Industrial Utility Efficiency

# Fayetteville Wastewater Treatment Plant Lowers Operational Costs, Increases Efficiencies

The Fayetteville Wastewater Treatment Plant (WWTP) in Fayetteville, Tennessee, is an example of a treatment plant that does more than just talk about efforts to achieve water quality and effluent goals – while holding down costs. Instead, it puts words into action.

At the Fayetteville WWTP, action has taken the form of a forward-thinking approach to plant operation and multiple initiatives designed to lower the costs of operation and improve efficiencies. Among its initiatives is a \$5 million plant upgrade involving the installation of advanced technology, including: • A Supervisory Control and Data Acquisition (SCADA) system. • Updated aeration basins featuring Luminescent Dissolved Oxygen (LDO) probes. Before the plant upgrade, it also installed Variable Speed Frequency Drives (VFDs) on mechanical surface aerators used on the aeration basins. • High-efficiency aeration blowers for optimization of its digester storage tanks. • A state-of-the-art dewatering system, featuring a high-efficiency centrifuge and other equipment designed to save costs and more. ##### Fayetteville Wastewater Treatment Plant Supervisor Dwight Jeans. The plant upgrades, in combination with a progressive management strategy, allows the plant to consume less energy and reduce its reliance on outside contractors for biosolids removal, resulting in total operational savings of approximately \$60,000 per year.  The plant is also positioned to efficiently manage the area’s wastewater for decades to come.

“As a publicly owned wastewater treatment plant our job is to put out quality water in keeping with state and federal regulations, while keeping costs down,” said Fayetteville Public Utilities (FPU) CEO/General Manager Britt Dye. “It’s why we’ve always taken a proactive approach to investing in the future and upgrading our plant. For us, it’s all about moving forward.”

### Oxidation Ditch Process

Located approximately 90 miles south of Nashville, Tennessee, Fayetteville is a city of approximately 7,000. FPU manages the plant and the city’s water services.

Fayetteville WWTP treats approximately 1.5 million gallons per day (MGD) of municipal wastewater with an influent BOD5 of approximately 225 mg/l. The plant uses an oxidation ditch process with two parallel ditch trains to treat 3.35 MGD at average daily flow conditions and 7.7 MGD of peak daily flow. An oxidation ditch is a modified activated sludge biological treatment process that utilizes long solids retention times (SRTs) to remove biodegradable organics.

The final effluent is discharged to the Elk River with monthly average National Pollution Discharge Elimination System (NPDES) effluent limits for both BOD5 and suspended solids of 30 mg/l. The U.S Environmental Protection Agency (EPA) establishes NPDES limits.

Since mid-2009 the average daily flow has been approximately 1.5 MGD, but peak daily flows can exceed five to six MGD, requiring the operation of both ditch trains. The plant consistently produces a high quality effluent with BOD5 values averaging 5 to 8 mg/l. and Total Suspended Solids (TSS) values averaging 5-9 mg/l.

### Energy Management Initiatives Launched

FPU and WWTP operators have continuously looked to lower plant operating costs since the plant’s inception. Yet FPU accelerated its cost-savings measures at the plant in 2011 when the EPA (Region 4 – Atlanta) and the Tennessee Department of Environment and Conservation (TDEC) assembled a team to conduct an Energy Management Initiative (EMI). Since then, the plant has never looked back.

The EMI process included an energy assessment, as well as various workshops to help the plant operate more efficiently and cost-effectively. The team included EPA R4, TDEC, the Tennessee Department of Economic and Community Development and the Tennessee Valley Authority (TVA). It also involved the help of the University of Memphis – Civil Engineering Department, University of Tennessee – Municipal Technical Advisory Service, and the University of North Carolina Environment Finance Center.

“FPU is an example of a utility that fully appreciates the value of measuring and controlling energy use at its wastewater treatment plant in addition to implementing ongoing best practices in environmental stewardship,” said Ben Bolton, an energy programs administrator with TDEC. “It is this type of commitment that makes Tennessee an attractive place to live, work, and visit.”

Through the EMI process, the plant identified a number of opportunities to save energy. One such measure included the decision to reduce the run times of the blowers used on its aerobic digesters. Doing so allowed the plant to save considerable energy costs. Two years later, the plant took yet another major step toward energy reduction by only operating one of its two oxidation ditch trains during normal conditions.

### An Eye Toward Continued Efficiencies

Since completion of the plant upgrade in 2017, the plant saves an estimated \\$60,000 in operational costs thanks to advanced, energy-saving technology and FPU’s decision to produce Class-A biosolids for use throughout the community.

According to Dye, the cost-savings measures at the plant are the result of a forward-thinking approach and a commitment to continuous improvement. As an example, he said, the WWTP is developing plans to operate its dewatering process during electric utility off-peak hours to save energy.

“We decided long ago to be a leader in wastewater treatment,” Dye said. “Thanks to the help of the EPA, TDEC and other organizations in the community, as well as our knowledgeable staff, we’ve been able to make substantial improvements that not only save on energy and help us reduce costs, but also enhance the plant’s ability to protect the environment for decades to come.”

All photos courtesy of Fayetteville Public Utilities.