From the Toilet to the Tap


Cloacina was the ancient Roman goddess of sewers. Think about that for a minute. To the Romans, the ability to take vile, disgusting wastewater and just get it the heck out of Rome was such a miraculous feat that they created a whole deity to watch over and protect the pipeline.

Now, how much more impressive would Cloacina have been if she could turn the sludge into usable water again?

Today, cities around the world are shifting away from the historical focus of wastewater management (i.e. the miracle of making the wastewater go away somewhere where we can't see it) and adopting a new paradigm of re-use. David Sedlak, professor of civil and environmental engineering at UC Berkeley, studies wastewater and spoke about water recycling at the 2009 Nobel Conference on water conservation issues at Minnesota's Gustavus Adolphus University. He said that people are often turned off by the idea of cycling water from the toilet to the tap and back again, but water recycling is very different from simply filling a glass out of the John.

In fact, you could be drinking recycled water and not even know it.

The idea of reusing wastewater isn't really anything new. Back around the turn of the 20th century, U.S. farmers used to set up shop at the end of sewage pipes, flooding their fields with wastewater fertilizer. Sewage farms grew massive, prize produce. Unfortunately, they were also breeding grounds for parasitic worms and other nasty gastrointestinal diseases.

It wasn't until the 1970s and 80s that people began to take a second look at watewater reuse. Orange County, Cali. began purifying sewer water in 1976, injecting it back into local aquifers to protect them against infiltration by salty seawater. Just about two years ago, the county launched a massive expansion of this program, opening the world's largest wastewater recycling plant. About 10 percent of the water people drink in Orange County comes from highly purified wastewater, Sedlak said.

"The system basically starts with effluent, the output from conventional sewage treatment, and subjects that first to micro-filtration, and then to reverse osmosis, and then to advanced oxidation and disinfectant and then out in the environment," Sedlak said. "Most of the advanced treatment plants built in the US use something called UV peroxide process, which treats water with ultraviolet light in the presence of hydrogen peroxide. The UV splits the hydrogen peroxide and forms hydroxl radicals, strong oxidants that break down organic contaminants and destroy microbes. Usually, the water isn't reused straight, but after these treatments it gets injected into a groundwater aquifer and recaptured later on."

And it's not just happening in the Southwest. Over the past decade, Sedlak said, cities in Texas, Georgia and Florida have picked up on water re-use as well.

The really interesting thing here, though, according to Sedlak, is that water recycling forces us to think about all wastewater in a different way. In reality, no matter where you live, effluent makes up a large part of the free-flowing rivers and lakes. That effluent is treated and cleaned, but nowhere near as extensively as the stuff coming out of Orange County's recycling plant. And, ultimately, it's recycled, too. Effluent-laced water is used by farms, it becomes a place where fish and other animals live, and it's part of the hydrologic cycle--eventually ending up back in the tap.

But most of us don't think of wastewater as something that's reused and we don't pay attention to what goes into our sewers. Sedlak hopes intentional community wastewater recycling will change that. We need to think about our sewers less like they're a fast train out of town, he says, and more like they're a part of our ecosystem.

Recognizing that water goes down the drain ends up in surface waters or drinking water supplies might decrease the unnecessary use of toxic household products, like socks that are coated with silver nanoparticles or shirts and hats that are coated with insecticides," he said. "These products are leached from clothing in the wash and end up in sewage. They'd be filtered out by a water recyling system like Orange County's. But the toxic compounds can pass through standard treatment processes, and they have the potential to harm aquatic organisms in rivers."

Watch David Sedlak's Nobel Conference Lecture

Image courtesy Flickr user glenjdiamond, via CC


  1. “In fact, you could be drinking recycled water and not even know it.”

    “Could be?” Unless you’re sipping the exhaust of a fuel cell or melting comet ice, I’m pretty sure you’re definitely drinking “recycled” water. Recycling plants just make the natural process faster and cleaner (yes, I realize that’s the point of the article).

    1. If I had the hardware, I would be out there in the Oort cloud, bottling comet-ice to market to rappers right now

  2. “To the Romans, the ability to take vile, disgusting wastewater and just get it the heck out of Rome was such a miraculous feat that they created a whole deity to watch over and protect the pipeline.”

    To be fair, the Romans had gods for just about everything. Perhaps they needed to give thanks somehow for the Cloaca Maxima, without which Rome would be a stinking swamp of festering disease, like the towns those dirty Gauls lived in.

    And there were deities like Vacuna, said to be the goddess of vacations, and Mefitis, god of stink. I’d be thankful to Vacuna, but Mefitis?!

  3. All water is dinosaur pee, deal with it. Even created water will most likely have been water at one time. The ingredients just keep getting stirred around and around.

