The Texas city of Midland needed a new clean-water plant. Pioneer Natural Resources needed an alternative to groundwater for its oil and gas fracking operations.

The result is the Midland Water Reclamation Facility, completed last March and now producing 10 mgd of tertiary-treated water that meets or outperforms Texas Type II reuse requirements — a tenfold improvement in effluent quality over the previous facility.

Pioneer has built a pipeline network that enables it to pump water to its various operations throughout West Texas. Cory Moose, assistant utilities director for Midland, calls the facility a huge win-win for the city and Pioneer.

“The upgrade limits the need for freshwater for oil and gas operations in the area,” says Moose. “It creates an affordable, reliable, long-term source of water for Pioneer, while providing the city with necessary infrastructure improvements. In an area where water resources are scarce and depleting, this project was critical to securing the water needs of the oil industry.”

A comprehensive training program has helped the plant team members adjust quickly to a treatment process with which few had previous experience. The plant went online in April 2021.

Significant upgrade

Before building the new facility, the city operated with preliminary and primary treatment only. Wastewater was delivered to a set of eight facultative lagoon cells where settling reduced the BOD content to about 30 mg/L, well below the permit level of 100 mg/L.

The effluent from the ponds was applied by spray irrigation on some 3,000 acres owned by the city and leased to farmers who raise alfalfa and other crops for animal feed. The same land was used for land-applying biosolids.

In 1974 the city built a 6.0 mgd (design) secondary treatment facility with mechanical aerators and clarifiers to supply reuse water to golf courses. “But it couldn’t remove nitrate to a level where it could prevent the grass from burning,” Moose says. It remained in minimal operation as insurance toward meeting the BOD permit limit.  

In time, nitrate levels began to rise in the groundwater table below the land application field, “So we were looking at something to be more environmentally friendly,” Moose says. “We were looking at ways to stop using that land.”

Meanwhile, “People were starting to get a bad taste in their mouth from oil and gas companies pumping water out of the ground for fracking.” In 2014, the city issued a request for proposals seeking an oil and gas company to purchase 100% of the effluent from a new state-of-the-art water reclamation facility. The city chose Pioneer as the best-qualified bidder to install the infrastructure needed to accept the water. 

Brand new process

The plant was constructed by Jacobs under a design-build contract. “Once we knew that Pioneer was going to invest in the secondary and tertiary parts of the plant, we upgraded our primary portion,” Moose says. Influent passes through a RakeMax bar screen and RotoMat rotating drum screens (Huber Technology), followed by a PISTA Grit system (Smith & Loveless) and a cyclone grit washer (Jim Myers & Sons). Shaftless screw conveyors move screenings and grit; existing grit pumps were replaced with submersible pumps (Flygt, a Xylem brand).

New primary sludge pumps (Trillium Pumps USA - WEMCO) feed primary sludge to the anaerobic digesters, and the primary clarifiers have new mechanisms (Walker Process). The primary treated water passes through a junction box to three bioreactor basins with oxic and anoxic zones and a swing zone with Flygt mixers.

Four turbo blowers (Sulzer) deliver air by way of fine-bubble diffusers (Sanitaire, a Xylem brand). The flow then passes to three circular secondary clarifiers (Walker Process), followed by two Aqua MegaDisk cloth filters (Aqua-Aerobic Systems) and two UV disinfection channels (WEDECO).

The vast majority of the final effluent is delivered to a pump station owned by Pioneer. The plant retains the option to send effluent to the existing ponds, or discharge via cascade post-aeration to the Midland Draw, an intermittent creek.

In addition, influent can be diverted to the ponds if ORP probes at the junction box or at the end of the biological process indicate something out of the ordinary. “If somebody dumps a toxic load, gates will automatically shut off the water and send it out to our ponds,” Moose says. “We do that to protect our secondary process.”

The solids side includes a return and waste activated sludge pump station (Flowserve), aerated sludge holding (Flygt decanters), two anaerobic digesters heated by Cleaver-Brooks boilers and Walker Process heat exchangers, a gas handling and flare system (Varec Biogas), and five screw presses (Huber) for biosolids dewatering. Most biosolids are landfilled, and plans call for 100% landfilling, after contracts with farmers for land application expire in 2022.

Biological treatment is regulated by way of dissolved oxygen measurement, or direct measurement of ammonia with online probes in the basins. All online instrumentation is from Hach; all flow- and pressure-measurement devices are from Endress+Hauser. “We tried to make all the equipment as universal as possible,” says Moose. “Maintenance is easier when there are fewer manufacturers.” A new SCADA system uses Wonderware software (AVEVA).

