The research program of Wetsus is divided in several themes. Within these themes research topics have been defined, which are being addressed in the form of PhD-projects.
We are looking for:
PhD-students (m/f)
Clean water technology
1.1: Advanced oxidation with a new ozone plug flow reactor in combination with UV
treatment.
In this project a new advanced oxidation technology (DOPFR-UV), based on a new UV
reactor developed in a parallel running TTI-W project and a Dissolved Ozone Plug Flow
Reactor (DOPFR) will be developed. In this concept a double barrier for pathogens and
organic micro pollutants exists. The combined systems offer a large flexibility as a water treatment system. Fine tuning of the ozone and UV dose will provide opportunities to fine tune the system to the required disinfection and organic contaminant control.
Furthermore, no excess hydrogen peroxide has to be removed after treatment.
The project is carried out at Technical University Delft
1.2: Air/water cleaning to control membrane fouling
Background
High-pressure membrane processes, i.e. reverse osmosis (RO) and nanofiltration (NF), are increasingly used in drinking water treatment, seawater desalination, waste water reclamation and for the production of water for industrial uses. The potential for the removal of salts, pathogens, pesticides, hormones, pharmaceuticals and other possible threatening priority compounds from feed waters by NF/RO make these membrane processes highly attractive in a world with shortage of clean and fresh water. The largestproblem in using membrane processes, however, is the occurrence of membrane fouling resulting in performance loss and operational problems resulting in an increase of the total treatment cost which limits the use of NF/RO. The new and innovative AiRO process uses air/water cleaning of vertically positioned membrane elements to control membrane fouling.
Research questions
To effectively apply AiRO in practice, an alternative NF/RO design is necessary using
vertically positioned membrane elements, completely different from conventional NF/RO design applied worldwide. The most efficient use of the AiRO technology depends on the optimal use of air/water cleaning in membrane elements. Although initial research showed the effectiveness of the process, many fundamental questions still remain unanswered. Some of these questions involve:
the mechanical/physical understanding of air/water cleaning of membrane elements,
the effectiveness of the air/water cleaning process in relation to different feed
components, the long term behaviour of air/water cleaning.
The first two research questions will be investigated using CFD modelling parallel to
laboratory tests and will be the heart of the PhD project. Long term air/water cleaning
behaviour will be investigated in on-site pilot-scale research in a parallel research project.
Research project
The research will be carried out by a PhD student and is supervised by prof. Walter van
der Meer of the University of Twente (Enschede) and dr. Emile Cornelissen of Kiwa
Water Research (Nieuwegein). Furthermore, we participate in this project with other
research institutes (Wetsus) , system suppliers (Hatenboer) and all the Dutch drinking
water companies (e.g. Vitens, Waternet, Evides, PWN,…).
The project is carried out at KWR Water Cycle Research Institute Nieuwegein
Distribution
2.1: Characterization of plastic pipes by accoustic measurements
No specific information available yet.
Research theme ideas: Producing, and especially distributing, drinking-water is a great
job because it’s such an important product for us all.” Jenne van der Velde, theme
manager for Water Distribution, and Asset Manager at Vitens, discusses his theme.
The network of drinking-water Pipelines in the Netherlands is very extensive. It varies in
age between being laid today and a century ago, and many different materials and laying methods have been used. The replacement value of the whole network is more than €10 billion. The condition of the network is hard to gauge, mainly because it is all
underground and we are not always completely sure where. One specific section of the
network could be leaking while another section, a metre further up, could be in perfect
condition.
New technologies are vital, especially for keeping an eye out for future developments
while choosing whether to repair or replace a pipeline. Within the BTO, research has
been going on for years into the various facets of water distribution; design, breakdown
mechanisms and modelling. This research will deliver new inspection techniques,
allowing the condition of pipelines and appendages to be determined at low cost.
Developments such as (ultrasonic) sound, magnetic wave and radar technologies are
very relevant today. Fundamental research is necessary to correlate the condition of a
pipeline to specific, measurable parameters and to the breakdown mechanism.
The ambition for this theme is to work together towards an ultimate goal – the in-line and on-line inspection of pipelines for €500 per kilometre, and the ability to make wellfounded decisions about the possible replacement of pipelines.
2.2: Localization and integrity of pipes in the underground
See project 4.
Desalination
7.1: Surfactant-based reversible salt concentration.
In this project mixtures of polyanions and polycations will be used to concentrate saltcontaining streams from “low” salt concentrations of below 5% up to concentrations of above 20%, thus avoiding the common water evaporation step. The principle for this is based on the tunable binding properties of polyanions and polycations: by changing
temperature and/or presuure, it is expected that binding can be changed from Na+ to the polyanion and Cl- to the polycation towards a mutual binding between the two polyions as a result of increased apolarity of the polyions and stronger electrostatic interactions. As a result, NaCl will be expelled, which is expected to happen at high NaCl concentrations. An ultrafiltration step will be used to retain the polyions together with the bound NaCl and to provide a desalted water stream.
