Performance evaluation and microbial community of a pilot-scale denitrifying phosphorus removal system with low-strength wastewater under different additional carbon sources

Low-organic matter content wastewater is one of the main reasons for the poor nitrogen and phosphorus removal in full-scale WWTPs, and additional carbon sources are one of the efficient ways to solve the problem. The study explored the performance and microbial community of a pilot-scale DPR system with low-strength wastewater under different additional carbon sources. Results showed that highly efficient DPR (78%) and endogenous denitrification (NED=39%) were successfully achieved when the mixed carbon source (acetate: propionate=1:1) was fed, and the average PO43--P and TIN removal efficiency were 89.4% and 69.2%, respectively. Based on the mass balance and dominant functional bacteria analysis, DPAOs (3.27%) were the significant contributions to nutrient removal with a high abundance, and certain DGAOs (1.73%) participated. Ammonia assimilation efficiency was significantly enhanced when acetate was used, and the ratio of TIN removal through assimilation (NASS) was 50%. Principal Components Analysis (PCA) indicated that Proteobacteria (27.73%) and Bacteroidota (8.44%) were mainly responsible for ammonia assimilation. Glucose was favorable for heterotrophic denitrification (NHD) but detrimental to the DPR process, and DGAOs (2.01%) were not the main reason for the failure of DPR.