Environmental biotechnologist Professor Mark Van Loosdrecht is the winner of this year's Lee Kuan Yew Water Prize for helping to integrate the use of Anammox in wastewater treatment. Here he catches up with WWi magazine on the development of the technology and his predictions on future water reuse.
Firstly Prof van Loosdrecht, congratulations on winning the 2012 Lee Kuan Yew Prize. Tell us how your process – Anammox – came about?
In the sixties and seventies, people regularly reported that ammonium was mysteriously disappearing from treatment systems. It was Arnold Mulder in Delft who did a similar observation, but then decided not just to report it but also to investigate it. And it was microbiologist Prof. Kuenen who dared to postulate that this was a completely unknown microbial process.
It took many years to indeed prove that Anammox bacteria exist, mainly because of their slow growth rate (which is also how they escaped attention before). Knowing these bacteria exist, we realised that this is a great opportunity for a paradigm shift in wastewater treatment: the shift from energy consumption to energy conversion.
So from the mid-nineties onwards, we have been working on concepts to introduce Anammox bacteria in wastewater treatment. Currently, we are investigating the potential for municipal wastewater on side streams, industrial wastewater and in pilot plants.
How did this compare to existing wastewater treatment processes at the time?
Normally, ammonium is removed by oxidising it first to nitrate (at the expense of aeration energy), and then nitrate to nitrogen gas (at the expense of organic carbon, which otherwise could have been converted into biogas). In the Anammox process, ammonium is directly converted in nitrogen gas, requiring no organic carbon and minimal use of energy. The microbiological paradigm shift was that bacteria do not need oxygen to oxydise ammonium.
Last year's Lee Kuan Yew Prize winner, Dr James Barnard, was also awarded for his work in wastewater treatment and reuse. Surely it's not a coincidence this theme has been awarded two years in a row? There has been a lot of attention directed towards better and more efficient nutrient removal and recovery systems in the past decade (partly driven by need for water reuse), and this gave room for breakthrough innovations.
The Anammox process has been touted as helping to reduce overall energy consumption, chemical usage and carbon of a wastewater treatment plant. How much per m3 can the process reduce the cost of wastewater treatment/reuse?
This is a difficult question. These costs partly depend on local situations, for example, local energy taxation. Let's say that the Anammox process will require similar costs but make the overall treatment of wastewater more sustainable (less consumptions of resources and lower climate footprint). In many cases, 10% - 50% cost reduction can also be obtained depending on local conditions.
Do you expect PUB to roll out this process commercially following a pilot trial? The potential we have seen and the fact that temperatures are higher in Singapore (compared to e.g. Netherlands) are beneficial for the process that I expect will be introduced in Singapore. Side streams from sludge digestors can be a very short term process, but the full wastewater treatment process will take a bit longer since process development has to take place and will involve very large infrastructural works.
