More Than a Pretty Face: Alabama Plant Exceeds Requirements

Quality treatment, water reuse, energy savings and I&I reduction are just some accomplishments of the ingenious staff in Athens, Alabama.
More Than a Pretty Face: Alabama Plant Exceeds Requirements
The plant team includes, from left, Jason Fielding, relief operator; David Oliver, laboratory technician; Skylar King, relief operator trainee; and Virgil White, superintendent.

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Visitors to the Athens (Alabama) Wastewater Treatment Plant may feel that they are entering a botanical garden: Its lush landscaping makes it inviting.
But there’s more to this plant than a pretty setting. The staff has raised the bar in important ways, exceeding permit requirements by producing effluent with 6.2 mg/L TSS and 2.7 mg/L CBOD.

They reuse the effluent for landscape irrigation and in-plant needs. They’re reducing energy costs with LED lights on motion detectors and with more efficient equipment operation. The utility is also replacing 60- to 100-year-old leaky clay sewer pipes, which will help reduce inflow and infiltration.

It’s a huge improvement over the previous 7 mgd trickling filter plant, built in the late 1950s. Even with two major upgrades, the old plant was limited by peak flows and outdated equipment that was difficult to maintain.

The new 9 mgd (design) activated sludge plant started up in September 2009. It presented some training and startup challenges, including a foaming issue in the aeration basins and an increase in effluent TSS. The operations staff solved those problems by diligently tracking operations data and staying proactive.

Staff members work well together and take pride in a job well-done. Their work has paid off in 2013 and 2014 Best Operated Plant awards (5.1 to 10 mgd category) from the Alabama Water and Pollution Control Association (AWPCA). The plant also received a 2014 Alabama Water Environment Association (AWEA) Award of Recognition.

Better performance

The plant is operated by Athens Water Services, a division of the City of Athens Utilities. The utility provides water to 10,600 customers and sewerage service to 7,200. The original trickling filter plant was upgraded in 1973 with three more clarifiers, trickling filters and digesters. Activated sludge and final clarification were added in 1988, along with UV disinfection (TrojanUV) to replace chlorine gas.

I&I was a problem: The collections system delivered flow that the main lift station couldn’t pump, and the lift station pumping capacity was already greater than the plant could handle. “This was an issue when I started at the plant in 2004 and is the main reason we built the new facility,” says Virgil White, plant superintendent.

The new process is more streamlined and is computer-automated. Raw water flows through two screens (Andritz Separation), then through two grit collectors (Smith & Loveless), two grit slurry pumps (WEMCO), two grit cyclone separators (WEMCO) and two grit classifiers (Smith & Loveless).

Three pumps introduce return activated sludge to the raw water flow, creating mixed liquor that flows to three aeration basins and then to two clarifiers (Evoqua Water Technologies). Clarifier effluent is sent to UV disinfection. “Our plant reuse water is collected after disinfection but before our Parshall flume total plant effluent flow measurement,” says White.

Plant reuse water is delivered through two 40 hp pumps (Patterson Pump Company) to a strainer (S.P. Kinney Engineers) that removes particles that could clog the equipment spray nozzles. The entire measured effluent flow is discharged to Town Creek.

Waste activated sludge is sent to two lagoons, and the supernatant is recycled to the plant effluent stream. “This process produces next to zero biosolids,” White says. “The remaining biosolids stay in the two lagoons totaling 20 acres and 10 feet deep. We expect this to be sufficient until 2029.”

Dealing with I&I

Although the increased capacity and collections system improvements reduced I&I, operators still have to deal with peak flows during heavy rains. “January is our rainy month,” says White. “Last year, our average flow was 5.8 mgd, and in January 2015 it was 8.7 mgd.

“We can handle peak daily flows up to 20 mgd for short periods since we can send around a quarter of that directly to the fourth zone of our aeration basin trains just before clarification. This allows us to send what is mostly rainwater through one aerated zone and mix that back into the portion of the flow from the aeration process.”

The collections team is about halfway through a project to replace leaky clay piping. There are two lift stations at the treatment plant. The main station has two 140 hp ABS pumps (Sulzer Pump Solutions) and a 47 hp ABS pump (Sulzer Pump Solutions) programmed through the SCADA system to run as needed with fluctuating flow rates. The Braly station has 15 hp and 20 hp pumps (Flygt, a Xylem Brand) that cycle alternately.

The collections team maintains 10 other lift stations and 152 miles of pipe. Although most pipe is less than 20 years old and in good shape, about 20 percent is more than 60 years old. The team works eight hours a day, five days a week to replace old pipe with PVC lines.

