European centre of excellence
for sustainable water technology

Science & technology Newsletter, June 2016

Published: 20 juni 2016

Articles in this edition:
- Scientist’s work on water desalination takes him back to his birthplace
- Pioneering Wetsus researcher tackles micropollutants and antibiotic resistance
- More than just a party trick, the floating water bridge holds insight into nature and human innovation
- How one Wageningen professor juggles research, teaching, supervising, and family

Dear Reader,

Bert Hamelers

This edition of the Wetsus S&T Newsletter shows the multifaceted nature of water technology. To an outsider, clean water technology and wastewater technology might look like different fields, with their own objectives, technology base, conferences, etc. However, both fields are becoming more and more closely interknit, as they operate within the water cycle and are confronted with similar challenges from outside, such as climate change and resource depletion stress.

Fresh water is a very stressed resource, since in many areas around the world water is used at a rate higher than that at which it can be replenished. Using sea or brackish water alleviates this pressure but at the expense of a high energy usage. There is thus a clear need for more energy-efficient desalination processes.

Capacitive desalination is an innovative process that promises to give more energy-efficient desalination, especially for brackish water. We are happy that prof. Matthew Suss, a renowned scientist in this field, will share his thoughts on this topic, together with some observations on international scientific cooperation.

Everything not removed during wastewater treatment is brought into the water cycle via the effluent. We rely on the self-cleaning function of our waterbodies to remove the last traces of pollution still present in the effluent. However, not all compounds are removed (at a sufficiently high rate), and unwanted compounds like pharmaceuticals might show up in our fresh water resources. UV degradation of such compounds can be used to remove these compounds. This technology could be considered as pretreatment for drinking water production or post treatment in case of wastewater treatment. Wetsus is cooperating with Imperial College to study the degradation route of compounds under the influence of UV. Lucia Hernández Leal will share some insights on a recently published paper on this topic.

Most researchers at Wetsus are PhD candidates who finish their research project with a PhD defense. A PhD defense is always special, but in Leeuwarden it is a little extra special, and this year we had two such defenses in Leeuwarden: Adam Wexler from Wageningen University and Anna Casadellà from University of Groningen. Adam Wexler not only successfully defended his thesis on the “water bridge” before a committee in Leeuwarden, but also received the Marcel Mulder award for his accomplishment of connecting more fundamental science on water with application.

Energy scarcity is not only driving research into more efficient water technology, but conversely water technology could also be at the basis for solving problems in the energy field. An example of this is the bio battery that stores energy in the form of simple organic molecules as acetate. In times of energy excess, acetate is produced, while in times of energy shortage, electricity can be produced from oxidizing the acetate. Such alternating periods of either excess or shortage of electricity will be more common in a future that uses wind and sun as energy sources. Annemiek ter Heijne, who is assistant professor at Wageningen University, will inform us on this timely development. The battery technology builds on the work she did during her PhD period at Wetsus and the work performed for her VENI Scholarship in Wageningen.

Bert Hamelers

Scientist’s work on water desalination takes him back to his birthplace

When Matthew Suss relocated to Haifa, Israel, from the US in 2014 to join the Technion – Israel Institute of Technology as an assistant professor, the move was a homecoming of sorts. Suss was born in Tel Aviv, and although he has lived most of his life in Canada and the US, both he and his wife have family in Israel.

Technion also offers an ideal environment for Suss to expand his work on developing next-generation electrochemical systems for water treatment and energy storage. He is particularly interested in capacitive deionization (CDI), a method of water desalination, which has led him to collaborate with several researchers from Wetsus. Suss also recently became the Chairman of the International Working Group on Capacitive Deionization, which was established in Leeuwarden in 2014.

CDI research and commercialization efforts have grown exponentially over the past few years, and Suss and other Wetsus-connected scientists are at the forefront of this growth. Together, the scientists are spearheading efforts to further improve CDI, which may one day outperform established technologies such as reverse osmosis.

In this interview, Suss explains what led him to his career path, what it’s like being back in Israel, and where he sees capacitive deionization technology headed.

Can you give a short biography of yourself, perhaps including how your experiences as a university student led you to your career today, and to your interest in electrochemistry and water research?

