This paper studies electro-coagulation (EC) as a potential alternative to chemical coagulation for the treatment of water and wastewater. Prior research around this technology has been centred on application-specific research leading to a lack of fundamental studies and understanding of the process principles governing the technology. Developing on previous work, a theoretical study employing model solutions of arsenic is presented to demonstrate not only how it is possible to systematically evaluate the performance of the process, but also how process performance is regulated by the amount of coagulant in solution and, therefore current intensity employed. The data is in strong contrast with literature reporting on the impact of flow rate and current density on process performance. Here it is demonstrated that when the key process parameter dosed coagulant concentration is kept constant, variation of flow rate and current density does not affect process performance.