Background and aims: Nitrate is one of the most important contaminants in nature that makes serious threats to health and quality of water resources. Electrocoagulation is one of the most efficient methods to remove this pollutant.

Methods: This experimental study was conducted in a pilot scale. The samples were prepared using synthetic water at 100-300 mg/l initial concentration of nitrate. The independent variables were reaction time, electrical difference potential and pH. The process performance was evaluated based on nitrate removal efficiency. The number of experiments, statistical analysis of experimental data and optimization of nitrate removal efficiency were determined by using central composite design (CCD) and response surface methodology (RSM).

Results: The results showed that nitrate concentration (A), reaction time (B), voltage (C), pH (D), square terms of nitrate concentration (A²), and interaction terms of AB, AC, AD, BC was the most effective parameters on nitrate removal efficiency using electrocoagulation. The efficiency of nitrate removal at optimal conditions (reaction time 68 minutes, the electric potential difference 17 volts and at pH 10) was obtained 88%. In these conditions, model validation was 98%.

Conclusion: Electrocoagulaion was an effective process for nitrate removal and also RSM (CCD) was appropriate to optimization of the variables affecting nitrate removal using electrocoagulation process.