I was born in Tel Aviv, Israel, and my family moved to Canada before I was a year old. I grew up in Montreal, Canada, and then went to the U.S. for graduate school and postdoctoral work. I lived 7 years in the U.S., including in Stanford, California (for M.Sc. and PhD at Stanford University) and Cambridge, Massachusetts (for postdoctoral work at MIT). My degrees are all in Mechanical Engineering, and my postdoctoral work was in the Faculty of Chemical Engineering.

During my PhD, I was working in a microfluidics lab, but began a new project investigating water desalination with capacitive deionization in 2010. This project was done together with Lawrence Livermore National Laboratory (LLNL), where I was a Lawrence Scholar (so spent half my time at LLNL and the other half at Stanford). I greatly enjoyed this project and the potential applications of my work towards technologies which could solve crucial societal needs, and it was this experience which led me to pursue a career in electrochemical systems rather than my initial field of microfluidics.

Towards the end of my PhD, I actively searched for postdoctoral work in electrochemical systems in order to expand my experience in this field, and found a position in the lab of Prof. Martin Bazant at MIT, where I worked on developing next-generation flow batteries for grid-scale energy storage for a year and a half.

In October 2014, I began a tenure track assistant professor position at Technion – Israel Institute of Technology in Haifa, Israel, where I hold a Horev Fellowship and an Alon Fellowship. [The Alon Fellowship is a highly competitive award given to the most promising new faculty members in Israel]

Why did you choose to work at Technion?

I came to Israel for several reasons. First, I was looking for a faculty position in a place where my wife Naomi and I had family connections and which felt like home to us, and Israel was one such place. The move has allowed me to return to the country of my birth and re-connect with family members who live in Israel. My wife and I came along with our two young daughters, Bella and Shira, both of whom were born in the USA.

Secondly, Israel is a country very focused on developing next-generation technologies and bringing them to market through entrepreneurial efforts such as start-up companies. This is very much in line with my motivations in my career, which is to develop next-generation electrochemical systems for water treatment and energy storage, and help bring them to market.

In what ways is living and working in Israel different than in the US?

Israel is a much smaller country than the USA, and being a country younger than 70 years old, it is generally less developed, but the students here are often highly motivated and intelligent, the entrepreneurial ecosystem is highly developed, and there is a strong local need for additional water supplies, all of which makes it a good place to establish a laboratory focused on innovating next-generation technologies for water treatment and energy storage.

Can you describe some of the research you’re doing now, especially the projects that have water applications?

At Technion, I have established a laboratory focusing on theory and experiments in electrochemical systems for water desalination and energy storage applications. We have an in-lab rapid prototyping facility (including CNC milling machine and laser cutter) in order to turn our knowledge and insights into high-performance prototypes and proof-of-concept demonstrations. We currently have five graduate students, two postdocs, and three undergraduate researchers, and have hosted two visiting graduate students from Wetsus on their internships.

Currently, a significant thrust of my laboratory is towards developing capacitive deionization for water treatment. We have several ongoing projects in this direction, including applying capacitive deionization together with microbial cells to wastewater treatment, establishing fundamental theory for capacitive deionization cells with alternative architectures, and developing the new field of fluidized bed capacitive deionization together with Wetsus. We are fascinated by the use of suspension electrodes, such as fluidized beds, to treat water.

When and how did you first become associated with Wetsus? And how do you continue to be associated with Wetsus today?

I first met Maarten Biesheuvel [Scientific Project Manager at Wetsus] at a conference in the summer of 2012 in Barcelona, Spain, and then our first joint publication on capacitive deionization was in 2014, which came out of my PhD work.

Initially, my connection to Wetsus was mainly through Maarten, but now I have come to know and collaborate with many others there, including Bert Hamelers [Program Director], Slawomir Porada [Scientific Project Manager], and PhD student Jouke Dykstra. Our most recent publication (open access) deals with the discovery of two novel modes of operation in CDI, allowing for a significant increase in salt adsorption capacity of carbon electrodes (almost a factor of two we estimate).

