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Wetsus PhD positions

Wetsus, European Centre of Excellence for Sustainable Water Technology

EMPOWER is a doctoral programme co-funded by the European Commission. The objective of EMPOWER is to create a highly demanded type of professional in STEM (Science, Technology, Engineering and Mathematics), with the skillset to operate between academic chairs, established knowledge-intensive companies, start-ups, public authorities and the general public, to develop and realise solutions for the challenges of the 21st century in the field of water. Therefore, the EMPOWER programme is offering 14 PhD positions integrated with business oriented training, which is fundamental to prepare the selected Early Stage Researchers (ESRs) for their future entrepreneurship-research career.

Wetsus is the main beneficiary and project coordinator of the EMPOWER programme. The research projects will be conducted together with three university partners Wageningen University (WUR)University of Groningen (RUG), and University of Twente (UT).

All the available research positions can be found below

Call opened on the 6th of September 2021

We proudly present the first Empower call on this website containing 14 PhD positions. The deadline to submit your application is on Friday, 29th of October 2021.

Please do not send your application to the email address of the Universty of Twente and Wetsus supervisors. Only complete applications received via the official application form on this website will be considered for evaluation.

Positions Wetsus & UT

  • Stable polyelectrolyte multilayer based membranes for water treatment under harsh conditions

    Topic background

    Complex oil/water/solids mixtures are found in many industrial processes and water treatment facilities. One key example, so called “produced water”, makes up one of the largest aqueous waste streams in the world, generated by oil and gas (enhanced) recovery operations. Produced water is a complex mixture of organic and inorganic compounds, that are present in both a dispersed and a dissolved state. But rather than viewing this as a problematic waste stream, one can also see this as a promising resource that can be treated for re-use, helping to alleviate the world-wide shortage of clean water. Unfortunately, the stream can have very harsh conditions, including very high salinities, extreme pH values and the presence of dissolved solvents organics and problematic chemicals such as hydrogen sulfide. Clearly, a high stability against these harsh chemicals will be required for any approach to treat produced water.     

    Research challenges

    Many technologies are available to treat produced water, including gas flotation, hydrocyclones, adsorption, media filtration and membrane technology. Typically, multiple of these techniques need to be incorporated in the treatment process to give the required result, becoming part of a larger process layout. Here, membrane technology is especially interesting as it is one of the few approaches that can successfully remove the smallest (< 10 µm) and most stable oil droplets. For this purpose, microfiltration and especially ultrafiltration (UF) have been shown to be very suitable techniques. Moreover, denser membranes such as nanofiltration (NF) and Reverse Osmosis (RO) membranes can remove heavy metals, multivalent ions and for RO also the monovalent ions. Essential steps to make produced water ready for re-use. But especially these dense NF and RO membranes often lack the stability to be used under the required harsh conditions.

    Objectives and methodology

    For treatment of complex oil/water/solids mixtures, such as produced water, nanofiltration is very interesting, due to the ability to de-oil and to have control over the ionic composition of the permeate at acceptable fluxes. In this project we will develop NF membranes that are stable under harsh conditions on the basis of so called polyelectrolyte multilayers (PEMs). These PEM coatings have the potential to provide such membranes with excellent characteristics, in the form of selectivity, water flux and resistance to fouling. In this project we will further their development to push them towards excellent stability under the harsh conditions that can be found in produced water treatment. This will be achieved by innovative combinations of ionic and covalent crosslinking.  In collaboration with the involved companies we will then translate obtained insights into relevant process designs for the treatment of specific produced water streams for re-use. 

    Students’ requirements

    We are looking for a highly motivated candidate with a background in physical and/or organic chemistry, materials science or chemical engineering (MSc degree). The candidate will require a high level of independence and will need to be able to work from an interdisciplinary perspective.

    Academic supervisors

    Prof. Dr. Wiebe M. de Vos and Dr. Esra te Brinke (University of Twente, Membrane Surface Science, Membrane Science and Technology Cluster).

    Wetsus supervisor

    Dr. Ettore Virga (Theme coordinator Desalination & Concentrates)

    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/

  • Steering protein functionality by smart dehydration

    Topic background

    Within the Dehydration research theme of Wetsus, we focus on efficiency of water removal, and for this specific project we do this also to steer protein functionality. We work on plant-based proteins that are present in various waste streams of the food industry (e.g., washing water of processes for starch and sugar). We will investigate how proteins can effectively be separated or fractionated and thus made into a sustainable alternative source of proteins with tailored functionality. In feeding a growing world population with sufficient and healthy foods, especially proteins play a pivotal role, since their origin, animal or plant, has a huge impact on sustainability. Ideally, proteins are of plant origin as put down in the European Green Deal, and within this project we contribute to this higher target.

