Enhanced nitrogen removal via SNAD-IFAS process treating THP-AD liquor: microbial community and co-metabolism mechanism

Abstract

The anaerobic digester liquor after thermal hydrolysis pretreatment (THP-AD liquor) is a highly hazardous wastewater containing high concentration of ammonium. Herein, a novel two-stage tandem-type simultaneous partial nitrification, anammox, and denitrification-integrated fixed biofilm activated sludge (SNAD-IFAS) hybrid process was successfully constructed for treating THP-AD liquor. The average removal efficiencies of ammonium, total nitrogen, and chemical oxygen demand in the stable phase were 94.0%, 89.9%, and 66.8%, respectively. The specific anammox activity of the two SNAD-IFAS reactors was 68.72 and 42.15 mg N/(g VSS·h), respectively. Candidatus Kuenenia and Candidatus Brocadia (13.49–20.94%) were the main genus of anammox bacteria. Although the relative abundance of Nitrosomonas (0.21–1.67%) was very lower than other bacteria, Nitrosomonas was a central genus in the co-occurrence network. Moreover, the genes involved in pyridine, dioxin, protein, and carbohydrate degradation were remarkably enriched in SNAD-IFAS, indicating the co-metabolism mechanism of refractory organic degradation. This study provides a low energy consumption, high efficiency, and low-carbon technology for treating THP-AD liquor.