Urban Waste Water

Ultrasonic treatment of waterworks sludge: development and testing of a semi-industrial process technology

The successful testing of one process for dilute suspensions and suspensions of high solids content respectively has been completed. The treatment of waterworks sludge in static ultrasonic fields resulted in improved sedimentation and the more rapid clarification of the fluid phase.

 

Summary

For the processing of residues from drinking water treatment, ultrasonic technology has a number of advantages over chemical or physical treatment methods:

  1. The process involves no chemicals, thereby reducing quantities of sludge,
  2. Treatment is completed over a short timescale,
  3. No error-prone chemical dosing technology is involved.

In consequence, the treatment of waterworks sludge in static ultrasonic fields is associated with the improved sedimentation of solids and the more rapid clarification of the fluid phase.

This project involved the laboratory development and testing of two processes, which were then successfully transposed to a semi-industrial scale:

  • Dilute suspensions were treated in a continuous throughput installation at frequencies of 3.3 MHz.
  • Sludge of high solids content was concentrated using ultrasonic transducers operating at a frequency of 40 kHz in a batch-processing system.

Both model suspensions (bentonite, yeast/water) and industrial suspensions were selected for treatment.

Results:

  • At a throughput of 150 l/h, the dry solids content of filter backwash water has been reduced by 94%.
  • Within 30 minutes, flocculated sludge from surface water treatment was reduced to 25% of its initial volume. For the pilot-scale project, the calculated throughput in batch-sequence processing is up to 400 l/h.

Results obtained from the ultrasonic treatment of further types of actual waste water have confirmed the broad scope for the application of the system in various areas of process technology.

More Project Informations

Project title:  Ultrasonic treatment of waterworks sludge: development and testing of a semi-industrial process technology

Project number:  02WT9678/9

Project period:  01.01.1997 - 30.11.1998

Project region:  Germany (Berlin)

Project contact:

Herr Prof. Dr. Jekel

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Source: German National Library of Science and Technology Hannover (TIB)