This is a feasibility study that evaluates the use of collected sewage water from modern Andean city for small hydropower production. Arequipa, a Peruvian city located at 2335 meters above the sea level, has been selected as case study. The geographical conditions (mountains and canyons) around Andean cities are suitable for the electricity production in a small hydropower stations. The produced electricity could be used for the energy needs of the treatment facilities or for commercialization in the electrical system (Distributed Power Generation). Synergy effects between the water supply industry and electricity energy production, based in Hydropower, in cities at high altitude are analyzed. A similar facility located in Stockholm (Sweden), The Hammarbyverket an energy plant (315kW Hydropower), is used as model for future integration of Sewage Treatment Plants and Hydropower Production. The study case for Arequipa is presented, where two new sewage treatment plants are under construction.