Treatment of landfill leachate by an ultrasonic-three-dimensional electrode coupled reaction system

Advanced oxidation technology has a very good treatment effect on refractory wastewater. This paper takes the leachate from a closed municipal solid waste landfill in alpine regions as the research object. Conventional, unmodified, and low-cost electrode materials were used to construct an ultrasonic-three-dimensional electrode coupled reaction system to explore the effectiveness of this technology on refractory wastewater in alpine region. The results showed that under the optimal treatment conditions, the COD removal rate and UV254 removal rate were 98.15% and 96.32% after reacting for 120 min. This performance significantly surpassed those of single ultrasound (COD and UV254 removal efficiencies were 53.13% and 60.74%, respectively) and single three-dimensional electrode (COD and UV254 removal efficiencies were 73.84% and 87.57%, respectively). Kinetic analysis shows that the reaction process presents the characteristics of a pseudo-first-order reaction in two stages. The calculated synergistic index (SI₁ = 1.26, SI₂ = 9) demonstrate significant synergy effect in the coupled system. The free radicals in the coupled reaction system were detected by methylene blue-spectrophotometry, the results showed that [·OH] can reach up to 9.8×10-6 M. The steady-state free radical generation rates of the two kinetic reaction stages were 9.7×10⁻⁹ M s⁻¹ and 2.67×10⁻⁸ M s⁻¹, respectively. This study confirms that the ultrasound-three-dimensional electrode coupled reaction system has the advantages of efficient treatment of leachate, and simple operation, and low cost, and no addition chemicals, and provides feasible solutions for engineering applications of refractory wastewater treatment in alpine regions.