The purpose of the project was the implementation of a tertiary treatment system in the Grota do Vale wastewater treatment plant. An ultraviolet disinfection system with filtration upstream was designed. In addition to the tertiary treatment system itself, it was envisaged the construction of a set of supportive infrastructures, including a building for the tertiary treatment system equipment, a storage tank for treated effluent water with 100 m3 capacity and a treated wastewater distribution system within the premises of the treatment plant.