Desalination, 2nd Edition

Chapter 11Ion Exchange in Desalination

Bill Bornak

Recirculation Technologies LLC, Warminster, PA, USA

Abstract

Ion exchange is not used in direct desalination; limitations in resin capacity preclude this in favor of membrane-based options. Ion exchange resins, however, play a key role in desalination systems by way of pre-softening the RO feed and in the selective removal of contaminants leaking past the membrane step. One of the most commercially successful post-treatment resin applications is the selective removal of boron from RO permeate. Fixed bed geometry is used in most large-scale B-removal systems, and the advent of Uniform Particle Size resin products allows for smaller vessels for a given fl owrate. Even the resulting packed bed geometry is still used in a batch/cycling sequence. Continuous geometries have been proposed in patents and the technical literature, but have seen limited commercial success.

Welcome to what is possibly the shortest chapter in this book. The short length is not due to a lack of industry on the part of the writer, but stems directly from the nature of ion exchange: a finite resin capacity used, for the most part, in a batch operation. That’s why “ion exchange” and “desalination” are not often used in the same sentence, let alone together for a full chapter.

11.1 Introduction

Ion exchange predates commercial RO by at least two decades, but as RO moved from lab bench to commercial practice, three advantages were touted.

1. Firstly, in the earlier ...