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A sustainable remineralisation process for hybrid water treatment

Almohanad Abusultan (UT)

PhD project

Supervisors: Walter van der Meer (UT), Antoine Kemperman (UT), Jeffery Wood (UT)

Duration: 2017-2021

Funded by Water Company Oasen

In the last few decades, the amount of drinking water produced with reverse osmosis (RO) technology increased enormously [1]. Moreover, high water quality standards have been adopted which promoted the development of novel post-treatment processes. Remineralisation of RO permeate is a post-treatment process required to protect public health and safeguard the integrity of the water distribution system. Currently, remineralisation is done by either passing the RO permeate over a calcite (calcium carbonate) bed, introducing lime (calcium hydroxide) in the treated water stream together with carbon dioxide or blending with another water resource [2]. 

The research main goal is to develop a sustainable remineralisation process by investigating and optimizing the recovery of divalent ions (Ca2+, Mg2+) from anaerobic groundwater using ion exchange resin-based chromatography and bipolar membranes electrodialysis.

The research consists of two main processes: Ion exchange resin-based chromatography and bipolar membrane electrodialysis. In the first process, we will investigate and optimize the separation of hardness ions required for RO permeate remineralisation process (Ca2+, Mg2+) from other mono/ multivalent ions. In the later process, we will investigate the acid/salt generation from RO brine using bipolar membrane electrodialysis (BMED). Moreover, the research will study the characteristics of the bipolar membranes stack and its tendency to fouling or scaling. Finally, the optimal operational procedure obtained from the lab experiments will be tested in a pilot scale plant. 

Ion exchange has been used for a long time ago to remove hardness (calcium and magnesium) from drinking water [3]. The process is based on the exchange of charged ions with a similarly charged counter ions bound to a resin. Since the resin has a limited capacity (the quantity of the counter ions); it has to be regenerated to recover its original capacity. In the regeneration process, the hardness ions can be recovered and separated from other cations based on their affinity to the ion exchanger. The regeneration process of the resin is done either by acid, base or salt depending on the type of counterion that has to be bound to the resin. The production of these acids, bases or salts could be done using electromembrane processes [4]. 

The project is funded by the Dutch water company Oasen. The duration of the project is from January 2017 to December 2020.


  1. GWI-DesalData/IDA, Section 1: Market profile. IDA Desalination Yearbook 2016-2017,2016. 
  2. Birnhack, L., N. Voutchkov, and O. Lahav, Fundamental chemistry and engineering aspects of post-treatment processes for desalinated water – A review. Desalination, 2011. 273(1): p. 6-22.
  3. Luqman, M., Ion Exchange Technology I; Theory and Materials. 2012: Springer Netherlands.
  4. Strathmann, H., Ion-Exchange Membrane Separation Processes. 2004: Elsevier Science.