The recently completed $310 million final phase of a wastewater recycling program is helping the Orange County Water District meet a challenging mission: Keep replenishing the Orange County Water Basin, arguably the region’s most valuable natural resource.

Protecting the 270-square-mile basin is critical because it’s the main source of water for roughly 2.5 million residents in Orange County, just southeast of Los Angeles. In fact, the recycled-water program — called the Groundwater Replenishment System — supplies 77% of the county’s drinking water.

And that figure is expected to rise to 85% this spring due to increased production of recycled water and recent increases in stormwater, says Mike Markus, general manager of the OCWD. The organization is headquartered in Fountain Valley.

Throw in the fact that the semi-arid desert region receives an average of just 13 inches of rain per year — and much less in recent years — and has suffered from drought for decades and it’s easy to understand why the GWRS is such a critical component of the district’s water portfolio.

“The GWRS is the largest potable recycled water system in the world,” Markus says. “It’s also nationally and globally recognized for its innovative approach to groundwater management.

“Groundwater costs about half of what imported water costs, so it’s very important to provide as much groundwater as we can while still sustainably managing the Orange County basin,” he adds. “We don’t want to over-pump the groundwater basin, so we have to ensure we have a sufficient supply of water to refill the water basin.

“With the third phase of the GWRS in place, we now can continuously replace about 130 million gpd in the basin.”

Collaborative project

The water-recycling system was developed in collaboration with the Orange County Sanitation District. Normally, the OCSD would safely discharge treated water into the Pacific Ocean. Instead, it’s now diverted via gravity feed to a nearly adjacent water treatment plant operated by the water district.

The water then proceeds through a three-step purification process — microfiltration, reverse osmosis and ultraviolet light — that converts it into high-quality, near-distilled water that exceeds state and federal drinking-water requirements.

From there, the water is pumped through a 13-mile-long pipeline to four recharge ponds in the city of Anaheim, where it percolates back into the aquifer. Anaheim was selected as the site for the recharge ponds because of its naturally course-grained soil, which is conducive to water percolation.

The first phase of the GWRS, which went online in January 2008 at a cost of $481 million, produced 70 mgd of high-quality drinking water. In 2015, a second phase — which cost nearly $143 million — was completed; that increased the system’s capacity to 100 mgd.

Roughly $100 million of the total cost of all three phases was paid with grants. Revenue generated by user fees pays for the balance, funded by municipal bonds.

Over the years, the OCWD has received many visitors from other states and even foreign countries who want to study the replenishment system’s operation.

“Our water-recycling program is nationally and internationally recognized,” Markus points out. “We’ve had visitors from South Korea, Japan, England, India and other countries.”

In addition, the GWRS has earned more than 80 awards, including the prestigious U.S. Water Prize in 2014, the Lee Kuan Yew Prize in 2014, the American Society of Civil Engineers Outstanding Civil Engineering Achievement Award for the most outstanding national engineering project in 2009 and the Stockholm Industry Water Award for the most outstanding international water project in 2008.

Going with the flow

To further understand the importance of the GWRS, it’s helpful to look at how water management has evolved in Orange County, which is adjacent to Los Angeles County.

The basin ­— which extends from the Pacific Ocean to Yorba Linda (roughly 35 miles southeast of Los Angeles) and holds more than 40 million acre-feet of water — used to naturally recharge itself, primarily via the Santa Ana River, which flows westward from the San Bernadino Mountains and is replenished by rainwater and snowmelt.

But when the county was beset by periodic dry spells and fluctuating water flows from the Santa Ana, the OWCD began importing water, starting with the Colorado River in 1949.

Around 1977, the OCWD added water from the Sacramento-San Joaquin River Delta to its portfolio. Together, the two sources provide 23% of the county’s drinking water, which is purchased from the

Metropolitan Water District of Southern California, a regional water-management organization and water wholesaler.

In turn, the OCWD distributes and sells a blend of imported and recycled water to 19 retail water agencies throughout Orange County.

“They pump the water and serve it through their distribution networks to commercial and residential customers,” Markus explains.

History of innovations

Another key component of the OCWD’s water system is roughly two dozen more recharge ponds, in addition to the four in Anaheim that receive recycled water. These recharge basins  — essentially small lakes or large ponds that cover more than 1,000 acres and range in depth from 5 to 150 feet — accept water diverted from the Santa Ana, Markus explains.

The system relies on two inflatable rubber dams to direct stormwater flows from a 6-mile stretch of the river owned by the OCWD in Anaheim. The water then is transported to the recharge basins via a complex, computer-controlled network of pipelines, channels, valves, sensors and pumping stations.

“The majority of water going to percolation ponds just sinks into the ground,” Markus says.

The OCWD uses monitoring wells to track the level of water in the aquifer.

Another aspect that sets the OCWD apart from similar organizations is its state-of-the-art research and development facility: the Philip L. Anthony Water Quality Laboratory, which opened in 2009 and is named after a late, long-standing member of its board of directors. It now handles more than 400,000 analyses of nearly 20,000 water samples a year.

“We’re one of the few water agencies that has its own research department that looks for ways to improve processes,” Markus explains. “It’s a fair statement to say we have a reputation for innovation.”

For example, in the mid-1990s, researchers pilot-tested different products from microfiltration and membrane manufacturers to see how the microfiltration, reverse osmosis and ultraviolet-light technologies would work together in the OCWD’s water treatment plant for the GWRS.

“At that time, we were one of the first water agencies to utilize membrane technology to take secondary effluent and turn it into near-distilled water,” he says. “There’s a reason why our slogan used to be ‘tradition in innovation.’”

One of the lab’s current priorities is determining the best ways to remove PFAS — so-called “forever chemicals” — during water treatment. In fact, the agency’s laboratory was the first public-agency facility to achieve state certification to test for PFASs in drinking water.

Poised to face challenges

Between drought conditions, little rainfall, and serving a large, high-density population with limited water resources, the OCWD has its share of challenges. But Markus believes the agency is up to the task, especially with the last phase of GWRS now in place.

“We’ve remained steadfast in our mission of managing the Orange County groundwater basin and we will continue to do everything we can to protect our current supplies and create locally-controlled, drought-proof sources. Whether it’s increasing stormwater capture, enhancing operations, researching innovative technology and science or investing in new infrastructure, it’s our responsibility to consider all options.”