Application of microturbines in improving the energy efficiency of municipal wastewater treatment plants in Missouri.

Abstract

Hydropower is a source of renewable energy. It is possible to combine a hydropower installation with an existing wastewater plant while ensuring it still performs its basic purpose. The multipurpose scheme would be integrated into the facility to generate hydropower while also fulfilling its primary role of treating wastewater. The wastewater plant can generate renewable energy and benefit from introducing microturbines. The turbine system is moved by the power in the flowing treated water that is transformed into mechanical energy which rotates the generator and in turn generates electrical power. In this work, the potential for power generation from the energy in the outflow along with the economics of the system in wastewater plants in the state of Missouri was investigated to improve the energy efficiency of the municipal wastewater treatment plants. Data like the daily flow rate, speed of flow, available head, etc about the wastewater plants in Missouri were collected and some interviews held with plant managers of the wastewater treatment plants. The investigation revealed that there are 127 wastewater treatment plants in the state of Missouri with 32 plants discharging less than 1 Mgd, 74 plants discharging between 1 Mgd and 5 Mgd, 13 plants discharging between 5 Mgd and 20 Mgd while just 8 plants had an outflow between 20 Mgd and 120 Mgd range. The flowrate helps in calculating and determining the theoretical and actual amount of power that can be gotten from the micro hydropower system in the wastewater treatment plant. For the actual amount of power gotten, the efficiency factor (efficiency of the turbine, and efficiency of the generator) of the generating system is considered. A brief study on the turbine system was conducted and a crossflow turbine was selected as the most suitable for the wastewater treatment plant as a vast majority of them had low head and high flow capacity. The analysis showed that out of the 127 wastewater treatment plants in the state of Missouri, only 21 treatment plants have the maximum potential to generate power and reduce operating costs. Also, two plants were selected for case studies. The operating cost is reduced because of the decrease in demand for electrical power from the grid. The 21 treatment plants have a daily outflow between 5Mgd to 120Mgd and could produce power through an axial flow turbine that utilizes the kinetic energy in the flow volume.