    1. Hmm, I ran the math on that, and it is possible that all water, or at least a large portion of it, was part of dinosaur pee. However,dinosaurs would have to have to pee (on average) almost as much as 1.5 times the current population of the planet.

      On a side note, google search is going to get some weird ideas about me. What with em googling how much people pee, how much elephants pee (no answer, btw. I assume it would have been useful to estimate how many dinosaurs there would have to be, being generous to the average bladder output of dinosaurs.) and dinosaur population…

      1. Ha! Well, you could say that all terrestrial water is dinosaur pee in the homeopathic sense, at any rate.

        Which means, of course, that we should all be safe from extinction. “Like cures like.” Right? Right?

  4. My father has been an engineer in city utility departments for a good part of his life, so it’s not really news to me. I’m always surprised more people don’t know how much of their sewage is recycled. The only problem with this information is that it isn’t really a great conversation starter.

    “Hey! Coffee! You know it was probably just as brown a few days ago in the settling tank…”

    1. recycling for non-drinking use has been around for ages, but recycling water directly for drinking out the tap at home is quite new. I don’t think many (any?) states allow that as the guidelines don’t cover checking for the kind of pollutants found in water after humans have used it, ie pharma rather than microorganisms, as noted by previous poster. sure the water that’s recycled gets back into the groundwater intentionally as greywater, or after agricultural uses, and all the frogs die and ppl get sick, but that’s progress.

      1. You may be blissfully unaware that a number of river systems in the US have both water and waste water plants located along the banks in no particular order. Our local utility cleans waste water to the point that it is cleaner returning to the river than it was leaving the river upstream at the water treatment plant intake. Which, incidentally, is downstream of another community’s waste water plant. EPA treatment standards have been more stringent at the potable treatment end of the cycle for what should be obvious human health protection reasons. That, however, does not mean that the EPA is lax on imposing new standards on drinking and waste water treatment as contamination concerns and emerging research warrant.

        ab3a- No one really notices or even cares about what we do until something breaks. I resigned myself to that truth before I entered the working world after having to painstakingly explain to relatives just what, exactly, it was that I was studying. Would you really have chosen your profession if you wanted fame, anyway?

  5. Interesting side note about Roman sewers: apparently, some of them are still functioning – after thousands of years of neglect – as part of the modern system. Cool.

  6. Silver nanoparticles and insecticides? You should probably be more worried about the wonderful world of pharmaceuticals and other related goodies. If you’re bored, read up on how effective your average treatment plant is in filtering things like antiseptics, contraceptives, contrast agents,… Yummy!

  7. #3 said:
    “Even created water will most likely have been water at one time.”

    I tried to understand this sentence and got a nose bleed.

  8. My campmates and I have been working on this on a small scale at Burning Man the last few years. It’s quite amazing to watch wastewater become cleaner and cleaner as it gets filtered various ways. We don’t drink the result (although it ought to be potable, given enough testing), but use it for swamp cooling.
    An important aspect of this is to get the water dirty in the right way – using the correct (i.e. Dr. Bronner’s) soap goes a long way to making the water cleanable.

  9. I wonder what the effect of moving water out of the natural cycle has on the surrounding eco-systems?

  10. Yes, it’s true that direct recycling from sewage to faucet is relatively new.

    But don’t delude yourself…every drop of liquid you drink contains water…which was once peed by a dinosaur, or perspired by an ancient Egyptian, spit out by a Renaissance scholar…you can completely gross yourself out if you think about.

    Peed by a dinosaur…washed into a river by a rainstorm…evaporated into steam in the jungle…condensed into another rainstorm somewhere else…drank by the Egyptian, perspired out into vapour, condensed into another rain cloud somewhere over Rome, where it percolated down into the well where our thirsty scholar washed his mouth out…evaporated again….to where it now sits right there next to your elbow in your coffee cup, but you don’t like think about that, because you poured it out of that expensive bottle that says it came from the mountains of France.

    Sorry, kiddo — it’s all the same water.

  11. Perhaps it is a coincidence but this year both NYT and Frontline dedicated a lot of attention to the subject of contaminated water.

    NYT has a series on dirty water: Toxic Waters

    Frontline did a special on it: Poisoned Waters

    Those articles do not paint a rosy picture, btw.

  12. Cloacina was an aspect of Venus (Venus Cloacina), and had her own temple in the Forum. I’m not surprised that the Romans thought she was important enough to be worshipped; I am a little surprised that the goddess of love was the first thing they thought of when the subject of sewers came up.

  13. It helps to think of water as a solvent to remove the (mostly) liquid trash, not only for your body, but for cities as well.

