Investigation on reuse of energy at a sewage treatment plant and payback period

The reuse of energy is a topic currently being widely discussed around the world. This study analyzes the potential for energy reuse in treatment plants. Sewage Treatment Plants are responsible for treating the water present in the sewers of cities. The treated water returns clean to the river, and generally, the place of discharge has a high height and flow rate that can be harnessed for the generation of electric energy. This work investigates the feasibility of installing a Micro Hydroelectric Plant in the Treatment Station of the Uberaba River in Brazil. Hydraulic potential and investment analysis were used as viability criteria. For the study, a height of 6 m and an average flow rate of 0.465 m3/s were considered, which could generate about 22.51 kW using a Bulb water turbine. This power represents a return of US$1651.26 per month from the generation of electric energy. The estimated installation cost was US$32,966.73, and the payback period was found to be less than 2 years. There are 702 sewage treatment plants in Brazil alone, and hypothetical analyses were performed with flow rates ranging from 0.2 to 1 m3/s and heights ranging from 1 to 9 m. Motivating results with payback periods of less than 4 years were obtained for numerous hypothetical situations, which demonstrates the feasibility of installing Micro Hydropower Plants and achieving savings in the sewage treatment system.