Technical and economic feasibility of the concurrent desalination and boron removal (CDBR) process

Abstract

Reverse osmosis membrane technology offers an alternative for producing water for agricultural use from seawater where freshwater resources are scarce. An important concern is boron removal from seawater during desalination. Desalination and boron removal can be achieved through multi-step processes using pH adjustment, adsorption, ion-exchange, and electrodialysis, thereby increasing the cost and complexity. In a prior study of the authors the concurrent desalination and boron removal (CDBR) process was advanced that employs only membrane technology without any pH adjustment. This paper explores the economic and technical feasibility of the CDBR process relative to a two-pass process with inter-pass pH adjustment for seawater containing 35,000 ppm of total dissolved solids (TDS) and 10 ppm of boron to produce a product water containing ≤100 ppm TDS and 0.5 ppm of boron. Commercial design software is employed to incorporate the irreversibilities ignored in the prior analysis of the authors based on design at the thermodynamic limit. This study indicates that at 58 bar an overall water recovery above 60% can be achieved via CDBR employing commercially available membranes at a cost comparable to the two-pass RO system with pH adjustment that has a recovery of only 48% at the same pressure.