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Closing the Water Cycle OPEN ACCESS

How do You Get Someone to Drink the Water They Flush Down the Toilet? It takes One Part Technology and One Part Psychology.

[+] Author Notes

Michael Abrams is a writer based in New York City. He is a frequent contributor to Mechanical Engineering magazine.

Mechanical Engineering 137(04), 44-49 (Apr 01, 2015) (6 pages) Paper No: ME-15-APR-3; doi: 10.1115/1.2015-Apr-3

This article discusses how wastewater can be recycled for consumption if there is scarcity of water. It gives the example of the Orange County plant that is in operation since 2008, and is the largest “indirect to potable reuse” plant in the world. It is “indirect” because that water does not flow straight from the plant to the faucet. Instead, after being treated with microfiltration, reverse osmosis, and then ultraviolet light, the water is pumped back into the ground. Pumping water to an underground basin gives the county time to react if there’s a problem. The soil also works to remove accidental contaminants. The Orange County facility processes some 70 million gallons of water a day, using 14 different reverse osmosis units. Currently, the water is tested – for total organic carbon – at the point where it is all mixed to a single stream.

Water flows downhill. But as anyone with a working knowledge of American vernacular knows, water isn’t the only thing that makes its way downhill. That fact wouldn’t be a problem if we all lived downstream of a pure mountain spring and upstream from no one, but that's not the way we’ve settled.

We are, all of us, nearly, downstream of someone else, and usually there's someone thirsty not far from our own sewage outlet.

And the water is getting dirtier on both sides. The water that flows from every home to every sewage plant is a potent mix of detergents, pharmaceuticals, leftovers, and, of course, bodily waste. You wouldn’t want to drink it. But when fresh water starts drying up and the technology for removing those contaminants is advanced enough, communities start thinking the formerly unthinkable. They start weighing the cost of pumping water to and from treatment facilities, the cost of pumping water against reverse osmosis membranes, the likelihood of reservoirs dipping dangerously low, the difficulty of meeting regulations, and looming large above these, public revulsion.

California's Orange County was faced with just such a reckoning at the turn of the century. After years of debate, county officials decided that the cheapest option available to them was recycling their wastewater.

“It makes sense from an energy point of view,” said Mike Markus, the general manager of the Orange County Water District. “Compared to the cost of bringing in imported water from the North Colorado, the energy cost is about half. Compared to using sea water, it's about a third.”

In operation since 2008, the Orange County plant is the largest “indirect to potable reuse” plant in the world. It's “indirect” because that water doesn’t flow straight from the plant to the faucet. Instead, after being treated with microfiltration, reverse osmosis, and then ultraviolet light, the water is pumped back into the ground.

There's nothing wrong with the water. It's essentially distilled when it leaves the plant. But regulations do not currently allow it to be sent directly from plant to consumer.

“Ground water is considered an environmental buffer,” Markus said. “The water we’re putting into the basin is higher quality than the ground water.”

Right now, the only thing standing in the way of closing the water cycle that runs from the consumer, the water treatment plant, and back again is the “ick” factor. Many people are repulsed at the thought of drinking toilet water, however it's been treated. But if water supplies fail to keep up with demand, thirsty populations may learn to overcome their squeamishness.

When the reservoirs in Wichita Falls, Tex., started drying out (left), the city ran a pipe (red line on the map) taking water from its wastewater treatment plant to its drinking water plant.

Grahic Jump LocationWhen the reservoirs in Wichita Falls, Tex., started drying out (left), the city ran a pipe (red line on the map) taking water from its wastewater treatment plant to its drinking water plant.

“What is the purpose of the environmental buffer?” asked Stuart Khan, a civil engineer at the University of New South Wales near Syndey, and author of Drinking Water Through Recycling: The Benefits and Costs of Supplying Direct to the Distribution System. “I did a survey of 80 water industry people in Australia and that was the question I asked them. There were probably ten or twelve distinctly different answers that came back. However, no one has really quantified it.”

One answer is that the environment adds a buffer, not for contaminant removal, but of time. The water on the other side of a reverse osmosis membrane is measurably, and palatably, pure. But direct use of the water offers no margin for error.

Orange County, Calif., treats 70 million gallons of wastewater (the facility is shown above and left) and pumps it into the ground, where it can then be drawn out for human consumption.

Grahic Jump LocationOrange County, Calif., treats 70 million gallons of wastewater (the facility is shown above and left) and pumps it into the ground, where it can then be drawn out for human consumption.

Purple pipes carry non-potable water for non-human consumption. Such water can be used to irrigate golf courses or to carry heat away from industrial buildings.

Grahic Jump LocationPurple pipes carry non-potable water for non-human consumption. Such water can be used to irrigate golf courses or to carry heat away from industrial buildings.