Since I began at Technion, two M.Sc. students from Wetsus have come to my lab during the summer to perform their internship, which has resulted so far in a joint publication between my laboratory and Wetsus regarding using fluidized bed electrodes for capacitive deionization. In all, Wetsus and my lab have published together three joint publications in my first year and a half at Technion.

Wetsus has impressed me with its unique positioning, being between industry and academia, and its high concentration of talented people and deep knowledge in water treatment and related technologies. I have certainly benefitted much from collaborations with Wetsus employees, as I have been able to gain access to their excellent experience and guide talented M.Sc. internship students in my lab. We certainly hope to continue such strong collaborations for many years to come.

As Chairman of the International Working Group on Capacitive Deionization, what is your role and what are your goals for the group? And in a broader sense, how do you envision the CDI-electrosorption field developing?

The working group was initially established by Maarten in 2014, and I currently serve as its (second) chairman. The group was established to organize the fast-growing research field of capacitive deionization, which has seen an explosion of interest since 2010. My current role is to help facilitate further interconnectedness between researchers in the field, researchers just entering the field, and industrial companies or start-ups looking to bring to market a capacitive deionization-based technology.

One of the main outputs of the working group is the dedicated CDI conference held once every two years. The first such conference was in 2015 in Saarbrücken, Germany, hosted admirably by working group member Prof. Volker Presser [at Saarland University], and where there were over 100 attendees. The next conference will be hosted by working group member Prof. Jeyong Yoon in South Korea in summer 2017, and then the conference will be in Haifa, Israel, in 2019.

In addition to the stand-alone CDI conference, we look to run symposia in established conferences, such as this year in the ISE (International Society of Electrochemistry) conference, where Maarten, myself, and two other members of the working group are co-organizing a symposia focused on CDI and related technologies. I am currently looking to expand to a symposia in a major conference in the USA, which we hope to accomplish in the near future.


Pioneering Wetsus researcher tackles micropollutants and antibiotic resistance

Working at Wetsus since 2005, Dr. Lucía Hernández Leal has played a fundamental role in Wetsus’ growth over the past decade. During this time, she has seen Wetsus evolve from its origins as a first-of-its-kind presence in the northern Netherlands to a research institute that connects scientists from around the world.

lucia hernandez leal

“I first came to Wetsus via Wageningen University, where I directly contacted Grietje Zeeman [Professor of Environmental Technology] with whom I wanted to work,” Hernández Leal said. “She told me about a position at the then-not-so-well-known Wetsus.”

Today, Hernández Leal is the scientific project coordinator of the Wetsus theme “Source-Separated Sanitation.” Her research focuses on micropollutants in wastewater that come from pesticides, medication, and household products, among other sources.

Since this research has such far-reaching implications, it often involves collaborating with researchers on a global scale. Recently, Hernández Leal has been working with scientists from Imperial College London, including supervising the work of PhD student Sofia Semitsoglou-Tsiapou.

Their work focuses on developing water treatment processes to remove toxic, non-biodegradable pesticides from the water supply that are not effectively removed by current water treatment processes. This treatment is vital for safe drinking water: one of these pesticides, metaldehyde, which is a molluscide used for controlling slugs and snails, was responsible for one-third of the water quality failures in the UK in 2009, according to the UK Drinking Water Inspectorate Annual Reports.

In a recent paper published in Water Research, the scientists investigated the safety of a new treatment method, UV-H2O2, which can effectively degrade metaldehyde and other difficult-to-remove pesticides.

“The question was if this process would result in products of concern, such as carcinogens or estrogenic compounds,” Hernández Leal said. “This study focused on three pesticides, and for these compounds no dangerous products were detected. Further, fundamental information regarding kinetics was generated, which can be applied regardless of the type of water that is treated.”

A related area that Hernández Leal is working on is the possibility that antibiotics in wastewater are providing a breeding ground for antibiotic-resistant bacteria.

“As it turns out, low concentrations of antibiotics in water can act as a trigger for bacteria to share and spread antibiotic-resistant traits,” she said. “Wastewater treatment plants have been in the spotlight as hotspots for spreading antibiotic resistance. Literature in the topic is still mixed and not all the time thorough. So we aim at understanding if that is indeed the case, how it happens (under which conditions like temperature, oxygen concentration, heavy metals, antibiotics, etc.) and getting a better idea of how to prevent it.”

