Treatment of wastewater from food waste hydrothermal carbonization via Fenton oxidization combined activated carbon adsorption

Hydrothermal carbonization (HTC) of food waste can produce hydrochar for further utilization as high-quality fuel or carbon materials, but the by-product of liquid effluent, named HTC wastewater, has a high chemical oxygen demand (COD) content and other organic pollutants. This study focused on the feasibility of Fenton oxidation combined with activated carbon (AC) to reduce COD in HTC wastewater. The effects of different parameters including pH, dosage of hydrogen peroxide, molar ratio of Fe²⁺/H₂O₂, and reaction time were tested and discussed. Eventually, through the optimized Fenton oxidation (pH = 3, H₂O₂ dosage = 1.5 mol/L, Fe²⁺/H₂O₂ = 1:15, reaction time = 60 min) combined optimized AC adsorption process (AC dosage = 30 g/L), the COD value reduced from 42,000 mg/L to 3075 mg/L, indicating a COD removal efficiency of 92.7% and a color removal ratio of 91.9%, respectively. The comparison of GC/MS (gas chromatography mass spectrometer) and FTIR (Fourier transform infrared spectrometer) of liquid residual from different treatment methods also indicated that the types of organic substances in HTC wastewater were significantly reduced through Fenton oxidation and AC adsorption.