Recovery of fresh water and minerals from inland brackish desalination brine via persulfate-based photochemical treatment and demineralization

Managing inland brackish desalination brine is challenging but critical to future water security. This study investigated the use of a treatment train with an ultraviolet persulfate (UV/PS) oxidative pre-treatment followed by chemical demineralization (CDM), microfiltration (MF) and secondary reverse osmosis (RO) to achieve antiscalant degradation, scale-forming constituent removal, mineral recovery, and fresh water recovery from an inland brackish RO brine. Results showed that the UV/PS pre-treatment efficiently degraded the phosphonate antiscalant ubiquitously present in the brine within 20 min of UV irradiation and improved mineral resource recovery from the brine in a subsequent CDM process. Analyses of the recovered minerals revealed that calcium, magnesium, and silica were the major chemical components, and calcite was a major crystallized mineral. The MF process successfully separated solid and liquid from the CDM process, and MF membrane fouling potential was significantly reduced with UV/PS-CDM treatment. The CDM process, coupled with UV/PS pre-treatment, mitigated membrane fouling and improved fresh water recovery during a subsequent RO step due to the lower magnesium and silica concentrations and the removal of phosphonate antiscalant. Over 40 % of total dissolved solids in the raw brine (>2.1 g⋅L−1) were recovered as mineral resources from the raw brine, and over 75 % fresh water recovery was achieved. The results demonstrated the benefits and applicability of a persulfate-based photochemical treatment followed by CDM, MF, and RO for inland brackish water brine treatment and recovery of additional water.