Pumping water to an underground basin gives the county time to react if there's a problem. And, of course, the soil itself would work to remove accidental contaminants.

“If you go direct and you have a problem, it goes right into the water supply,” said Markus. “We’re trying to find new tools from a control perspective, more online monitoring, so if something arises, the plant immediately shuts down.”

The Orange County facility processes some 70 million gallons of water a day, using 14 different reverse osmosis units. Currently, the water is tested—for total organic carbon—at the point where it's all mixed to a single stream.

“What regulators might want is a TOC on each of the units,” Markus said. “Then if there were a breakthrough, it doesn’t get blended with the other 13.”

From an engineering standpoint, the risk of such an accident is extremely low. But need for better testing instrumentation—and the reason for plopping the environment between the plant and the end consumer—has less to do with practicality and more to do with psychology.

“The water we’re putting into the basin is higher quality than the ground water.”

— MIKE MARKUS, ORANGE COUNTY WATER DISTRICT.

“If you can have this water meandering its way down a little stream, bubbling over rocks, with birdies landing in it and drinking from it,” said Carol Nemeroff, a professor of social and behavioral sciences at Lewiston-Auburn College in Maine, “it comes across not only as pure, but as living— which is really funny, because the birds that are drinking from that add contaminants.”

Working with Markus of the Orange County water department, Nemeroff ran a study that examined people's reaction to the possibility of drinking reclaimed water. She found that people come in three essential types: the first is willing to try it, another sits on the fence until further informed, and a final rejects the concept out of hand. Fence-sitters, she found, could be convinced with reassurances and a little data, but the third group could not be persuaded.

“Nothing will get through, no matter how much effort you put into it,” Nemeroff said. Detailed descriptions of the tools, explanations of the necessity for recycling, and elucidation on the results of testing the water have no effect.

To the thoroughly revolted, the water has some kind of homeopathic memory: though it contains not a single molecule of contaminant, it somehow has a memory of where it's been.

What to do about this group? “One school of thought says let them be,” Nemeroff said. “Those guys can drink bottled water or whatever.”

For everyone else, there's marketing. Singapore, for instance, dubbed its direct-to-potable reuse water system NEWater, replete with ad campaign and smiling droplet mascot (named Water Wally). Others think such marketing can backfire, making the public feel like they’re being sold to.

But anyone who still responds to the words “recycled water” with revulsion should have a good look at “Assessment of De Facto Wastewater Reuse Across the U.S.: Trends Between 1980 and 2008.” That 2013 paper published in the journal Environmental Science and Technology examines 25 different drinking water systems and shows that, on average, 15 percent of the source water is straight waste from somewhere else. And, astonishingly, for many of those systems, in dry years that percentage goes up to 100.

Where drought has increased desperation, municipalities have considered direct potable reuse. But when those same droughts come to an end, the public often seems to forget that another might be around the corner.

In Australia, Brisbane's ticket to fresh water was clearly in the gutter a decade ago. With no rain in sight, the government pumped a good two billion dollars into building direct potable reuse plants.

“Then politics got in the way,” Khan said. “Just prior to the election, politicians said they would only flip the switch if the reservoir dipped below 40 percent capacity. Then it started raining. It's not likely to go below 40 percent again for at least 15 years.”

Singapore keeps its citizens hydrated by mixing treated wastewater (the treatment facility is shown below) with captured storm water and desalinated sea water.

Grahic Jump LocationSingapore keeps its citizens hydrated by mixing treated wastewater (the treatment facility is shown below) with captured storm water and desalinated sea water.

The plants sit unused, and because of the high cost of keeping the facilities in working order, politicians are considering decommissioning them.

Where politics can be minimized, direct potable reuse has proven incredibly effective. Singapore's government, for instance, is “much more nimble than what we have,” said Shane Snyder, a professor of chemical and environmental engineering at the University of Arizona. He's also on the World Health Organization's Drinking Water Advisory Panel, and is a visiting professor at the National University of Singapore.

“Singapore is diversified; it's not one system versus another,” Snyder said. Its recycled water, for instance, is mixed with captured storm water, and desalinated ocean water.

Last year the region received the lowest total rainfall since 1869. “Malaysia's reservoirs crashed. They had to truck water in for millions of people. Singapore's reservoirs never fell below 90 percent. That's an amazing story line.”

— SHANE SNYDER, UNIVERSITY OF ARIZONA

Last year the region received the lowest total rainfall since 1869. “Malaysia's reservoirs crashed,” Snyder said. “They had to truck water in for millions of people.

“Singapore's reservoirs never fell below 90 percent. That's an amazing story line.”

