As droughts threaten water supplies across the planet, some municipalities aim to utilize an untapped resource: sewage water.
- Water recycling, or water reclamation, involves cleaning water with filters and chemicals to make it environmentally safe.
- In Texas, El Paso's water utility is taking this a step further by building a closed-loop system that will directly convert sewage water into drinkable water.
- Unsurprisingly, surveys show that most people don't like the idea of drinking recycled water, but public outreach programs seem able to change minds.
Of all the projects aiming to make the world more sustainable, none is less appealing than toilet to tap, a water recycling process where wastewater is converted into potable water.
But despite the gross-out factor, a handful of governments have already invested in the technology, including those in Singapore, South Africa, Belgium, California, and Texas. Soon, others may have few other options. El Paso is leading the way.
The case for drinking treated wastewater. (Yes, from the toilet.) | Just Might Work by Freethink www.youtube.com
Depletion of resources and climate change are threatening to dry up parts of the global water supply. By the late 21st century, the number of people impacted by extreme droughts is projected to double, a shortage that would not only affect the health of millions of people but also potentially create catastrophic socioeconomic problems and geopolitical conflicts.
The U.S. is already feeling the heat. In May, California declared a drought emergency in 39 counties. It wasn't really a shock to the state, which has endured severe droughts over the 20th century, including a historical five-year drought from 2012 to 2016. The U.S. Forest Service has warned that droughts like these could render half of the nation's freshwater basins unable to consistently meet monthly water demand by 2071.
The causes are twofold. One is a growing population that will demand more water. The other is that global warming is evaporating more water from soil, lakes, reservoirs, and rivers, while climate change alters patterns of precipitation and snowmelt, which feed the rivers and lakes from which we get much of our drinking water.
Facing a dry future, some municipalities have accepted the crappy-sounding reality: Converting sewage water into drinking water through water recycling may be the best way to prevent a crisis.
The average adult flushes about 320 pounds of poop down the toilet every year. Where does it all go?
When you flush your toilet, the water swirls through a U-shaped pipe, called a trap, that prevents sewage gases from entering your home. That toilet water — along with other wastewater from your sinks, washer, and shower — flows into a sewer line, which is connected to the buildings and homes in the immediate area. These sewer lines can be big. In New York City, for example, combined sewer lines can span more than 12 feet wide, enough space for a subway car.
These pipes carry wastewater to municipal water treatment plants for cleaning. In the U.S., the water treating process typically involves steps like:
- Odor control: Chemicals help mute foul odors.
- Screening: Wastewater is moved through screens to separate larger solids and trash.
- Primary treatment: Water sits in large tanks, allowing solid material to settle at the surface. Material is scraped off and disposed of.
- Aeration: Water is stirred to release gases, and air is pumped through the water to allow bacteria to act on organic matter, which helps it decay.
- Remove sludge: Solid material settles to the bottom and is removed.
- More filtration: Water is filtered through sand to reduce bacteria, odors, iron, and other solids.
- "Digest" the solid material: Solid material is heated to break it down to nutrient-rich biosolids and methane gas.
- Disinfection: Water is treated with chlorine to kill bacteria.
After wastewater is treated and deemed clean enough for the environment, it's used for crop irrigation, or it's discharged back into streams, rivers, and lakes. But some municipalities take water reclamation several steps further, purifying wastewater to the point where it's safe to drink.
Wastewater treatment facilitySongkhla Studio via Adobe Stock
Today, drinking water in places like Northern Virginia, Phoenix, and Southern California is, at least in part, reclaimed wastewater. But in some parts of the U.S., climate change poses such a severe threat to the water supply that more drastic measures are required.
A closed-loop water recycling system
El Paso, Texas, is an exceptionally dry city. Located in the Chihuahuan Desert where only nine inches of rain falls per year, it's drier than some parts of sub-Saharan Africa. The city has historically received half of its water supply from the Rio Grande, but the river has been steadily drying up, forcing officials to turn to other solutions, like building the nation's largest inland desalination plant and establishing incentives that encourage residents to use less water.
In recent years, El Paso has been working on what officials call the next logical step: Creating a closed-loop water recycling system that purifies wastewater and sends it right back into the drinking water supply.
El Paso and other U.S. cities already clean wastewater and pump it back into the aquifer, an underground layer of rock. But while this water reclamation process is environmentally safe, it can take years for the recycled water to make its way back into the drinking supply. A closed-loop system would speed things up.
The process will begin at El Paso's conventional water treatment facility, which cleans water according to long-established standards. But then the water will be piped nearby to the city's Advanced Water Purification Facility to undergo several additional cleaning steps:
- Water is filtered through thin sheets of material that remove salts, viruses, and contaminants, in a process known as reverse osmosis.
