Electrochemical oxidation combined with reagents of O₃, H₂O₂ and FeCl₂ was conducted in this study to treat the wastewater from wet fermentation of Yunnan arabica coffee. In addition, the effect of oxidants on the efficiency of wastewater treatment, the binding capacities of the oxidants to proteins, the degradation of organic pollutants in the wastewater, and the formation of oxidized organic components were systematically investigated. The results reveal better performance of O₃-combined electrochemical oxidation (63.60% COD removal efficiency) for treatment of organic species in coffee wastewater than that of the electrochemical processes with H₂O₂ (47.70% COD removal efficiency) and FeCl₂ (34.48% COD removal efficiency). The synergy of the electrooxidation/O₃ process (0.0133 A/cm², 20 mg/L–2 L/min) could not only raise the pH value (3.70~4.20, 5.14~5.44) of the wastewater and reduce the NaOH dosage of 2.80~3.7 g/L, but also effectively degrade the proteins, lipids, unsaturated hydrocarbons, and carbohydrates, with a total chemical oxygen demand (COD) value above 20,000 mg/L. After the oxidation treatment, some organic components remained in the wastewater, including 31.94% of S-containing organics, lignin, condensed aromatic compounds, and aromatic structural compounds, which are difficult to be utilized by microorganisms. In addition, it was found that OH⁻ could bind to proteins and affect the required amount of NaOH addition, whereas the protein binding energy of O₃ is higher than that of H₂O₂, indicating a stronger ability of O₃ to oxidize proteins. Therefore, the combination of O₃ and electrochemical oxidation can be considered as an effective method to treat organic pollutants in the wastewater from wet fermentation of Yunnan arabica coffee.

High-concentration refractory coffee wastewater containing about 2,000 mg/L of biotoxic lactic acid is treated by microwave technology. At a microwave power of 900 W, a large amount of activated carbon (AC) reduces the number of hot spots. After microwave radiation, the lactic acid concentration drops to 200 mg/L, with a removal rate of 90%. CaO promotes the process. In the microwave-AC-CaO method, “hotspots” on AC generate free radicals. The effects of microwaves degrade lactic acid into CO₂ and H₂O. The microwave-AC-CaO method can rapidly degrade lactic acid. The degradation rate of lactic acid can be further improved by adding transition-metal oxides to modify AC.