Working toward these goals, Hernández Leal and other researchers at Wetsus are currently building a research program that covers the different aspects of the environmental problem of antibiotic resistance.

The program involves several participating institutions aligned with four PhD projects: implications for the health sector (with the University Medical Center Groningen); gene transfer at wastewater treatment plants (with TU Delft); the impact of livestock production on the water cycle (with the Institute for Risk Assessment Sciences of Utrecht University [IRAS] and the Central Veterinary Institute); and the development of a treatment technology to specifically target and destroy bacteria (with Wageningen University).

“The problem of antibiotic resistance is huge; much must be done in the way antibiotics are administrated both to humans and animals,” Hernández Leal said. “Since we know that the environment plays a role in the spread and evolution of resistance, at Wetsus we want to take our stake and do our part to contain antibiotic resistance.”

As part of Wetsus’ responsibility, Hernández Leal emphasizes the importance of bringing together the top experts in these areas, who come from many different institutions. Sometimes this level of collaboration can be challenging, since it requires convincing university supervisors of the benefits of researchers working together at Wetsus, and not solely at their home universities.

“Wetsus is strong in joining different parties to a common goal, both from different universities and companies of all sizes,” Hernández Leal said. “I expect that this role will continue to grow.”

More than just a party trick, the floating water bridge holds insight into nature and human innovation

Dr. Adam Wexler has spent the past six years of his life studying a 4-cm-long string of water: the so-called “floating water bridge.” The effect is created by applying a high voltage to two containers of water, which causes the water to climb out of the containers and form a bridge in mid-air as the containers are slowly pulled apart. Wexler and his colleagues at Wetsus have discovered that this seemingly simple experiment holds a wealth of information, both for our understanding of the natural world and for guiding future developments in sustainable technology.

“The water bridge is this beautiful and peculiar phenomenon which, despite being discovered more than a century ago, had been largely ignored by the scientific community,” said Wexler, who recently completed his PhD on the subject. “In fact, it was a novelty item passed along from generation to generation as a nerdy party trick that eventually made it to YouTube where two of my promoters, Jakob Woisetschläger and Elmar C. Fuchs, found it. Regardless, anyone who has had the good fortune to see a floating water bridge is instantly mesmerized by the simplicity and grace of what is there before their eyes—a little rope of water hanging in mid-air between two wine glasses.”


Wexler received his PhD for his research on the properties of the water bridge on April 19th, one day after his 42nd birthday. His doctorate was granted by Wageningen University in cooperation with the Graz University of Technology in Austria. Today, he works at Wetsus as both a researcher in Applied Water Physics and as the head of the Arie Zwijnenberg Laboratory for Advanced Microscopy and Optical Metrology.

Although creating a water bridge is fairly straightforward, the science behind it is astonishingly complex. Not only does the floating water bridge provide a deeper fundamental understanding of water, it also offers insight into areas ranging from desalination and zero-waste manufacturing to biochemistry and injury rehabilitation, and even to the question of what it means to be living vs. nonliving. By connecting so many diverse areas, the water bridge is a bridge both physically and metaphorically.

Below, in his own words, Wexler reveals how a tiny string of water holds much more than meets the eye.

On the ordinary and extraordinary properties of the water bridge:

Taking some more time to watch the bridge in action, one is stupefied by the complexity. The water movement is bidirectional, i.e., it simultaneously flows in both directions, and the shape and diameter of the bridge is constantly changing. The bridge also has a lot of strange optical properties like weak birefringence and mixed refractive index, which make it appear somewhat different than “ordinary” water, even to the naked eye!

There is practically nothing ordinary about the water in an active floating bridge, and this is no esoteric experiment, as the strength and shape of the electric field we apply in the water bridge is nearly ubiquitous throughout nature. It turns out that if we examine the electric fields present in nature, such as those in living cells, around soil particles, or in clouds, we find that the field strengths are on the same order of magnitude—megavolts per meter. Which incidentally is the same in the water bridge, not to mention inside many electrochemical and biochemical fuel cells that are now being used to develop the next generation of resource recovery technologies.

