Efficiency of Electro-Persulfate Process Optimized with Hydrogen Peroxide in Removal of Hospital Wastewater COD by Response Surface Methodology

Hospital wastewaters contain persistent substances such as microbial factors, deterjents, halogenated organic compounds, hormones, antibiotics, and radioactive isotopes that are produced by a variety of research and treatment activities. This study aimed to remove COD (Chemical Oxygen Demand) of hospital wastewater by optimized electro-persulfate process using response surface Methodology In this laboratory study, an electrochemichal batch reactor equipped with four iron electrodes connected to a DC power supply was used for eliminating COD of wastewater. The independent variables (current density, initial pH, H2O2 dosage, persulfate dosage) against COD removal as the dependent variable were investigated using 8.0.6 Design Expert software by the response surface method, and the proposed model was analyzed using ANOVA. The optimal operational condition for COD removal with current density of 40 mA/cm2, initial pH of 5.2, persulfate dosage of 31 mg/L, and hydrogen peroxide dosage of 45 mM was 92.6%. High value of coefficient of determination was 92.4 % and low value of coefficient of variation 4.58%. The response surface method showed that there was an agreement between the predicted values by the model and the results obtained from the experiments. Simultaneous use of two reactives (persulfate/H2O2) increaces the COD removal efficiency. Therefore, it seems that electro-persulfate oxidation with hydrogen peroxide is an effective method for the the removal of hospital wastewater COD. Designing experiment using response surface methodology can show the best conditions for COD removal through reducing the number of experimental tests.