- Water is treated with hydrogen peroxide and UV light, both of which deactivate or destroy pathogens.
- Finally, the water is passed through granular-activated carbon that's been superheated to help trap any remaining particles.
As El Paso's reclaimed water goes through these additional purification stages, technicians at El Paso Water will monitor the water in real-time to ensure it meets safety standards.
"The water we're going to produce out of the Advanced Water Purification plant is the safest water that could be produced through treatment processes these days," Gilbert Trejo, EPWater's chief technician officer, told Freethink.
Freethink recently visited El Paso Water to get an up-close look at what is set to be the first closed-loop water recycling system in a major U.S. city. (See video above.)
In addition to cleaner water, water recycling facilities like El Paso's would also be cheaper and more practical than solutions like desalination. After all, not every city lives close to the ocean, and even those that do have to pay to transport saltwater to the treatment plants. But practical benefits aside, toilet to tap is tough to sell to the public.
Clean but spiritually contaminated?
The prospect of drinking recycled water unsurprisingly elicits a disgust response in many people, some more so than others. A 2015 survey of more than 2,000 U.S. residents across the nation found that: "Approximately 13% of our adult American sample definitely refuses to try recycled water, while 49% are willing to try it, with 38% uncertain," the researchers wrote. "Both disgust and contamination sensitivity predict resistance to consumption of recycled water."
For a minority of people, it seems no amount of purification through technical means will render the water potable. That's because of "spiritual contagion," which the researchers said is "conceived of in terms of the entrance into the target of some spiritual essence which does not resemble standard physical entities. It does not respond to washing, boiling or filtering, but remains as a permanent essence."
But even though water reclamation is generally unpopular, and some people may always resist it, research suggests that people become more accepting of water recycling as they learn more about the process.
That's why El Paso has aimed to be transparent and proactive in explaining the process to residents through public outreach programs. In 2016, nearly 90 percent of El Pasoans supported the idea of producing more drinking water through the city's Advanced Water Purification Facility.
Trejo said it's about establishing trust with residents:
"I think it's very exciting for El Pasoans to know that what we're doing here in El Paso is going to change the water industry. The engineering community and the water community knows and understands that these treatment processes treat the water and produce a very high-quality water. It's a matter of which community is going to be the first one to have absolute trust in their water utility, and in the water, and that's what we're about to do here in El Paso.
Scientists at Washington University are patenting a new electrolyzer designed for frigid Martian water.
- Mars explorers will need more oxygen and hydrogen than they can carry to the Red Planet.
- Martian water may be able to provide these elements, but it is extremely salty water.
- The new method can pull oxygen and hydrogen for breathing and fuel from Martian brine.
When people finally get to Mars, there are a two things they're going to need lots of: oxygen and fuel. (Drinking water, too, but that's another story.) They'll need more than they could reasonably bring with them. Fortunately—we now know—there's plenty of water on Mars that could potentially serve as a source of oxygen and of fuel in the form of hydrogen that could get our explorers back home at mission's end.
On Earth, we can extract the elements from pure water using a process called electrolysis. On Mars, though, the water contains a fair amount of magnesium perchlorate — salt. It is too "dirty" for electrolysis, and that process also requires heat, an issue in Mars' frigid climate. Engineers at Washington University (WashU) in St. Louis may have the solution. They've developed and are in the process of patenting a method for extracting oxygen and hydrogen from water like Martian brine, and it works perfectly well in sub-zero temperatures.
"Our Martian brine electrolyzer radically changes the logistical calculus of missions to Mars and beyond," says WashU's Vijay Ramani.
The system is described in a paper published in PNAS.
The WashU electrolyzer
The WashU electrolyzer—it has no snappy acronym yet—will not be the first device capable of extracting oxygen from Martian water. That honor goes to the Mars Oxygen In-Situ Resource Utilization Experiment, or MOXIE, which is en route to Mars onboard NASA's Perseverance rover. The rover was launched on July 30, 2020. It will arrive on February 18, 2021, and will perform high-temperature electrolysis to extract pure oxygen, but no hydrogen.
In addition to being able to capture hydrogen, the WashU system can even do a better job with oxygen than MOXIE can, extracting 25 times as much from the same amount of water.
The new system has no problem with Mars' magnesium perchlorate-laced water. On the contrary, the researchers say it ultimately makes their system work better since such high concentrations of salt keep water from freezing on such a cold a planet by lowering the liquid's freezing temperature to -60 °C. He adds it may "also improve the performance of the electrolyzer system by lowering the electrical resistance."
