Sewage Sludge

Autoheated Thermophilic Aerobic Digestion ATAD

Class A Biosolids – a valuable fertilizer

FUCHS Autoheated Thermophilic Aerobic Digestion (ATAD) does not only stabilize the sludge, it also disinfects it. The product is a valuable fertilizer meeting highest international quality standards (Class A according to regulation US EPA 503). Municipal as well as industrial sludge and manure may be treated in the ATAD.

With the aerobic thermophilic digestion at temperatures around 55 °C (131 °F) reaction times can be short. As a result the foot print and investment costs are low. Our sturdy machines and the stable process lead to reliable operation with simple handling.

Thanks to continuous development our ATAD concept could be further improved. The FUCHS ATAD became more efficient by increasing the oxygen input at the beginning of the process and by using the latest odor treatment technology.

The first FUCHS ATAD plant started up in 1977 and is still in operation. More than 80 ATAD plants followed. Take your benefit from our experience in sludge treatment.



Autoheated Thermophilic Aerobic Digestion (ATAD)

  • Approved process technology through 30 years of experience 
  • Simultaneous stabilization and disinfection
  • Short retention times of ~9 days
  • Small footprint
  • Low investment costs
  • Excellent process stability and reliability
  • Flexible operation
  • Easy extension of capacity
  • The product: Class A Biosolids
  • Meets or exceeds international biosolids standards (US EPA 503)
  • Many municipal and industrial installations worldwide

Case Studies

Autoheated Thermophilic Aerobic Digestion
A case study from Poland


Aerobic sludge treatment at thermophilic temperatures needs sturdy and efficient equipment. FUCHS Aerators and Foam Controllers are specially designed for this purpose and have proven their excellent proficiency for many decades now – even under extreme circumstances. As a principle we only use high-quality components. Our machines have no bearings or seals in the immersed part. All submerged components are made of stainless steel or plastics. 


An effective ATAD Process involves aspirators which provide excellent aeration and mixing of the sludge. A FUCHS Spiral Aerator is mounted tangentially through the reactor wall and provides a circular flow pattern, which is overlapped by a vertical loop.

For circular reactors with a larger diameter an additional centrally-mounted FUCHS CENTROX Aerator is required. It generates a vertical loop, which prevents settling in the middle of the tank.

The result of operating both aerators is horizontal as well as vertical mixing of the complete reactor contents with simultaneous aeration.


The aeration of sludge generates foam. Dense foam layers build up rapidly on the surface. They improve oxygen transfer and thus contribute positively to the process performance. However, the height of the layer must be kept under control. Effective foam control is an essential element of ATAD technology. For this purpose FUCHS has developed a special foam cutter.