Now proven at full-scale for new and upgrade projects, Ephyra was originally developed by Royal HaskoningDHV in cooperation with STOWA (Foundation for Applied Water Research), Waterboard Zuiderzeeland. (The project was co-financed with a contribution from the LIFE financial instrument of the European Union and with the Top Sector Energy subsidy from the Ministry of Economic Affairs.)

In comparison to a conventional sludge digestion installation, Ephyra provides:

  • Significantly greater breakdown (20-30% more) of organic substance for different sludge types

  • More sustainable energy in terms of increased biogas production

  • Less residual sludge

  • Much shorter payback time of only two to five years

  • Reliable operation at lower retention times to increase throughput by up to 50%

  • Shorter hydraulic retention time, resulting in smaller tank volume or increased capacity of existing tanks.

The process

Ephyra operates three or four digesters in series to achieve high-rate plug-flow anaerobic digestion. Controlled recirculation optimizes the conditions in each digester. A unique feature of Ephyra is that it enables digestion at a very short sludge retention time of just six to eight days. These short retention times result in increased reactor capacity and a reduced footprint for new build digesters. The system is operated by an advanced software platform, the Aquasuite® Ephrya Controller, which ensures stable operation of the Ephyra digesters and includes adjustable recirculation for optimum process performance.

The benefits

In comparison to a WWTP with a traditional sludge digestion installation, Ephyra operates at significantly lower retention times to increase throughput by up to 50%. As well as being suitable for optimizing new advanced digestion installations, the technology can be easily retrofitted, providing a no-build solution through reconfiguration for optimum performance. It can improve the performance of existing digesters and increase their capacity by 50-80%. Ephyra also uses less energy, and fewer chemicals while producing more biogas, making it a highly sustainable process. It also allows for the use of modern heating alternatives, such as heat pumps.

Operational benefits 

  • Expansion of sludge processing capacity by 50-80% without increasing reactor volume
  • Enhanced (20% to 30%) biogas production, due to a higher breakdown of sludge
  • Up to 20% improvement of the total energy consumption of the WWTP 
  • Smaller reactors required, due to a higher sludge concentration
  • Compact construction
  • Easy to retrofit and to operate
  • Improved conventional anaerobic digestion
  • Lower use of chemicals for sludge thickening
  • Better dewaterability of the digested sludge