Naturally-occurring arsenic contaminates groundwater in Nepal in concentrations up to 200 ppb, constituting a significant health threat to Nepalis relying on well water. Students of Thayer School of Engineering's Bachelor of Engineering capstone design course chose to solve this problem, which was submitted to Thayer by VillageTech Solutions (VTS), a non-profit focused on improving life in rural Nepal. The three students collaborated with VTS to define the problem, understand end-user constraints and culture, and integrate the design with pre-existing re-chargeable battery technology. After analyzing the current state of the art for arsenic removal, the students used evolutionary prototyping to refine and optimize electrochemical arsenic-removal processing, system usability, and cost. Students employed sophisticated chemical reaction modeling, electrical and mechanical design and construction, leachate testing research, and economic analysis. The final design uses an electro-coagulation process powered by a 6-volt battery; the iron oxyhydroxide precipitates produced bind to the arsenic and are removed from the water by a sand filter. The unit purifies 15-liter batches of water to well below the 10-ppb World Health Organization arsenic level standards at lower cost and higher efficiency than current systems. Designed for ease of use and sustainability, the system utilizes locally available parts, includes a visible bubble chamber that shows when the system is working, and comes with a pictures-only instruction manual. VTS's David Sowerwine calls the solution "extraordinary" and is working to implement it in Nepal and elsewhere.