Quick and creative action helped Wichita Falls develop a direct potable water reuse system in the face of an historic four-year drought.
Drought. You wouldn’t call it a blessing in disguise, but it may have a positive side.
That’s becoming evident at Wichita Falls, Texas, where the utility fast-tracked an emergency direct potable reuse (DPR) system three years ago and is now converting it into an indirect potable reuse system (IPR) designed for the long haul. Customers have become well educated about drought and water reuse, and water safety and supply are now top of mind at the city Public Works Department.
“With rains last spring, we’re in pretty good shape now,” says Mark Southard, water purification superintendent. But the utility and community are much more water-conscious than before; overall water consumption is down since the drought ended, and the water treatment operation is more focused on saving water.
For one thing, Southard says, “We’re concentrating on capturing and reusing as much filter backwash water as possible.”
High and dry
Wichita Falls draws its raw water from area lakes that depend on rainfall, normally averaging 28.5 inches a year. In 2011, as temperatures exceeded 100 degrees F for 100 straight days, rainfall dropped to 13 inches, after 19 inches fell in 2012, making the two-year period the driest on record. There were only modest improvements in 2013-2014, and the overall effect was that the source water lakes dropped to record low levels.
The city took bold action in permitting, designing, building, testing, certifying and starting up the direct potable reuse system in less than 27 months. A 12-mile, 32-inch HDPE pipeline laid on the surface (pipe supplied by ISCO Industries) carried 5 to 7.5 mgd of secondary wastewater from the River Road Wastewater Treatment Plant to the Cypress Water Treatment Plant. That represented a large share of the city’s potable water output of 10.5 mgd.
“That 10.5 mgd was achieved through water conservation and drought restrictions,” notes Daniel Nix, utilities operations manager. “Before the drought we normally averaged 22 mgd with a summer month average of 30 mgd.”
At the Cypress facility, the water passed through existing microfiltration and reverse osmosis units, then flowed to a lagoon where it was blended half and half with lake water before being sent back through the water treatment plant for conventional treatment. The MF and RO units were already in place since they had been used in the past to treat surface water from a brackish source.
Besides taking advantage of the existing equipment, the new flow scheme yielded savings because the conventional water plant no longer had to use its lime softening and CO2 restabilization processes.
Public safety was paramount. Nix observes that the city analyzed and tested for corrosion control and used multiple levels of disinfection throughout the process: “We monitored cumulative virus, Giardia and Cryptosporidium log removal every eight hours.” Concentration and time calculations were tracked across all disinfection zones. In addition to the pipeline ($9 million), the only other major expense was for online monitoring equipment. “As far as large plant improvements were concerned, there were none,” says Nix.
The Wichita Falls DPR system ran for 12 months without any operational issues. It was shut off in July 2015. There were no health effects or quality issues. “Our customers felt the taste and quality of the water was superior to what they had been receiving before,” Nix says. “We actually had some folks ask us to turn the reuse system back on.”
More than adequate rainfall in 2015 allowed the utility to discontinue direct reuse, and allowed time to model the indirect reuse system, obtain permits, complete design and begin installation. The pipeline has been cut into sections and is being reassembled in a trench that will take treated wastewater from River Road to Lake Arrowhead, one of the city’s source water lakes.
There it will mix with the lake water before being pumped to the Cypress and Jasper water treatment plants and fed into the distribution system. The local firm of Biggs & Matthews did the design for the DPR pipeline. The IPR pipeline was designed by Corlett, Probst and Boyd.
Nix expects the indirect system to be up and running by the end of 2017. Capacity will be 16 mgd, but Nix expects the average daily flow to be about 10 to 12 mgd.
No improvements will be required at the two water treatment plants, which employ conventional treatment including pre-disinfection, coagulation and sedimentation, filtration and post-disinfection. Clearwell capacity is 1/2 million gallons; inground storage basin capacity is 18 million gallons at both plants for a total of 36 million gallons.
Southard says the inground storage basins enable the plants to remineralize the RO water, which can be aggressive. Plant production capacity is 52 mgd at Cypress and 24 mgd at Jasper.
River Road upgrades
Meanwhile, $30 million is being spent to upgrade treatment at the River Road plant. Improved nitrogen and phosphorus treatment systems are being added. In a design by CDM Smith, a new liquid oxygen system will boost dissolved oxygen to maintain required oxygen levels at the end of the reuse pipeline, and lime will be used for alkalinity adjustment.
Cloth disc filters (Aqua-Aerobic Systems) will provide a barrier against Giardia cysts and Cryptosporidium cysts while boosting phosphorus removal. The system will be equipped with new high-service pumps. All chlorinators and sulfonators will be replaced with the most current models. To improve monitoring, a new SCADA system with PLCs, servers and several HMI consoles will be installed.
Still, that’s considerably less than what would have been required if Wichita Falls had continued with direct reuse. “If we’d stayed with DPR, we would have had to spend another $40 to $50 million on a new advanced water treatment plant,” Nix says.
The IPR system will sustain the city’s water supply into the future and will also be more efficient. The direct system saw water losses of about 20 percent because MF and RO systems produced brine, which also needed disposal. Nix notes the indirect system will make 100 percent of the water available for reuse: “Indirect reuse will be our long-term solution.”