Cold itself is no issue for the WashU system. It's been tested in a sub-zero (-33 ⁰F, or -36 ⁰C) environment that simulates Mars'.
"Our novel brine electrolyzer incorporates a lead ruthenate pyrochlore anode developed by our team in conjunction with a platinum on carbon cathode," explains Ramani. He adds, "These carefully designed components coupled with the optimal use of traditional electrochemical engineering principles has yielded this high performance."
"This technology is equally useful on Earth where it opens up the oceans as a viable oxygen and fuel source," Ramani notes. His colleagues forsee potential applications such as producing oxygen in deep-sea habitats with ample water available, such as underwater research facilities and submarines.
The study's joint first author Pralay Gayen says that "having demonstrated these electrolyzers under demanding Martian conditions, we intend to also deploy them under much milder conditions on Earth to utilize brackish or salt water feeds to produce hydrogen and oxygen, for example, through seawater electrolysis."
A clever new design introduces a way to image the vast ocean floor.
- Neither light- nor sound-based imaging devices can penetrate the deep ocean from above.
- Stanford scientists have invented a new system that incorporates both light and sound to overcome the challenge of mapping the ocean floor.
- Deployed from a drone or helicopter, it may finally reveal what lies beneath our planet's seas.
A great many areas of the ocean floor covering about 70 percent of the Earth remain unmapped. With current technology, it's an extremely arduous and time-consuming task, accomplished only by trawling unmapped areas with sonar equipment dangling from boats. Advanced imaging technologies that work so well on land are stymied by the relative impenetrability of water.
That may be about to change. Scientists at Stanford University have announced an innovative system that combines the strengths of light-based devices and those of sound-based devices to finally make mapping the entire sea floor possible from the sky.
The new system is detailed in a study published in IEEE Explore.
"Airborne and spaceborne radar and laser-based, or LIDAR, systems have been able to map Earth's landscapes for decades. Radar signals are even able to penetrate cloud coverage and canopy coverage. However, seawater is much too absorptive for imaging into the water," says lead study author and electrical engineer Amin Arbabian of Stanford's School of Engineering in Stanford News.
One of the most reliable ways to map a terrain is by using sonar, which deduces the features of a surface by analyzing sound waves that bounce off it. However, If one were to project sound waves from above into the sea, more than 99.9 percent of those sound waves would be lost as they passed into water. If they managed to reach the seabed and bounce upward out of the water, another 99.9 percent would be lost.
Electromagnetic devices—using light, microwaves, or radar signals—are also fairly useless for ocean-floor mapping from above. Says first author Aidan Fitzpatrick, "Light also loses some energy from reflection, but the bulk of the energy loss is due to absorption by the water." (Ever try to get phone service underwater? Not gonna happen.)
The solution presented in the study is the Photoacoustic Airborne Sonar System (PASS). Its core idea is the combining of sound and light to get the job done. "If we can use light in the air, where light travels well, and sound in the water, where sound travels well, we can get the best of both worlds," says Fitzpatrick.
An imaging session begins with a laser fired down to the water from a craft above the area to be mapped. When it hits the ocean surface, it's absorbed and converted into fresh sound waves that travel down to the target. When these bounce back up to the surface and out into the air and back to PASS technicians, they do still suffer a loss. However, using light on the way in and sound only on the way out cuts that loss in half.
This means that the PASS transducers that ultimately retrieve the sound waves have plenty to work with. "We have developed a system," says Arbabian, "that is sensitive enough to compensate for a loss of this magnitude and still allow for signal detection and imaging." Form there, software assembles a 3D image of the submerged target from the acoustic signals.
PASS was initially designed to help scientists image underground plant roots.
Although its developers are confident that PASS will be able to see down thousands of meters into the ocean, so far it's only been tested in an "ocean" about the size of a fish tank—tiny and obviously free of real-world ocean turbulence.
Fitzpatrick says that, "current experiments use static water but we are currently working toward dealing with water waves. This is a challenging, but we think feasible, problem."
Scaling up, Fitzpatrick adds, "Our vision for this technology is on-board a helicopter or drone. We expect the system to be able to fly at tens of meters above the water."
Scientists discover that under certain conditions two kinds of water exist.
- Water can be in two liquid states under cold temperatures, shows new research.
- The scientists used x-ray lasers and computer simulations.
- The discovery has applications across a variety of fields due to water's ubiquity.
Water is an essential life force for humanity and our planet. But despite it's omnipresence, there's much we have still to learn about the fateful combination of hydrogen and oxygen atoms that comprises this near-magical substance. Now a new study proves water can have two different liquid states, in one of its most unusual properties.
