Understanding the factors that shapes the microbial community assembly in activated
sludge wastewater treatment processes provide a conceptual foundation for improving
process performance. The aim of this study was to compare two major theories
(deterministic theory and neutral theory) regarding the assembly of microorganisms in
activated sludge: Six lab-scale activated sludge sequencing batch reactors were
inoculated with activated sludge collected from three different sources (domestic,
industrial, and sugar industry WWTP). Additionally, two reactors were seeded with
equal proportion of sludge from the three WWTPs. Duplicate reactors were used for
each sludge source (i.e. domestic, industrial, sugar and mix). Reactors were operated in
parallel for 11 weeks under identical conditions. Bacterial diversity and community
structure in the eight SBRs were assessed by 16S rRNA gene pyrosequencing. The 16S
rRNA gene sequences were analyzed using taxonomic and clustering analysis and by
measuring diversity indices (Shannon-weaver and Chao1 indices).
Cluster analysis revealed that the microbial community structure was dynamic
and that replicate reactors evolved differently. Also the microbial community structure in
the SBRs seeded with a different sludge did not converge after 11 weeks of operation
under identical conditions. These results suggest that history and distribution of taxa in the source inoculum were stronger regulating factors in shaping bacterial community
structure than environmental factors. This supports the neutral theory which states that
the assembly of the local microbial community from the metacommunity is random and
is regulated by the size and diversity of the metacommunity. Furthermore, sludge
performance, measured by COD and ammonia removal, confirmed that broad-scale
functions (e.g. COD removal) are not influenced by dynamics in the microbial
composition, while specific functions (e.g. nitrification) are more susceptible to these
changes.
| Date of Award | Jul 2011 |
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| Original language | English (US) |
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| Awarding Institution | - Physical Sciences and Engineering
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| Supervisor | Pascal Saikaly (Supervisor) |
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