Anaerobic Degradation of Polyhydroxyalkanoate Accumulated in Activated Sludge in the Absence of Anaerobic Digested Sludge

Anaerobic degradation of polyhydroxyalkanoate (PHA) accumulated in activated sludge was studied to estimate its stability during sludge thickening process. Activated sludge was incubated with acetate only or acetate and propionate under aerobic condition to allow microorganisms to accumulate PHA. Af...

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Bibliographic Details
Published in:Journal of Water and Environment Technology 2016, Vol.14(4), pp.236-246
Main Authors: Huda, S. M. Shamsul, Satoh, Hiroyasu, Mino, Takashi
Format: Article
Language:English
Subjects:
Acetates
Acetic acid
Activated sludge
Adenosine triphosphate
Aerobic conditions
Aerobic microorganisms
Anaerobic digestion
Anaerobic treatment
ATP
Biodegradable materials
Biodegradation
Degradation
Fatty acids
Fermentation
Incubation period
Microorganisms
polyhydroxyalkanoate
Polyhydroxyalkanoates
Polyhydroxyalkanoic acid
Propionic acid
Sludge
Sludge digestion
Sludge thickening
Stability
Substrates
Thickening
Volatile fatty acids
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Summary:Anaerobic degradation of polyhydroxyalkanoate (PHA) accumulated in activated sludge was studied to estimate its stability during sludge thickening process. Activated sludge was incubated with acetate only or acetate and propionate under aerobic condition to allow microorganisms to accumulate PHA. After the aerobic incubation, PHA-accumulated activated sludge was incubated anaerobically at 20°C, 30°C and 37°C. At 20°C for the whole incubation period of one week and at 30°C for initial couple of days, degradation of PHA was slow. These results suggested that PHA can stably be retained during sludge thickening. On the other hand, at 37°C, PHA was easily converted to volatile fatty acids (VFA) and was expected to be utilized as substrate for methane gas generation, if the thickened sludge is to be treated by anaerobic digestion. Accelerations of PHA degradation were observed during incubation, and as an explanation for it, formation of adenosine triphosphate in the fermentation of PHA to VFA was proposed. Some part of the PHA remained undegraded. As one of the keys to understand different degradation patterns of PHA, their location, whether they are inside or outside cells, was suggested.
ISSN:1348-2165
1348-2165
DOI:10.2965/jwet.15-037