Topic background - Access to safe drinking water is a human right. The main challenge is to deliver a product that is microbiologically and chemically safe. Although surface water is treated and disinfected before distribution, in drinking water distribution systems (DWDS) biofilms are existing and adhering to pipes and appendages. Biofilms are a source of bacterial contamination, negatively affecting drinking water quality and promoting material corrosion. It is therefore essential to monitor biofilm formation in real time, especially at early stages. Yet so far, detecting characteristics of early stages of microbial adhesion and biofilm growth remains challenging. Existing detection technologies rely on pressure drop changes, differential heat transfer, or differential turbidity, but none of these methods can reliably detect biofilms at an early stage. Changes are detected when it is already too late and the developed biofilm reaches maturation and detaches, or develops further becoming a shelter for pathogenic bacteria.

Research challenges - Novel approaches to build reliable biofilm growth sensors are needed. Sensors have to be able to detect biofilm formation at a much earlier stage than currently possible and offer a cost-effective solution to integrate in existing DWDS. The combination of chemosensors with conventional sensing technologies have already found successful application in biomedical and food sciences, in which the early detection of contamination and infections is paramount. This existing knowledge can guide the development of biofilm sensors for the drinking water industry, focusing on the minute, but molecularly detectable, changes in physical and chemical properties during bacterial adhesion and subsequent biofilm growth in DWDS. As example, targets on the pipes surface could be the formation of a conditioning layer, mechanistic changes due to primary bacterial adhesion, or specific molecules produced by microorganisms after secondary irreversible adhesion. The data collected could help in real-time monitoring of DWDS also via machine learning approaches.

Objectives and methodology - The aim of the project is to develop compact sensors to predict and monitor the formation of biofilms in selected hotspots throughout the DWDS. Such sensors will help drinking water industries to plan and apply cleaning strategies in time. Moreover, sensors may reveal the presence of pathogens growing in drinking water biofilms, such as Legionella through peculiar sensory fingerprints. Based on the mechanistic understanding of biofilm formation, the PhD candidate will identify target processes for sensing biofilm growth, e.g. mechanochemical sensing of adhesion or targeting of biofilm-specific chemicals. The device will be developed and tested on real biofilms (both pure and mixed microbial cultures), KIWA certified polymeric pipes, and purification membrane materials (e.g. UF/RO). Microscopy techniques (confocal laser scanning, scanning electron, and atomic force microscopy) will provide vital information on the stages of growth and allow to benchmark the effectiveness of the approach through stages of biofilm growth.

Students’ requirements:

• MSc degree in Chemistry, Biochemistry, Chemical Engineering or equivalent.
• Supplementary experience/studies in microbiology and electrical engineering are of added value.
• Ability to work in a multi-disciplinary, international team.
• Experience with lab work and setup building.
• Fluency in English, both written and spoken.

Salary and working conditions are according to the collective labor agreement of the Cooperative Association of Dutch Universities (VSNU) for PhD students. Per 1-7-2021, the salary for a PhD student as determined by the collective labor agreement are (in Euros before tax per year): €34076 (year 1), €39732 (year 2), €41832 (year 3) and €43554 (year 4). PhD students are appointed by one of the three cooperating universities, but research is conducted at the Wetsus laboratory in Leeuwarden.

Wetsus

Wetsus, European centre of excellence for sustainable water technology is a facilitating intermediary for trendsetting know-how development. Wetsus creates a unique environment and strategic cooperation for development of profitable and sustainable state of the art water treatment technology.