Ahrensburg WWTP, Germany




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Improvement of anaerobic digestion by ultrasound technology

Brief snapshot of the plant

  • Design capacity: 50,000 PE
  • Actual loading: 38.000 PE
  • Biological wastewater treatment :
    - Street 1: High-performance activated sludge process (C-decomposition), Slurry tank, Trickling filter (nitrification)
    - Street 2: Anaerobic tank (P-elimination), Anoxic tank (upstream denitrification), Aerobic tank (C-decomposition, nitrification), Slurry tank
    - Street 1 + Street 2: Fixed bed reactor (denitrification), P precipitation by Fe(3+), Filtration
  • Sludge treatment: no primary sludge, thickened waste activated sludge, Co-substrate
  • Separate waste activated sludge thickening: filter band (operating 24 hours)
  • Anaerobic sludge stabilisation: 1 digester (mesophilic, 4,000 m), 40 days hydraulic residence time
  • Degradation rate of volatile solids (VS): 40% of VS as per cent of dry solids ( before the preliminary trial)
  • Digested sludge dewatering: Centrifuge
  • Sludge disposal: Incineration

Objective of the ultrasound disintegration system

- Improvement of volatile solids destruction
- Increase of biogas production
- Reduction of polymer consumption in sludge dewatering


Preliminary trial of the ultrasound disintegration system

  • Test phase of eight months (November 2007 June 2008)
  • 50% of the total TWAS flow were treated with 1 ULTRAWAVES US unit 5kW, operating 24 hours per day


Scheme of sludge treatment on WWTP Ahrensburg


  • Intensification of sludge digestion
    - Degradation of the volatile solids were improved from 40% to 46%
  • Production of biogas
    - 20% increase in biogas production
    - Elevated production of 276m/d
  • Reduction of polymer consumption for sludge dewatering
    - from 10 to 9 kg polymer / t TR


Comparison total gas and specific gas production before, during and after the US test


Payback time

Based on these results, the payback time for the ultrasound installation is calculated with 3 years.


Full-scale Installation

In May 2009 the ULTRAWAVES ultrasonic reactor was implemented on WWTP Ahrensburg. And since is in operation 24 hours per day.


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