California drought gives new impetus to wastewater recycling

Reuters News
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Posted: Jul 16, 2015 7:07 AM

By Steve Gorman

LOS ANGELES (Reuters) - In the sprawling Orange County suburbs south of Los Angeles, home to Disneyland and upscale beach towns, much of the drinking supply for more than 2 million people originates from the sewer. And that number is about to grow - on purpose.

The recycling of wastewater for human consumption is gaining greater credence in drought-stricken California, where scarce drinking supplies, changing economics and a newly proven technology has led more local leaders to embrace a concept once derided by critics as "toilet-to-tap."

But experts warn that regulators and politicians must take care to educate and reassure a wary public in casting wastewater as a largely squandered resource.

"The yuck factor is still an issue," said Frances Spivy-Weber, vice chair of the state Water Resources Control Board. "You have to be quite straightforward with the public ... so they don't feel like they're being tricked."

By all accounts, the tide of public opinion appears to be turning. A number of cities, including Los Angeles and San Diego, have moved to emulate Orange County's advanced purification system, the largest of its kind in the world, which has been producing 70 million gallons of fresh water daily from sewer effluent since 2008.

That system puts pre-treated waste discharge through a process of microfiltration, reverse osmosis, ultraviolet light and hydrogen peroxide disinfection to render enough potable water, nearly distilled in quality, for over 500,000 people.

Yet this water does not go directly to homes. It is first pumped into the county's groundwater basin to recharge depleted aquifers, receiving another, natural level of filtration before being drawn back to the surface for drinking and bathing.

In May, daily output was increased to 100 million gallons. The groundwater basin as a whole, a third of it now derived from recycled waste, is the principal drinking source for 2.4 million people in northern and central Orange County.

INDIRECT VS. DIRECT

This "indirect potable reuse" of wastewater, in the parlance of engineers and regulators, is seen as a promising new approach for ensuring dependable water supplies as California struggles through a fourth straight year of drought.

The state water board last year formalized the first regulations for the type of recycling operation pioneered in Orange County.

The agency has until December 2016 to adopt new rules for indirect potable reuse of highly purified wastewater that gets blended with and stored in large freshwater surface basins, such as reservoirs or lakes, rather than groundwater, before people drink it.

Even then, the water would make one last stop at a conventional treatment plant en route to household taps, as it does now in Orange County.

Regulators will turn next to "direct potable reuse," in which purified wastewater would be fed straight into a traditional treatment plant without first pausing in some kind of environmental holding buffer. A feasibility study is due by the end of next year.

Texas is the only U.S. state so far to approve direct potable recycling, with two small-scale systems in towns that went online last year amid severe drought and water shortages there.

The success of Orange County's Groundwater Replenishment System, a name that conspicuously omits the words "waste" or "sewage," has gone a long way toward winning greater support for potable reuse.

SUPPLY AND DEMAND

A record dry spell that has left reservoirs badly drained, forced irrigation cutbacks by farmers and led to drastic new mandatory conservation measures for homes and industry is also driving support.

At the same time, the drought has raised the costs of piping in fresh water from the Colorado River and elsewhere, making capital investments in recycling plants more attractive by comparison.

"You can build one of these types of water plants for about the same cost as purchasing imported water," said Michael Marcus, general manager of the Orange County Water District.

Cost considerations also give recycled wastewater an edge over desalination, the process of distilling fresh water from the sea, as ocean water contains 30 times more dissolved impurities than pre-treated sewer effluent and requires much more energy to purify.

The Pacific Ocean does offer a theoretically unlimited raw supply of water. But the amount of unused wastewater currently flushed into the ocean is staggering, an estimated 1.3 billion gallons daily off Southern California alone, Marcus said.

For those who may still be squeamish, he points to an oft-overlooked fact: The Colorado River has long contained large volumes of treated waste discharged by Las Vegas and other cities upstream of Southern California's water intakes.

"People have been drinking wastewater their entire lives; they just haven't realized it," he said.

(Reporting by Steve Gorman; Editing by Cynthia Johnston and Leslie Adler)