OXxOFF regulates aeration full-automatically and reduces energy consumption by 25% without performance reductions

Experience from a long range of manual measuring in process tanks at various purification plants indicates that optimal aeration in tanks can be very difficult to achieve.

Basically, one is often left with a long list of unanswered questions that can only be answered by carrying out continuous measuring:

  • Should the aerators be exchanged when oxygen transfer gradually deteriorates?
  • Is the aeration level too high or can this particular level lead to improved oxygen and energy consumption utilisation?
  • Does aeration ensure optimal nitrogen purification?
  • Is a high ammonium concentration or a low oxygen concentration caused by a high load level or surface-active matters?
  • Does an unchanged pressure from the compressor indicate a good level of efficiency?

Stjernholm OXxOFF continuously collects all parameter-relevant data so that regulation of compressors, valves and biological processes is as optimal as possible.

Data is continuously supplied either through a wireless or cable connection. Based on both real time data and historical data, the following information is calculated and presented graphically:

  • oxygen transfer efficiency (OTE)
  • standard oxygen transfer efficiency (OTE) adjusted for oxygen content in water phase (SOTE)
  • air flow Nm3/air/m2/hour
  • oxygen transfer, g oxygen/m2/hour

Stjernholm OXxOFF is manufactured in our own factory. Electronic components are supplied by well-known suppliers and the system is constructed within a moulded housing made of glass fibre. The OXxOFF system is designed to float at the surface but taking into consideration any service and inspection tasks, the unit is hung in a special service fitting which is installed on the tank wall. In this way, the OXxOFF unit can be lifted and lowered from the tank, turned 360 degrees and locked in any position.


When you cooperate with us, you know that we are focusing on delivering a solution to you that adds value to your facility.


  • Documented reduction of 25% of bottom aeration without performance reductions. That means fewer hours of operation, less wear, longer component service life and less service hours.
  • Continuous data from the OXxOFF unit ensures that oxygen is only supplied to the extent needed, keeping energy consumption at a minimum.
  • Savings of 15-30% which have resulted in payback times of 2.4 to 6.8 years.


  • Too much aeration increases the risk of nitrous oxide emission which affects the climate 310 times more than CO2.
  • The automatic 24/7 OXxOFF surveillance system ensures that decreasing efficiency levels are identified immediately in order to avoid environmental impacts.
  • Aeration fans use a lot of energy but significant energy savings are created through energy optimisation, meaning lower levels of CO2 emission.


  • A comparison of operational parameters based on data collection facilitates an evaluation of the best time to carry out a service.
  • No maintenance apart from cleaning the sensors.
  • Measuring various parameters provides better process insights.

Thomas Fleischer Christiansen

92 15 22 15

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Stjernholm A/S

Stjernholm A/S
Langelandsvej 4A
8940 Randers SV
CVR: 28 88 49 66

+45 70 20 25 05


Stjernholm US Inc

Post Oak Blvd.
Suite 1910
Houston, TX 77056 US

+1 346 388 2791