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.

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