Abstract
A sequencing batch reactor fed mainly by acetate was operated to perform enhanced biological phosphorus removal (EBPR). A short-term pH shock from 7.0 to 6.0 led to a complete loss of phosphate-removing capability and a drastic change of microbial communities. 16S rRNA gene pyrosequencing showed that large proportions of glycogen accumulating organisms (GAOs) (accounted for 16% of bacteria) bloomed, including Candidatus Competibacter phosphatis and Defluviicoccus-related tetrad-forming organism, causing deteriorated EBPR performance. The EBPR performance recovered with time and the dominant Candidatus Accumulibacter (Accumulibacter) clades shifted from Clade IIC to IIA while GAOs populations shrank significantly. The Accumulibacter population variation provided a good opportunity for genome binning using a bi-dimensional coverage method, and a genome of Accumulibacter Clade IIC was well retrieved with over 90% completeness. Comparative genomic analysis demonstrated that Accumulibacter clades had different abilities in nitrogen metabolism and carbon fixation, which shed light on enriching different Accumulibacter populations selectively.
Highlights
Enhanced biological phosphorus removal (EBPR) is a cost-effective and environmental friendly technology to promote excess phosphorus (P) removal from wastewater
Comparing the genomic information of CAP IIC HKU-2 and CAP IIA UW-1, we found that CAP IIA UW-1 had genes required for carbon fixation, the key genes required for the Calvin cycle, ribulose-1,5-bisphosphate carboxylase/oxygenase and ribulose-phosphate 3-epimerase (Rpe) appeared to be absent from CAP IIC HKU-2
This study revealed the population dynamics of Polyphosphate-accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) involved in the EBPR process
Summary
Enhanced biological phosphorus removal (EBPR) is a cost-effective and environmental friendly technology to promote excess phosphorus (P) removal from wastewater. Among the PAOs, a population of microorganisms named Candidatus Accumulibacter phosphatis ( referred to Accumulibacter) was readily enriched with acetate as the primary carbon source in sequencing batch reactors (SBRs) [1] and thought to be responsible for EBPR in both lab-scale and full-scale plants [2, 3]. The Accumulibacter lineage can be subdivided into five clades in Type I and seven clades in Type II based on the phylogenetic distance of the gene encoding polyphosphate kinase (ppk1) [4,5,6]. Another population of putative PAOs, members of genus Tetrasphaera which can be phylogenetically divided into.
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