The Rockefeller Foundation is providing support to this Seeker for the design of a low cost water treatment system based on solar radiation and titanium dioxide (TiO2). A prototype design will be required using known proven technology supplied by the Seeker. This is a Theoretical Challenge which requires a written proposal only. The Solver will not have to come up with the mechanism of purification as that will be provided. The Solver will come up with the design of the system incorporating this technology that is low cost and low touch to operate. The proposal will be evaluated on a theoretical basis considering the current state of the art knowledge.