    Research challenges

    Given the low protein concentration present in the previously mentioned streams, effective separation is needed. Thus, different separation technologies that are in line with the industrial partners in the project will be explored, and compared based on their water removal efficiency. The big challenge will be to do so while keeping the functionality of the protein intact. For dairy proteins, it is known that the processes used for their isolation greatly determine their technological functionality (related to the degree of unfolding of the molecules). Therefore, this project focusses not only on separation, but also on the functional characterisation of the obtained fractions, and isolates. Until now, nobody has been able to link separation processes to protein functionality. If this would become available, this would imply that healthy food design would be speeded up greatly.

    Objectives and methodology

    The aim of the project is to develop separation technology to tailor the technical functionality of proteins, and develop microfluidic tools to investigate this functionality. This will be investigated via the two (low temperature) dehydration technologies currently present in the Dehydration theme: Eutectic Freeze Crystallisation (Cool Separations) and Super Critical CO2 (Feyecon). Both are well suited for food products containing heat-sensitive proteins. Besides, also membrane filtration will be considered as an alternative. Proteins play a key role in emulsification, i.e. they prevent coalescence of e.g. oil droplets coated with the particular protein and with that phase separation. For protein functionality measurements, we will use a combination of tailor-made microfluidic technology and high speed camera imaging to monitor how well the proteins are able to stabilize small oil droplets.

    Students requirements MSc degree in Chemical Engineering

    • Process Engineering
    • Food technology or equivalent.

    Academic supervisor

    Prof. dr. ir Karin (CGPH) Schroën (University of Twente, Faculty of Science and Technology, Membrane Processes for Food).

    Wetsus supervisor

    Dr. Henk Miedema (Theme Coordinator Dehydration).  

    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/ 

  • Optics-based distributed sensing for the management of groundwater quality

    Topic background

    Aquifers form a major source for drinking water production. However, the groundwater quality is threatened by anthropogenic pollutants, periods of drought, saltwater intrusion, and interference from other underground applications. Geohydrological and reactive-transport models help to predict how these threats play out over time and distance, and to evaluate possible mitigation strategies. However, the power of these models is limited by the heterogeneity of the underground and the diffuse nature of the threats. Distributed measurements could be used to inform these models and make them more accurate. Recent research showed the potential of fibre optics based sensors, especially Fibre Bragg Grating (FBG). FBGs are individual sensors engraved in a fiber optical cable that reflect a particular wavelength. This reflection is affected by bending, stretching or compression of the cable. Fibre optical cables with FBGs can be installed vertically into the subsurface and provide continuous high-resolutions real-time information about the aquifer.

    Research challenges

    The challenge for subsurface distributed sensing is to measure without introducing electrical wires, electrodes and/or potentially harmful materials into the aquifer, as this would severely complicate the installation, robustness and safety of the sensor. This challenge can be overcome by making use of the FBGs, since these sensors do not rely on electronic circuits or electrochemical measurements. Two novel water quality sensing capabilities will be developed:

    FBR for refractive index sensing

    The refractive index of water changes with salinity. This principle will be used to develop a Refractive index sensing optical cable.

    FBG for chemical sensing with selective materials

    Materials can react physically to chemical changes, e.g. materials can swells or shrinks when absorbing a salt. FBG are highly sensitive to such physical effects. This principle will be used to develop an optical cable with salt-sensitive coatings for chemical sensing.

    Objectives and methodology

    This PhD research aims to develop a robust FBG-based water quality sensor with a long expected lifetime and sufficient sensitivity.

    The research comprises the following steps:Design and build a FBG-based refractive index sensor.

    1. Identify and test salt-sensitive coatings; testing durability, sensitivity and specificity.
    2. Test the FBG-based sensor in a laboratory set-up that mimics the aquifer.
    3. Test the FBG-based sensor in the field.

    Students’ requirements

    • MSc degree in the field of applied physics, chemistry or related scientific discipline.
    • Furthermore, the candidate should have adequate experimental skills and experience with optics, sensors or electronics.
    • Knowledge in the field of geosciences is useful.

    Academic supervisor

    Prof.dr.ir. Herman L. Offerhaus (Optical Sciences group, University of Twente)

    Wetsus supervisors

    Dr.ir. Martijn Wagterveld (Theme coordinator Sensoring), Dr. Renata van der Weijden (Senior advisor biogeocheminstry), Dr.ir. Roel Meulepas (Theme coordinator Groundwater Technology)

    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/


Positions Wetsus & other universities

  • Optimisation of manure processing: towards more sustainable application of manure-based fertilizers.