Megavolts per meter seems to be this kind of universal constant of field strength in aqueous systems. It’s such an enticing observation that, during my defense, one of my opponents made a point to ask whether I thought this was just a coincidence or indicated some deeper truth that we are as yet unaware. Of course I had to answer the latter, as I am a firm believer that nature is quite deliberate in its construction and there are really no accidents.

On using the water bridge as a tool for understanding water and electric fields:

This electrically excited state of water in the water bridge is likely the most common state encountered in our daily lives, but is often overlooked because it was experimentally inaccessible (and thus unknown!) until our work on the floating water bridge. The liquid state is exceptionally sensitive to perturbations, and the floating water bridge provides a new opportunity to look at how electric fields can influence the dynamics of the hydrogen bonding network.

Developing a clear understanding of the physical and chemical properties of water under the influence of such electric fields is essential to the successful upscaling of many technologies, such as electrochemical and biochemical fuel cells. The problem has been that, until now, it was not possible to reliably measure the influence of electric fields. This is because, unlike in the water bridge, in most other examples where electric fields and water interact, the physical distances are very short, between a few tens of nanometers out to at most a millimeter or two.

The water bridge is a macroscopic object that provides enough sample volume to use in modern materials characterization experiments like X-ray and neutron scattering, or NMR, ultrafast vibrational, and Raman spectroscopies. These are the tools we and others used to examine whether anything unusual about the way the molecules in the bridge behaved. We also performed an electrochemical analysis because it was a bit puzzling as to why there was so little electrolysis of the water during bridge operation.

It turns out that the water bridge can teach us important lessons not only about electrohydrodynamics but also about water. The floating water bridge is a long-lost piece of the puzzle in understanding why water is such an unusual substance. What we had missed was that, in liquids there exists an intrinsic disequilibrium which continuously drives the system around within a big basin of possible configurations; and water is again exceptional. When we apply the electric field, we perturb the dynamics and change the shape of the attractor basin. This in turn changes the flow of energy through the system and may even liberate stored energy that is inaccessible when the liquid is in the ground state.

On the challenges with models:

The key in my view is that when we are dealing with water in the condensed phase, we find there is a serious limitation imposed by the necessary step of model creation, which we then use to interpret our experimental data. The arbitrary choices we make regarding which spatial and temporal length scales to include are only the beginning of the trouble. We are also faced by the problem of what types of forces to turn on or off. For example, some recent calculations by Prof. John Swain at North Eastern University in Boston showed that, if we use a quantum mechanical description of water to calculate the total energy in the system, we arrive at a value 3.7 times that found with the classical approach!

Before coming to Wetsus, I worked on trying to understand how the macroscopic behavior of the liquid arises from the molecular level—we examined polymer interfaces, colloids, bubbles, and droplets. In all of these experiments, it seemed we kept running up against the question of how to delineate simple but effective assumptions in our interpretations of experiment. When I shifted my focus to the water bridge I found this situation only intensified, and yet there were some in the community who thought everything could be found in textbooks. Lucky for us they were wrong.

On two recent papers, “A floating water bridge produces water with excess charge” in the Journal of Physics D: Applied Physics and “Non-equilibrium thermodynamics and collective vibrational modes of liquid water in an inhomogeneous electric field” in Physical Chemistry Chemical Physics:

The two papers both challenge several long-held assumptions, the first being charge neutrality, and the second the so-called isotropic limit in liquids.

The water bridge allows us to create an electrochemical system whereby we store energy in the two liquid streams produced during bridge operation. This is essentially the same principle working in reverse electrodialysis systems, but here we don’t need a membrane to sort ions, and we further stabilize the produced solutions using injected electrical charge. Wetsus was awarded a patent last year for these findings, and we are now pursuing ways to upscale the technology for practical use. At the moment we are testing a reactor which can produce pure water with different pH values but that does not contain a chemical acid or base.

We also found that if we suddenly disrupt a stable water bridge that has been operating for 30 minutes or more, we measure a residual electrical charge in the two beakers. The charge sign is opposite in the two beakers and is accompanied by a change in the pH as well. If you are worrying that we have violated charge neutrality, when we recombine the two liquid volumes we find that they neutralize each other. We have found a trick for temporarily bending the rules and we are relieved to see that charge is conserved over the entire system. The trick has to do with the way that the water bridge operates, and this brings me to the second paper.

