Pollution Mitigation in Vermicelli Wastewater: Integrated Fenton and Aerobic Sludge Treatment for Water Quality Improvement

Abstract

Vermicelli production generates wastewater that is rich in organic and nutrient pollutants, which poses significant environmental challenges. Conventional biological treatments, either alone or in combination with other methods, often fail to achieve high efficiency and operational stability. This study explored the potential of the Fenton process, followed by aerobic activated sludge treatment, to enhance the biodegradability and mineralization of organic substances in vermicelli wastewater. Orientation experiments were performed to examine the effects of operating variables such as pH, reaction time, settling time, and ratio H2O2/Fe2+ on COD removal in order to select the optimal conditions for operating the model in a batch of 20 L, that is, pH = 3, reaction time of 90 min, settling time of 90 min, and ratio of H2O2/Fe2+ used 3 : 1 (4.5 : 1.5 g/L). The removal efficiencies of COD, BOD5, TN, TP, and SS reached 75.83%, 67.26%, 28.24%, 26.63%, and 91.9%, respectively. The BOD5/COD increased from 0.52 to 0.63, facilitating aerobic activated sludge, which had batch conditions of 15 L with pH of 6.5–8.5, DO ≥3 mg/L, additional nutrients with a dose of 12 mg/L, retention time of 14 h, and settling time of 2 h. As a result, the removal rate of those parameters climbed quite notably, except in SS (95.6%, 96.0%, 84.6%, 84.1%, and 83.6%), and their concentration parameters remained within the allowance levels of the National Technical Regulation in Vietnam before being discharged into the environment. However, the efficiency of treatment in the aerobic activated sludge stage for removing COD and BOD5 was not as high as anticipated (83% and 87.33%, respectively) owing to the influence of the high TDS concentration. Thus, additional research is required to address this challenge. The integrated treatment system combining the Fenton process with aerobic activated sludge demonstrated significant potential for the effective reduction of organic and nutrient pollutants in vermicelli wastewater, thereby achieving compliance with regulatory standards. However, the observed limitations in COD and BOD5 removal efficiency, likely due to elevated TDS levels, indicate the need for further investigation and optimization to enhance the overall treatment performance.