Nereda: a new technique for water purification
Nereda is the innovative and award-winning wastewater treatment technology. The Nereda treatment process purifies water using the unique features of aerobic granular biomass.
The Nereda method is sustainable, biological and cost-effective.
The idea was to let micro organisms clump together – that digest waste under oxygen-rich conditions – in letting grains so it will sink faster and easier in a water treatment plant. Dr.ir. Merle de Kreuk examined how they could develop a ‘aerobic granular sludge.’ He called the process ‘Nereda’, an eponymous first practice, operational since 2012 in the Netherlands.
This is how it works
During the wastewater treatment, the Nereda bacteria transforms waste into harmless substances. Nitrification organisms like ammonium are transformed into nitrate.
Other, ‘heterotrophic’ organisms degenerate waste products into organics, for example with the aid of oxygen or nitrate.
In a standard water treatment reactor these bacteria will transform into flakes. But these flakes are difficult to separate from the purified water. In traditional installations, this happens in the big round sedimentation bassins.
With grains the process is much faster (up to 30% energy saving during the process) and in much smaller tanks, which results in a space saving of 70%.
4 main benefits
Nereda results in construction costs that are lower than for conventional technology, which is understandable, because the plant footprint is up to a factor 4 smaller, tank volumes are smaller and less equipment will be required. The investment savings are however very site specific and thus will vary per project, which makes it difficult to give a generalized answer. The investment savings are significant.
- Small footprint
- Compared to conventional biological nutrient removal activated sludge processes with clarifiers, savings on footprint can be up to 75%. Compared to conventional SBR’s saving on footprint is approx. 50% (because of the optimized cycle and the higher biomass concentration (MLSS).
- Compared to conventional activated sludge systems Nereda is significantly more energy efficient as it requires a lower amount of mechanical equipment. The energy savings are often in the range of 20-30%. On top of that, additional energy savings are expected as a result of a higher than normal aeration efficiency.
Nereda has proved in operation to satisfy the most stringent purification requirements. Thanks to the nature of the technology, plant operation is easy and process performance robust. Every Nereda plant is equipped with anAquaSuite Nereda Controller, a smart, integrated process controller. This ensures fully automated plant operation, reliable performance and ease-of-operation. It even enables unmanned or remote control – for example – from our central control room
the effluent can be reused. The biological process ensures a strong reduction in organics, harmful bacteria and if targeted: nutrients as well. Similar to conventional treatment the effluent will contain some suspended solids, which can be easily removed if so required. Advantage is that relative easily filtration seems to be possible, but also membrane filtration (like in MBR) would be an available option. For example the effluent from the Gansbaai plant is reused for greening and irrigation after pond sedimentation.
WWTP performance results March-May 2012
The wastewater temperature ranged from 14oC to 16oC.
|Parameter||Influent (mg/l)|| Average Effluent
|BOD||333||< 2,0||> 99,4%|
|N-Total||< 4,0||> 94,7%|
|Suspended Solids||341||<5,0||> 98,5%|
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