Unraveling the effects of inorganic non-metallic ions in landfill leachate on ozonation

This study investigated the complex influences of inorganic anions (Cl^-, SO₄^2-) and ammonia nitrogen (NH₄⁺-N) on the ozonation process for landfill leachate treatment. Our findings revealed that chloride ions (Cl^-) exhibited a significant inhibitory effect on the degradation of humic substances, as evidenced by a 14.1 % decrease in the Fluorescence Regional Integration (FRI) reduction rate compared to the control. Conversely, sulfate ions (SO₄^2-) were observed to have no significant impact on the process. The role of NH₄⁺ was found to be distinctly concentration dependent. High concentrations of NH₄⁺-N (1000–1300 mg/L) negatively impacted ozonation efficiency, with the COD removal rate decreasing by up to 24.1 %. In contrast, low concentrations of NH₄⁺-N (100–500 mg/L) demonstrably promoted the degradation process. Specifically, at an optimal concentration of 500 mg/L, the COD removal rate increased from 61.5 % (control) to 67.3 %. This promotional effect is attributed to the maintenance of alkaline pH conditions favorable for ·OH radical formation. Understanding these quantitatively defined, intricate processes is crucial for optimizing ozone-based technologies to overcome ionic inhibition in complex wastewater.