    We recycle water all the time. The communities upriver from us take water, and discharge it back to the same river a little further downstream. Almost nobody BUYS water. It isn’t consumed. We Rent it. It is our responsibility to restore it to as good or better quality than we found it.

    And that’s what I do for a living. I work for a water and sewer utility. It isn’t a fancy job. Nobody gets rich doing this. I doubt I’ll ever be known by the public for this work. But it is because of people like me that we have the standard of living that we enjoy today. Modern sanitary water systems have done more to improve the average health of our citizenry than the rest of modern medicine combined. Think about that the next time you turn on the tap to wash your hands…

  14. With so much of municipal water sourced from rivers, it never ceases to amaze me how often the average citizen forgets that fish poop, too.

  15. On this topic, while it isn’t the *point* of the novel, I must recommend Nicola Griffith’s book Slow River, which delves deeply into bioremediation and recycling water.

  16. I did a post on the Newtown Creek Wastewater Treatment facility here in NYC a while back, and Cloacina came up.

    Here’s the post:

    from Wikipedia

    The Cloaca Maxima was one of the world’s earliest sewage systems. Constructed in ancient Rome in order to drain local marshes and remove the waste of one of the world’s most populous cities, it carried an effluent to the River Tiber, which ran beside the city.

    The name literally means Greatest Sewer. According to tradition it may have been initially constructed around 600 BC under the orders of the king of Rome, Tarquinius Priscus.

    This public work was largely achieved through the use of Etruscan engineers and large amounts of semi-forced labour from the poorer classes of Roman citizens.

    Although Livy describes it as being tunnelled out beneath Rome, he was writing centuries after the event. From other writings and from the path that it takes, it seems more likely that it was originally an open drain, formed from streams from three of the neighbouring hills, that were channelled through the main Forum and then on to the Tiber. This open drain would then have been gradually built over, as building space within the city became more valuable. It is possible that both theories are correct, and certainly some of the lower parts of the system suggest that they would have been below ground level even at the time of the supposed construction.

  17. The key is to recycle water and not tell anyone about it, people are finicky, but don’t think about these things.

  18. Make every city live downstream of itself. That is, make its sewerage outflow be located upstream of its water inlet.

  19. It’s a truism that anything that comes out of a water tap in London has already been through 3 Scotsmen.

    There’s some evidence that certain of the higher levels of filtration take out organisms or other stuff that we actually need. Some studies show greatly increased incidences of, for example, Crohn’s Disease or other Irritable Bowel spectrum diseases in towns with a lot of filtration. My hometown of Burlington Ontario was the first in Canada to attain its level of water treatment (probably in reaction to the steel mills across the bay) and it was a hotbed of Crohn’s.

    Still, could be a correlation without causation as no one has actually looked into this.

    Ditto on the comments about how the sewage guys have saved more lives than any other profession in human history. Interestingly, the guy who set up the original waterworks in Hamilton, Ontario (which is still open as a steampunk’s wet dream of a museum) decided that it was needed to replace the local wells after a really nasty bout of cholera before the germ theory of disease was invented. He was just working off of a statistical analysis showing an inverse correlation between central water supplies and cholera.

    Google “Hamilton museum of steam and technology”.

    A while ago it turned out, after many painful deaths, that the sewage guys in Walkerton, Ontario were illiterate alcoholics who got their jobs through the patronage system. This being Canada though, no one was punished or blamed for this.

  20. I see lots of comments from people that didn’t grow up at the mouth of (or close to) the Mississipi River. New water? What’s that? It’s been recycled a hundred times over.

  21. Couldn’t we use our dirty bath/shower water for toilet water? I would imagine that would save a lot of water/energy. I never saw the point in using clean water if you’re just dirtying it up and flushing it anyway.

    1. There are systems that you can install in your home that reuses gray water like this. there are a lot of zoning issues with it and it can be expensive since you’re dealing with two separate water systems (disposal, anyway). I’ve seen some stuff in Mother Earth News about it. Interesting.

  22. This is really nothing new to people who have had to live off the “water grid”, that is, anyone who had a house with a well and a septic system. I hadn’t really thought about it until a friend in such a set up told me living there made him much more aware of what he poured down the drain since he knew it could wind up coming back up the well eventually.

  23. VenerableBean… there is really only one problem with reusing shower water for your toilet and that is when your done with the water it’s usually lower then the toilet tank… so it has to be pumped back up to the hight of the toilet tank… no magic and very little plumbing to be done really… no reason not to do it…

    simply run all your gray water off into a cistern and with a small pump… take the valve system out of your toilet tank and replace it with a float operated switch that turns on/off the pump… easy as installing a modern toilet and it’s very cheap do to as well… and the little bit of soap in the water helps keep your toilet bowl clean too… it’s a win/win/win…

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