More than twenty years from its introduction, new treatment plants using the Aerobic Granular Sludge technology continue to be installed worldwide thus multiplying the sustainability impact of this valuable solution. Following last year's announcement of the 100th Nereda waste treatment plant built in Florida (US), there are currently 115 Nereda projects and 65 plants operating in 21 countries on six continents, from Brazil to the United States and from South Africa to Sweden. Why does its use continue to grow?

Waste to Worth: greener, smaller and more efficient

Aerobic Granular Sludge (AGS), also known by its trade name Nereda, purifies wastewater that is produced by industries or residents in urban and rural areas. This biological treatment process uses up to 50% less electricity and little or no chemicals compared to conventional sewage treatment plants.

What makes this treatment method so special is that the bacteria grow in granules instead of flocs, which settle much faster: easily reaching settlement rates of 1 m / 4 minutes, which is considerably quicker than the 1 m / 60 minutes achieved with conventional treatment methods. 

Not only does granular sludge exhibit excellent settling properties, but each single granule can also host all organic treatment processes at the same time. This is because the pellets contain oxygen-rich, oxygen-poor and anoxic zones, enabling different types of bacteria to get to work simultaneously. This marked a significant departure from traditional water treatment techniques, which required different spaces for different processes. As a result, all the energy-guzzling pumps and other mechanical equipment needed to move the organisms from one space to another were promptly eliminated. This, in turn, has given rise to greener, simpler plants. In fact, Nereda plants can be up to four times smaller and 50% more energy-efficient, while requiring no or far fewer chemicals.

Furthermore, the use of this new technology goes now beyond sustainable treatment alone: further research by the Mark van Loosdrecht's group into how the bacteria attach themselves to each other, led to discovering a new raw material (kaumera) extracted from the excess sludge produced in the Nereda treatment process, which is now making its way to the market as a new biopolymer for the sustainable construction, agriculture and materials industries. 
 

Multiple prize winner

Hailed in 2020 as the ‘Best water technology breakthrough of the past decade’ by the Global Water Intelligence (GWI), this ground breaking innovation by TU Delft’s researchers and online instructors Mark van Loosdrecht (chair professor in Environmental Biotechnology) and Merle de Kreuk (professor Environmental Technology) has won public recognition several times.

It was awarded, amongst others, the Stockholm Water Prize 2018, the Wastewater Project of the Year - Global Water Awards 2019 and the De Vernufteling prize in 2021, which is considered the most prestigious award for Dutch engineering firms.

Last year, van Loosdrecht received the 2022 Novozymes Prize for his pioneering work in copying and reusing nature’s mechanisms in wastewater treatment and resource recovery. The Novozymes Prize, awarded by the Novo Nordisk Foundation, recognises outstanding research or technology contributions that benefit the development of biotechnological science for innovative solutions. De Kreuk and van Loosdrecht were also awarded the Simon Stevin Prize – the Dutch highest recognition for research with societal impact – in 2007 and 2013 respectively.
 

Online Course

The inventors of this technology also developed an online course for professionals in the water industry – engineers or consultants, technologists, innovators, policy makers and anyone interested in gaining in-depth knowledge of AGS. The course shows how the technology works and how to implement it. Participants get to hear directly from users of AGS and even take a VR-tour of a functioning treatment plant. Read more

“The water and wastewater industry will continue to evolve with new processes. I see the role of a water and wastewater operator involving more instrumentation maintenance and the ability to interpret process faults and find solutions to correct them. This short course has improved my understanding of the processes and has provided me with further skills to undertake my role into the future.” – Andrew Watson, Senior Treatment Plant Operator

Based on articles by TU Delft News and the TU Delft Extension School for Continuing Education.