Active Return Sludge Process (ARP-Process)


About Author

EnviDan is a full service environmental company offering professional solutions within the drinking water, wastewater, biogas and environment.

See partner

EnviDan supplies innovative solutions to the challenges regarding overload and bypass of existing plants.

We can successfully implement the ARP-process at any WWTP to increase the organic or hydraulic capacity with up to 60% and thereby avoid or limit an expansion.

When using ARP, a part of the biological process is moved from the original activated sludge plant to a volume, including only the return sludge, with varying nitrification and denitrification and with a concentration of sludge that is significantly higher than in the activated sludge plant. Depending on the needs and the plant configuration the ARP process can be used for increasing the hydraulic and/or organic capacity of the existing WWTP.

This way we can improve the volume utilization considerably. The ARP-process can also be used to a faster treatment of highly concentrated nitrogen sources, as for example reject water from sludge digestion, where the high sludge concentration in the ARP tank is used for a more effective nitrogen removal.

Use EnviDan to implement the ARP-process because:

  • We have solid experience with ARP
  • We have references supporting our expertise
  • We are visionary and innovative thinking
  • We have a client centric approach
  • We will together with you find the right solution for your plant
  • We are a trustworthy company with a solid financial foundation
  • We have developed the process

ARP is the right choice because:

  • ARP can be used for sludge minimarization
  • ARP does not require the construction of new volumes
  • ARP ensures faster removal of highly concentrated nitrogen sources
  • ARP significantly improves volume utilization.
  • The ARP solution is profitable over short time
  • ARP can be used for biological P-removal

Did you like this solution?

  • 14 Solutions
  • 1 News
Primary contact
Gitte Nabe Kristensen
+45 27 15 01 07


Looking for our logo?

Find it in the State of Green Toolbox together with loads of materials to help you promote Denmark’s green solutions abroad.
Visit toolbox