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Ultrasound sludge disintegration of sewage sludge
used as internal carbon source for denitrification

Plant data

  • Design capacity: 40,000 PE
  • Actual loading : 54,000 PE
  • Biological sewage treatment:
    - P-elimination
    - alternating nitrification and denitrification at a sludge age of about 22 days
    - addition of methanol as external carbon source
    - secondary clarifier
  • Sludge treatment:
    - No primary sludge
    - thickened waste acktivated sludge
  • Separate waste activated sludge thickening: Belt press (operating 24 hours)
  • Anaerobic sludge stabilization: 2 digester, mesophilic, HRT: 40 days
  • Digested sludge dewatering: Centrifuge
  • Sludge disposal: Incineration


Objective of the ultrasound sludge disintegration

Use of disintegrated TWAS as an internal carbon source for the improvement of the denitrification process.


Preliminary trial of the ultrasound disintegration system

  • Test phase of four months (March 2006 – June 2006)
  • 50% of the total TWAS flow were treated with 1 ULTRAWAVES US unit 5 kW, operating 24 hours per day and feed in denitrification basin .

Scheme of sludge treatment WWTP Bünde



  • A significant reduction of the nitrogen concentration in the effluent (N < 3 mg/L)
  • Avoid of methanol as external carbon source
  • Waste activated sludge: Reduction of the sludge mass by 13%
  • Reduction of the organic fractions
  • Improvements in dewaterability of the sludge by 2%
  • No foaming or bulking sludge in the activated sludge tank.

Comparison of N-concentration in effluent before (2005) and during (2006) the US test, and Volume of sonicated sludge fed in denitrification basin.


Payback time

Immediately, because of reimbursement in form of reduced public sewage fees as a result of decreased nitrogen concentrations in the effluent of the plant and cost savings of avoided methanol.


Full-scale installation

In September 2006 the ULTRAWAVES ultrasound system was implemented on WWTP Bünde. And since is in operation 24 hours per day. WWTP Bünde bought a second ULTRAWAVES ultrasound system for the improvement of anaerobic digestion in 2007.


Installed ULTRAWAVES ultrasonic system with thickener at WWTP Bünde


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