The response surface method (RSM) was used to find out the best conditions for the nitrate removal by electrocoagulation (EC) process with aluminum electrodes. The independent variables were initial nitrate concentration, reaction time, initial pH, and cell voltage. A statistical analysis of variance (ANOVA) was performed for optimization of parameters obtained from the experimental data. A quadratic model was suggested as a good model for prediction of nitrate removal efficiency. The optimum conditions were obtained at pH 10, 17 V voltage, and 68 min when the initial nitrate concentration was found to be $226\mathrm{mg}/\mathrm{L}$ . At the best conditions, the nitrate removal efficiency and energy consumption were obtained as 87.95% and $144.15\mathrm{kWh}/{\mathrm{m}}^3$ , respectively. In terms of nitrate removal efficiency and energy consumption, the coefficients of determinations were found to be 0.95 and 0.99, respectively. The results indicate that the initial nitrate concentration, reaction time, and cell voltage were found to be the most important parameters. The results also show good agreement between experimental data and the predicted equation.

Background: Considering the carcinogenic effects of heavy metals, such as chromium, it is essential to remove these elements from water and wastewater. Direct osmosis is a new membrane technology, which can be a proper alternative to conventional chromium removal processes. Methods: The wastewater samples were collected from an electroplating unit, located in Alborz industrial city, Qazvin, Iran. Magnesium chloride was used as the draw solution, and a semipermeable membrane (Aquaporin) was used in this study. The experiments were designed, using response surface methodology (RSM) and central composite design (CCD) with draw solution concentration (0.5- 1.5 M), feed solution concentration (4-12 mg/L), and experiment time (30-90 minutes) as variable factors. The chromium concentration and water flux were also measured, based on atomic absorption spectrophotometry and water flux equation, respectively. Results: Direct osmosis was highly efficient in chromium removal and water recycling. Water flux and chromium removal efficiency were 15.6 LMH and 85.58%, respectively, under optimal conditions (draw solution = 1.27 mol/L, feed solution = 4 mg/L, and experiment time = 90 min). In terms of validity, the results predicted by the quadratic polynomial model were in good agreement with the responses reported in the laboratory. Conclusion: In direct osmosis, the use of magnesium chloride as the draw solution resulted in the acceptable chromium removal from electroplating wastewater. Using this method, chromium concentration in wastewater reduced to a level lower than the discharge standards, established by Iran’s Department of Environment.

Environmental Health Engineering And Management Journal مجله مدیریت و مهندسی بهداشت محیط

Background: Due to the complexity and interdependence of water resources, the evaluation of the efficiency of water resources management is difficult. So, it is necessary to use effective modeling methods to study and recognize the feedback loops available in water resources systems. Regarding the importance of domestic water for the ...