By skillfully managing a combination of old and new, the Duck Creek Wastewater Treatment Plant has racked up an enviable compliance record and a wall full of awards.

Maintenance has been the key. Under the direction of Don Dudley, recently retired, Duck Creek plant’s nine-person maintenance team has kept the facility operating at peak performance. The plant, in Garland, Texas, never misses its permit requirements for CBOD, TSS and ammonia nitrogen.

Built in 1962, the plant (40 mgd design) has been expanded and upgraded several times since. Some of the key equipment dates back to the 1970s. “Maintenance is important for sure,” says Alex Stuart, plant superintendent. “Operators can only do so much. If it’s not working, we can’t move water.”

The facility has earned four Gold Peak Performance Awards from the National Association of Clean Water Agencies and has platinum in sight for 2019. In addition, the plant was named 2018 Category 3 Municipal Treatment Plant of the Year by the Water Environment Association of Texas and won the association’s 2018 George W. Burke Jr. Award for safety. 

Removing nitrogen

Duck Creek plant, one of two plants serving the Garland area, accepts flow from the west side of Garland, the Town of Sunnyvale, and parts of Richardson and Dallas. ABS raw water pumps (Sulzer Pumps Solutions) feed an average flow of 22.5 mgd to the headworks, which consist of step screens (HUBER Technology), a vortex grit removal system and a Muffin Monster grinder (JWC Environmental).

After settling in a group of five circular primary clarifiers, the wastewater flows either to the old section of the plant, which includes trickling filters and solids contact, or to the new section where it is aerated by fine-bubble polyethylene diffusers in basins operated in the step-feed mode. Hibon - Ingersoll Rand blowers supply the air; variable-frequency drives throughout the plant were supplied by Robicon (Siemens Industry).

“We have 12 basins,” Stuart says. “That includes 12 anoxic zones and 12 aerobic zones. It works really well.” The step-feed system has actuator valves that allow operators to control the flow of primary effluent to anoxic zones, aerobic zones, and back again to accomplish the required nitrogen removal. The configuration also provides the crew enough redundancy to take down specific basins for repairs.

Final treatment

After the secondary clarifiers, the water is filtered in deep-bed mixed-media filters filled with gravel, sand and anthracite coal. Chlorine is used for disinfection and sulfur dioxide for dechlorination.

Operators feed eight 1-ton chlorine cylinders at a time, keeping eight as backup, as well as four 1-ton cylinders of sulfur dioxide at a time, with four as backup. Final effluent flows to Duck Creek, a tributary of the Trinity River, which flows into the Gulf of Mexico.

Solids are not processed at the Duck Creek plant. The material is stored in two former sludge digesters that have been converted to holding tanks and then sent by two large diaphragm pumps (ABEL Pumps technology) through a 13-mile pipeline to the city’s Rowlett Creek Wastewater Treatment Plant, where it is dewatered and landfilled.

The Duck Creek plant is fully automated, using a SCADA system and Toshiba controls. Operators stay in touch via cellphones and email. Plant performance is consistent and exceptional. Effluent easily meets permit requirements of 10 mg/L CBOD, 15 mg/L TSS and less than 2 mg/L ammonia nitrogen.

Keeping it going

The Duck Creek plant maintenance staff is charged with keeping the old and new plant systems coordinated and functioning well. The crew of nine, consisting of mechanics and instrumentation electricians, uses a Cityworks software system to manage preventive maintenance, work orders and equipment history.

The more experienced team members work four 10-hour shifts per week, while newer members work five 8-hour days. Once they have enough experience, they move up to four 10-hour shifts. “We all help them along,” Dudley says. On a typical day, staff members come into the office to see if there are any pressing issues, then attend to 10 to 20 work orders generated by the maintenance software.

Dudley notes that the different types and ages of equipment can present unique challenges.

“The 200 gpm positive displacement sludge transfer pumps have operated relatively trouble-free since they were installed in 2008, but they are large and feature critical components,” Dudley says. “It’s a long line to the other plant. We look after the check balls and the diaphragms, which are hydraulically driven. Each pump has a 75 hp electric motor.”

The old trickling filters also run well despite their age, but the crew pays attention to the motors, slowing them down to remove biomass as needed and let the units regenerate. Piping around the plant presents another maintenance challenge.

“Ever since they were installed, we’ve had a number of piping problems,” Dudley says. “The previous staff put in several different pipe clamps. Some have lasted; others haven’t. We’re constantly repiping the older lines, taking one down at a time to work on it.”

The plant’s conveyors need to be cleaned regularly to remove snails, which end up in a dump container. Old wiring that often dates to the original 1962 plant needs to be replaced. The plant’s instrumentation and electrical team has updated the plant controls “to the speed of light,” in Dudley’s words.