Prepping the team

Bringing operators up to speed was a critical challenge; training began at an early stage.

 “As construction was going on, we had the operators on shift accompany the superintendent on site, or the startup and commissioning manager,” says Moose. “They walked around to see where everything was, the current construction activity, where the valves and piping were located, what each process did, why it was important, what to look for.”

The Jacobs process engineer started formal training two months before startup. Operators received training on each piece of equipment, broken down into two sessions. Operations and maintenance training was conducted multiple times so all staff could attend. It covered the preliminary, primary, secondary and tertiary processes.

“We have facility training scheduled again at one year,” says Moose. “This will give the operators a chance to ask questions about the issues they’re seeing in the field. It’s difficult to know what questions to ask during initial training because you have never operated the equipment before.”

Moose notes that the team members caught on quickly: “They went from strictly mechanical treatment to a biological system where they have to pay attention to bugs.” An instructor gave basic microscopy training to the operators and a more advanced version to the lab staff. 

To guide the staff, the city hired Bennie Jordan as plant superintendent; he came with nearly three decades of experience with activated sludge plants and having trained hundreds of operators in how to run them. “We brought him on board so he could keep an eye on things,” says Moose. “We didn’t have anybody with activated sludge experience. We’d been reading about it in books, but it’s different when you’re out there smelling it, feeling it, doing it.”

Collaborative leadership

As construction proceeded, Moose held meetings with the staff to share the plans and specifications and to seek their input on the SCADA system and instrumentation. “That helped create buy-in,” he says. “If they have some say-so in what’s to be put in, people tend to take care of it better.”

Construction proceeded smoothly, without delays. “It was one of the most professional construction jobs I’ve ever been on,” Moose says. “The Jacobs team did a lot of homework up front, and it showed.

For maintenance the facility taps into the Cityworks program Midland uses for its wastewater collection and water distribution systems. “We’re putting all the maintenance on Cityworks so it will generate work orders for us and we can track everything,” Moose says. “We have limited maintenance staff, so we want to make sure we’re not missing anything. We have all the assets identified and GPS-tagged.”

The scheduled preventive maintenance program is augmented by predictive maintenance, using tools such as quarterly infrared thermography on motors, motor control centers and termination panels, and vibration analysis on rotating equipment such as motors, pumps and blowers. Maintenance contracts cover major process equipment including the blowers, UV disinfection systems, bar and drum screens and screw presses. Moose expects that comprehensive approach to enable equipment to exceed its normal life expectancy.

Critical lab role

Moose cites the lab team, led by Angelica Olivas, lab administrator for environmental compliance, and Alma McCammond, quality assurance/quality control manager, for playing a critical role in startup and in continuing operations. 

“The increase in the lab’s workload was significant,” he says. “We have to meet Type 2 effluent requirements if we send the effluent to Pioneer. That’s a different standard than if we discharge to the draw, and there’s a different standard if we send it to the land application site.

“So based on where it’s going and what we’re doing, we have to monitor different parameters. That increased load the on the staff in grabbing the samples. And because the plant has doubled in size, from 11.5 to 20.5 acres, their rounds take twice as long with the same number of people. Before all this was built, they took about 1,200 samples a month. Now take about 3,150 samples to meet the different requirements we have.

“There was a point where the lab was working 12 or 13 hours a day. They did a lot of the startup testing on the performance criteria. They did that for about three months during startup to make sure everything was in compliance and the equipment was meeting the manufacturer specifications. Now that the plant is running, there is constant communications between the operations and lab staffs.”

Running the show

The Midland facility is staffed 24/7/365 with 12-hour shifts. To meet the challenge of finding qualified operations staff, the city offers competitive wages along with pay increases for each advancement in licensure. “We’ve also created a leveling scheme so that operators don’t feel stuck at one level until someone leaves or retires,” says Moose. “There is opportunity for advancement even if the retention rate is 100%.”

The plant requires an operator with at least a Class B license (second highest in Texas) on every shift. As of last May, six operators had reached or exceeded that level. Operators take advantage of local training programs and have a training room on site where they can access online classes. “We’ve been fast-tracking them, giving them as much training as they can handle, so they are able to advance quickly in licensing,” Moose says.

Team members still at the land application site are being cross-trained to operate the plant, “because eventually the land application site is going away.”

In the end, says Moose, “This facility also serves as an example of how public and private entities can maximize conservation efforts and resources by working together.”