8.1: Capacitive Deionization.
Biofouling
10.1: Control of biofilms on membranes used in drinking water production.
Starting from April 2009 we are looking for new PhD students in the area of control
of biofouling and biofilm research.
Waste water technology
Algae
14.1: Optimization of lipid productivity
Micro-algae are promising production organisms for the production of sustainable biofuels, because many microalgae contain high concentrations of lipids and microalgae can be produced in areas that are not suitable for agriculture.
The aim of this project is to obtain more insight in the lipid accumulation process in algae with respect to the rate of accumulation and the mechanism that triggers accumulation as well as the composition of the accumulated fatty acids. This insight should lead to an increase in the volumetric lipid productivity of algal cultures through increasing the specific lipid productivity of the algal biomass as well as strategies to engineer the composition of the fatty acids towards biodiesel.
To reach this two approaches will be undertaken. The productivity will be optimized experimentally using random optimization techniques (genetic algorithms) and experimental design. In addition, metabolism will be studied in more detail using metabolic flux analysis in combination with 13C labeling and gene expression analysis to get insight in the mechanism of lipid accumulation and possible bottlenecks.
The project is carried out within the Bioprocess Engineering Group of Wageningen University. Final approval of this project is in progress, and is expected in first half 2009.
Membrane bioreactors
19.1: Robustness of MBR treatment of industrial wastewater under varying conditions*
Compared to conventional activated sludge treatment, membrane bioreactors (MBR)
offer several (potential) advantages including a smaller foot-print and, because it is free
from solids, the possibility to re-use the effluent as process water. A major question
however is the robustness of the system under conditions of shock-loads of pollutants
such as organic compounds and ammonium (in case of a nitrifying MBR) and strong
fluctuation in environmental conditions such as temperature and salt concentration. The
questions that need to be addressed are (1) how does the MBR system respond to
changes in the aforementioned parameters with respect to biological performance and
membrane fouling, (2) what are the underlying mechanisms (flocculation, conversion
rates, recovery rates, etc.) and (3) what are possible solutions to counteract these
disturbances.
* Final approval of this project is in progress, and is expected in first half 2009.
19.2:Treatment of nanofiltration concentrates
Nanofiltration (NF) of the effluent of municipal wastewater treatment plants (WWTPs) is a promising technique as it results in a permeate that can be used as a source for
(industrial) process water, irrigation water or even for the production of drinking water. A
major bottleneck is the NF concentrate that somehow needs to be disposed of, which
accounts for the majority of the costs. However, NF concentrates also presents some
interesting opportunities because several compounds are present at enhanced
concentrations such as phosphorus, heavy metals, multivalent cations and organic
micropollutants. This may allow (1) then recovery of phosphorus for direct reuse as a
fertilizer, or for the production of higher grade phosphorus products, (2) easier removal of the concentrated heavy metals, (3) recirculation of multivalent cations to the biological
reactor stimulating flocculation of the sludge and (4) an improved and/or easier removal
of the organic micropollutants. Research aspects that need to be addressed include the development of an innovative WWTP flow scheme based on NF polishing and NF
concentrate treatment, technology selection for removal of heavy metals and organic
micropollutants, and the effect of NF concentrate recirculation on the primary functions of the WWTP, i.e. flocculation, COD removal and nitrogen removal.
19.3: Use on-line measurement of sludge filterability to control membrane operation in municipal MBRs**
In a previous study at Wetsus an improved flux-step method was developed to assess
the effects of membrane properties on membrane fouling in MBR systems for the
treatment of municipal wastewater. When applied on-line, this method can also be used to determine the optimum flux at which membranes are operated. In this manner energy can be saved which otherwise would be consumed to clean the membrane surface. This optimum flux not only depends on the properties of the membranes that are used, but in particular on the properties of the feed sludge. These properties vary in time caused by changes in wastewater quantity, wastewater composition and environmental conditions.
The research questions that need to be addresses are (1) what are typical variations in
sludge filterability, to be determined with the flux-step method, (2) how should membrane operation respond to this with a suitable control strategy and (3) are other (automated) options available to counteract (temporary) decreases in sludge filterability, f.e. the addition of additives such as powdered activated carbon.
