Removal behavior of biological nitrogen and phosphorus, and prediction of microbial community composition with its function, in an anaerobic-anoxic system from weak sewage

An easier way of understanding the BNR system was proposed from the study on substrate, nutrient removal tendency, microbial community and its metabolic function by applying the municipal settled sewage. During the anaerobic period, the phosphorus release rate per VFACOD was varied depending on the phosphorus content in the sludge. When the phosphorus content in the sludge was 6% VSS, according to influent VFACOD, the phosphorus release rate and PHA production were 0.35 gPO₄P/gVFACOD and 1.0 gPHA/gVFACOD, respectively. The NO₃N requirement for the phosphorus uptake as an electron acceptor was about 0.5 gNO₃N/gPO₄P_uptake, based on the proposed equation with PHA, biomass production, and the concentration of phosphorus release/uptake. Bacterial-community analysis of the sludge, as determined by FISH and 16S rDNA characterization FISH, revealed that the beta-subclass proteobacteria were the most abundant group (27.9% of the proteobacteria-specific probe EUB338), and it was likely that representatives of the beta-subclass played key roles in activated sludge. The next dominant group found was the gamma-proteobacteria (15.4% of probe EUB338). 16S rDNA clone library analysis showed that the members of β- and γ-proteobacteria were also the most abundant groups, and 21.5% (PN2 and PN4) and 15.4% (PN1 and PN5) of total clones were the genera of denitrifying bacteria and PAO, respectively. Prediction of the microbial community composition was made with phosphorus content (Pv, % P/VSS) in wasted sludge and profiles of COD, PHA, PO₄P, and NO₃N in an anaerobic-anoxic SBR unit. Generally, the predicted microbial composition based upon metabolic function, i.e., as measured by stoichiometry, is fairly similar to that measured by the unculturable dependent method. In this study, a proposal was made on the microbial community composition that was more easily approached to analyze the reactor behavior.