Background - Desalination has become a significant alternative water source due to the growing
water demand and inadequate conventional water sources in many regions. Desalination removes
excess salts and other dissolved solids from water to get clean water for human utilization.
Research and development and resulting innovations often aim to lower energy consumption or
reduce desalination costs. However, with the available mature membrane and thermal
technologies, there seems not to be much room for improvements in both aspects.
Thus, we believe other drivers for innovation can be: (1) decreasing the environmental impact by
avoiding chemicals additions and effects of brine discharge, (2) creating valuable water streams or
mining of the valuable compounds from brines, while avoiding excess amounts of invaluable
compounds, and (3) increasing the added value of already used desalted water for a second use in
agriculture or aquifer recharge.
Research challenges - Despite many studies and potential innovations are aiming for the highest
possible water recovery, even up to zero liquid discharge (ZLD), real-life applications stay limited.
Often these ZLD schemes include recovering solid salts (or organics) from brines, which only
occasionally will provide a reasonable business case when the plant owner can reuse these onsite
safely and sustainably. Technologies involved use additional chemicals for regeneration, acids and
bases for temporary pH adjustments, antiscalants and dispersants, cleaning chemicals. Moreover,
high amounts of energy per kilogram of recovered solid and ultimately per water produced are
employed. In this project, we aim to create a desalination scheme that splits the saline source
water into demineralized product water and multiple concentrated waste streams, with the desired
specifications for eventual post-processing and recycling. We aim to achieve these goals without
adding (high amounts of) salts or other chemicals, to avoid accumulation of sodium and/or chloride
in brines onsite or in the product water for first and second use. Advanced electrodialysis (ED)
configurations enable to achieve desalination by manipulating ionic compositions with the feed
water and electrical energy as the sole inputs.
Objectives and methodology- In this project, we will advance on chemical-free ED configurations
in hybrid desalination schemes. Feed water compositions (overall salinity, monovalent-divalent
ionic ratios; eventual valuable elements or organic molecules) will define the possibilities to
constitute the best output streams for given use cases from our industrial partners. For selected
cases, an ED stack configuration will be designed and tested, based on mass balance and
transport rate modelling. The selectivity needed to obtain the multiple concentrate streams will be
reached by applying selective membranes (e.g. bi-polar, monovalent/divalent selective
membranes) and by controling operational conditions. Input parameters of the model will be based
on literature and membrane charachterization experiments. The design will be realized in a
laboratory scale ED setup. The setup will be run with both well defined salt water mixtures to
validate the model assumptions, and with water from the selected cases as a prelimaniry test for a
pilot scale study.
Keywords: Electrodialysis metathesis (EDM), bipolar membrane electrodialysis (BPMED),
Selective electrodialysis (SED), ion-selective membranes, bipolar membranes
Academic supervisors: Prof. Dr. Huub H.M. Rijnaarts (promotor), and Dr. Harry Bruning
(Environmental Technology (ETE), Wageningen University)
Wetsus supervisor: Dr. Jan W. Post (Theme Coordinator Desalination)
Only applications that are complete, in English, and submitted via the application webpage
before the deadline will be considered eligible.
Guidelines for applicants: https://phdpositionswetsus.eu/guide-for-applicants/
|Title||PhD project - High recovery and chemical-free desalination using advanced electrodialysis schemes|
|Job location||Oostergoweg 9, 8911 MA Leeuwarden|
|Published||September 6, 2021|
|Application deadline||October 29, 2021|
|Job types||PhD  |
|Fields||Chemical Engineering,   Water Science,   Electrochemistry  |