Constantly Changing Source Water Is No Problem for This Award-Winning Water Treatment Plant

An Arizona plant succeeds with operational excellence and dedication, despite rapid raw water quality fluctuations and seasonal algae.
Constantly Changing Source Water Is No Problem for This Award-Winning Water Treatment Plant
Brian Warner, lead operator, cleans the 2100AN turbidimeter (Hach) in the treatment building at the Superstition Area Water Plant.

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When the Superstition Area Water Plant began operation in June 2016, customers got to choose the name. “The plant sits at the base of the Superstition Mountains, and that was the name the majority of our users chose,” says Brian Warner, lead operator. The 2.0 mgd (10 mgd design) plant serves about 14,000 people in Apache Junction, Arizona.

Owned and operated by the Apache Junction Water District, the plant draws surface water from the Central Arizona Project canal, which is fed by the Colorado River. Before the $9 million facility came online, the city of Mesa treated the majority of the district’s water.

The new plant is integrated into the district’s distribution system and provides 80 percent of the water demand; it can supply 100 percent if needed. Warner deals daily with changing source water turbidity and seasonally with algae outbreaks, both of which he manages with help from instrumentation, lab testing, and experience.

In 2016, the facility won the Small Treatment Plant of the Year and Project of the Year awards from the Arizona Water Association. “We won these awards because we have a great team who planned out a great water plant and a district and board that supports us,” Warner says. The plant also won a 2017 Project of the Year Award from the Water Infrastructure Finance Authority of Arizona.

From idea to reality

Warner is the sole operator and handles laboratory testing, grounds maintenance, equipment lubrication/calibration and housekeeping. “I love keeping the plant looking new,” he says. Being the only operator has its challenges. Fluctuations in raw water quality and a recent algae outbreak have caused some headaches.

Warner’s dedication and nearly 20 years’ water treatment experience allow him to meet such challenges head-on. Finished water quality has 0.037 NTU turbidity and 0.6 to 0.75 mg/L chlorine residual. The idea for the plant was first discussed in 2008 and picked up steam in spring 2015. “It took a year to complete,” says Frank Blanco, district director. “Brian came on board three months after we broke ground.” He and Mike Loggins, water district engineer, worked with the contractor and design engineer.

Warner recalls, “I provided feedback on the design, and they made changes based on my input. A big part of that input was to design and equip a lab.” Equipment includes a Hach DR6000 UV VIS spectrophotometer, Hach 2100AN turbidimeter, and pH and conductivity probes. Warner performs daily conductivity, pH, UV254 tests, and compliance testing for turbidity and chlorine.

Control of destiny

The plant gives the district control over the delivered water quality. “I can monitor the raw water temperature and pH changes and also better examine contaminant levels,” Warner says. “We can store water, ensuring a two-day supply in case of a canal outage.” An emergency generator can run the entire plant if it loses grid power. Indoor and outdoor LED lighting and pumps with variable-frequency drives reduce energy costs.

Raw water enters two self-priming suction pumps (Gorman-Rupp) mounted on a bridge over the Central Arizona Project canal. The water is sent to an automatic strainer (R.P. Adams) for preconditioning and is then treated with aluminum sulfate and polymer. Preconditioned water enters the 1,400 gpm upflow adsorption clarifier (AWC Water Solutions).

Clarified water is sent to two multimedia filters and then to sodium hypochlorite post-disinfection on its way to the finished water clearwell. After contact time, the water is pumped to offsite storage facilities where it undergoes chlorine residual boosting before delivery to customers. The plant is fully automated and has a SCADA system with FactoryTalk ViewPoint software (Rockwell Automation) and four programmable logic controllers with Allen-Bradley processors that Warner can access from offsite.

Handling solids

Roughly 10 percent of the spent water is recycled back to the head of the plant. “Our wash-water recovery system sends all recovered waters, from the auto strainer, flushing and backwash processes, instrumentation and floor drains, to the equalization basin,” Warner says. From there, the water is transferred to a conical-bottom reclaim tank with a floating decant suction intake. Recycle pumps do the rest.