    Topic background

    Increasing soil carbon sequestration while lowering GHG-emissions and maintaining crop yields is one of the biggest societal and scientific challenges. Manure is commonly used as organic fertilizer and source for organic matter and nutrients in agriculture. However, current manure application often leads to increased GHG emissions as well as eutrophication of surface waters. Moreover, the effect of treated manure on the composition and functioning of soil microbiome and the subsequent implications for carbon sequestration and stabilization in soil, are not well understood. Optimization of manure processing may enable a better use of the nutrients, e.g. by adapting composition to enhance higher nutrient uptake rates. Focusing on the bioprocesses occurring during manure treatments and on the interaction between manure-associated microorganisms and soil properties bears the potential to reduce GHG emissions from the agricultural sector while contributing to the circular economy by sequestering more carbon.

    Research challenges

    Manure digestion and other (post- or pre-) treatments can improve the sustainability of agriculture practices by allowing increased reintroduction of carbon and nutrients in the food chain. However, the impact of such treatments on C and nutrient fluxes needs to be elucidated, especially in relation to the effect of the processed manure on C-uptake and GHG emissions in soils. Key factors to achieve more effective use of manure in agriculture are to elucidate the effect of organic inputs (and the microorganisms associated) on microbial community in relation to soil C dynamics. Insight obtained from this research will enable the development of manure treatments strategies to maximize soil functionality and fertility.

    Objectives and methodology

    The goal of this research project is to test and design manure treatments for agriculture use in order to achieve most optimal effects with respect to organic matter stabilization and reduction of nutrient loss and GHG emissions. The approach of this research consists in coupling bioprocesses technology and soil science. A first step will be to select and characterize manure treatments and identify suitable processes and related parameters as potential engineering targets for optimized manure treatments. Second step will be to optimize the processes via organic source addition with the aim to optimize nutrient stoichiometry. The third step will be to assess the effect of treated manure on soil properties with regards to C-uptake and GHG emission and identify the best manure treatments for the development of manure-based bio-fertilizer.

    Students’ requirements

    We are looking for a highly motivated biotechnologist (MSc degree) with affinity for soil microbiology. The ideal candidates should be a team player with excellent communication skills. Knowledge of complex analytical tools for microbial and/or organic matter characterization and of the basics of composting/digestion/fermentation is considered an advantage.

    Academic Supervisors

    Dr. Miriam van Eekert (Environmental Technology (ETE), Wageningen University) and Dr. Paul Bodelier (Microbial Ecology department Netherlands Institute of Ecology - NIOO-KNAW)

    Wetsus Supervisor

    Dr. Valentina Sechi (Theme Coordinator Soil)

    University promotor

    Prof. dr. ir Cees J.N. Buisman (Environmental Technology (ETE), Wageningen University)

    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/

  • Enhancing the local water cycle via evaporation for a sustainable water supply

    Topic background

    In many arid regions, water resources are scarce due to the low rainfall. Scarcity of water leads to lowered agricultural productivity and impairs the health and wellbeing of the population. This situation is expected to deteriorate due to climate change, growing population, and agricultural activities. Desalination techniques are available to produce drinking water, however they do not solve the root cause of the problem i.e. a lack of sufficient precipitation. To make more freshwater available, we propose a novel approach that aims at restoring the local water cycle sustainably. Counter-intuitively, restoring the water cycle requires additional evaporation of water, to lower the condensation level in the atmospheric boundary layer, which turn is expected to give enhanced water precipitation in the watershed making more water available. A restored water cycle can sustain itself as the evaporated water returns as precipitation within the watershed. Enhanced recycling can mitigate water scarcity issues as more useable water that is fully cleaned becomes available.

    Research challenges

    Crucial for restoring a well-functioning local water cycle, is the availability of water. Here we will look into technology that produce water vapour from brackish or seawater, via direct evaporation, driven by the abundant solar energy. The basic principle is that solar radiation is converted into heat that is used to increase the water temperature. This increased temperature leads to an increased vapour pressure, which in turn drives the transport of the water vapour to the atmosphere through a suitable membrane. This membrane is the interface between the seawater and the atmosphere and is required to prevent leaking of the brine to the environment. We will investigate the suitability of different processes namely membrane evaporation vs. pervaporation. The performance of this process will depend on the atmospheric conditions, like solar irradiation, turbulence in the lower boundary layer, temperature, wind speed and humidity profiles. These conditions are strongly variable in time and space. It is therefore of paramount importance to connect the mass transport inside the membrane with that of the atmospheric boundary layer. For this, a micrometeorological numerical model (such as PALM: Parallelized Large-Eddy Simulation Model) is employed to quantify the local scale environmental/hydrometeorological impacts of the membrane-based evaporation system.

    Objectives and methodology

    The aim of the project is to understand the performance of direct evaporation technology under realistic atmospheric conditions. As most membrane systems are used in engineered relatively constant environments, little is known on this interaction. As this direct evaporation technology is quite young, a prototype oriented approach will be used, i.e. prototype will be developed both to assess the performance and study underlying fundamental thermodynamic and transfer processes. The micro data obtained from the prototype are upscaled and validated using a process-based micrometeorological model. The model will assess the overall performance and impacts of the established membrane system on the localized water cycle for the target region. Therefore, the focus of the project lies in understanding the relation between performance of the membrane system and the surrounding lower boundary-layer atmosphere. 

