ENGINEERING JOURNAL CHIANG MAI UNIVERSITY

Volume 26, No. 01, Month APRIL, Year 2019, Pages 45 - 58

Optimization modeling for treatment of wastewater containing phosphate by electrochemical process

Sattawat Thuangchon, and Wacharawish Daosawang

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This research studied the mathematical modeling for optimization of the operating conditions and investigation of factors affecting on treatment of wastewater containing phosphate by electrochemical process. A central composite experimental design (CCD) combining with response surface method (RSM) and multiple regression analysis was employed to establish the model and to study effects of four independent variables on phosphate removal. These variables included initial concentration of phosphate in wastewater, electrical discharging time, applied current and initial pH of wastewater. Levels of significance for the operating conditions were tested by means of the analysis of variance (ANOVA) with 95 % confidence limits (𝛼𝛼𝛼𝛼 = 0.05). All tests were conducted with batch experiments using reactors of working volume of 200 ml filled with synthetic wastewater. Two Aluminium plates with effective areas of 10 cm2 were used as electrodes with a separation distance of 2 cm. Results indicated that all operating conditions were at the significance level of 0.05 (P<0.05). The optimum conditions were obtained by solving the quadratic regression model. The model validation was conducted using one of the experimental trials, which had the initial phosphate concentration of 13.34 mg/l and required a 80% removal efficiency. The model optimization provided an electrical discharging time of 10.82 minutes, applied current of 9.19 mA and initial pH of wastewater of 7.73. An average experimental value for phosphate removal was 81.78%, which was slightly 1.77% different from the modeled value. However, the application of this optimization model was limited to the certain conditions including, a 10 - 35 mg/l initial phosphate concentration range, a 5 - 35 minute electrical discharging range, a 5 - 12.5 mA applied current range, and an initial pH range of 6 – 9. The predicted phosphate removals were expected to be 70 - 90%.

Keywords

phosphorus, removal, electrocoagulation

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