Big changes in water treatment like this don’t just happen. Staff training has been a key to the success of the reuse innovations. Because the reuse systems involve both the wastewater and water treatment plants, the utility took the opportunity to cross-train the operators.
“We took the water treatment operators to the wastewater plant and showed them how it worked,” says Southard. “Then, we reversed the roles and took the wastewater plant staff to the water plant so they could learn about water treatment. They’d been operating parallel to each other for years, but they needed to communicate in order to know what each other needed.”
One of the understandings that came out of the cross-training had to do with ammonia. “At the wastewater plant, they’d been trained to take out as much ammonia as they possibly could, but the operators at the water plant explained that they needed some level of ammonia in the feedwater so they could create chloramines in the pre-disinfection process,” says Southard. “It was like, ‘Please leave some ammonia in the water.’ It was important that both operational teams understood why this was so important.”
Potable reuse systems create a number of new challenges for operators. For one thing, a new certification process is called for. The utility took the lead in working with the Texas section of AWWA and Water Environment Association of Texas to put together a reuse certification program. “Currently, we’re developing a curriculum and training certification process,” Nix explains. “Both Texas and California are sharing ideas.”
He expects the program to be complete within 12 to 24 months, and that the entire Wichita Falls water and wastewater staffs, including operations and maintenance, will become certified before startup of the IPR system.
Training and certification were also critical during the operation of the MF and RO units during operation of the DPR. About half the water plant staff members were on board when the RO units were started up to treat brackish water, but the others had been hired since and required training on the advanced filtration system operation and maintenance.
“We worked with the Texas Commission on Environmental Quality (TCEQ) to get all our operators fully trained and certified,” says Southard. “The South Central Membrane Association approved the modules.”
Harold Burris, wastewater plant superintendent, says all operators are certified for wastewater by TCEQ. “We also require all mechanics to be certified,” he says. “They need to understand the process and what the potential consequences may be if they make an equipment change. We also have budgeted for employees to be cross-trained in water treatment. Even though they currently can’t obtain their water operator certification, we feel it will help them understand the process and what is required to treat water to drinking standards.”
Even though water levels in the source water lakes are back to normal, Wichita Falls is taking whatever steps it can to make sure enough water will be available in the coming years to meet demand. Southard says the backwash water from the filtration process is now being pumped into a lagoon, then pumped back into the water treatment plant and retreated.
“We can use up to 50,000 gallons to backwash, and it doesn’t make sense to waste that water,” Southard says. The RO units are a different story. They’re still in use even though the DPR system has been shut down, filtering brackish water from Lake Kemp as a supplement to the other source water lakes.
“We don’t have the ability to reuse backwash water from the RO units,” Southard notes. “It’s a little more difficult because the RO wash water is so concentrated. While we can’t recycle it, we are adjusting the recovery rates on the RO units from 70 to 80 percent, again, as a way to conserve water in the treatment process.”
It took a team to get through the most serious drought in Wichita Falls history, and city officials have been generous with praise for the utility management and staff, as well as the citizens. Darron Leiker, city manager, observes, “Bringing the DPR project to life was a team effort, including the citizens who had to implement significant water conservation strategies. These, along with the DPR project, helped extend the life of our water supply.”
The project received a Municipal Excellence Award from the Texas Municipal League, the Alan H. Plummer Environmental Sustainability Award from WEAT, and a Project of the Year award from the Texas Public Works Association.
Mayor Glenn Barham adds, “This is special. The awards recognize all the hours, days and months of researching, planning, testing, overseeing and constructing the DPR project.
“When our backs were against the wall and we were facing the drought, with no good news in sight, our people stepped up and found a solution to keep water flowing to our residents.”
Acceptance through education
Potable water reuse systems, direct or indirect, often spark public controversy. Some people say, “I’ll get a second chance to drink my beer.” And the media contribute the overused “toilet to tap” label.
Wichita Falls officials credit an effective education program with helping the city’s direct and indirect potable reuse systems gain acceptance and understanding. “Education is the key,” says Daniel Nix, utilities operations manager.
“We did several things that I believe worked in concert with each other to gain the public’s acceptance of the direct potable reuse system. First, we kept them completely informed about the drought situation and how long we were projecting the remaining water would last. That way they knew the seriousness of the situation.
“Second, we relied heavily on the local media. When we proposed the DPR, we brought them all in for a brunch and discussed the entire thing with them from the wastewater plant through the water treatment processes. They did nonstop stories on the drought and the DPR.
“Not only did they do stories on each process and what it accomplished, but they also highlighted the state-of-the-art laboratory we had as well as the training and certification all our operators possessed. In 365 days, our local newspaper ran over 280 stories. We needed the public trust, so we were completely transparent about everything, even if it was bad news.”
Finally, Wichita Falls enlisted the help of the medical profession and a local university to help validate the safety of the system. “We felt that if they heard from medical doctors and academic people with pedigrees, the public would be more accepting than just hearing it from city officials,” says Nix. “We toured them through the plants and asked them to make statements on a video that we released. It’s still on YouTube.