    Students’ requirements

    The candidate must hold a MSc degree in Process engineering, Environmental engineering with an interest in mass transfer processes at all scales, and also good understanding and knowledge in earth sciences, meteorology and hydrology.  Fluency in English, both written and spoken. Ability to work in a multi-disciplinary, international team. Both experience with setup building and modelling. Good programing skills (e.g. Python, R, Bash) are required.

    Academic supervision

    Prof. Dr. Ir.  Bert Hamelers (Environmental Technology (ETE), Wageningen University)

    Wetsus supervision

    Dr. Mohsen Soltani (Theme coordinator Natural Water Production)

    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/

  • Beyond chlorine: alternative sustainable compounds to remove biofilms in drinking water environments

    Topic background

    Within Drinking water distribution systems (DWDS), at least 95% of the total microorganisms grows on pipes surfaces, in the form of biofilms. In biofilms, microorganisms produce extracellular polymeric substances (EPS) to form a matrix protecting them from external stresses. Biofilm formation and its detachment into the water stream affects the taste, odour and colour of drinking water, and constitutes a risk for contamination when pathogens are present. Currently, no single practice so far appears to be sufficiently effective for the management of biofilm growth/persistence in DWDS. One of these measures includes the application of disinfectants. Chlorine, the most widely used water disinfectant in Europe, has limited penetration within the biofilm due to its reaction with organic and inorganic compounds; these reactions also produces harmful and carcinogenic disinfection by-products (DPBs). The low efficiency of such disinfection treatments warrants the investigation into novel anti-biofilm agents, which can be more effective than and with less side effects. Research into the application of natural anti-biofilm agents is at the core of this project.

    Research challenges

    The formation and development of biofilms is a complicated procedure involving different stages, which can be the target of natural anti-biofilm agents for the prevention of their growth. Once established, biofilms are very difficult to eradicate because the EPS, made of proteins and polysaccharides, protect bacteria from disinfectants.  Considering the applicability in drinking water environments, we focus on antimicrobial natural amino acid derivatives, because their utilization is compatible with human consumption (in water), and they can affect biofilms at different stages. An example is N-acetyl L-cysteine, an acetylated derivative of L-cysteine, which is able to inhibit cell adhesion on a surface and EPS excretion (initial phase), and can disrupt or degrade EPS, causing the dispersal of existing biofilms. The same anti-biofilm effects were observed for other molecules like D-tyrosine. A disinfection strategy applying these (tested) molecules is not expected to place any selective evolutionary pressure on microorganisms to develop antimicrobial resistance, and does not drive any DBPs production, reducing the long-term impact that is observed with the use of chlorine-based disinfectants.

    Objectives and methodology

    The aims of this project are to 1) identify natural, sustainable compounds applicable in drinking water environment (from pipe materials to filtration membranes), 2) understand their fundamental mechanism of action, and 3) produce a cost-effective protocol to be used as maintenance strategy or in contingency situations.

    The disinfection approaches will be tested on;

    • Mixed planktonic cells from drinking water sampled from both the production site and from the tap, to assess the effects on biostability.  
    • Biofilms developed in DWDS simulator (already present at Wetsus) to test the effectiveness on biofilms dispersal and EPS biopolymers in a drinking water asset.
    • Biofilms grown on real pipes surfaces and developed on membranes materials, in order to assess the role of support material on the disinfection effectiveness.
    • Pure cultures of known microbial strains, including Legionella and (bio)corrosive microorganisms.

    In search of a cost-effective strategy, additional research will be dedicated to the ex-novo synthesis of a molecule which exert the same effects of the natural products. Novel anti-biofilm compounds may be produced using organic chemistry techniques. Several molecular biology and applied microscopy techniques will be applied to assess the effectiveness of the methods and understand the exact antibiofilm mechanisms of the natural molecules in drinking water environment.

     Students’ requirements

    • MSc degree in biochemistry, microbiology, biotechnology or equivalent, with an interest in molecules.
    • Additional knowledge in chemistry and microscopy is desirable.
    • Ability to work in a multi-disciplinary, international team.
    • Experience with lab work and setup building. 
    • Fluency in English, both written and spoken.

    Academic supervision

    To be determined (University of Groningen)

    Wetsus supervision

    Dr. M. Cristina Gagliano (Theme coordinatoor Biofilms)

    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/

  • High recovery and chemical-free desalination using advanced electrodialysis schemes

    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.

