An unexpected journey

This story starts in the year 2012. I had been working in the hydraulics department of DHV for 13 years, I had done some really nice projects, had been a project leader, and had decided I would never want to be a boss or do project management. I basically had no specific plans for the rest of my career. I found myself in a meeting with Paul Janssen, who at the time was head of the process engineers, talking about an offer for the Dutch foundation for water education. The idea was to build a “flight simulator” for wastewater treatment plants - in the modern era we would call that a digital twin - and since I had already built something similar for the drinking water industry, we were discussing how to approach this proposal. The simulator was meant as a training tool in the HTAZ course. While working on the proposal, Paul told me that this course was actually mandatory for people in his department. He added that if I would follow this course, it would mean a possible ticket for me into his department. I was not completely sure if I was offended - I graduated from the Wageningen University as a wastewater engineer - or grateful for the opportunity given. I decided on the latter.

This course was given by water professionals from both Dutch water authorities and consultancy companies. One of the teachers was my colleague Helle van der Roest. His enthusiasm and endless energy made him an excellent teacher and I enjoyed his teachings. I graduated top of the class and, more importantly, impressed Helle. So, at the graduation party he asked me to join the “Nereda core team”, a new team he was building with five or six experts from within the company to accelerate the Nereda^® development. I had been involved in the development of Nereda^® from the sideline from about 2006, since scale-up of the new technology was for some part a hydraulic question and I was in the hydraulics department. I had already been involved with measuring settling characteristics of the aerobic granular sludge in pilot reactors and the hydraulic design of the first full-scale reactor in Epe. But that did not make me a logical choice for this team, at least in my opinion, but Helle thought differently. So, I dropped all my projects and joined the team.

In the first year Helle continued his role as a teacher, and I learned a great deal on aerobic granular sludge. Slowly my role in the team started to change, while I was searching for the fundamentals of this new technology. The first version of the granulation model - which can be found in chapter On the mechanisms of this dissertation - was born early 2014. In this year I met Mario Pronk, who was finalizing his PhD research on aerobic granular sludge. We found that we think alike and immediately started working together, both being explorers of new knowledge. While I was diving more and more into research, the inevitable question started to pop up: why not start your own PhD research. For almost two years my standard answer was: I am busy as it is, I already have a job. Meanwhile I had started to go to the university one day per week. DHV had become Royal HaskoningDHV and the new management had decided we would not have our own desk anymore, so I thought it was a good idea to partially move to the university. I was going there more often anyhow, because I was supervising some students doing their master thesis and I was having regular meetings at the university. Mario started to be more and more convincing about starting my own PhD research…

In November 2016 there was a formal state visit by the Belgian government to the Netherlands. In the signing ceremony we would sign a collaboration agreement between Ghent University, TU Delft and Royal HaskoningDHV. I was carpooling with René Noppeney - at that time the director responsible for Nereda^® - and I told him about this idea of starting my PhD research. He was really enthusiastic and supportive about the idea. So, the next day I planned a meeting with Mark van Loosdrecht to discuss the possibilities.

It took about half a year to sort out all the contractual issues and in May 2017 I finally started my research. The idea was I would spend 1 day per week on the PhD research and for the rest I would continue my job as a researcher at RHDHV. That basically meant not much changed for me, because I had already been going to Delft once a week for more than a year and my job was already about research full-time. The challenge was in finding topics suitable for publication. My main topic was rather vague, because I had a long list of Nereda^® related research topics I was working on and there was not much consistency in that list. So, in the beginning I always answered “Nereda” when people asked what my topic was, which most of the time led to a somewhat uncertain “OK”. Later I changed it into “scale-up of AGS technology”, which apparently was a much more acceptable research topic, although in reality it also did not quite cover it.

In the first year I discovered a few things about myself and the organization I was working for. I was very happy with my role as a PhD researcher. In retrospect that was primarily because I was intellectually challenged by the people in Environmental Biotechnology - the group of Mark van Loosdrecht. Not only Mark, but also my room mates Viktor, Jure and Morez played an important role in that. I also found that I had been quite naive about how the company would deal with my PhD research. There was a clear conflict between the commercial interest of the company and my own ambition to play in the Champions League. I needed to carefully pick my topics to be able to publish them. In my first year the TU Delft also organized the IWA Biofilm conference, and I was asked by Merle de Kreuk to be one of the keynote speakers. I think that was the first time it really felt I was part of the Champions League…

After this first year I just continued. The research topics kept popping up and I think only a small part found its path into this dissertation. While I am writing this preface, I still have not decided on the title - I think that is inherent to the path I took. Still, I am very proud of this book and that I finalized this journey I started, contributing to the deeper understanding of aerobic granular sludge technology.