This work presents a simulation model for a UV water treatment system, powered by a photovoltaic generator, which relates the current consumed by the lamp to the UV flux and water quality. The overall system also includes electronic converters, electronic ballast (RLC resonant circuit), a UV lamp (UV irradiation source), and a centrifugal pump. To optimize the power transfer from the PV generator to the ballast and the UV lamp, a Maximum Power Point Tracking (MPPT) device is used. The overall water treatment system presents a complex model due to its hybrid components. The bond graph tool with a multidisciplinary vocation allows precisely, by its graphic nature, using a unified language, to explicitly display the nature of the power exchanges in the system and facilitate its control. This tool is a solution for non-linear systems that guarantees and facilitates their modeling without difficulties.