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Starting small, thinking big

Miniature treatment plant helps engineers reduce cost, footprint of new facility.
Ezzie Sauter Baca, water treatment technician (left), and Andrea Song, water treatment engineer (right), discuss an experiment using the pilot treatment plant’s replica filters. The filter tubes are filled with anthracite and granular activated carbon to strain out particles from the water.

How do you design a new water treatment plant that will cost several hundred million dollars and last more than 50 years — and make sure you get it right?

Start small.

One of Denver Water’s most important construction projects in three decades begins in a small room tucked away inside the 78-year-old Moffat Water Treatment Plant.

There, in a storage room 18 feet wide and 37 feet long, engineers and plant operators are running tests on a miniature version of a treatment facility that will eventually be the prototype for the real thing.

The results of those tests will be used to design the North System Renewal Water Treatment Plant at Denver Water’s Ralston Reservoir site near Golden, Colo. The new facility is expected to be built in the next 10 years.

The scaled-down version of the plant consists of two main components: a large tank that replicates the pretreatment process and four large tubes that filter the water.

“It really is a cutting-edge system,” said Andrea Song, pilot plant manager and water treatment engineer.

The pilot treatment plant replicates the processes used by a full-size water treatment plant. The pilot plant consists of two main components that replicate the pretreatment and filtering processes.

Song, along with water treatment technician Ezzie Sauter Baca, are among the engineers and operators running the tests. “It’s neat to see the treatment process happen before your eyes — usually it’s all underground,” Sauter Baca said. The pretreatment and filtering processes take about 3.5 hours in the pilot plant compared to 10 to 16 hours in the actual plant.

Song has designed water treatment plants across the country and is passionate about doing it right. “We want the most cost-effective design, but a design that also will stand the test of time,” she said.

They’re using the test model to determine the right size and flow rate for the new treatment plant’s filters. Filters are large concrete structures filled with sand and anthracite coal or granular activated carbon. The materials strain particles from the water, a critical final step in producing high-quality water.

The biggest challenge: trying to demonstrate how much water per square foot the filters can process in a minute. The current treatment plant has 28 filters. Determining the correct flow rate and filter material is essential in designing the number and size of the filters in the new plant, according to Zack Alabbasi, Moffat Water Treatment Plant supervisor.

“If we can build filters that can process more water, we won’t have to build as many. That means the footprint of the new plant will be smaller and cheaper to build,” Alabbasi said.

Moffat Water Treatment Plant has 28 filters. The tests using the pilot plant will determine the size and number of filters needed in the new North System Renewal Treatment Plant.

Denver Water purchased the pilot plant for $368,000, but Alabbasi said that building fewer filters could end up saving tens of millions of dollars in construction costs at the new facility.

Once the experiments at Moffat are complete, engineers and operators will use the pilot plant to test various water treatment strategies at all four of Denver Water’s treatment facilities.

The experiments will make the new facility more flexible for future regulations and better equipped to handle changes in water quality.

“The impact of climate change, pine beetles, floods and wildfires is changing our water supply, and we need to be ready for those changes,” Song said. “When people look back in 50 years at what we did today, we want them to say we made the right decisions. Our customers depend on us for great water, and we intend to keep it that way.”

Take a virtual tour of Denver Water's treatment process.