An award-winning recycling plant relies on the ingenuity of its operators to provide excellent-quality water for its community while holding down costs
The Padre Dam Municipal Water District has been treating and recycling wastewater since the early 1960s — long before sustainability was a common buzzword.
“We were the first plant in the world to treat and recycle,” says Gary Canfield, plant manager at the facility in Santee, Calif., near San Diego. “The facility was built to decrease the district’s reliance on imported water from the Colorado River and delta.”
Today, the Padre Dam water plant has five operators who make sure it consistently meets California Title 22 reuse requirements. They also use their skills to save the plant money.
Their work has led to many awards over the years, including the 2010 Plant of the Year Award from the San Diego Section of the California Water Environment Association. The CWEA also recognized three of the operators for innovations that are saving Padre Dam ratepayers tens of thousands of dollars a year.
Recycling for recreation
The Padre Dam facility receives 5.2 mgd from Santee, El Cajon and Lakeside. Sixty percent of that waste is diverted to the City of San Diego Metropolitan Wastewater Department system for treatment at the Point Loma Wastewater Treatment Plant and offshore discharge into the Pacific Ocean.
The other 40 percent (2 mgd) is treated at the recycling plant and distributed to customers for irrigation and commercial reuse, and to maintain the Santee Lakes Recreation Preserve’s seven man-made lakes.
Each day, one million gallons of dechlorinated water flows from the recycling facility into the lakes to offset evaporation. The remaining one million gallons is distributed to 217 customers to help pay for treatment costs and reduce demand for imported water by 12 percent. The recycled water is used for parks, athletic fields, golf courses, public and commercial landscapes, ornamental water features, freeways, medians, construction and industrial purposes.
“The lakes have become internationally famous, as they were the world’s first example of how a community’s wastewater can be reclaimed and reused by people, with full public acceptance,” wrote Leonard A. Stevens in his book, The Town that Launders its Water.
Canfield observes, “The water that goes to the lakes is clean enough to allow public access.” The Santee Lakes Preserve sees more than 600,000 visitors a year for boating and fishing, camping, picnicking, fitness and special events on the lakes and 190 surrounding acres. Funded by camping and user fees, the preserve is hailed as a model for how communities might use recycled water to provide tax-free parks and recreation.
When rainfall is sufficient to reduce the need for irrigation, the excess recycled water is dechlorinated and discharged through the Santee Lakes into the San Diego River.
The influent flows to two rectangular primary clarifiers, a five-stage Bardenpho biological nutrient removal process designed by Dr. James Barnard, and two rectangular secondary clarifiers. From there, the water goes to two flocculation and sedimentation basins, four deep-bed sand filters (Tetra Tech) for denitrification, and finally to a chlorine contact basin for disinfection.
The original 1.0 mgd plant was built in 1959 at the south end of the property to meet local development needs without paying to transport wastewater to the San Diego metropolitan water system. The lakes were built one by one to use as oxidation ponds. Percolation beds were built with an underdrain system to collect the processed water to feed the lakes.
In 1968, the plant was moved three miles north to its current location, and three oxidation ponds were added with a total capacity of 40 million gallons for the secondary treatment process. Eleven percolation ponds were added for the effluent.
The water passed through percolation ponds and then was captured from underdrains, chlorinated, dechlorinated, and discharged to the lakes. The plant was upgraded again in 1997 to treat 2 mgd using the Bardenpho process. The recycling facility no longer needs the oxidation and percolation ponds.
Treating wastewater to the tertiary level takes about 24 hours. Computers monitor and control the treatment process, flow levels and water quality, and log the data. The operators analyze the data and make daily adjustments to ensure that everything is working properly. “We are not only meeting the Title 22 standards, but are regularly outperforming them,” says Canfield.
A winning team
The Padre Dam plant has a staff of nine. Besides Canfield, there are five operators (Robert Northcote, Donald Denniston, Ryan Hughes, Ryon Dawson and Travis Tomlin) and three laboratory technicians (Debbie Schultz, Phillip Stevens and Jessica Bertasso).
Canfield, Northcote and Denniston are Grade 5 operators, Dawson and Tomlin are Grade 3, and Hughes is Grade 2, working on Grade 3. The lab technicians handle testing for the water recycling plant and the potable water system. For the recycling plant, they test for BOD, COD, TSS, volatile suspended solids (VSS), pH, conductivity, nitrates, nitrites, ammonia, phosphorous, bacteria and chlorine residual. Contract labs perform tests for metals, grease and oil, asbestos, cyanide, methyl tertiary butyl ether (MTBE) and trihalomethanes.
