Coupling effects of aureomycin and zinc ion on nitrification process and nitrification enzymes during the biological...

Aureomycin and Zinc ion (Zn²⁺) are common antibiotics and heavy metals that exist in livestock wastewater. The coupling effects of Aureomycin and Zn²⁺ on the nitrification process and nitrification function enzymes are crucial for controlling nitrogen removal in livestock wastewater. However, rare studies were focused on the coupling effects of Aureomycin and Zn²⁺ on nitrification. This study employed a direct equipartition ray method to investigate the coupling effects of Aureomycin and Zn²⁺ on nitrification. The results suggested three different ratios of Aureomycin and Zn²⁺ affected nitrification performance differently. Ratio 1 and Ratio 2 exhibited a promotion effect with low concentrations and an inhibition effect with high concentrations on nitrification performance. The critical concentration for Ratio 1 and Ratio 2 were 5.00 mg L^-1 and 1.90 mg L^-1, respectively. Ratio 3 exhibited both time-dependent and concentration-dependent inhibitory effects on nitrification performance. The maximum inhibitory efficiency on nitrification performance was 90.0%, with a concentration of 34.5 mg L^-1 at 96.0 h. The effects of binary mixture on nitrogen removal performance were attributed to the effects of binary mixture on nitrite oxidase activity. The qualitative evaluation of the concentration addition model and independent action model indicated Aureomycin and Zn²⁺ showed a synergistic effect with strong concentration-dependent and time-dependent in the whole concentration area. The synergistic effect of Aureomycin and Zn²⁺ on nitrite oxidase activity mainly depended on the concentration of Aureomycin. This study offers new insights into the effects of antibiotics and heavy metals on the biological nitrogen removal process.