| This research focused on two issues in enhanced biological phosphorus removal (EBPR). The first issue encompassed the effect of glucose and butyrate on the microbiology of EBPR. The second issue addressed the influence of denitrification on EBPR. The first issue was investigated in SBRs system fed exclusively with glucose and butyrate. The second issue was investigated in batch tests using wastewater and different levels of acetate and propionate. In the case of first issue, the phosphorus removal was negatively affected by glucose and effective by using butyrate as a sole carbon source. Fluorescence In Situ Hybridization analysis revealed that Candidatus Accumulibacter phosphatis (CAP), a PAO was not selected in the glucose fed reactor. However, glucose selected for Microlunatus phosphovorus, a PAO, Candidatus Compatibacter phosphatis (CCP), a GAO and Micropruina glycogenica, a GAO. In the case of butyrate, CAP and Defluvicoccus -related tetrad-forming organisms, a GAO were selected in the reactor. However, butyrate did not select for CCP. The % RA of GAOs and % P removal did not show good correlation in the butyrate fed reactors, which might indicate the presence of other potential GAOs not targeted in the present study. In the case of issue two, the addition of supplemental carbon source at stoichiometric level improved the phosphorus uptake under aerobic conditions when nitrate was introduced during the anoxic period. However, the addition of carbon source at a higher than stoichiometric level did not improve phosphorus uptake under the aerobic condition when denitrification was incorporated during the anoxic period of EBPR process. The results of this research have direct implications on the design of treatment plants to remove phosphorus from wastewaters. |