Usually when we perform engineering calculations on a system using water, we assume that the material is essentially uniform in all directions and that any instantaneous fluctuations are countered by a recoil somewhere else in the system, i.e. the isotropic limit. The water bridge shows us that these assumptions are patently false even at macroscopic length scales.

What we have found is that water molecules are easily excited into a collective vibrational mode that extends over a huge number of molecules. This state has the peculiar property of lowering the energy required for the nucleus of the hydrogen atoms (i.e., protons) to become delocalized (or shared) between two adjacent water molecules. This excited vibrational state is shared as a collective mode which stiffens the whole network, increasing the elasticity modulus of the liquid. This is part of why a water bridge can be stretched over a 4-cm gap!

By shaping the electric field, it is possible to spatially vary the physical and thermodynamic properties of water. The liquid is still a continuous system, but now we can direct the flow of energy (both kinetic and potential) and thus achieve local regions with very different physical and chemical properties.

On the water bridge and biochemistry:

The floating water bridge provides us easy experimental access to generating and studying water under the influence of moderately strong (i.e., relative to the direct coulombic interaction between neighboring water molecules) electric fields—the same field strengths that are present in living cells and in the natural environment. From studying the floating water bridge, we have learned that water under such conditions is anything but passive. Water, it seems, is not merely the background for life, but rather it plays an active role in shaping the biochemical machinery upon which life depends.

There are a number of nice animations and even a documentary-length visualization on the inner life of the cell available on the internet, but in all of these videos we only see proteins, lipids, and genetic materials. The water is completely missing from the picture, and this is an unfortunate omission—because we are left with the impression that the cell components interact in a vacuum, which certainly they do not! This reflects a limitation biologists face because we really can’t yet see what water is doing in the cell.

Despite lacking direct visualization, we do know that biomolecules can possess hydrophilic and hydrophobic regions, and that these are arranged in a precision architecture that can shape the dynamics of nearby water molecules. Where steep electric field gradients are also present, the collective vibrational modes found in the bridge would carry this influence deeper into the liquid body. I believe we will find that this selective control of water dynamics is at the heart of enzyme activity, pore selectivity, and even circadian clocks.

On water and life:

When we look at proteins, we find that they have an intimate connection with water, which is the only material flexible enough to fulfill the myriad tasks given by the biochemical engine of life. Water is not only a transient scaffold for life, but also plays an active role in the delivery and polymerization of cytoskeletal components in the cell.

Gaining a better understanding of how life works at its most basic level can lead to a much more clear view of health and healing. It may not be a comfortable admission, but we as yet do not know the difference between the living and non-living states. Many great minds have pondered this question and as yet we only keep confusing the issue rather than clarifying it. I tend to be a systems thinker (I love swarms), and I often wonder how good we would be at making microprocessors if we had no idea about the fundamental science governing transistors.

In my previous life as an injury rehabilitation therapist, I often engaged my colleagues in long discussions about healing, and in the end I concluded we lacked the critical understanding necessary to make any kind of intelligent assertion on why someone would recover while another would not. Beyond all the external factors, there always seemed to be some very bothersome additional factor (e.g., an uncontrolled parameter) that was deterministic in the process.

Now humans are horribly complicated creatures so I don’t want to give the impression that this is all a matter of water… but it was this discussion which ultimately led me to study water, because life (as we know it) is inextricably linked with water. But much in the same way that the electrohydrodynamic theory cannot predict the formation of a floating water bridge, an a priori consideration of the water molecule would never lead one to consider the existence of life.

On the role of water in zero-waste manufacturing:

Along more economically practical lines of thought, when I compare how humans produce goods and materials to how nature does it, the inefficiencies are appalling. For example, there is no dead volume in a cell, but every human built reactor vessel I know of suffers this problem. The generation of side-products in the chemical industry is just an accepted fact of modern plant operation, but for an organism such inefficiencies can be fatal.

