Case Study: 75% Energy Savings at a Wastewater Treatment Plant

摘要

This article is a case study for an energy savings performance contract (ESPC) at the wastewater treatment plant for the City of Riverbank in California. The existing plant has an average of 1.67 million gallons per day (MGD) flow and consists of the headworks, four treatment ponds, and seven percolation ponds. Prior to the project, the treatment ponds used surface aerators to provide oxygen for the biologic process. The plant was primarily operated manually with limited dissolved oxygen control. The utility bills showed excessive energy use-annual usage was 5,673 kWh/MG/yr. Schneider Electric and the City of River-bank entered into a construction contract to retrofit the treatment ponds with blowers and fine-bubble diffusers for more efficient oxygen transfer. Additionally, a control system was installed to maintain a dissolved oxygen set point. This scope of work is estimated to save 75% of the electricity consumption at the wastewater treatment plant and will save the city 65% of their electric bill, or $240,129/yr. The energy and utility analysis was done by following a five-step process: 1. Benchmark baseline energy data 2. Analyze baseline utility data and model utility rates 3. Model baseline energy consumption 4. Model estimated energy consumption after the scope of work is installed 5. Determine estimated dollar savings associated with the scope of work This case study outlines these processes and discusses the customized energy model that was developed for this analysis. Financial parameters of the project are discussed, including the city's payback criteria, final project costs, and utility incentives. Finally, a discussion is presented on the benefits of using an ESPC for this type of project and why the city chose to use this contracting method to accomplish their goals.