Bamberg WWTP, Germany




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Improvement of anaerobic digestion by ultrasound technology

Brief Snapshot of the Plant

  • Design Capacity: 230,000 PE
  • Actual Loading: 289,000 PE
  • Biological wastewater treatment: P-Elimination, Denitrification, Nitrification, Downstream P-precipitation by Fe3+, Secondary clarification
  • Sludge treatment: Primary sludge, Thickened waste activated sludge
  • Separate waste activated sludge thickening: Centifuge
  • Anaerobic sludge stabilisation: 3 Digester mesophilic (2.000 m, 3.000 m, 2.000 m), 18 days total hydraulic residence time
  • Degradation rate of volatile solids (VS): 34% of VS as per cent of dry solids (2003)
  • Digested sludge dewatering: Centrifuge
  • Sludge disposal: Incineration


Objective of the ultrasound disintegration system

Improvement of the anaerobic digestion to avoid the construction of a fourth digester (initial plan was the construction of a fourth digester (3,000m) to increase the hydraulic residence time from 18d to 25 d).


Preliminary trial of the ultrasound disintegration system

  • Test phase of four months  (May August 2002)
  • 30% of total TWAS flow were treated with 2 ULTRAWAVES US units 5 kW, operating 8 hours per day


Current Bamberg WWTP Sludge Flow Sheet


The Results and Benefits of Using Ultrasound

  • Intensification of sludge digestion
    - Reduction of the volatile solids (as per cent of DS) from 60% to 54%
  • Biogas production
    - 30% increase in biogas production
    - Elevated production of 2,270 m/d


Sludge feed and degradation of volatile solids



Total biogas production, biogas production 1st stage, biogas production of 2nd stage and fraction of biogas production 1st stage


Full-scale Installation

Two ULTRAWAVES US systems 5 kW are implemented since August 2004. In the beginning the recommended part (30% of the total TWAS flow) was treated at operating 8 hours per day. The thickening process was automated to operating 24 hours per day. Today the treated part amounts to 90% of the total TWAS flow.


Payback time

Based on early results of the full-scale operation the payback time is calculated with three years.The construction of a fourth digester could be avoided.


Installed Ultrasonic Reactors







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