Energy and environmental issues of seawater reverse osmosis desalination considering boron rejection: A comprehensive review and a case study of exergy analysis

Abstract

Recently, the rapid worldwide growth of seawater reverse osmosis (SWRO) desalination capacity has reignited the boron removal challenge in drinking water. The objective of this review is to discuss the recent advances and patents in boron mitigation strategies in SWRO systems, and to present the energy and environmental concerns of SWRO desalination system with boron rejection. First, the operating parameters of SWRO systems that affect boron removal are presented, before we discuss the reported findings and patents of boron control improvement from the standpoint of membrane materials advancement and from the development of various configurations, such as double pass reverse osmosis and hybrid SWRO processes with other separation technologies like ion exchange (IX), nanofiltration (NF), and electrodeionization (EDI). Thereafter, issues over SWRO desalination's detrimental environmental impact are reviewed: thus, seawater intake, brine discharge, and energy consumption constitute the main weaknesses. Then, sustainable solutions are proposed to reduce the environmental burdens. As SWRO desalination is an energy intensive process, exergy analysis emerges as a key tool to assess the performance of this process. Therefore, the use of exergy analysis to SWRO desalination in general and, as an example, to a full-scale SWRO desalination plant located in Spain, are discussed. The findings indicate that the SWRO unit is responsible for over 64% of exergy destruction due to the irreversibilities associated with the large pressure drop and the high salinity of the brine.