The Nereda installation at wwtp Epe, the Netherlands, uses 21,2 kWh/p.e.150 eliminated.year, whereas an average conventional wwtp in the Netherlands uses 37,5 kWh.

For fully loaded conditions a potential energy consumption as low as 16,3 kWh has been calculated.

This is one of the important outcomes of a study, conducted by the water research institute Stowa, on the first full scale Nereda installation (53.000 p.e., 1500 m3/d) that is in full operation since January 2012.

Fast settling granular biomass
Nereda is a sequencing batch reactor (SBR) technology developed by Royal HaskoningDHV, in close cooperation with Delft University of Technology, Stowa and the Dutch water boards. It features a unique aerobic granular biomass of grain forming bacteria that quickly settles, compared to the flack shaped bacteria of classic aerobic activated sludge technology.

As a result Nereda does not require large settlement tanks. Not only reduces this the footprint of the installation, it also eliminates a pumping station for feeding back the sludge to the aeration tank. Other energy saving elements are the blowers (52%) and the mechanical sludge thickening (12%).

The study showed also that effluent complies with the very stringent nitrogen and phosphorous requirements of 5 mgN/l and 0,3 mgP/l.

Further improvements
"We are very pleased with this result", says Bert van Vreeswijk of the water board Waterschap Vallei en Veluwe who operates wwtp Epe. "We did not know exactly what to expect when we started. The installation has proved to be much better for the environment and requires less energy. This makes a big difference in our operational costs."

New Nereda plants
Since the commissioning of the Nereda plant at wwtp Epe in 2012, two other Dutch water boards selected the Nereda technology. Both wwtp Gamerswolde and wwtp Vroomshoop operate a Nereda plant.

Currently there are 10 plants in operation and more than 20 projects under development and construction throughout the world including in the Netherlands, Portugal, South Africa, Brazil and Poland.

Nereda is a new waste water treatment technology featuring a new generation aerobic granular activated sludge technology.

圖1 好氧顆粒污泥與活性污泥的沉淀特性比較（沉淀5min)

圖2 活性污泥絮體與顆粒污泥結構組成的不同

The technology is invented by Delft University of Technology and developed in a unique public-private partnership between Delft University of Technology, Applied research institute STOWA, the Dutch water boards and Royal HaskoningDHV.

There are currently about 12 international full-scale Nereda® installations in operation for the treatment of industrial and municipal wastewater, and the number of references is growing fast, as shown in table 1.

The Nereda® process operates intermittently, with the fill and decant phase occurring simultaneously. Due to good settling capacity of the aerobic granules, the process does not require mechanical decanters to ensure low solids in the effluent. The key advantages of Nereda® are summarized as follows:

- Cost-effective
• Compact and uncomplicated tank design
• Less mechanical equipment
• No separate clarifiers
• Lower capital expenditures
• Lower Operation & Maintenance costs
• No or minimal chemicals
• Lower energy consumption
- Easy to operate
• Easy plant operation
• Robust and reliable process performance
• Integrated AquaSuite® Nereda® Controller process controller
• Fully automated plant operation
• Remotely controlled or by a central control room
• Remote support capabilities by process specialists

- Sustainable
• Remarkably high effluent purity
• No or minimal use of chemicals
• Significantly lower energy consumption
• Less construction materials required
• As little as a quarter of the land area required
• More efficient nutrient removal
• Lower operational and embedded carbon footprint

The new Nereda plant at wwtp Garmerwolde was officially commissioned on 8 October 2013. It is the second full scale plant in the Netherlands, the first being the Nereda plant at wwtp Epe.

The installation was constructed by GMB Civiel and Imtech Infra. The total cost of the project was 20 million euro.

Largest Nereda installation to date
Secretary-general Siebe Riedstra of the Ministry of Infrastructure and Environment officially opened the new installation.

On the occasion Global director water products René Noppeney of Royal HaskoningDHV congratulated the water board with the milestone: "It is the largest Nereda installation to date. A beautiful project, which we can all be proud of".

The total cost of the new Nereda installation was 20 million euro.

Additional treatment capacity
The new Nereda system is added to the existing conventional treatment plant and gives an additional capacity for the waste water of 140,000 people with less energy and without chemicals .

Wwtp Garmerwolde is now in full compliance with current statutory requirements for purification and discharge of wastewater . The total purification capacity for the whole wwtp now amounts to 375,000 people

Two other Dutch Nereda plants are under construction at wwtp Vroomshoop and wwtp Dinxperlo. Both are expected to be commissioned next year.

Nereda in a nutshell
Nereda is a distinguished, innovative technology to treat wastewater using less energy and chemicals and a smaller footprint than conventional treatment plants. Nereda purifies wastewater with the unique characteristics of aerobic granular sludge. The purifying bacteria in creating Nereda compact granules with excellent settling properties.

The success of Nereda is its high water treatment capability in combination with significantly lower investment and operational costs, a very small physical footprint (up to a factor 4 smaller) and high energy savings (20-30%).