A Little Wastewater Change Produces a Lot of Savings

Tennessee Partnership Wants to be Role Model

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Posted: Wednesday, March 25, 2015 10:58 am

Communities frequently begin energy efficiency projects with lighting or mechanical system upgrades in public buildings, or by looking at the fuel efficiency of their vehicles. However, one of the largest energy consuming operations in most cities is often a missed opportunity:

Drinking water and wastewater treatment systems.

Typically these systems account for 30-40 percent of a city’s total energy demand. A unique partnership led by the Tennessee Department of Environment and Conservation and the U.S. Environmental Protection Agency is proving that low-cost changes to water and wastewater treatment plants can have big energy and cost savings.

The program, known as the Tennessee Water and Wastewater Energy Efficiency Partnership, was formed in 2011 as a collaborative effort between local utility districts, the U.S. EPA Region 4, the Tennessee Department of Environment and Conservation, the Tennessee Valley Authority, the University of Memphis and the University of Tennessee’s Municipal Technical Advisory Service. This first statewide effort of its kind in the Southeast has drawn 16 communities to participate so far in a series of workshops and facility energy assessments. Each utility identifies low- or no-cost operational changes and earmarks larger energy efficiency investments that are incorporated when planned capital improvements occur.

Seven participating utilities in the first round completed their improvement projects in 2011. Another eight utility districts and one correctional facility participated in the recently completed second round. The focus of the program is to determine how to best reduce energy usage at plants without the financial burden of expensive capital projects, with many participants seeing almost immediate benefits.

“What the partnership did for us was make us really take a measured look at our operation and where we could be more efficient without sacrificing service or quality,” said Mark Williams, City of Columbia Wastewater director.

The Columbia Wastewater Treatment Plant was last expanded and upgraded in 2000. The largest energy demand of the plant are the four 625,000-gallon activated sludge basins and four 380,000-gallon aerobic digesters. Air supply was provided by three 450-horsepower blowers, with one that ran 24 hours a day and one that ran 12 hours a day. An energy management team made up of partnership members was able to work with plant staff to determine that a single 450-horsepower blower would be sufficient to operate the plant under normal loading conditions. As a result, the second 450 horsepower blower that ran 12 hours a day was shut down, resulting in an immediate annual energy savings of 1.9 million kilowatts per year, or a costs savings of $160,000. This was an energy reduction of 24 percent.

The City of Fayetteville made a similar, but even more significant discovery. The energy management team for the City of Fayetteville Wastewater Treatment Plant determined that the best opportunity for savings was the aerobic digesters for the plant’s holding tank. The greatest opportunity for energy savings was to reduce the run times on three 125-horsepower aerator motors. This provided a savings of 800,000 kilowatts per year and reduced the annual operation costs by 30 percent. The total savings in annual energy costs was more than $50,000.

As a direct result of participation in the partnership, the City of Franklin formed its own energy management team to look at potential savings in the Franklin Water Reclamation Facility. The wastewater system discharges to the Harpeth River and much of the effluent is used by the city for irrigation and coarse bubble aeration systems. The team identified that the operating time of the aeration system could be reduced without compromising performance. The savings from this project funded a lighting upgrade and a solar array installation to supplement power. Combined with other measures, such as meter change-outs and off-peak operating hour adjustments, it amounted to an annual savings of more than $127,000.

In total, the first round participants have realized annual savings in excess of nearly 7 million kilowatts per year at a cost savings of more than 650,000. Some of the successes of the utilities involved in the first round of energy assessments include:

Caryville-Jacksboro Utilities Commission (188,000 killowatts, $15,750)

First Utility District of Knox County (710,000 kilowatts, $68,000)

Lenoir City Utilities Board (523,000 kilowatts, $42,000)

Nashville Metro Water Services (2,400,000 kilowatts, $210,000)

An interesting spin-off occurred in the second round. United South and Eastern Tribes began attending the workshops and saw the importance of the assessments to the facilities. They learned about the various ways to reduce operational costs and have since begun assessments at many south and eastern tribe facilities in Alabama, with the support of the EPA Region 4 and the University of Memphis’ Dr. Larry Moore.

“Discussions with the Environmental Protection Agency Region 4 concerning energy and sustainability really sparked the formation of the Tennessee Water and Wastewater Utilities Partnership,” said Jennifer Dodd, with the Tennessee Department of Environment and Conservation Division of Water Resources. “We are extremely proud to have participated in a program that has delivered significant savings to our communities and reduced energy consumption.”

The Tennessee Water and Wastewater Utilities Partnership is planning the third round of energy assessments. The partnership wants to be a role model for others around the country.

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