BACKGROUND: In recent years, the application of electrochemical wastewater treatment processes has proven to be very efficient in the removal of recalcitrant organic compounds. However, the scale-up of the boron-doped diamond (BDD) anode system for industrial applications has not been sufficiently evaluated. This study assesses the effect of increasing the number of compartments in the same electrochemical module (DiaCell(R) 1001) on the treatment of synthetic wastewater with pesticide 2,4-D and chlorides. This commercial module can be considered to be a stack of cells, in which the number of single cells varies from 2-10 and the anode areas range from 140-700 cm(-2). RESULTS: The results of the study demonstrate that an increase in the number of cells and a decrease in the resulting current density at the same current intensity caused an increase in the removal and mineralisation rates. Complete mineralisation was attained in all configurations tested. The production of hazardous species, such as chlorates and perchlorates, are also affected by the number of stacked cells, which causes them to be positioned lower in the stack due to the large number of cells. CONCLUSIONS: No distinct differences in electrochemical efficiency are observed among the different configurations tested. However, a distinct improvement in the energy efficiency (g kWh(-1)) with an increase in the number of stacked cells is observed due to the reduced stack potential caused by applying the same current intensity to the stack with the higher number of cells. (C) 2015 Society of Chemical Industry