PhD position Wetsus: Characterisation and tuning of DOLLOPs in potable waters (9.3)

 Wetsus  Leeuwarden
Recent reports [1-3] suggest that thermodynamically-stable prenucleation clusters exist in undersaturated CaCO3 solutions and they can account for as much as half the calcium present in solution [2]. These “sloppy” objects have earned the felicitous name “DOLLOPs” (dynamically-ordered liquid-like oxyanion polymers) [4]. The hydrated multinuclear carbonate complexes of calcium and other divalent cations are found to aggregate into much larger (4–100 nm) particles, forming a liquid emulsion at neutral pH [5]. Independent from that, nm-sized objects in natural waters were discovered [6] consisting mostly, but not entirely, of CaCO3. Little is known about the concentration, size distribution, structure and dynamics of DOLLOPs in potable waters. Investigating these parameters offers the chance of extending the parameters of water quality. The chemistry of aqueous systems [7] can be understood and dealt with more accurately if DOLLOPs are taken into account and characterised properly. Moreover, it has been suggested recently that DOLLOPs provide the basis for a plausible mechanism for magnetic treatment based on the gradient of the applied field rather than its absolute strength [8,9]. That is of imminent importance for the drinking water industry, since the ratio of Ca2+ in DOLLOPs compared to the overall Ca2+ concentration provides a completely new physical water quality parameter.

Activities and responsibilities

Research challenge
The goal of this project is to establish a new, more precise definition of the hardness of. This will be achieved by characterizing how Calcium and Magnesium are dissolved in water in addition to their total amount, namely how much is dissolved in ionic form, and how much in colloidal (“DOLLOPs”) form. Moreover, shifting their population between ionic and colloidal phase will be investigated. Thus, the student will first have to do fundamental work: Characterize the number and size distribution of DOLLOPs in different drinking waters. Several different drinking water samples will be characterized and the structure of the DOLLOPs themselves will be investigated. The number of DOLLOPs in relation to the overall hardness will be established as new, physical parameter of water quality. These results will lay the foundation of the practical, applied work to change the DOLLOP population with wet chemistry and magnetic fields. Tests will include the investigation of the influence of such treatment not only on the DOLLOPs but also on other ions in the solution, their solubility product and their precipitation behaviour.

Qualification profile

PhD Candidate: The ideal candidate has an MSc degree in physical chemistry, chemistry or physics with experience in optics and a solid knowledge about programming (Python, MATLAB, etc.) and data evaluation. Knowledge about magnetism and experience with wet chemistry is an advantage.
Additional scientific support: Wetsus AZL - DLS or comparable optical instrument build and commission, Post-Doc (Gerwin Steen), other in-house support (wet chemical analytical tests – ICP)
Additional partner support: , NHL (Dr. Luewton Agostinho – laser-optical techniques in co-operation with Wetsus AZL), WLN (other wet-chemical tests), Brabant Water (samples, field trials)


This research project is part of the Wetsus research theme Applied Water Physics. The following companies are part of the theme: Brabant Water (NL), WLN (NL), IPF/Grander (AT), Schauberger Nature Technologies (AT), Integro (DE), H2MOTION (NL) and Coherent Water Systems (UK).

Promotors: Prof. Herman Offerhaus (Twente University), Prof. Jakob Woisetschläger (TU Graz)
Wetsus Supervisors: Dr. Gerwin Steen (optics), Dr. Elmar C. Fuchs (general, wet chemistry), 

For more information contact

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About Wetsus

Wetsus, European centre of excellence for sustainable water technology, is a network university. In Wetsus 22 universities from all over Europe cooperate on a research program which is defined by 105 partners from industry. Wetsus creates a unique environment and strategic cooperation for development of profitable and sustainable state of the art water treatment technology. The inspiring and...

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