     Students’ requirements

    • MSc degree in chemical engineering or a related discipline
    • Knowledge of water chemistry, electrochemistry, membrane technology, and process modeling
    • Ability to perform water quality experiments and technology assessment at laboratory and pilot scale

    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/

  • Energy-efficient electrochemical phosphate recovery (EPR) – optimisation and upscaling

    Topic background

    Phosphorus (P) is an essential element for life, and our society is mainly dependent on the use of P derived products, including fertilisers and various other chemicals. The industrial source for P is phosphate-rich ores (phosphate rock). Known phosphate reserves are scarce, and their geographical spread is limited, with no substantial phosphate deposits found within the EU. Additionally, the quality of these deposits is decreasing over time due to increasing contamination with heavy metals. Therefore, phosphate was classified as a critical raw material (CRM) by the EU in 2014. Substantial amounts of phosphate can be found in our domestic and industrial wastewater originating from food production, consumption, and other manufacturing processes. Wastewater as a secondary phosphate resource is largely underexploited as the main focus of wastewater treatment plants (WWTPs) is phosphate removal. Therefore, WWTPs relies on either chemical phosphate removal (CPR) or enhanced biological phosphate removal process (EBPR).

    Research challenges

    Conventional P recovery processes from wastewater have severe limitations. EBPR recovers approximately 10-30% of the incoming phosphate load and requires Mg dosing for struvite precipitation. CPR involves adding Al or Fe salts to form insoluble aluminium - or iron phosphate, which can be recovered from the sludge. Electrochemical Systems (ES) are a suitable alternative to conventional phosphate recovery approaches. Previous research has shown that an ES can recover calcium phosphate (CaP) as hydroxyapatite or amorphous calcium phosphate. CaP recovery relies on the hydrogen evolution reaction at the cathode, which increases the local pH sufficiently for CaP precipitation. Contrary to CPR and EBPR, electrochemical phosphate recovery (EPR) does not require any chemical addition and solely relies on electrical energy. While EPR was proven at a laboratory scale with real wastewater and first steps have been made towards upscaling, further insights are needed into this technology for future upscaling and competitiveness.

    Objectives and methodology

    This PhD project will focus on optimising electrochemical phosphate recovery in terms of energy use and recovery efficiency of the system. Therefore, different system designs, material choices, and electrode materials and modifications will be investigated. The optimisation process will involve both experimental and modelling work. Another focus point will be the “harvesting” process and product quality of the recovered CaP product. Working under realistic conditions (real wastewater) and collaborating with the participating companies in the “Resource Recovery” theme will allow upscaling the electrochemical phosphate recovery process. 

    Students requirements

    • MSc degree in Environmental technology, chemical engineering, or equivalent with excellent grades
    • Strong background in electrochemistry and hands-on experience with electrochemical workstation
    • Ability to work independently in the laboratory and to rigorously design and perform experiments in a result-oriented and thorough manner
    • A strong interest in carrying out multidisciplinary research in an international environment
    • Excellent interpersonal skills to work effectively with team members from different backgrounds
    • Good oral and written communication skills in English
    • A strong interest in personal development and career growth
    • A strong interest in advancing scientific knowledge into real-world application

    Academic and Wetsus supervisors

    Dr. Philipp Kuntke (Scientific project manager, Wetsus) and Dr. Renata van der Weijden (Senior advisor biogeocheminstry - Environmental Technology (ETE), Wageningen University)

    University promotor

    Prof. dr. ir Cees J.N. Buisman (Environmental Technology (ETE), Wageningen University)

    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/

  • Towards a circular sulphur economy

    Topic background

    Since biogas and landfill gas streams are renewable energy sources, their global use has increased during the last decades and is expected to remain rising. Typically, toxic hydrogen sulphide (H2S) needs to be removed from these gas streams to prevent harmful sulphur dioxide emissions. The biological gas desulphurisation process under haloalkaline conditions is a cost-effective and environmentally friendly alternative for the conventional physical-chemical gas desulphurisation processes. In addition to H2S removal from these gas streams, biologically produced elemental sulfur can be harvested from the process, as well. Especially the relatively small particle size and hydrophilicity of the biologically produced elemental sulfur are benefits for application as fertilizer and/or fungicide. As the research in the Sulfur Theme of Wetsus focusses on the optimization of the biological desulfurization process, it facilitates the transition towards a circular sulphur economy.

    Research challenges

    In the biological gas desulphurisation process, gas, liquid, and solid phases co-exist. For instance, in the absorber, a gas phase (sour gas) is contacted with a liquid phase (haloalkaline solution), which contains solid phases (biosulphur particles and microorganisms). While the microbial community and its associated kinetics have been extensively studied, a number of phenomena in the biological gas desulphurisation process are not yet fully understood. The recently discovered electron shuttling capacity of sulfide oxidizing bacteria is one of these. Due to these phenomena, dissolved sulfide is removed from process solution, without consuming oxygen. Other not fully understood phenomena are, for instance, the enhancement of H2S absorption by bacteria and the sulfur crystals formation. All of these processes are hypothesized to occur at the interfaces of the biological desulfurization process. Hence, research is required to investigate the interplays between kinetics of chemical and biological reactions and transfer rates at the interfaces.

