Treatment of Efluents by Protein Precipitation in Industrial Production of Soy Sauces

Abstract

The main raw material of oriental sauces is soy, in addition other organic additives, microorganisms and enzymes for fermentation generated in the process biochemistry. This produces high organic contamination evidenced in the high average value of initial chemical oxygen demand (COD) of 1,746 mg/L, while Peruvian regulations require a maximum of 1,000 mg/L of COD in the sewage network discharge. The study focused on advanced oxidation methods (oxidation technology that generates hydroxyl radicals during its process, without producing more dangerous pollutants). Four different methods were applied. The pollutant removal efficiency is evaluated to identify which methods reach COD levels under the maximum admissible values (VMA), according to current regulations of the Peruvian Ministry of Housing, Construction and Sanitation. We then analyze the economic viability, defined for the present study by the OPEX costs of chemical products. Based on it, the most appropriate method to design a pilot project in the plant and to check dosages of chemical reagents, retention times and operating variables is determined. Laboratory tests showed that the treatment technology that best meets criteria described above is the sequence alkalization - protein precipitation - coagulation - flocculation, followed by solid - liquid separation with the stages of clarification, filtration and adsorption with activated carbon.