The operators do all the maintenance and share their skills. They have learned how to use the tools in the shop and can all step in and do repairs. Training is important, and Canfield encourages his staff to pursue professional development. He also recommends that each operator attain Grade 3 certification.
Employees attend classes at Cuyamaca College in nearby Rancho San Diego, which has a wastewater treatment plant operator certification program. They also take one- and two-day seminars offered by the CWEA and many companies. Operators are required to complete as many as three Web-based training programs a month, and they also take part in hands-on Level A safety training, conducted by outside consultants.
Besides the day-to-day plant operation, the staff members give tours of the facility. In 2010, they gave 25 tours for about 450 people, including a two-day tour for 50 engineers and plant operators from Mexico. “Rob Northcote is in charge of that, and we have elementary school kids, college students, park visitors,” says Canfield. “I think the tours are a great thing, because they help people accept and support recycling.”
The plant’s greatest challenge is operating the system at 100 percent performance, 100 percent of the time. “It’s our goal, but we run into problems, since rain can affect the biological process,” Canfield says. “We had a lot of rain in January and February this year, and when the rainwater gets into the system, the microbes don’t like that.”
To offset biological system upsets, they use chemical treatment (aluminum sulfate and methanol). “The challenge is to keep water quality at a high level all the time while keeping costs as low as possible,” Canfield says.
Three of the plant’s operators won the 2010 CWEA award for innovation. Operations supervisor Northcote and operator Hughes won the Gimmicks and Gadgets Award for a screening system they designed, fabricated and installed using spare parts like motors, gears and piping.
“During the plant upgrade in 1997, we decided to continue operating without a screen, since we were able to operate so many years without it,” says Canfield. “We annually took the plant offline and manually removed the rags from the tanks, pumps and piping.” The screening system Northcote and Hughes built is an 18-inch-wide rubber belt with quarter-inch holes spaced one inch apart.
The belt is driven around two 6-inch pipes spaced eight feet apart. That allows the belt to travel through the flow stream, pulling out rags and larger material. The screenings are sent to a waste pipe and returned to the main sewer system, which carries the material on to San Diego’s Point Loma plant. The system cost $3,500, versus $60,000 for a commercial system, not including installation.
“The main cost was for the belt and a concrete structure that needed to be cleaned, rebuilt and epoxy-coated before putting the system together,” says Canfield. “The rest of the equipment was pretty much on hand at no cost.”
Northcote recalls, “It took us a month or so to complete, and the longest time was waiting for the concrete to be coated by an outside company.” Says Hughes, “We enjoy doing these types of projects, and we like to do them at the lowest possible cost.”
Operator Denniston won the CWEA Peter B. Fiedler Award for creating a portable nitrate analyzer that lets plant operators monitor nitrate levels and maximize nitrogen removal anywhere in the treatment process.
Canfield explains, “Don used an existing analyzer that was permanently mounted on one of our tanks. He wired a transmitter into the analyzer and then found a location in the treatment plant where a receiver could be mounted and connected to our SCADA system. He also had to build a clamping system that allowed the unit to be moved from tank to tank.”
The analyzer cost $2,600, most of which was for the transmitter and receiver, versus $45,000 for a commercial system. It took Denniston a few weeks to acquire the equipment and a week or so to put it together, between his normal daily tasks. “I was given the task of making this portable analyzer, and I enjoyed the reward of creating it. It’s unique to our treatment plant,” says Denniston.
Canfield adds, “Our operators are always thinking outside the box in trying to optimize plant operation. Rob, for example, is very good at building something out of nothing, and he enjoys doing it. He has trained the rest of the staff on how to fabricate.”
Canfield stresses that the plant is successful not only because of innovation, but because the staff enjoys their work. “Our weekly pizza parties help with that,” he says.
The Padre Dam plant is conducting a feasibility study on expanding to 4.4 mgd to keep up with the community’s demands for recycled water. At some point, the staff would like to expand the facility to 10 mgd to provide recycled water treated to an advanced level for two groundwater recharge projects.
In the meantime, Canfield and his crew will keep striving for excellence. His advice for other operators is to think outside the box.“It’s OK to use manuals from your designers, but every plant has its own personality,” he says. “A biological system is a living thing, and you need to be intimately involved in how it responds to adjustments.”
Many years of wastewater experience have helped the Padre Dam team. Canfield has 29 years, Denniston 27 and Northcote 14. “Most of us have grown up here,” says Canfield. “We know when our bugs aren’t happy, and we respond!”