The use of ultrasound to accelerate the anaerobic digestion of sewage sludge

The slow degradation rate of sewage sludge in anaerobic digesters is due to the rate limiting step of sludge hydrolysis. The effect of ultrasound pretreatment on sludge degradability was investigated using ultrasound at a frequency of 31 kHz and high acoustic intensities. Ultrasound treatment result...

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Bibliographic Details
Published in:SLUDGE RHEOLOGY AND SLUDGE MANAGEMENT 1997, Vol.36 (11), p.121-128
Main Authors: Tiehm, A., Nickel, K., Neis, U.
Format: Article
Language:English
Subjects:
anaerobic degradation
Anaerobic digestion
Anaerobic treatment
Applied sciences
Biogas
Biological and medical sciences
Biological treatment of sewage sludges and wastes
Biotechnology
Cavitation
Chemical oxygen demand
Degradability
Degradation
Disintegration
Environment and pollution
Exact sciences and technology
Fermentation
Fermenters
Fundamental and applied biological sciences. Psychology
Industrial applications and implications. Economical aspects
Other industrial wastes. Sewage sludge
Pollution
Pretreatment
Raw sludge
Residence time
Sewage
Sewage sludge
sewage sludge treatment
Size reduction
Sludge
Sludge digestion
Sludge solids
Sludge treatment
Ultrasonic imaging
Ultrasound
ultrasound disintegration
Volatile solids
Wastes
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Summary:The slow degradation rate of sewage sludge in anaerobic digesters is due to the rate limiting step of sludge hydrolysis. The effect of ultrasound pretreatment on sludge degradability was investigated using ultrasound at a frequency of 31 kHz and high acoustic intensities. Ultrasound treatment resulted in raw sludge disintegration as was demonstrated by increase of Chemical Oxygen Demand in the sludge supernatant and size reduction of sludge solids. Semi-continuous fermentation experiments with disintegrated and untreated sludge were done for four months on a half-technical scale. One fermenter was operated as a control with a conventional residence time of 22 days. Four fetmenters were operated with disintegrated sludge and residence limes of 22, 16, 12, and 8 days, respectively. In the fermenters operated with identical residence times of 22 days reduction of volatile solids was 45.896 for untreated sludge and 50.3% for disintegrated sludge. The fermentation of disintegrated sludge was stable even at the shortest residence time of 8 days with biogas production 2.2 times that of the control fermenter. Due to ultrasound disintegration a better degradability of raw sludge was achieved that permitted a substantial increase in throughout.
ISSN:0273-1223
1996-9732
DOI:10.1016/S0273-1223(97)00676-8