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

•Screening of factors influencing electrocoagulation process by Plackett-Burman design (PBD).•Modelling of nitrate removal, ammonium generated, process cost and floc mass by Box-Behnken design (BBD).•Obtaining optimal conditions through multi-response optimization.•Better reduction of nitrate with low ammonium formation and operating cost. 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.