“We have a timer that allows solids to settle into the hopper bottom of the tank,” Warner says. “We typically allow 30 to 60 minutes of settling time before the decant pumps start.”

Accumulated solids are transferred to above-ground thickening tanks. When solids consistency reaches a greater than 30 percent settled volume, the solids are dewatered and removed by a belt filter press (Alfa Laval) and landfilled. Filtrate water from the belt press can be recycled back to the equalization basin for treatment or sent to the wastewater treatment plant.

Doing it all

Warner started with the district in February 2016. He holds Class 4 Water and Distribution Operator and Class 1 Wastewater Collections licenses. He reports to Loggins (Class 4 Water and Distribution). During plant startup and commissioning and through the first year, Warner was often at the plant seven days a week, eight to 12 hours a day, and he was on call around the clock. Now, a 40-hour work week is more typical.

In August 2017, the district hired Hazel Hannah, a senior at Arizona State University, as a part-time intern. “She’s majoring in environmental resources management and works weekdays around her class schedule,” Warner says. “She’s been learning day-to-day operations, water quality testing, equipment calibration and maintenance.”

The main treatment challenge is the raw water turbidity. “It can be 10 to negative 20 NTU from February to April,” Warner says. “At least 95 percent of our monthly finished water samples must be less than or equal to 0.3 NTU.”

“The heavy, silty, loamy stuff that settles quickly is easier to remove,” Warner says. “The lighter, fluffy stuff is not easily settled, is very hard to manage, and clogs the filters. The automatic strainer helps. It only takes an hour or so to remove and replace the tubes in the carousel and give the plant a better opportunity to do its job by screening out some of the turbidity before it enters the train. I also have three different pore-size elements with a reverse-wedge wire wrap and a mesh wire orientation, which I use as a toolbox to deal with the changing water quality.”

Dealing with algae

In 2017, a summertime algae bloom in the canal system, which included Lake Pleasant water, created some operating challenges. “The particular offender is a diatom known as Cymbella, or rock snot, that forms long fibers,” Warner says. “It is an intake- and filter-clogging nuisance organism.”

The situation was especially bad in June, when the temperature peaked at 122 degrees F. “The algae was plugging the automatic strainer tubes, forcing the strainer to backwash based on differential pressure every six minutes,” Warner says. “The strainer had to be manually cleaned every two hours, which required shutting down the plant.” During that time, Warner enlisted the help of district staff.

Changing the raw water ratio helped: “We changed the ratio of the percentage of water coming out of Lake Pleasant with water currently in the canal. We also lowered the total volume pumped from the lake. By doing this, we were able to change the ratio of lake versus pass-through water, which is primarily Colorado River water.”

In spite of all this, Warner enjoys the challenges of surface water treatment: “I like the fact that the water quality changes daily, hourly, by the minute. It keeps me on my toes. It also allows me to learn new things while troubleshooting the process, like trying to predict needed changes based on equipment readings and past experience.”

Community outreach

Warner gives back by conducting plant tours through the Arizona Water Association. He and Loggins are involved in the Apache Junction Water Festival, held every April in a park and coordinated by the district, the University of Arizona and other sponsors. It’s geared to fourth-graders, who learn about watersheds, groundwater, the water cycle and water conservation.

“We divide the kids into four groups of roughly 20 to 30 and have preset stations where we present 30-minute topics,” Warner says. “There are models that show a cross section of the Earth and how surface water and runoff impact the water level in the aquifer, both with pollution and recharge. The teachers provide some pre- and post-festival testing as part of their curriculum. It’s been a successful program.”

As for the future, Warner sees the plant expanding to its full 10 mgd capacity with the addition of four more treatment trains: “That would depend on whether the state land around our plant is released for development. We have the water rights, so we’re poised to make that happen.” The plant may also add a sedimentation basin.

Warner plans to stick around: “This is my home away from home. I start at 6 a.m. and work until I’m done. Although I operate the plant independently, it’s the planning and design work of Frank and Mike, and the support of the field and office staff, that make what I do here possible. They’re the best.”




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