduction of chemicals and total costs as well as environmental concerns related to brine disposal.