Chemistry

Enhanced biological phosphorus removal
(EBPR) from wastewater relies on the preferential selection
of active polyphosphate-accumulating organisms (PAO) in
the underlying bacterial community continuum. Efficient
management of the bacterial resource requires understanding
of population dynamics as well as availability of bioanalytical
methods for rapid and regular assessment of relative
abundances of active PAOs and their glycogen-accumulating
competitors (GAO). A systems approach was adopted here
toward the investigation of multilevel correlations from the
EBPR bioprocess to the bacterial community, metabolic, and
enzymatic levels. Two anaerobic-aerobic sequencing-batch
reactors were operated to enrich activated sludge in PAOs and
GAOs affiliating with “Candidati Accumulibacter and Competibacter
phosphates”, respectively. Bacterial selection was
optimized by dynamic control of the organic loading rate and
the anaerobic contact time. The distinct core bacteriomes
mainly comprised populations related to the classes
Betaproteobacteria, Cytophagia, and Chloroflexi in the PAO
enrichment and of Gammaproteobacteria, Alphaproteobacteria,
Acidobacteria, and Sphingobacteria in the GAO enrichment. An
anaerobic metabolic batch test based on electrical conductivity
evolution and a polyphosphatase enzymatic assay were developed for rapid and low-cost assessment of the active
PAO fraction and dephosphatation potential of activated
sludge. Linear correlations were obtained between the PAO
fraction, biomass specific rate of conductivity increase under
anaerobic conditions, and polyphosphate-hydrolyzing activity
of PAO/GAO mixtures. The correlations between PAO/
GAO ratios, metabolic activities, and conductivity profiles
were confirmed by simulations with a mathematical model
developed in the aqueous geochemistry software PHREEQC.