Conditioning of waterworks sludge by ultrasonic treatment

Ultrasonic has been used for the successful conditioning of sludges from various sources and containing various concentrations of solids. This treatment has a number of advantages over conventional processes: reduced consumption of energy and chemicals, with a simultaneous reduction in the quantity of sludge.

In a number of drinking water treatment processes, separated water-bearing materials in the form of sludge-bearing waters or sludges are produced during treatment.  The water content of these residues must be reduced before recovery or disposal.  Since the concentration or dehydration of these wastes is often problematic, expensive pre-treatment by physical or chemical conditioning will be required.

This project involved the investigation of ultrasonic technology as an alternative method for the treatment of waterworks sludge.  To this end, experimental investigations have been undertaken in a batch processing and continuous processing system.


Results:

• Suspensions have been conditioned by treatment in a stationary ultrasonic field.  This has improved the effectiveness of the subsequent solid-liquid separation.
• Sludge-bearing filter backwash water can be effectively treated at frequencies of 2 – 3 MHz.  Up to 96% efficiency may be achieved.
• Frequencies of 40 – 300 kHz are suitable for the thickening of flocculator sludges.  Volume reductions of up to 75% can be achieved.
• Results obtained will allow this process to be implemented on a semi-industrial scale.

Conclusion:

Ultrasonic treatment represents a chemical-free and low-residue alternative to conventional conditioning processes.


Source Of Supply: The final report (call number F 97 B 947, in German) can be borrowed from Technische Informationsbibliothek (TIB) Hannover, Welfengarten 1B, 30167 Hannover.



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