Microbial Ecology of Autothermal Thermophilic Aerobic Digesters

Systematic and Applied Microbiology 34 (2011) 127–138

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Microbial ecology of autothermal thermophilic aerobic digester
(ATAD) systems for treating waste activated sludge
David Hayes, Leonard Izzard 1 , Robert Seviour ∗
Biotechnology Research Centre, La Trobe University, Bendigo, VIC 3552, Australia

a r t i c l e

i n f o

Article history:
Received 3 June 2010
Keywords:
Waste activated sludge
ATAD
Thermus thermophilus
FISH/MAR
DGGE

a b s t r a c t
Despite their widespread use, our understanding of the microbial ecology of the autothermal thermophilic aerobic digesters (ATAD) used to dispose of sludge from wastewater treatment plants is poor. Applying both culture-dependent and molecular methods to two ATAD systems in Victoria, Australia treating different wastewaters revealed that their communities were highly specialized. Denaturing gradient gel electrophoresis (DGGE) profiling suggested differences in their population compositions and both changed over time. However, both showed low level biodiversity, and contained several novel bacterial populations. 16S rRNA clone library data and FISH analyses showed that Thermus thermophilus dominated both communities and that of a third ATAD plant in NSW (more than 90% of the total bacterial biovolume in repeated samples taken from each of the three ATAD plants). Culture-dependent methods also showed
Geobacillus spp. were present in both Victorian communities. Nevertheless, the ecophysiology of these populations and their putative roles in sludge digestion remain unclear. FISH/microautoradiographic studies did not provide conclusive data elucidating which substrate/s T. thermophilus might utilize in the
ATAD reactors.
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Introduction
Most activated sludge plants generate large volumes of secondary

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