Metagenomics deciphers the function of biochar in alleviating zinc ion stress during sulfur autotrophic...

Sulfur autotrophic denitrification (SAD) process has significant potential in treating low carbon/nitrogen ratio wastewater. However, the presence of zinc ions (Zn²⁺) adversely affects the denitrification performance. This study investigated the effect of biochar prepared at 300 °C (BC300) and 600 °C (BC600), as well as dosing strategy, on denitrification performance in the SAD process under Zn²⁺ inhibition. Firstly, BC600 had a higher maximum adsorption capacity for Zn²⁺ than BC300 in nitrogen-containing wastewater. Surface complexation was mainly adsorption mechanism. BC300 exhibited a greater ability in enhancing denitrification ability than BC600. The strategy of synchronous addition is more effective than pre-adsorption. Firstly, BC300 enhancing humic-like component secretion. BC300 enriched higher abundance of sulfur-oxidizing bacteria. More importantly, BC300 counteracted the negative effect of Zn²⁺ by enhancing glycan biosynthesis and metabolism, enriching functional genes, and increased the level of quorum sensing. The study presents a sustainable approach for maintaining denitrification performance under environmental stress.