Arsenic occurs naturally in the environment and as a by-product of some agricultural and industrial activities. It can enter drinking water through the ground or as runoff into surface water sources. Since human exposure to arsenic creates severe short- and long-term health effects, different physico-chemical techniques have been employed around the world for its removal. Electrocoagulation (EC) is an emerging and very efficient electrochemical technique for this purpose. Until now, the mechanisms behind this process have not been well understood. This is of profound importance for the design, optimization and control of the new EC systems that are now emerging. In addition, fundamental understanding of the interactions between EC produced materials and the coupled solution, solid state, electrochemical and interfacial chemistries are necessary for the optimal application of the EC technique. In this paper, we discuss our recent experimental data and design, optimization and control efforts using systematic mechanistic pathways of arsenic removal. The results will be discussed in terms of Pourbaix and solubility diagrams, solution chemistries, electrochemical processes and interfacial reactivity patterns.