Synergistic Treatment of Typical Pollutants in Waste Leachate by Micronano Bubbles Coupled with UV-Activated KHSO5

Abstract

Landfill leachate is a complex, high-concentration organic wastewater that poses challenges for stable and efficient degradation using conventional treatment methods. Advanced oxidation technologies based on sulfate radicals ( SO 4 − · ) have garnered significant attention due to their strong oxidizing capacity and long half-life. This study developed a micro-nano bubble (MB) coupled with ultraviolet (UV)-activated potassium metabisulfite ( KHSO 5 ) system ( MBs / UV / KHSO 5 ). Simulated leachate (with hexanoic acid as the target compound) and ultrafiltration effluent from actual landfill leachate were used as treatment subjects. to investigate the impact of varying reaction conditions on chemical oxygen demand (COD) removal efficiency. Radical quenching experiments and electron paramagnetic resonance spectroscopy were employed to characterize reactive species and elucidate the reaction mechanism. Results demonstrated that the MBs / UV / KHSO 5 system exhibited significant synergistic degradation of simulated hexanoic acid wastewater, achieving a COD removal rate of 99.25% after 180 min of reaction, with a synergistic index of 43.76. Optimal process conditions were determined as a KHSO 5 dosage of 6    g · L − 1 , an MBs gas flow rate of 30    mL · min − 1 , a UV power of 10 W, and an initial pH of 4, achieving a total organic carbon (TOC) removal rate of 73.15%. Radical identification experiments confirmed that sulfate radicals ( SO 4 − · ) and hydroxyl radicals ( · OH ) were the dominant active species in the system. The introduction of micro-nano bubbles significantly enhanced radical yield by improving mass transfer, providing physical activation, and enriching reactants. In practical leachate validation experiments, the MBs / UV / KHSO 5 system also demonstrated excellent treatment performance. At a KHSO 5 dosage of 12    g · L − 1 , the COD removal rate reached 84.56% after 180 min of reaction. This study elucidates the synergistic mechanism of the MBs / UV / KHSO 5 system and validates its feasibility in practical wastewater treatment, providing an efficient and viable technological solution for advanced treatment of landfill leachate.