The Tennessee Water and Wastewater Energy Efficiency Partnership began in 2011 as a collaboration of U.S. EPA Region 4, the Tennessee Department of Environment and Conservation, the Tennessee Valley Authority, the University of Memphis, the University of Tennessee’s Municipal Technical Advisory Service, the Environmental Finance Center (University of North Carolina), and Schneider Electric. It was the first statewide effort of its kind in the Southeast. The collaborative effort is focused on providing Tennessee’s water and wastewater utilities with energy efficiency tools, expertise, and support – assisting them in reducing energy costs and pollution, while saving money and benefiting their ratepayers.
Each of the seven utilities participated in workshops and conducted energy assessments to determine how best to reduce energy use at their respective plants. Operational improvements ranged from minimizing the number and use of blowers to adjusting collection, UV disinfection, and aerobic digestion processes to optimize performance. In addition, two utilities added solar panel arrays to their plants, allowing them to realize further energy savings. The utilities used EPA’s online ENERGY STAR Portfolio Manager to benchmark and track energy use and savings at their facilities.
According to then-EPA Regional Administrator Gwen Keyes Fleming, “Drinking water and wastewater systems account for approximately 3-4% of energy use in the United States, adding over 45 million tons of greenhouse gases annually.” She continued, “EPA applauds these utilities in Tennessee for their leadership in reducing energy use, which is expected to save costs and yield substantial health and environmental benefits across the state and Southeastern region.” The second round of this initiative is currently underway.
Results to Date:
The following is an example of the results achieved by utilities in the first round. The partnership worked with the Columbia Wastewater Plant staff to evaluate the plant loadings and oxygen demand in the aeration basins. That analysis showed that a single 450 hp blower would provide adequate oxygen to the fine bubble system for the actual plant loading during all normal conditions, with additional aeration possibly needed if high peak flows occurred for extended periods. Also, due to problems with the turbidimetric controls in the UV system, the plant had to operate with excessive UV lamp usage to assure adequate disinfection. Plant staff was able to shut down the second 450 hp blower (previously operated 12 hours/day), producing an immediate energy savings of approximately 120,000 kWh per month. The plant also completed repairs to the UV control system to significantly reduce UV lamp usage. Those improvements produced total measured energy savings of almost 2 million kWh per year, compared to the two previous years of energy use. On an energy use per million gallons (MG) treated basis, the plant has reduced its energy use by over 20% and saved more than $150,000 per year in the cost of energy.
As of the beginning of 2014, total documented savings for all the participating utilities was more than 5 million kWh per year and $400,000 per year in energy costs, with greater than 4,800 tons CO2 reduction already achieved.
Environmental Protection Specialist, Water Resources Division
Tennessee Department of Environment and Conservation