PhD project

A Novel Hybrid Ion Exchange - Bipolar Membrane Electrodialysis Remineralisation Process for Reverse Osmosis Permeate

Introduction
Post-treatment i.e., remineralisation of reverse osmosis (RO) permeate, is required to improve water chemical stability and increase hardness. The commonly applied remineralisation processes are blending, direct and indirect dosage (e.g., calcite dissolution) of chemicals. While blinding results in less control over final water quality, other methods require either chemicals use or frequent refreshment of the calcite material. This research presents and investigates a novel, continuous, and chemically sustainable remineralisation process. 

Key words
Reverse osmosis, ion exchange, electrodialysis, bipolar membrane, remineralization

Research goals
The main goal is to develop a novel and sustainable remineralisation process for reverse osmosis permeate using ion exchange resin and bipolar membrane electrodialysis.

The research sub-goals are:

• To investigate the use of preparative ion exchange chromatography principles in cation exchange column for the recovery of hardness ions (calcium and magnesium).
• To optimize the bipolar membrane electrodialysis process for the production of HCl acid and NaOH base from NaCl salt at more than 95% purity.
• To understand the Cl into HCO₃ conversion using anion exchange resin in terms of equilibrium in batch and column process.
• To investigate the interplay between the process components in terms of mass balance and life cycle analysis.
  
   

Figure 1. Schematic drawing of the proposed remineralisation process for RO permeate using anion and cation exchange resins to recover hardness ions, moreover, bipolar membrane electrodialysis is used for HCl and NaOH production.