Inside The Technology That Cuts The Crap From Water.


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Categories: Green

As more and more cities around the world struggle to provide water to it's population, new technologies are born to try and recycle as much of the water waste to be re-used. Some water treatment plants just turned these into gray waters that have been used in agriculture, or just sent into the ocean. Others are trying to turn this waste water into potable drinking water, so is the case of Snehal Desai.

“This is step one of the filtration process,” says Snehal Desai, struggling to suppress his gag reflex. “We call it the big-tooth comb.” There’s a torrent of raw sewage streaming through a channel below us at an Orange County Sanitation District facility that treats waste from the toilets, showers, and sinks of 1.5 million Californians. An enormous rake descends into the depths of the sludge and brings up a load of detritus—cardboard, wet wipes, tampons, marbles, toys, tennis balls, sneakers—that can’t fit through the screen covering the plant’s intake.

The flow that passes through has now begun its journey in an advanced purification process, and that’s what Desai and I have come to see. This plant is right next to the county’s water treatment facility, and together they perform a kind of alchemy, converting human sewage into purified water so clean it can go right back into residential faucets. The plants pump out 100 million gallons of drinking water daily, enough to supply 850,000 Orange County residents, which makes this the largest “toilet-to-tap” facility on the planet.

For decades, sewage has been treated and used for irrigating crops, parks, and golf courses, but making it fit for human consumption requires a much more rigorous filtration technology using polymer membranes. No thicker than a human hair, the membranes are at once delicate and durable. Using pores smaller than one-millionth of a millimeter, they’re capable of wiping out microscopic contaminants.

That’s Desai’s specialty—manufacturing membranes that cut the crap, literally, from sullied water. He’s come to see his products at work in the plant, which has become a global proving ground for toilet-to-tap technology. Desai is 52, but even with his salt-and-pepper hair he looks a decade younger, wearing jeans, a pastel plaid button-down, and thick-framed glasses. The global business director for the water division at Dow Chemical, he pulls in more than $1 billion in sales annually. The membrane market is growing more than 10 percent a year in part because of increasing water scarcity worldwide and ever more pressure to develop drought-proof water supplies from new sources.


“Recycled wastewater will probably be the single largest source of water for California over the next quarter century,” says Tim Quinn, executive director of the Association of California Water Agencies. “And it isn’t just happening here—the same goes for many water-strapped regions of the world.” San Diego recently announced plans to produce 33 percent of its water from recycled sewage by 2035, up from none today, and is designing a toilet-to-tap facility even bigger than Orange County’s. Governments in Australia, China, India, Israel, and Spain, and throughout the Middle East and sub-Saharan Africa have developed recycled wastewater systems for irrigation; many are beginning to convert their systems to make drinking water. Singapore has the largest program, producing a third of its potable water from sewage.

When you see and smell the noxious muck that courses into a sewage plant and consider everything it holds, it’s hard to believe the purification process is even possible. It’s harder still to accept that the end result can be delicious. “The purity you get from this process is quantifiably better than the water you get from traditional treatments—better even than some bottled water,” Desai says. “What flows from our membranes is essentially the Rolls-Royce of municipal water.”

Dow Chemical is the company that gave the world napalm, Agent Orange, silicone breast implants, and plutonium triggers for hydrogen bombs. “If not Dow, then who?” Desai asks. The company has been a dominant player in advanced materials engineering for more than a century; it does business in 180 countries and has revenue of $57 billion a year. “The future water supply is a big-ass problem,” he says. “We’ve got growing urban populations, growing industries, and dwindling resources. Who can tackle something of this magnitude? You need patience and horsepower to come up with solutions and to scale them. You can’t do that without big-boy company money.”

Andrew Liveris, Dow’s chairman and chief executive officer, sees only opportunity. “Communities and companies are increasingly realizing the economic value of clean water—and that’s driving growth in Dow’s water business at two times [the rate of] the global GDP,” he says.

There’s one lingering hitch: the gross-out factor. Even given the desperation of drought, drinking your own waste is nobody’s first choice. “Accepting recycled wastewater is kind of like being asked to wear Hitler’s sweater,” says Paul Rozin, a social psychologist at the University of Pennsylvania who’s researched consumer response to toilet-to-tap programs. “No matter how many times you clean the sweater, you just can’t take the Hitler out of it.”

That’s certainly how I feel at the end of our tour of the Orange County sewage and water plants, when we arrive at a shining stainless-steel sink. What just hours earlier was raw sewage is flowing crystal clear from the tap. Desai fills two Dixie cups. “To the future!” he toasts. I shudder as I knock mine back. Somehow, there’s no trace of the Hitler. The stuff tastes every bit as good as water that bubbles up from a spring in the Alps. I pour myself a second cup.

The whole concept of recycled sewage might be harder to swallow if there weren’t already so much sewage in the water sources we routinely draw from. The Colorado River, for example, a primary source of drinking water for Southern California, receives billions of gallons a day of treated sewage: More than 200 plants in six states pump their effluent into the river. The Mississippi is also inundated. By the time water gets to New Orleans, it’s been ingested and expelled by people in more than a half-dozen cities farther upriver.

“Very little of our water supply today is naturally pure,” Desai says. In fact, the very reason chemists created these synthetic membranes decades ago is that, increasingly, humans have been contaminating the water supply. Industries have emerged, meanwhile, that need purer water for manufacturing. Most major players in the automotive, beer and wine, food processing, petrochemical, pharmaceutical, and semiconductor industries, for example, rely on water purified by membranes.

“Hyperpure water is how you get to precision electronics,” Desai says. “When you’re making a microchip—if you have even one little tiny particle of contaminant from the water used to clean the components, it could fail.”

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