Effect of ultrasonic pretreatment on the semicontinuous anaerobic digestion of waste activated sludge with increasing loading rates

Anaerobic digestion (AD) is the most widely used method to stabilize and recover energy from waste activated sludge (WAS). However, AD of sludge results in a low biogas yield. Ultrasonic pretreatment (USp) is the most effective sludge disintegration technology and has elicited interest to increase t...

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Bibliographic Details
Published in:International biodeterioration & biodegradation 2018-05, Vol.130, p.32-39
Main Authors: Lizama, Alfredo Córdova, Figueiras, Cristian Carrera, Pedreguera, Alejandro Zepeda, Ruiz Espinoza, Juan Enrique
Format: Article
Language:English
Subjects:
Activated sludge
Anaerobic digestion
Biodegradability
Biodegradation
Biogas
Biogas production
Bioreactors
Disintegration
Groundwater pollution
Load distribution
Loading rate
Organic loading
Organic loading rate
Pretreatment
Raw sludge
Semicontinuous anaerobic digestion
Sludge
Sludge digestion
Ultrasonic pretreatment
Ultrasonic technology
Waste activated sludge
Waste to energy
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Summary:Anaerobic digestion (AD) is the most widely used method to stabilize and recover energy from waste activated sludge (WAS). However, AD of sludge results in a low biogas yield. Ultrasonic pretreatment (USp) is the most effective sludge disintegration technology and has elicited interest to increase the biodegradability and improve the efficiency of the AD. This study investigated the influence of USp on the semicontinuous AD of WAS as a strategy to increase its performance. During an experiment lasting 90 days, 0.8-L digesters were semicontinuously fed under different conditions: raw sludge and sonicated at 15000, 25000 and 35000 kJ/kg TS (total solids); and an increase of the organic loading rate (OLR) from 1 to 3 kgVS/m3·d, for 30 days each. The maximum biogas rate (0.218 L/d) was reached at 25000 kJ/kg TS and 3 kgVS/m3·d. The highest VS removal efficiency (23.7%) was observed at the highest USp and the lowest OLR. The reactors fed with raw sludge had a lower performance compared to the sonicated WAS in terms of VS reduction and biogas production. In contrast, the USp allowed the bioreactors to be operated at a high OLR (3 kgVS/m3·d) without inhibition. Finally, a kinetic analysis of accumulated biogas was performed. •The effects of USp on the semicontinuous AD of sludge were studied.•Different specific energies and organic loading rates were evaluated.•Ultrasonic pretreatment allowed reactors to operate at a high OLR (3 kgVS/m3·d).•The maximum biogas rate (0.218 L/d) was reached at 25000 kJ/kg TS and 3 kgVS/m3·d.
ISSN:0964-8305
1879-0208
DOI:10.1016/j.ibiod.2018.03.013