Advanced Oxidation Processes and Nanofiltration to Reduce the Color and Chemical Oxygen Demand of Waste Soy Sauce

Resumen

Currently, the ozone (O₃) oxidation efficiency in the treatment of waste soy sauce provides 34.2% color removal and a 27.4% reduction in its chemical oxygen demand (COD). To improve the O₃ oxidation efficiency, hydrogen peroxide (H₂O₂) is used to cause a H₂O₂/O₃ process. In H₂O₂/O₃ process experiments, a previously optimized pH of 11 and applied O₃ dose of 50 mg L⁻¹ were used and the H₂O₂/O₃ ratio was varied between 0.1 and 0.9 in intervals of 0.2. The results show that an H₂O₂/O₃ ratio of 0.3 results in the highest efficiencies in terms of color removal (51.6%) and COD reduction (33.8%). Nanofiltration (NF) was used to pretreat the waste soy sauce to improve color removal and COD reduction. The results showed that NF with an NE-70 membrane results in 80.8% color removal and 79.6% COD reduction. Finally, the combination of NF and H₂O₂/O₃ process resulted in the best treatment efficiency: 98.1% color removal and 98.2% COD reduction. Thus, NF & H₂O₂/O₃ process can be considered as one of the best treatment methods for waste soy sauce, which requires high intrinsic color removal and COD reduction efficiencies.