    Objectives and methodology

    This project aims to understand the interplays between the kinetics of the biological reactions, the kinetics of the chemical reactions, and the transfer rates around the various gas-liquid and liquid-solid interfaces in the biological gas desulphurisation process. In the last decennia, a large number of projects have been executed, resulting in a vast amount of experimental data. However, a minimum amount of the full potential of the work has been utilized, since the majority has not been used for modelling to unravel the aforementioned phenomena. Hence, part of this work will be focussing on developing models describing the transfer and reaction kinetics at the interfaces. In addition, next to utilizing data obtained in previous work, experimental work will be performed in batch and/or continuous bench scale setups to gather data for model validation and calibration. Furthermore, when required, pilot plant facilities (owned by Paqell B.V.) may be used validate the developed models.

    Students’ requirements

    • MSc degree in environmental technology, biotechnology, chemical technology or related field.
    • Proven experience with modelling software, such as Matlab and Comsol
    • Interest in transfer processes
    • Strong analytical skills
    • Ability to work in a multi-disciplinary team
    • Experience with lab work
    • Fluency in English, both written and spoken

    Academic supervisor

    Prof. dr. K.J. Keesman (Mathematical and Statistical methods, Wageningen University).

    Wetsus Supervisor

    Dr. Ir. Jan Klok (Theme Coordinator Sulfur)

    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/ 

  • Production of PHA from municipal primary sludge VFAs in support of upscaling of PHA production from municipal surplus activated sludge

    Background

    Leading developments and innovations with methods for biopolymer (polyhydroxyalkanoate or PHA) production and recovery, using wastewater and organic residuals as carbon sources, are undertaken within the Wetsus theme Biopolymers from Water. This theme bridges science and engineering in bioprocess and materials.  It is with potential for meaningful downstream societal contributions and industrial opportunities from biopolymers produced and recovered as a part of water quality engineering services. The Dutch Water Authorities act on goals of renewable resource cycles (Routekaart Afvalwaterketen tot 2030), wherein energy, mineral, and biopolymer products are to be parallel value-added outcomes to the principal task of environmental protection from treating municipal effluents. This research project will be to contribute with innovations in fundamental details of bioprocess in anticipation and cooperation within ongoing steps to scale up and integrate industrial scale PHA production from municipal waste.  Research questions will relate to key factors that ultimately stand to have significant bearing on the success of scaled up process through anticipated influences on production productivity, economy, and polymer quality (value).

    Research challenges

    PHA production at industrial scale requires skills and technique in fed-batch bioprocess, and its control.  A sufficient mass of VFA rich substrate must be supplied in the right way to a mass of polymer accumulating activated sludge.  Principles of process need to manage the polymer quality with respect to co-polymer composition and molecular weight distributions, and mitigate flanking microbial population activity and growth, while maintaining optimal overall metrics of the economics in productivity.  Innovative industrial scale bioprocess methods, based on exploiting fundamental principles of biomass dynamic response and polymer storage kinetics, are required for a successful robust upscaled design.  These details are novel to the industry, and they will be essential in anticipation of successful industrial scale facilities.  This project is also about fundamental innovations that can come from connecting a spectrum of ideas and principles together, and it is directed with purpose towards the real-life goal for the Dutch water authorities to successfully scale up technology for PHA from Dutch regional municipal wastewater treatment residuals. 

    Objectives and methodology

    The research is interdisciplinary, involving applied microbiology, process monitoring and control, and polymer science.  The project will apply practical bioprocess experimental work at laboratory and pilot scales, alongside modelling and applying theory and observations, of biomass response, monitoring and control, towards effective advanced process solutions.  The objectives are to:

    • Define and optimize specific requirements of method and bioprocess to reliably produce PHAs with municipal surplus activated sludge using volatile fatty acid (VFA) rich streams coming from acidogenic fermentation of municipal primary sludge.
    • Optimize the process with respect to exploiting flanking populations of nitrifying bacteria in the activated sludge while mitigating growth of other bacteria that would reduce productivity.
    • Optimize the process with respect to predictable control of polymer quality through the biological production, but also through post accumulation, and recovery/purification steps.
    • Integrate findings and developments of this work through techno-economic evaluation and with direct link to the demonstration plant activities of a demonstration scale project, which will be underway in parallel during the PhD project.

    Students’ requirements

    The candidate is a self-driven bioprocess and/or chemical engineer (MSc degree) who takes own initiatives and can also blend in team collaborative R&D.  An aptitude for practical experimental work at laboratory and pilot scales is essential, as well as skills and passion for data analysis, programming, and modelling. 

