Nitrate removal by electrocoagulation process using experimental design methodology: A techno-economic optimization

Abstract

The aim of this study was to evaluate nitrate removal from simulated effluent by electrocoagulation (EC) process using experimental designs methodology (EDM). Plackett-Burman design (PBD) was firstly used for screening of five factors, such as current intensity (0.5–2 A), treatment time (20−60 min), initial effluent pH (4–10), electrode type (Fe, Al) and electrolyte type (Na2SO4, NaCl), on nitrate removal. Respective contributions of factors were 41.56 %, 26.51 %, 7.04 %, 23.98 % and 0.91 %. Results showed also that high current intensity, high electrolysis time, low initial pH as well as the use of aluminum electrodes, are favorable to high nitrate removal. Then, Box-Behnken design (BBD) was used to optimize nitrate removal while minimizing ammonium generated and operating cost. The optimal conditions obtained are the following: intensity 1.80 A, time 33.0 min and pH 8.73. Under these conditions, 73.8 % of nitrate were eliminated against 12.02 mg/L of ammonium and 1.8 g of metallic residues generated for an operating cost of 1.3 $ US/m3. Based on these results, EC can be considered as an efficiency process for nitrate removal. Also, it was found that BBD could be a reliable statistical tool to model the process and to determine the optimal conditions in terms of cost-effectiveness.