Single SWRO Pass Boron Removal at High pH: Prospects and Challenges

Efficient removal of seawater boron species in reverse osmosis (RO) plants is gaining momentum as the guidelines for maximal B concentrations in desalinated water are becoming stricter, driven by the adverse effects that boron has on agricultural crops at concentrations higher than ∼0.7. mg/L. This chapter explores alternatives for reducing B concentration in the permeate water to below 0.7. mg/L in a single RO pass operated at high pH, without promoting chemical fouling of the membrane elements. The second part of the chapter is dedicated to the challenge of modeling the performance of RO units with respect to boron removal at high pH. Special attention is given to the role of acid-base equilibria and B speciation, which are also discussed with respect to the difficulties related to pH measurements in highly concentrated brines. It is shown that available B simulation models do not yield accurate results and an alternative simulation approach is suggested.