    Academic supervisors

    Prof. Robbert Kleerebezem and Prof. Mark van Loosdrecht (Environmental Biotechnology, TU Delft)

    Wetsus supervisor

    Dr. Alan Werker (Theme coordinator Biopolymers from water)

    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/

  • Untapping the energetic potential of grey water: microbiological safety and downstream re-utilization routes

    Topic background

     mWater circularity has become a requirement for new urban developments, as preserving usable water represents a basic, but an important first step for a sustainable economy. Separation of wastewater streams at the source is a valuable approach for the effective recovery of resources such as nutrients, water and organics. For instance, concentrated toilet water can be treated via anaerobic digestion to produce energy in the form of biogas, and phosphorus can be recovered as calcium phosphate in the same anaerobic reactor. High quality reuse water and heat can be extracted from greywater (discharges from laundry, showers and sinks) after treatment with nanofiltration membranes, among others. Nanofiltration reduces the organic matter content and microorganisms, which otherwise would promote the growth of biofilms and pathogens downstream. In this framework, biofilm formation is an event naturally occurring in many water distribution environments which can be detrimental, posing a serious threat for the safety of water re-utilization. Thus, a step further into circularity can be achieved by tapping out the energetic potential of grey water in a microbiologically safe manner. 

    Research challenges

    The energy potential of grey water lays in the relatively large volumes produced, which have high temperatures. The idea is to use residual greywater for district heating, by applying heat pumps in a decentralized approach, closing the energy loop in a household. The system will be applied at a neighbourhood level, where grey water is first treated aerobically to remove organic matter and nutrients. Thereafter advanced treatment is applied by means of a nanofiltration unit. In this stage, bacteria and micropollutants are removed. Warm effluent is then stored (at a temperature around 20°C) and with the use of a heat pump, the energy is extracted and stored in a high temperature storage tank for reuse in households.

    Dependency by fossil fuels and natural gas, and an abundance of greenhouse gas emissions are just some of the negative side-effects of our current heating systems. Clearly, there's an urgent need to transform this obsolete system into a sustainable one. This project idea satisfies three main targets set by the European Green Deal, namely investing in environmentally-friendly technologies, decarbonising the energy sector and ensuring buildings are more energy efficient.

    Objectives and methodology

    The focus of this project will be in recovering energy and produce reusable, high quality water in a decentralized manner. A multidisciplinary approach will be used to draw all the possible scenarios, from initial water purification to its final re-utilization.

    In the first phase a lab-scale setup will be realized, with particular attention to the (polymeric) materials utilized because of their strict relationship in promoting bacterial/biofilms growth (including pathogens). Within the setup, the microbiological safety of the water during the whole cycle will be assessed via several analytical and microbiological techniques. 

    Lab-scale investigations will focus on

    • Quality of greywater after the nanofiltration treatment, assessing analytical and microbiological parameters.
    • Characterization of the bacterial population growing inside the system setup.
    • Assessment of energy efficiency of the whole process via mathematical modelling.
    • Effects of storage of grey water after nanofiltration and the greywater effluent reuse after storage at high temperature.
    • Possible disinfection/cleaning strategies to be applied at different levels of the system. 

    Students’ requirements

    • MSc degree in Biotechnology or Environmental engineering, with a strong interest in microbiology.
    • Additional knowledge in thermodynamics is desirable. 
    • Fluency in English, both written and spoken.
    • Ability to work in a multi-disciplinary, international team.  
    • Experience with lab work and setup building.

    Academic supervision

    prof. Henny van der Mei (University Medical Center of Groningen)

    Wetsus supervision

    dr. Lucia Hernandez (Theme coordinator Source separated sanitation), dr. M. Cristina Gagliano (Theme Coordinator Biofilms), Ir. Robert de Kler (senior advisor Sustainable energy production)

    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/ 

  • Inline electronic leak detection in water distribution systems

    Topic background

    There is about 130.000 kilometre of water distribution mains in the Netherlands alone. Their lifetime is exceeding 50 years, and need gradually replacement.  Inspection methods to assess their status are available, but they are not sufficiently advanced to detect small leaks, or to easily find defects in plastic materials. In order to advance in this field, a new type of leak and defect detection method needs to be developed. The expected social impact is that the water mains network remains in good operation as long and as good as possible and that defects can be found before actual catastrophic failure of the piping occurs, leaving customers with an interrupted and sometimes fouled water supply.

    Research challenge

    The proposed method relies on an electric connection through the pipe which, when there are leaks in pipes, can give a signal. When the local electric field is measured, this gives information about the location of the leak.  Plastic pipes seem suitable to this method, perhaps other types of pipe too, rubber couplings can probably be inspected as well. To be able to do this, another electrical path is necessary, outside the area of that leak to the surrounding soil. This could be done by capacitively coupling an AC signal through the pipe, or by a 'tether' connection: a wire to outside. The change of the dielectric constant of the material can also be used, indicating partial failures.

