Performance evaluation, enzymatic activity change and metagenomic analysis of sequencing batch reactor under divalent...

Divalent zinc (Zn²⁺) are widely detected in domestic and industrial wastewater, and it is essential to evaluate the effect of Zn²⁺ on wastewater biological treatment process due to its bio-toxicity. In this study, the nitrogen removal rates and their corresponding enzymatic activities of sequencing batch reactor decreased with the increase of Zn²⁺ concentration. The Zn²⁺ accumulation in activated sludge caused significant antioxidant response, and the reactive oxygen species (ROS) production and antioxidant enzymatic activities were positively correlated with Zn²⁺ concentration. The presence of Zn²⁺ inhibited the metabolic pathways related to energy production and electron transport. The abundance decreases of nitrification and denitrification functional genes led to the deterioration of nitrogen removal performance under Zn²⁺ stress. The correlation analysis between functional gene modules and microbial genera revealed that Zoogloea had obvious Zn²⁺ resistance. This study can provide the insights into the influencing mechanism of Zn²⁺ on the biological nitrogen removal process.