“So far we’ve replaced 4 to 5 miles of sewer line in the last several years,” says Jon Lewonczyk, collections and maintenance superintendent. “We have about 38 miles of clay pipe still in the ground and will continue to replace leaking lines as long as we have funding. We perform a lot of maintenance, and that’s how we learn where the problems are.”

Growing pains

As for the new treatment plant, startup went smoothly; various equipment vendors came to train the operators. “We experienced some growing pains when we converted all our flow from the old plant to the new,” says White. “For example, we noticed a foaming issue in the aeration basins. After some research, we increased the return activated sludge flow ratio and reduced the mean cell residence time (MCRT) through increased wasting of activated sludge.”

Another issue was an increase in effluent TSS: “We built our MCRT back to a higher point while stopping short of where we were when the foam was there. That seemed to work for a few months.” But in fall and spring, the foam was back. Operators traced it to seasonal filamentous bacteria.

“This is the time of year when the MCRT should be adjusted because of weather, rainfall and flow changes, and we weren’t changing with the weather like we should,” says White. “We needed to anticipate it and keep it from forming.”

Operators developed a spreadsheet with mixed liquor pH and temperature, daily high and low ambient temperatures, rainfall and flow fluctuations, daily mixed liquor TSS data, and whether foam was present. “We examine this data daily, and over time we learned how to go from one flow pattern to the other without having to react to changes in our water,” says White. “Nothing has been as helpful as keeping up with our own plant conditions and data, so that there are no surprises.”

Dual certified

Seven operators, a laboratory technician and four maintenance technicians take care of the plant. Three dual-certified relief operators work there and the 13 mgd water plant, spending six weeks at each. John Stockton, water services manager, developed a plan to cross-train operations and maintenance personnel. All operators hired since 2002 are required to become dual certified. Maintenance technicians are encouraged to train and work as operators as needed.

White holds Grade IV wastewater and water operator certification and has been with the utility for 11 years. Other team members are:

  • Tim Norman, chief operator, Grade IV wastewater
  • Robert Shar, Michael Mewbourn and Cody Brown, Grade IV wastewater operators
  • Roger Miller, Jason Fielding and Eric Morell, Grade IV relief operators
  • David Oliver, laboratory technician, Grade IV wastewater
  • Dale Putman (Grade IV wastewater), Michael Furline (Grade IV water), Tommy Williams and Frankie Ezell, maintenance technicians

White says the team’s greatest strength is communication: “We are open and honest with each other. If someone has a gripe, I tell them to talk to the other person. I don’t need to be in the middle. If they’re working different shifts, I suggest they write a note. They may not see each other face to face, but one of them is going to get a note.”

Using ingenuity

Team members are encouraged to make suggestions to improve operations. When Mewbourn had been at the plant for just two weeks as an operator trainee, he helped resolve a pump programming issue. The SCADA system had been programmed to work based on pump output percentage. When a second pump came online, the flow increased while the total pump output percentage dropped.

When two pumps at 70 percent output pumped more than one pump at 100 percent output, the screen channel gate would see the percentage drop and begin to close. “Operators found that they had to start controlling the gates in local/manual mode, rather than letting the SCADA control them,” says White. “That was inconvenient, as they had to walk 200 yards to the equipment and flip switches, usually in the rain, thunder and lightning, while the water continued to get deeper.”

The plant has float ball switches that trigger alarms to tell operators when the water upstream of the screens is deeper than desired. So, Mewbourn suggested programming the SCADA to open both screen channel gates so that both screens would come online if either of the three float balls triggered a high-level alarm. This solved the problem.

It was Norman’s idea to color code the valve covers to show their functions: “We call him the label master because he has labeled almost everything — valves, lab drawers, process gates and equipment. It makes the plant more user-friendly.”

Saving energy

Meanwhile, the staff is reducing energy use through thoughtful equipment operation and better use of SCADA controls and alarm setpoints. They work with Gary Huffman of Krebs Engineering to determine which equipment they can take out of service and still maintain adequate treatment.

Projects include switching to more energy-efficient lighting in the plant’s 50 pole lights and in the three maintenance buildings’ bay lights. “We are about halfway through that project and have replaced more than 30 100-watt high-pressure sodium lamps with 20-watt LEDs, an 80 percent energy savings,” says White. The team has also replaced three 400-watt high-pressure sodium lamps with 150-watt LEDs, a 62.5 percent energy reduction.

The team is also involved in outreach. That includes helping attract young people to the profession to offset retirements. White attends water conferences that reach out to college students and has presented at high school career preparation classes.

He also would like the community to understand and appreciate more fully what he and his team members do: “We’re seen as the people who keep digging up the roads. Maybe we should get a sign that says, ‘Please pardon our progress while we work tirelessly to keep sewage from backing up into your homes.’”


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