Finicky filters

The plant’s deep-bed filters are one of the staff’s biggest maintenance challenges. “They are the original filters, dating back to 1962,” Dudley says. “They’re old carbon filters turned into gravel, sand and anthracite gravity filters, with 20 concrete cells, each 22 by 25 feet, containing 12 feet of media. They’re a bit more mechanically intensive than we’d like, and they’ve occupied most of our maintenance time in the last couple of years.”

The biggest task is maintaining the filters on the 92 24-inch valves. “They’ve not lasted as long as might be expected,” Dudley says. “The sand eats up the shaft bearings in the valve housings.” Another issue is replacing underdrains that have given way. It takes the maintenance crew a couple of days to remove and then refill the media.

“All of the filter units have been rehabilitated a number of times over the years,” Dudley says. “In the 2003 upgrade, we changed over to fiberglass pipe and added valves to control the fill, drain and backwash cycles.”

Experience counts

The experience of the Duck Creek plant’s maintenance crew pays off in many ways, one example being the headworks screens. “Our step screens are situated in concrete alleys,” Dudley says. “We have to pick them up out of the alleys to perform maintenance on them. The original chain and hoist equipment supplied for the job was both cumbersome and dangerous.”

Instead, the staff started using the plant’s 30-ton crane to hoist the screens out of the channel and then place them on a steel beam and perform the maintenance. “It’s a better way to do things,” Dudley says. Most times, the staff performs all maintenance in-house, saving money on outside contractors. In some cases, like the current primary clarifier bridge mechanism replacement and improved sludge withdrawal system, the staff assists the supplier.

Stuart, who has been at the plant for 33 years, reflects on the challenges ahead for the Duck Creek plant. Nuisance odor control and infrastructure are the biggest. In addition to the new primary mechanisms, the plant team is repairing the headworks screens, replacing pumps and motors throughout the plant, and forecasting for capital improving planning.

Tackling odors

The team has also embarked on an extensive program to identify and monitor sources of odor and install new odor control technology. “In the headworks area, we’re doing a pilot study on the effectiveness of using a hydrogen peroxide additive,” Stuart says. “We are considering covering the headworks area in a future phase of the project.” Also in progress or planned are covers for the primary splitter boxes, roofs and lids for the primary tanks, and deployment of biofilters and chemical scrubbers.

The Duck Creek plant emphasizes training and career advancement. “Employees get pay raises based on what they know and what they learn,” Stuart says. “It’s a skill-based pay system employed by the City of Garland.” There’s a strong emphasis on safety. Stuart emphasizes confined-space entry, lockout/tagout, CPR, chlorine handling and first aid.

“It’s been a good career,” Stuart says. “I tell the young guys they won’t be millionaires, but they can drive a new car, eat and have a nice roof over their head.”

Changes? Stuart has seen plenty. “I started as a baby right out of high school,” he says. “It’s a lot more technical than it used to be.”

He calls the changes in controls “fantastic.” They give operators more time to focus on cleaning and the little things a plant needs, instead of having to manually adjust flows and pumps: “It’s been a big boost for us.”

The ability to make old and new work together and still meet permit is especially rewarding in Stuart’s view: “We’ve received the NACWA Gold Peak Performance Award four years in a row, and with our fifth, we’ll receive the Platinum Award. That would be a real feather in our cap.”

Lots of experience

When Don Dudley retired last winter from maintenance manager, he took nearly 30 years of experience with him. But he left behind a savvy maintenance team that, paired with the operational crew, gives the Duck Creek Wastewater Treatment Plant in Texas a ton of hands-on knowledge.

Earl Gibson, senior member of the maintenance staff, has 30 years on the job, starting out as a janitor. The rest of the maintenance staff consist of mechanics Oscar Hernandez (4 years), Juan Arroyo (12 years), Dustin Musgrave (3 years) and John Higgins (3 years).

Instrumentation electricians Alex Franclemont, Shane DeLaPena and Jorge Rodas have 15 years of experience among them.

On the operations side, Alex Stuart, plant superintendent, has worked at the plant for 33 years and holds a Class A wastewater license. Jim Griffin (32 years), Juan Rodas (30 years), Matt Cast (21 years), Zack James (12 years), Donovan Musgrave (7 years) and Robert Ramirez (4 years) also hold Class A licenses.

Brandon Little (4 years) and Angel Perez (5 years) hold Class B licenses. Jorge Jasso (2 years) holds a Class C license, and Chris Gates (2 years) holds a Class D license. Add it all up and it’s more than 200 years of experience.

Stuart observes, “Without these employees, we wouldn’t have won all the awards.”