[Comparison of biological phosphorus removal between different systems using O2, NO3(-) and NO2(-) as electron...

By parallel operation of three phosphorus removal systems (SBR) using different electron acceptors of O2, NO3(-) and NO2(-), process characteristics and inherent competition mechanism of microorganisms were discussed. Although NO2(-) had no direct inhibition on anoxic phosphorus uptake after the DPAO cultivation, system performance was still much lower than that with NO3(-) as electron acceptor. And it ultimately resulted from the washout of the group of DPAO (DPAO5) that lacked the ability to denitrify NO2(-) and the enhanced GAO growth in the system. Being the efficient electron acceptor, NO3(-) or O2 supplying SBRs removed phosphorus smoothly and comparatively, in viewpoint of stiochoimetry and constitution of functional bacteria. In all three test systems, mass of GAO was present to exhaust limited organics with PAO population. Moreover, total PAO could be divided into 6 distinct groups, i.e., PO, PN, Pn, PNn, PON and PONn, based on the abilities of utilizing different electron acceptors. And facultative PAO of PON and PONn were found as the main contributors for the phosphorus removal. The higher ratio they accounted in sludge, the more capacity the system possessed to remove phosphorus, i.e., SBR0 > SBRn5 > SBRn3.