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Hydraulic digester

for substrate with a high sediment content.

The AAT hydraulic digester produces more gas for almost zero operation costs.

In the AAT digester biogas is produced from dissolved and solid organic matter in an environment devoid of oxygen. By seperating the digester into a main and secondary compartment with an integrated substrate recycle a progress environment ideal for anerobic bacteria is created. Mixing of fees substrate and digester content is achieved by using the biogas generated within the digester.

Special design features provide dilution of foam and sediment layer as well as mechanical foam and sediment destruction. In series operation of main and secondary digester compartements prevents short circuiting and creates ideal conditions for degradation of recalcitrant components contained in the manure. Fleeding of the digester is within the upper part of the main digester compartment.The AAT system creates optimal process and mixing conditions for anerobic degradation of organic matter without moving parts placed in the digester and without an operator attendance result from the fact that no moving parts are located inside the digester.

Operating conditions

Maximum level difference between main-digestion-chamber and final treatment chamber.

The biogas head spaces of the main and secondary compartments are connected with a pipe including an automatic valve. By closing this valve biogas pressure increases in the main compartment and digester liquid is displaced into the secondary compartment creating a hydraulic gradient.

Mixing process

After a defined level difference is reached between the two compartments the automatic valve opens and the displaced liquid returns at a high flow rate (back flushing) to the main compartment.

State after mixing process

Displacement of digester liquid and back flushing between the compartments are arranged such that foam layer and sediment formation is prevented.


  • simple and robust construction
  • high treatement efficiency
  • very low operation- and maintenance costs
  • own ground sludge and floating sludge withdrawal
  • no moving parts inside the digester
  • higer gas production than with CSTR´s
  • up to 12% DS