According to R2 values of the model responses ( Table 2) all models explain the variance of final pH, apparent color, TOC, ζ-Potential, dissolved Al, and residual Al and Fe with high accuracy (R2 > 0.8). Lower R2 values were obtained for turbidity and residual Mn with Cell C. According to Q2 values of the model responses, the predictive ability of the model made for Cell C is significantly lower than the predictive ability of the models made for Cells A + C and Cell A. This can be due to the mechanism of aluminum dissolving from the cathodes, which does not behave linearly at the initial stage of the electrocoagulation process.