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

Hyun-Hee Jang,Gyu-Tae Seo,Dae-Woon Jeong

doi:10.3390/su10082929

Hyun-Hee Jang, Gyu-Tae Seo + Show 1 more

Open Access

https://doi.org/10.3390/su10082929

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Journal: Sustainability	Publication Date: Aug 17, 2018
Citations: 7	License type: CC BY 4.0

Affiliation: Changwon National University

Abstract

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.

Highlights

Waste soy sauce has a high chemical oxygen demand (COD)
The H2O2/O3 process were conducted under optimized conditions (H2O2/O3 ratio or 0.3, pH of 11.0, and applied O3 dose of 50 mg L−1), resulting in 51.6% color removal and 33.8% COD
This was primarily due to the high oxidation capability of O3 in the presence of the hydroxyl radicals introduced by the addition of H2O2

Summary

Introduction

Waste soy sauce has a high chemical oxygen demand (COD). It has an intense dark brown color due to the presence of caramel pigments and the occurrence of the Maillard reactions producing melanin or melanoidin [1,2]. Several processes are typically used to treat soy sauce wastewater including nitrification and denitrification, an activated sludge process, and biological treatments. It is difficult to control the stability of the soy sauce treatment processes because of annual fluctuations in the amount of waste soy sauce generated (47,914 tons were produced in 2016 compared to 37,232 tons in 2015 and 40,461 tons in 2014) [3]. It is necessary to decolorize waste soy sauce before it is discharged

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Results

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