Removal of As(V) from groundwater by a new air-injected electrocoagulation (EC) reactor using iron (Fe) ball anodes was investigated and the operating conditions were optimized. Effects of operating parameters such as initial pH (pH(i): 6.5-8.5), current (i: 0.1-0.5 A), operating time (t(EC): 1-3min), size of Fe anode ball (d(p): 5-10mm), initial As(V) concentration (C-o: 50-150g/L), air flow rate (Q(air): 2-10L/min), and column height of Fe ball (h: 2-8cm) in the EC reactor were evaluated with a three-level factorial design viz. Box-Behnken statistical experiment design. The model program provided with responses such as effluent As(V) concentration, removal efficiency, and operating cost for the EC process. Analysis of variance for all variables had confirmed the predicted models by the experimental design within 95% confidence level (R-2: 0.94, adj-R-2: 0.87), which ensured a satisfactory adjustment of the quadratic model with the experimental data. The maximum removal efficiency of As(V), minimum operating cost, and lowest effluent concentration at the optimized conditions (pH(i) 7.2, 0.5 A, 1.2min, 5mm ball size, column height of 4.8cm, and 9.9L/min) for initial concentration of 100g/L were obtained as 99.2%, 0.031$/m(3), and 0.4g/L, respectively.