Nereda is the wastewater treatment technology that purifies water using the unique features of aerobic granular biomass.

Nereda is sustainable and cost-effective: it requires a quarter of the area of conventional activated sludge installations and the process can reduce up to 50% on energy-costs. The award-winning technology was invented by the Delft University of Technology in the Netherlands and developed in a unique public-private partnership between the University, the Dutch Foundation for Applied Water Research (STOWA), the Dutch Water Authorities and Royal HaskoningDHV.

How does it work?

Biomass in Nereda develops as fast settling aerobic granular sludge.

These granules have excellent settling properties and therefore Nereda does not require a separate time-consuming decant phase like conventional SBR's. Further, all the biological treatment processes take place simultaneously in the granules, requiring only one tank.

Due to the distinctive characteristics of aerobic granular biomass, Nereda technology uses an optimised SBR cycle:

  1. Simultaneous influent feed and effluent discharge.
  2. Simultaneous biological removal of organic, nitrogen and phosphorous components.
  3. Fast settling phase, in this phase the biomass is separated from the effluent and Nereda is ready for a new cycle.

Since the effluent is pushed out of the tank, discharge of the effluent does not require moving decanters.



Depending on the wastewater flow and characteristics, a Nereda plant comprises multiple modular reactors (often 3) or a combination of a feed buffer tank plus one or two reactors.


Retrofit CAS or SBR

Since the detailed configuration of Nereda is quite flexible, the technology can often be used to convert existing conventional CAS or SBR plants into a Nereda. Often the technology enables the use of approximately a two times higher biomass concentration, with outstanding biomass settling characteristics. As result of a retrofit to Nereda, the biological and/or hydraulic capacity of existing plants will be significantly increased and/or the effluent quality will be considerably improved.


Hybrid capacity extension

In a hybrid application, a new Nereda plant is fed with only part of the plants raw wastewater while the remaining part is treated by the existing conventional treatment system. An important additional advantage of such a hybrid extension is that by feeding of granular surplus sludge from the Nereda into the conventional activated sludge reactors will augment the activated sludge. By this inoculation process, the sludge characteristics and settling performance of the activated sludge will improve, resulting in improved sludge settling characteristics, increased capacity and enhanced biological nutrient removal.