Microfluidic reactors provide a leap forward in chemical efficiency and many technologists are getting wise to the importance of reducing our processes to length scales similar to those over which nature works. It’s not just spatial length scales but also temporal scales that matter. Just-in-time manufacturing is a very biologically inspired concept, and in a similar manner, by using the principles we are now learning from the water bridge, we can move this idea to the molecular level.

I can imagine reactors which don’t hold large volumes of caustic materials but rather only produce the ion or pH needed at the place where it is needed. We can achieve this with very high precision and with at least the same processing speeds that common consumer electronics achieve. The miniaturization of the water bridge is already under way and we are closer than ever before to being able to program water to carry out specific reactions at specific locations. For me, it is not as important to achieve better control over the transport of materials in water, but rather to gain mastery over influencing the relationship between water and the material of interest that we must focus our efforts on.

On rethinking desalination:

I love the example of reverse osmosis desalination. Here we have a few percent of salt in a massive volume of water which entirely ruins the usefulness of the stuff, so we push 96+% of the material through some very tiny pores expending huge amounts of energy to get rid of this minor fraction of salt. Wouldn’t it be much better if we could ‘tell’ the water to drop the salt? I don’t know how to do that, but I know there are plenty of organisms that do and with much better efficiencies. For me the missing part in our understanding is that we still largely consider water as a passive material. That view has to change, and this is part of my mission to make more researchers in the world aware of the lessons learned from the floating water bridge. I think it will take a large concerted effort to embrace these insights and that this will be a driving force for transforming our technologies into something which resembles those found in nature.

On winning the Marcel Mulder prize, which is awarded to the Wetsus researcher(s) who made the most exceptional performance in the field of water technology in the past year:

2015 was the first year that the prize was split, and I shared it with my colleague Jouke Dykstra. I think this is not only a sign that Wetsus is growing, but that the quality of the work we are doing remains of the highest caliber. I received the award for my work on developing specialized optical spectroscopy instrumentation and for advancing our understanding of the interactions between water molecules—in particular the disequilibrium state over the mesoscale. It was great to be recognized for my contributions over the years, but without the help of many hard-working people behind the scenes I would not have been so successful.

While I was standing on stage at the Wetsus congress looking out into the crowd it was quite humbling to see so many smiling faces and to know that so many people had contributed to that moment. I received many compliments afterwards and many commented that I really deserved it. The best thing I can do with so much positive energy is to turn around and spread enthusiasm amongst my colleagues to really go for it. I think that we have a special opportunity to make a lasting and significant contribution to the future. It truly baffles me that there are still so many people on this planet who lack basic sanitation and drinking water! We can and should do more to alleviate this.

On becoming the head of the Arie Zwijnenberg Laboratory for Advanced Microscopy and Optical Metrology at Wetsus:

This laboratory is unique in that it is the only optical facility in Europe, and as far as I am aware, the world, that is dedicated to the application of optical science to advancing water technology. This is an excellent example of how the collaborative and cross-disciplinary environment within Wetsus functions. I have the opportunity to learn about the questions my colleagues are working to answer and to consider how we can cooperate in bringing new solutions and perspectives from one discipline to another.

The diversity of research topics at Wetsus pushes the bounds of both science and engineering. I am encouraged and supported to get involved not only with my fellow researchers but also with industry partners to build a stronger network and to improve the ease with which discoveries find their way into the real world. It is a very positive environment and we have a lot of freedom to explore and innovate.

Wetsus and our members benefit from the top research facilities and the diverse expert staff, but mostly from the interpersonal relationships that this unique environment forges. I have made life-long friends here and have a lot of respect for and fun with my colleagues. I know these connections will continue to influence what we do in the future no matter where life takes us.

On the future of water science and technology:

I think water science and technology has the ability to transform human technology in general. We have been locked in a stone-age framework for millennia—we like to build very complex but rigid systems and this goes completely against the way of nature. The natural world is fluid. Everything is always moving, changing, adapting. This kind of flexible, self-optimizing technology is what we need to move towards and we won’t get there by doing what we have always done. At Wetsus we have the opportunity to forge new scientific understandings and then immediately apply them to real-world engineering problems. We cannot only surpass our current limits of capability but also hopefully avoid the pitfalls of deploying technology we don’t understand.