    A number of research questions emerge

    1. Is the method suitable for existing water pipes, and which ones? The water pipes in the Netherlands consist of PVC, Polyethylene, concrete and iron.
    2. Which defects can be detected and how? One can think of cracks, holes, but also of a damage that is not completely 'through', or for example local crack formation or inclusions.
    3. Which parameters determine the sensitivity and in which way? Element size, wall thickness, crack shape, the effect of the contra-connection (tethering or a capacitive method),
    4. How can existing sensor data be merged to increase the resolution of detection? And how can false positives be avoided?

    The innovation opportunity will be the development of a novel inline inspection method for plastic piping systems, able to detect defects and small leaks before an actual problem is onset. The resulting knowledge will be used in actual inspection systems.

    Objectives and methodology

    The objective is to develop a method able to detect small defects and leaks inside water mains by means of a small (AC) voltage applied to the water in the pipe while being scanned from the inside. An advised start-up approach would be literature research towards crack and failure occurrence and potential risks, combined with initial steps of doing experimental work on the measurement principle and development of the measurement system. Next, experimental work combined with theory and modelling of the electric field in water will guide into the most promising direction. Data processing, combining other inspection data and control theory can lead to optimal detection. Finally, there is an opportunity to build a pilot system to be used in real life inspection equipment.

    Students’ requirements

    • The candidate must hold a MSc degree in electrical engineering, mechanical engineering or computer sciences.
    • We are looking for a tech enthusiast, with skills in the field of electronics, control theory, signal processing or similar, with experience in experimental work.
    • We offer a very social, challenging environment with lots of opportunities for self-development.

    Academic supervisors

    prof. dr. ir. Jacquelien Scherpen and prof. dr. ir. M. (Ming) Cao (Faculty of Science and Engineering, University of Groningen)

    Wetsus supervisor

    Doekle Yntema (Theme coordinator Smart Water Grids)

    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/

  • EPS-based solutions to increase soil structure and resilience to drought

    Topic background

    Almost 40% of the total agricultural land in Europe is prone to soil degradation, at a moderate or even severe level. Climate change, accompanied by increasing temperatures and less frequent but more intense rainfall events accelerates soil degradation and further decreases the capacity of soils to store and release the water and nutrients required for plant growth. Soil aggregates, made of particles held together by cohesive forces and organic matter are the basic units that form the soil structure and determine the physical and mechanical properties of soil, including water retention, water movement and aeration. Microbial organisms and their metabolic products affect soil structure by binding loose soil particles into stable aggregates. In particular, extracellular polymeric substances (EPS), produced by soil microorganisms, are known to have positive effect on water retention and aggregate stability.

    Therefore, agricultural strategies that enhance EPS production have the potential to improve soil structure and thus increase the ability of soil to store and provide water to plants during periods of drought.

    Research challenges

    Despite the recognition of the positive effect of EPS on soil structure and decades of research on the industrial potential of EPS (e.g. as bio lubricants, thickener and preservatives), the use of EPS-based products in agriculture as soil improver is still very limited. In addition, our knowledge on EPS composition, structure and function, is far from complete. Gaining understanding of the role of EPS in determining soil structure and aggregate stability and elucidation of the mechanisms that regulate the biosynthesis of EPS in soils, could enable the use of EPS-based solution in agriculture to improve soil structure and prevent soil degradation. 

    Objectives and methodology

    The PhD project aims to elucidate the effect of different types of soil amendments (complex as well as more readily biodegradable substrates), and of varying carbon to nitrogen ratio’s on the development of microbial communities in the soil, particularly on EPS producing and degrading microbes. The ultimate goals of the project is to develop nature-based solutions to increase soil structure and resilience to drought. To reach this goal we will identify key microbial groups responsible in soils for EPS production. We will test abiotic conditions (i.e. C:N ratio, nutrient availability) that may trigger EPS formation and thus influence soil properties.

    Students requirements

    • We are looking for a highly motivated soil scientist with a strong interest in (soil) microbiology, chemistry and with an affinity for agriculture (MSc degree).
    • The ideal candidates should be a team player with excellent communication skills.
    • Knowledge of microbial characterization and experience with microbiome analyses is considered an advantage.

    Academic Supervisor(s)

    prof. Hardy Temmink (Wageningen University - Environmental technology (ETE) and Prof. Martijn Bezemer (Leiden University - Institute of Biology Leiden)

    Wetsus Supervisor

    dr. Valentina Sechi (Theme coordinator Soil)

    University promotor

    Prof. dr. ir Cees J.N. Buisman - Environmental Technology (ETE), Wageningen University

    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/