The operating temperature affects the efficiency and pathogenic risk of wastewater treatment enhanced by slurry

Abstract

The insufficient availability of carbon sources in low carbon source wastewater has consistently hampered the nitrogen removal efficiency. This study explored the potential of using anaerobic digested slurry supernatant as an additional carbon source and examined the cost-effective temperature range. The results demonstrated that wastewater treatment within the temperature range of 28 °C to 38 °C could meet the discharge standards set by wastewater treatment plants. However, at 38 °C, the nitrogen-to-carbon consumption ratio decreased to 0.18 g N/g COD. Mechanistic analysis revealed that both excessively high and low temperatures reduced the diversity of microbial communities and influenced the composition of the microbial community through environmental selective pressures. Thauera, Acidovorax, Syntrophomonas, and Acidaminobacter were identified as the dominant genera for nitrogen removal at the temperature of 38 °C, 33 °C, 28 °C, and 23 °C, respectively. Furthermore, high temperature enhanced nitrogen removal performance by promoting microbial activity, microbial transmembrane substance transport process, and the abundance of key genes (HK, pgi1, pfkB, narG, narH, narI) at 38 °C. Importantly, factor score analysis confirmed that the risk of microbial pathogenicity was relatively low at 28 °C. This work provides valuable insights into the optimal temperature parameters and regulatory mechanisms for wastewater treatment systems utilizing slurry as a carbon source. It provides innovative ideas for the clean and safe development of low carbon source wastewater treatment technologies.