Boron rejection in SWRO at high pH conditions versus cascade design

Orthoboric acid dissociation, which affects boron rejection in RO membranes, depends on salinity, temperature and pH. Lately, increasing demand of permeate low boron concentration raises questions regarding the optimal method for boron removal in both technical and economical aspects. Several methods were presented in previous papers for boron removal, using RO membranes (SW & BW RO), at elevated pH and/or ion exchangers. In this paper, tests results of a full scale plant operation will be presented, at elevated pH of sea water feed to the RO membranes. Further, a techno-economical comparison will be presented, comparing two options for boron removal: SWRO operation at elevated pH versus Cascade design (I DE's patented design).