In Texas, Wichita Falls found that it was easier to get regulatory approval for direct reuse than indirect. In June the city opened the second direct potable reuse plant in the country, thanks to some streamlining of the permitting process by the Texas Commission on Environmental Quality.

Wichita Falls already had a reverse osmosis facility to process the brackish water of one of the three lakes the city drew water from. So when the lake levels sank to a quarter of their capacity, all the city needed to do was run a 13.5-mile pipe from its sewage treatment plant to the reverse osmosis plant. To keep the people of Wichita Falls hydrated, the Texas Commission on Environmental Quality was more comfortable sending the purified water straight to homes than back into a lake first.

“That would require a new discharge permit, something they couldn’t provide an exception to,” said Mark Southard, Wichita Falls’ water source purification superintendent.

“In my opinion we get a better quality of water, because of the amount of treatment, than we would with indirect,” Southard said.

Existing facilities, desperation, an absence of regulations at the federal level, and different sources of water all make it impossible to prescribe a single solution for every thirsty county.

“It's very rare that there is a single silver bullet for every situation. Context and social and political support really matter,” said Ben Grumbles, president of the U.S. Water Alliance and head of the EPA's Office of Water under President George W. Bush. “You have to use a variety of bullets.”

And not all those bullets have to come in a reverse osmosis casing.

“I think reverse osmosis is typically oversold as the panacea,” said Ben Stanford, director of applied research at Hazen and Sawyer, an environmental engineering firm in New York. “There are lower-cost, lower-energy alternatives.”

Where salinity is not a problem, Stanford and his group recommend a series of mechanisms that will render the water nearly as pure as that produced by reverse osmosis, but without the pumping costs.

This alternative to the “Full Advanced Treatment,” or FAT, Stanford calls the “Lo-Fat Diet.”

“The beauty of it is that it utilizes a lot of different mechanisms for contaminant removal,” Stanford said. These include the addition of coagulants, filtration, oxidation, biologically activated carbon, UV, and chlorine. Individually, each piece is technologically mature. “It's a powerful set of processes lined up that get you the equivalent of the RO process.”

But both reverse osmosis and the Lo-Fat treatment are intensive processes considering that less than a percent of the water that ends up in anyone's home ends up in anyone's mouth. Sanitary water is not needed for washing machines, showers, and toilets, to say nothing of lawns and golf courses. Why not send less thoroughly—and less expensively—treated water out for non-consumable purposes?

In California there are plans for distributing such lowerquality water through so-called purple pipes. The problem is that it's “amazingly expensive for a city to retrofit and lay pipes—one of the most expensive things to do,” according to Snyder at the University of Arizona.

But for towns that are developing previously unplumbed areas, and have to lay pipe anyway, there are many purple pros. Maricopa, Ariz., was just such an expanding community. The population grew from 500 in 2000 to 50,000 today.

“In order to generate enough water to service a community like that, we really had to think about reusing water,” said Graham Symmonds, who was the senior vice president of operations and compliance for the area's utility, Global Water Resources (and is now chief knowledge officer for Fathom, a Phoenix-based water management company).

As the town grew, developers needed permits to lay pipe in the huge virgin tracts of land they had bought up.

“As a utility we were able to dictate the water infrastructure, which is something you don’t have everywhere. It's a bit of a luxury,” Symmonds said. As a result, Maricopa uses 40 percent less raw water than communities of similar size in the area.

Wichita Falls hopes to benefit by using some of its water for non-potable purposes instead of sending it all through a reverse osmosis membrane. Its utility is working to pipe untreated water for use in a factory cooling system.

The cost of new pipes is not the only disadvantage to an additional purple pipe system: pipes break; mistakes happen; people try their own plumbing.

“My personal opinion is that the water should be safe coming out of any tap in the city, for anyone, for our children to drink and splash in,” Snyder said. “To let that system fall apart is just silly.”

When water is scarce there is no solution without costs and risks. To move forward without public protest, the technology and decisions made need to be as transparent as purified water.

“In the early years of commercial aviation, it was viewed as dangerous to get in an airplane, because you might not come back,” said David Sedlak, a professor of mineral engineering at the University of California, Berkeley, and the author of Water 4.0: The Past, Present, and Future of the World's Most Vital Resource.

“It wasn’t just a question of creating images and wording that got the public to support commercial aviation and consider it a legitimate technology,” Sedlak said. “It was a safety culture that responded to accidents, that was transparent about failure, and empowered the people involved to try to take corrective action.

“I think it's a very similar story with potable water recycling. Everyone involved needs to think about it in those terms. Here we are in a new era of water and we need to think about how to make our institutions more adaptable and proactive to avoid the mistakes that sometimes happen when a new technology is rolled out.”

Copyright © 2015 by ASME
Topics: Water
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