Drought-Stricken Southern California Survives by Drinking Recycled Wastewater

Most people who live outside California don’t know that a large part of the state was originally a desert, and without water, it will revert back to desert. So as the drought drags on, having enough water to keep lawns and tree-lined streets lush and sitcom green is making the scarce resource more and more expensive, especially in Southern California. 

That's why state officials wince as 1.3 billion gallons of expensively treated wastewater flow right through Southern California sewers and into the Pacific every year, when only 10% of it is actually used for drinking and cooking, and most of the rest is flushed. 

After being forced to be more resourceful, the state's cities are struggling to diversify their water sources as they cut per-capita water use 20% below 2013-2014.

But desperation may also by creeping into the utility boardrooms. To ensure long-term supplies, San Diego felt it was necessary to sign an expensive 30-year purchase agreement for water from Poseidon's $1 billion ocean desalination plant in Carlsbad. Environmentalists object to the 50 MGD plant because they feel it's too expensive and too energy-intensive, while discharging problematic brine back into the ocean.

Cooler heads prevailed thirty minutes up the coast, where Orange County — using similar desalination technology — has been turning wastewater into drinking water for over eight years.

An early adopter

Now California water management officials, who ditched the "toilet to tap" yuck factor long ago, are encouraging other water-short cities to use recycled wastewater like Orange County, which is one of the earliest adopters. 

Realistically, it's not a big change, possibly no change at all. Researchers point out that San Diego is already drinking recycled water because it imports 85% of its water long-distances from Northern California and the Colorado River, where upstream communities like Las Vegas discharge wastewater that is later treated and used downstream for drinking. Same old, same old. 

On June 27 officials from cities all over the state watched as Orange County unveiled the big $142 million expansion of its Advanced Water Purification Facility (AWPF). Now the largest facility in the world, production has ramped up from 70 million gallons per day to 100 million, while providing drinking water for 850,000 Orange County residents. 

This was only eight years after Orange County opened phase one to quench the thirst of its growing population and halt coastal salt intrusion into the groundwater. 

At the expansion launch, Michael Markus, the Orange County Water District's general manager, boasted to the Los Angeles Times, "We'll be discharging next to nothing to the ocean, 85% to 90% of the flow." Actually it's closer to 65%, but that's still a lot of water. 

Economically, it's a win-win for everyone. The purified water is sold to the Orange County Water District's member agencies for $294 per acre-foot, Markus said. In comparison, the cost to buy imported water is about $660 per acre-foot for untreated water and about $1,003 per acre-foot for treated water.

If Poseidon, coasting on its post-San Diego big-mo, ever gets the green light to build its proposed Huntington Beach plant, that water will cost about $1,800 an acre-foot.

Cheaper than ocean desalination

Before Orange County's wastewater can be round-tripped to consumers, it passes through three treatment steps at the AWPF: microfiltration, reverse osmosis, and ultraviolet light.

But before the wastewater arrives at the AWPF, it's already gone through primary treatment, where the water is separated from large particles. It then moves to sedimentation tanks where chemicals are used to make primary sludge settle to the bottom and scum rise to the top. Once the water is separated out and 80% of the solids have been removed, the wastewater's technically clean enough to be dumped into the ocean.

Instead, it's delivered by an underground pipe and first undergoes microfiltration to remove any solids, organisms, bacteria and some viruses.

Then, like typical desalination, the next step is reverse osmosis, where high pressure water pushes through 22,000 semi-permeable membranes to remove salt, viruses, and pharmaceuticals.

Compared with ocean desalination, Orange County's reverse osmosis uses much less energy because very little salt has to be removed.

Moving beyond the safety requirements of standard desalination, a final purification step mixes the water with hydrogen peroxide and ultraviolet light to kill any remaining bacteria and viruses.

"The entire process only takes about 45 minutes," Markus said.

The water is then shipped northeast through a 14-mile pipe where it feeds a series of recharge basins, which resemble small lakes. A lot of water goes in the ground in Anaheim, which is the upper end of the 350-square-mile aquifer system.

It percolates through the soil, and then after a 6-month waiting period, it ends up in drinking water well intakes. 

"It's the only thing that will get us through this [drought]," said Orange County Water District board President Cathy Green. 

Flying under the radar

Drinking treated wastewater is one of California's best-kept secrets. It dates all the way back to the 1970s, when the Orange County water agency built Water Factory 21, one of the first small facilities to use reverse osmosis to purify water, Orange County Water District's Michael Markus told the Los Angeles Times last year.

By the time Water Factory 21 went offline in 2004, it was a success, even though as a demonstration it only produced 15 million gallons per day. Meanwhile, Orange County wanted to take wastewater to the next step, and started developing an even a bigger facility.

Finally in January 2008, the first $481-million facility went online, providing up to 70 million gallons of potable water per day before the expansion. Orange County is now waiting for a study to help determine whether it would be feasible to send more water into the groundwater system.

Is this the beginning of a trend?

Image: Inspecting reverse osmosis filters, Black and Vetch