Near-zero liquid discharge and reclamation process based on electrodialysis metathesis for high-salinity wastewater with high scaling potential

This study describes an emerging technology for near-zero liquid discharge desalination (ZDD) and salt reclamation using electrodialysis metathesis (EDM) to treat high-salinity wastewater with high scaling potential. Response surface methodology was employed to determine the optimal conditions for EDM-based ZDD process, and Box-Behnken center-united experimental design was used to quantify the effects of superficial velocity, applied voltage, and volume ratio of diluate/concentrate streams (Vc/Vd) on the salt removal ratio and current efficiency. These parameters influenced the outcome with the impacts following: voltage > superficial velocity > Vc/Vd, and the interactions were generally weak. The concentration of Na- and Cl-type liquid salts reached 200 and 170 g/L, respectively, after seven batch operations without scaling risks. Moreover, the two concentrate streams could be combined to precipitate CaSO4 with about 60% removal of Ca2+ via production of a solid byproduct. Alkali-assisted precipitation of the residual stream demonstrated efficient recovery of Mg2+ resources. Additionally, the purified solution could be further utilized to recover chemical resources (NaCl and Na2SO4) through a partial crystallization process. This work thus provides an applicable approach for the ZDD and reclamation of high-salinity wastewater with high scaling potential, which exist widely in seawater desalination engineering and industrial wastewater treatment. [Display omitted] •An emerging zero-discharge desalination process without scaling potential was proposed.•EDM could be technically feasible to convert and concentrate wastewater with scaling potential.•Effects of typical EDM parameters on the wastewater conversion were systematic studied.•The two concentrate streams could be combined to precipitate CaSO4 with about 60% removal of Ca2+.