This study investigated the effect of electrocoagulation treatment on toxic pollutant removal from pulp mill effluents. Synthetic wastewaters containing wood rosin and copper or pure resin acids were used to investigate the removal of resin acids and copper by electrocoagulation. Removal of pollutants by electrocoagulation was also tested with real debarking effluent. In this study, statistical experimental design and partial least squares modeling were used to investigate the effect of initial pH, current (current density) and treatment time. Electrocoagulation and subsequent filtration removed resin acids and copper from the synthetic wastewaters with high efficiency. Toxicity to algae (Pseudokirchneriella subcapita) was completely eliminated by the treatment, however reduction of bacterial toxicity (Vibrio fischeri) was more limited. While the initial EC(50) value for bacteria in debarking effluent was around 8-14 vol%, toxicity was approximately halved by electrocoagulation. Toxicity removal from the debarking effluents was associated with color removal. (C) 2011 Elsevier B.V. All rights reserved.