The research, carried out by an international team of researchers, involved sophisticated experiments with x-ray lasers and computer simulations. The team, led by chemical physics professor Anders Nilsson from Sweden's Stockholm University, also included CUNY professor Nicolas Giovambattista. He explained in a press release that while it's been proposed about 30 years ago that water may have two different liquid states, this "counterintuitive hypothesis" was been hard to prove, due to the complexity of the experiments necessary. Ice tends to form at the conditions when the two liquids should exist.
The liquid state of water that we all know and encounter in our daily lives is how water behaves at regular temperatures – around 25 degrees Celsius (77 F) . What the new study showed is that at low temperatures of around -63 degrees C (-81 F), water can be found in two states: a low-density liquid at low pressures, and a high-density liquid at high pressures.
"What was special was that we were able to X-ray unimaginably fast, before the water froze, and could observe how one liquid transformed to the other", said professor Nilsson.
The researchers found that the difference in density between the two liquids was about 20 percent. A thin interface would form, given the right conditions, to separate the two kinds of water without mixing them. A similar phenomenon to what you observe when oil and water are combined.
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The scientists think their find can affect a variety of scientific and engineering uses of water. "It remains an open question how the presence of two liquids may affect the behavior of aqueous solutions in general, and in particular, how the two liquids may affect biomolecules in aqueous environments," Giovambattista explained. "This motivates further studies in the search for potential applications."
Besides CUNY and Stockholm University, scientists from POSTECH University in Korea, PAL-XFEL in Korea, SLAC national accelerator laboratory in California, and St. Francis Xavier University in Canada were also involved in the study.
Check out their new study in the journal Science.
An ancient Martian meteorite carries with it some compelling implications.
- The meteorite behind the new research, Black Beauty, is 4.45 billion years old. This means it is from right around the time when Mars formed.
- It contained intact, ancient water-bearing minerals.
- The research indicates later asteroid-impact effects that could only have occurred if water was already present.
Almost exactly two years ago, we wrote about a theory that about 1 in 100 of our water molecules came not from asteroids — as is widely believed — but from hydrogen in Earth's core, a remnant of dissolved gas from solar nebulae. Now, a study of a Martian meteorite suggests that most water may not come from space at all, but that it's a natural byproduct of rocky-planet formation. If true, this could mean water is everywhere, which would greatly increase the chances of extraterrestrial life.
The study's senior investigator is Martin Bizzarro and the lead author is Zhengbin Deng, both of the Centre for Star and Planet Formation at the Faculty of Health and Medical Sciences at the University of Copenhagen. It's published in the journal Science Advances.
The authors' research is based on a meteorite from Mars called "Black Beauty" that was found in the Moroccan desert. Black Beauty is 4.45 billion years old and comes from the Martian crust, providing a rare window into the early days of Mars and the solar system. "It is a gold mine of information. And extremely valuable," Bizzarro tells University of Copenhagen News. At $10,000 per gram, the researchers purchased 50 grams for $500,000.
Lake-floor sedimentary deposits on Mars
Black Beauty indicates that liquid water was present on Mars in the first 90 million years after it was formed. To deduce this, the researchers had to crush and dissolve 15 expensive grams of the meteorite for analysis. "It suggests that water emerged with the formation of Mars. And it tells us that water may be naturally occurring on planets and does not require an external source like water-rich asteroids," says Bizzarro.
Supporting this were signs of asteroid impacts that resulted in the release of a great deal of oxygen, something the scientists say could only have occurred if water was present. "We have developed a new technique that tells us that Mars in its infancy suffered one or more severe asteroid impacts" says Deng. "The impact, Black Beauty reveals, created kinetic energy that released a lot of oxygen. And the only mechanism that could likely have caused the release of such large amounts of oxygen is the presence of water."
Credit: University of Copenhagen
The analysis may also provide an answer to one of the lingering mysteries of Mars: How could such a cold planet have accommodated the water for the lake and river remnants we see there today, as shown above? Black Beauty bears indications that early asteroid impacts released a significant amount of greenhouse gases that warmed the now-chilly orb for a time. "This means," says Deng, "that the CO2-rich atmosphere may have caused temperatures to rise and thus allowed liquid water to exist at the surface of Mars."
The researchers are not yet finished with their expensive rock, and are currently engaged in further study of the microscope water-bearing minerals it contains. They appear to be present in their original, unchanged form. The authors of the paper believe Black Beauty was there at the long-ago moment when water first emerged on the red planet.