Toilet to Tap: Where Water Comes From

There have been many advancements in sewage treatment since the days of outhouses. But in these recycling-conscious times, scientists are busily finding new uses for the stuff.

by / March 7, 2013

When it comes to dirty jobs, sewage is the gold standard. And instead of being delicate about it, let's put on the waders and plunge right in.

There have been many advancements in sewage treatment since the days of outhouses. But in these recycling-conscious times, scientists are busily finding new uses for the stuff. In fact, the first manned trip to Mars will be shielded from radiation by astronaut poop, according to Wired magazine. And since 2008, astronauts have been toasting their health with recycled urine. Those who feel the beginnings of a queasy stomach should stop reading now, because it gets worse -- much worse.

But first, a philosophical context. According to Global Water Senior Vice President Graham Symmonds, the water from our tap is millions of years old, and is always being recycled and used over and over again. Astronauts, for example, live in a small closed system with "in your face" recycling of body wastes. While far less evident, it's much the same here on Earth, although the cycle of "toilet to tap" is much longer, and mostly hidden.

"The technologies exist to produce high-quality water from sewage," Symmonds said, "and the regulatory framework is under construction, but some places do it already."

He explained that in a "one water vision," all water is essentially the same H2O and can be made available at different qualities for different purposes. "As we move into a more sustainable environment, the general public is going to have to start thinking about its water more than just figuring it is available whenever they turn their tap on."

Some scientists see sewage as a good thing, a new source of fresh water, useful bacteria and biofuels, as well as recyclables, from fertilizer to meat substitutes. (OK, that's about as bad as it's going to get, mostly uphill from here on out.) 

So there you have it: Not all drinking water comes directly from artesian springs, from pristine snow melt or from softly falling rain. Some of it -- filtered, clarified and chlorinated -- comes from the sewer. And chances are, even that spring water, melting snow or rain has traveled through the innards of living things, but by a route that disappears in the Earth or the ocean and is thus a bit less objectionable.

In fact, the fluid in your bottled water or gushing from your tap at one time may have been urinated on by a Neanderthal. But evaporation leaves some of the wastes behind, soil and sand filters it, ocean salt and sunlight kill off many bacteria, and it becomes potable -- drinkable -- through time and tide. But the Earth's water is a closed system. "What ye excrete so shall ye drink," eventually anyway.

This "toilet to tap" cycle, however, is under increasing scrutiny lately, as our increasing use of antidepressants, birth control pills, anticonvulsants, pain relievers and so on have begun to affect the water supply.

Over the last decade or so, researchers have discovered that sewage contains small amounts of all the drugs -- illegal as well as pharmaceutical -- that a population disposes of in the toilet or excretes in bodily wastes. That's good news if you want to study how the war on cocaine or meth is going, how legalization affects marijuana use or study the use of antidepressants in a population. But it's bad news not only for the fish downstream, but for people as well, especially as "what goes around comes around" -- and traditional water treatment plants are not effective at removing these drugs, so concentrations could gradually increase.

Some rather grim observations have resulted from studies into the subject. Canadian researchers, for example, are linking estrogen from birth control pills in drinking water with an increase in male prostate cancer deaths. And "endocrine disruptors" -- which even in miniscule amounts can interfere with the body’s hormonal systems -- are likewise appearing with as-yet undetermined effects. And antidepressants have prevented some amphibians from developing normally.

The End of Abundance?

"Water scarcity is upon us," said Symmonds. "California, Arizona, Florida, Texas -- we're finally running into the end of abundance when it comes to water. We used to believe that our water resources would be very stable and our engineered solutions would be sufficient for meeting all our needs. As we've seen, the natural water delivery systems are increasingly fickle and more volatile with changes in precipitation patterns, changes in snowpack runoff, and all of that is leading to some real physical scarcity problems for the water industry."

And now, he said, the financial condition of many municipalities and utilities is quite stressed. "So you have a convergence of a water scarcity and no money to really solve it. Those are two converging elements of the future."

So what's the good news? Symmonds thinks that a "three-pipe" household system is a partial answer. "You have a potable water main, a non-potable water main, which would be used for irrigation or for industrial uses, and then you've got the sewer system."

A three-pipe system, he said, reduces the demand for potable water by 40 percent, and nonpotable water is much cheaper to treat. And while removing pharmaceuticals from water is very expensive, only the potable system would need such treatment. "Your grass," he said, "doesn't care if there is aspirin in the water."

Symmonds also suggests that smart water meters (Advanced Metering Infrastructure or AMI) can help struggling municipalities and utilities in several ways. First, it helps the public save water by allowing them to compare their consumption against neighbors or some ideal usage pattern. Also, as meters age, they become less efficient at measuring water flow and so "non-revenue" water drives up the cost. And finally, while installing an AMI system, the utility or municipality upgrades the infrastructure, discovers missing meters, or errors such as a three-inch meter registered as a ¾ inch meter, or undetected leaks. "So you can actually find a lot of revenue by cleaning up your system."

There are other promising lines of research popping up as well. KTH Royal Institute of Technology in Stockholm, for example, has developed a process called "membrane distillation" that separates most pharmaceutical residues from sewage.

So why is water so scarce if the oceans are full of it? Desalination could make seawater potable, but the process requires energy and has been rather expensive compared to traditional water treatment. Now renewable energy shows promise in powering desalination plants, and patents are spiking on innovative ideas to do so.

Even the smell of sewage has a new solution. Cloevis, an Australian company, has developed a process to stop the formation of hydrogen sulfide, which gives sewers their characteristic "rotten egg" smell. Hydrogen sulfide -- a byproduct of the breakdown of organic matter in sewers -- is the culprit, and is poisonous, explosive and smelly. In addition, its byproducts corrode sewer pipes, which costs the U.S. an estimated $14 billion per year.

Another company Bilexys, has a process to reclaim useful chemicals from industrial wastewater. The process uses organic content to drive a chemical reaction, said spokesman Paul Barrett. "The net is that this technology, if added to a treatment plant, reduces the need for that site to buy these chemicals, because they can make them from the waste products. Target chemicals include sodium hydroxide -- caustic soda -- and hydrogen peroxide.

Bacteria working on organic matter in industrial wastewater can even produce electricity. The process, electrogenic bioreactor or EBR, is under development by Emefcy. 

Earth Is a Closed System

Humans could not urbanize successfully without separating waste from drinking water, which eliminated a host of deadly diseases. The Romans were the first to do it successfully, with their systems of freshwater aqueducts and covered sewers. But keeping water pure took a lot of work, and was forgotten in the Dark Ages with terrible consequences.

In more recent times, we've been separating sewage and potable water more or less successfully since the Industrial Revolution. In that context, the idea of reclaiming drinking water from sewage sounds repugnant to most people. But Earth is a closed system, and water will be reused and recycled one way or another. So better methods of water treatment will be of increasing importance in coming years.

Image courtesy of Shutterstock

Wayne Hanson

Wayne E. Hanson served as a writer and editor with e.Republic from 1989 to 2013, having worked for several business units including Government Technology magazine, the Center for Digital Government, Governing, and Digital Communities. Hanson was a juror from 1999 to 2004 with the Stockholm Challenge and Global Junior Challenge competitions in information technology and education.