** Final approval of this project is in progress, and is expected in first half 2009.
Energy
16.1: Reverse Electrodialysis: Hydrodynamics, fouling and scale up (location: TTIW Wetsus, Leeuwarden, NL)
Reversed Electro Dialysis (RED) is a new and potentially very attractive technology for the production of energy from the mixing of fresh and salt water. In RED, a concentrated salt solution and a less concentrated salt solution are brought into contact through an alternating series of anion exchange membranes (AEM) and cation exchange membranes (CEM) to generate energy.
To improve the process and to come to further development towards large scale application, this project includes two directions: 1) the reduction of fouling and boundary layer effects, improvement of hydrodynamics in the different compartments of the RED stack and 2) further scale up of the system by integrating all insights from current research. Of course improvements regarding fouling and hydrodynamics will directly be implemented at the system level.
16.2: Reverse Electrodialysis: Anion exchange membrane design and development (Location: University of Twente, Enschede, NL)
Reversed Electro Dialysis (RED) is a new and potentially very attractive technology for the production of energy from the mixing of fresh and salt water. In RED, a concentrated salt solution and a less concentrated salt solution are brought into contact through an alternating series of anion exchange membranes (AEM) and cation exchange membranes (CEM) to generate energy.
One of the key issues in the RED process are the ion exchange membranes. Currently available membranes, which are not specially developed for RED do not fulfill the requirements for application in RED. Further improvement towards economically viable power production requires the development of ion exchange membranes especially designed and developed for RED. A large community of polymer chemists deals with the development of cation-exchange membranes, but the research on anion exchange membranes is only limited. This project aims at developing such anion exchange membranes for application in RED
Sensoring Monitoring en Control
Safety and Environment
20.1: Raman spectroscopic sensing of bacteria in water using photonic crystal cavities
The goal of this project is to study and establish the physical mechanisms for sensing of bacteria in water based on a nanocavity in a two-dimensional photonic crystal (PhC).
Such a crystal is a periodic modulation of the dielectric constant, with a modulation period comparable to the wavelength of light. The nanocavity is an ultra-small resonator for electromagnetic waves inside the crystal, leading to a greatly enhanced and locally
concentrated optical field. This property can be applied for both optical trapping of
bacteria in water and their subsequent identification by Raman spectroscopy. These
functionalities of PhC cavities will lead to rapid on-line sensing and identification of
bacteria in water. One candidate will concentrate on Raman spectroscopy and
cooperating with PhD student working on trapping bacteria in the phtonioc crystal
cavities. We look for experimental physicists (M.Sc.) with a background in photonics or
solid-state physics and with affinity to bio-sensing. Experience in device fabrication is
helpful. The project is carried out at the Technical university Delft
Process monitoring and control
21.1: Projects in first half 2009.
Interaction Natural Systems
New water sources
22.1: Algorithms for hydrogeological parameter estimation from sensor data of
interaction with natural systems
Analysis of groundwater head fluctuations caused by natural stresses using timeseries
measurements. The interactions with natural systems constantly stress aquifers
everywhere for free, including the effects of rainfall, evaporation, river stages, and
groundwater pumping. Some of these stresses are the result of natural processes such as the hydrological cycle. Others are the result of human activities, such as groundwater pumping and canal stage fluctuations of managed systems. These stresses will all be grouped under the term natural stresses. Novel and powerful algorithms for the determination of hydrogeological parameters from time series measurements of observed groundwater heads and natural stresses will be developped. Application of the algorithms will constitute an accurate, comprehensive, efficient, and independent approach to obtain values for hydrogeological parameters at a large number of locations in the system.
The project is carried out at KWR Water Cycle Research Institute Nieuwegein.
22.2 and 22.3: Sustainable subsurface storage of water (22.2) and energy (22.3)
The project is carried out at KWR Water Cycle Research Institute Nieuwegein.
Your profile
Are you one of the top 3 performers in your class?
Are you enthusiastic about multidisciplinary research?
If the answer to both these questions is "yes" and you have (or will
have) a university degree in environmental technology, chemical engineering, physics or a related discipline you could be the ideal candidate for a PhD project in Wetsus.
Our offer
You will be working in a new, innovative, dynamic and future-directed research institute. You will be able to put your stamp on the development of new water technology. You will work in close collaboration with our industrial partners and also with top research groups at various universities.
Salary and working conditions are according to the collective labor agreement of the Cooperative Association of Dutch Universities (VSNU) for PhD students. PhD students are appointed by one of the cooperating universities but research is mainly conducted at Wetsus in Leeuwarden.
How to apply
By post or email. Send your application to Wetsus, attn. Recruitment Department, PO box 1113, 8900 CC Leeuwarden, The Netherlands. Emails to recruitment@wetsus.nl.
For further information about our PhD projects or about Wetsus you can contact Dr. G.J.W. Euverink.
Phone: +3158-2846200 or Email: gertjan.euverink@wetsus.nl.