When we examine the technological history, we find that all too often we must expend tremendous resources to later remediate the damage caused by advancing technologies without properly understanding the mechanisms and interactions between human and natural systems. Challenges like nuclear waste, heavy metals contamination, persistent organic pollutants, antibiotic resistance, aquatic microplastics, biodiversity collapse, and climate change all have roots in the actions of our forbearers’ haste to revolutionize industry and to prioritize the metric of human gain over environmental stability. Today the pressure to advance is even stronger, and our responsibility as the current generation of leaders to carefully vet our choices is likewise amplified. This is what has given rise to the sustainability movement and here Wetsus is a front-runner.

Water is a unifying force on this planet, and while the technological challenges are great, the human and societal norms pose the biggest obstacles to change. The excellent outreach and the drive to deploy new technologies, often to those areas where it is most needed, is another important way that Wetsus makes a difference.

Raman measurements on the floating water bridge
Raman measurements on the floating water bridge

How one Wageningen professor juggles research, teaching, supervising, and family

For Annemiek ter Heijne, an assistant professor of renewable energy at Wageningen University, every day is filled with a variety of tasks that revolve around her area of expertise: using microorganisms to generate energy.

All of this work is highly collaborative. As ter Heijne explains, most of her time is spent teaching or supervising students, both at Wageningen and at Wetsus. Her first contact with Wetsus came back in 2006, when she was a student working on her PhD thesis on microbial fuel cells. Now the roles have changed.

“Right now, I am the university part linked to Wetsus, meaning that my input to Wetsus is in the form of supervising PhD students,” she said. “I come to Wetsus a few days per month to meet the researchers and discuss plans.”

Ter Heijne supervises approximately 10 MSc students per year, both at Wetsus and at Wageningen, as well as BSc students for their thesis, and of course the PhD researchers who make significant contributions to society—or, as ter Heijne quips, who do the “real work.”

One recent example comes from ter Heijne’s PhD student Sam Molenaar and others. In a paper published in Environmental Science & Technology Letters in March, the scientists reported the first-ever microbial rechargeable battery, which is a battery that combines two microbial processes—microbial fuel cells and microbial electrosynthesis—in a single device. The battery, which contains some microorganisms from cow manure, may one day offer an inexpensive, clean, renewable alternative to existing batteries.

With so many projects and students to supervise, ter Heijne said that she is very grateful for the immense help by many of the other scientists at Wetsus.

“I could not do all this without Tom Sleutels and Philipp Kuntke, who are co-supervisors of the PhD students,” she said. “Supervising from far away is not that easy, but their good contact and supervision makes it all possible.”

Besides supervising, teaching also makes up a large part of ter Heijne’s agenda, along with many other obligations.

“Throughout the year, I teach two courses (one BSc and one MSc level) that are clustered in 2x2 months,” she said. “In addition, I give some extra lectures related to renewable energy in other courses. In the time that is still left (which is not a lot...), I attend staff meetings, write project proposals, I try to write papers once in a while (but this is often too low priority), I supervise some students with group work, make and correct re-exams, travel to Leeuwarden and back, and try to do this all in a 32-hour (4-day) work week.”

All of this work has not gone unnoticed. In 2014, ter Heijne received the VENI grant for her development of an innovative method that uses microorganisms to convert the organic matter in wastewater into electricity.

“The VENI grant is a nice starting point for new opportunities for cooperation,” she said. “For instance, it opens up the possibility of a Van Gogh grant, which supports the exchange of researchers between France and Netherlands. It is also a very good start for my career at the university!”

At the end of the day, ter Heijne believes her family has helped her professionally by making sure she has time for life outside of work. She and her husband Dirk have two children: a daughter Tilia (seven years old) and a son Wietse (five years old).

“The balance between work and home is a continuous challenge,” she said. “My daughter likes to tell me that I am away too often for her taste, although I do spend maximum one evening away from home (dinner time) a week. Actually, the kids help me a lot to keep a healthy balance between work and home, because they force me to not spend too much time working. Also the fact that my husband Dirk works three days per week, as a postdoc researcher in Wageningen, and takes over many tasks makes this all possible for me.”

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