A comparison was made between two technologies: electro flocculation (EF) and chemical flocculation (CF), which may be used as pretreatment in wastewater treatment. Natural water reservoir or wastewater intended for reuse, that contains high concentrations of iron particulates, often requires particle destabilization and removal. These particles can be removed by flocculation process applying ferric chloride (CF) or by Fe3+ ion (EF) that change to Fe2+ in a short time. EF, a fairly new environmentally-friendly process has been developed with the aim of reducing, or even avoiding altogether, the amount of chemicals required during pretreatment. The behavior of iron oxide and hydroxide colloid in EF aims at solving the problem of contaminated water or industrial wastewater. In this paper EF with iron electrodes and chemical dosing with ferric chlorides were investigated for several types and different concentrations of iron suspension. The results show a gradual rise in absolute zeta-potential and an increase in particle size with flocculation time. The results of both processes were compared through the efficiency of solid/liquid separations performed by sludge sedimentation and filtration. Preliminary testing identified the process conditions, pH of the water treated, dosage of the coagulant, mixing conditions, conductivity, and current density. The target was to find the method which provides optimum coagulation and avoids excessively high energy consumption in EF.