[Effect of Carbon Sources on the Accumulation of Endogenous Polymers and Denitritation in the O/A-F/F Mode]

To accumulate endogenous polymers during the aerobic phase, the aerobic/anoxic-feast/famine (O/A-F/F) selection mode can be used. It can also be used in situ for endogenous denitrification by activated sludge during the anoxic phase. To further explore the effect of carbon sources on the activated sludge accumulation of endogenous polymers and endogenous denitrification, this study used acetic and glucose as the main carbon sources to investigate the accumulation of endogenous polymers, endogenous denitrification, and the structure and function of enriched activated sludge. The results show that acetic (Ac-SBR) and glucose (Gc-SBR) as the main carbon source systems achieved a 40 mg·L^-1 nitrate removal by endogenous denitrification when the influent chemical oxygen demand (COD) was~500 mg·L^-1 in the O/A-F/F selection mode. Both the Ac-SBR and Gc-SBR achieved partial denitrification, but the nitrite accumulation of the Ac-SBR was higher than that of the Gc-SBR. Acetic is favorable for the accumulation of endogenous polyhydroxyalkanoate (PHA); PHA drives the endogenous denitrification. The yield of PHA was 0.52 and the denitrification rate (DNR) was 9.65 mg·(L·h)^-1. The Gc-SBR system achieved the simultaneous accumulation of PHA and glycogen (Gly). The yield of Gly was higher than that of PHA and the DNR driven by Gly was 4.35 mg·(L·h)^-1. The Gly was the main driving force to achieve endogenous denitrification and contributed to 77% of the total nitrogen removal. The 16S rRNA high-throughput sequencing analysis of activated sludge flora shows that the class of β-Proteobacteria in the Proteobacteria was dominant, with an abundance of 40.56% in the Ac-SBR. However, the abundance of β-Proteobacteria was only 18.05% in the Gc-SBR. The class of α-Proteobacteria contributes to glycogen accumulation in the Gc-SBR. The PHA can be accumulated by β-Proteobacteria, Unclassified Bacteroidetes, and Lgnavibacteria in the Ac-SBR.