In the present paper, electrocoagulation (EC) was employed for removals of color, chemical oxygen demand (COD) and total organic carbon (TOC) from baker' s yeast effluents (BYEs) in a batch EC reactor using aluminium electrodes. Optimizations of anaerobic (AE) and anaerobic-aerobic effluents (AAE) were carried out by response surface methodology to describe interactive effects of the three main process independent parameters (initial pH(i), current density and operating time) on removal efficiencies of color. COD and TOC. The responses were related to maximize color, COD and TOC removal efficiencies and to minimize operating cost in the EC process. The quadratic model fitted very well with the experimental data. R-2 correlation coefficients (>95%) for the removal efficiencies showed a high significance of the model. The maximum color, COD and TOC were 88%, 48% and 49% at 80 A/m(2), pH(i) 4 and 30 min for AE and 86%, 49% and 43% at 12.5 A/m(2), pH(i) 5 and 30 min for ME, respectively. The operating costs for AE and AAE at the optimized conditions were 0.418 (sic)/m(3) and 0.076 (sic)/m(3). (C) 2011 Elsevier B.V. All rights reserved.