Toilet–to–Tap—Taking the Ick Out of Wastewater Recycling

Drinking water at a water treatment facility

The UN warns that by 2030, over half the world will be water-stressed, affecting food production and increasing exposure to waterborne disease. There is enormous potential in directly recycled wastewater. Unfortunately, attempts at wastewater recycling have historically been shot down by  the public.1 Thus, most treated wastewater is dumped into oceans and other water sources, becoming wasted water.2

Ironically, at the same time, we’ve been consuming indirectly recycled wastewater all along. Many municipalities treat their wastewater and release it into the natural waterways. The same waterways where they get their potable water. “De facto reuse” happens when a water treatment plant unintentionally obtains unregulated recycled wastewater because it’s located downstream from a wastewater plant. Regrettably, when wastewater recycling is a goal set by necessity, it is met with public disgust and distrust.2

For the Dogs

Although recycled wastewater is crystal clear, the thought of drinking it is more appalling to some than the reality of lead or radium in our tap water. In fact, public reactions from those who were offered free bottles of “toilet-to-tap” water varied from “eww,” to the suggestion that toilet water is for dogs.3  In Toowoomba, Australia, Citizens Against Drinking Sewage, successfully crushed proposals to use recycled water by citing health hazards and emotional sensitivities.1

In some states, like Arizona, regulations prohibit recycled water for potable use or for being used where people may have bodily contact, like recreational parks or pools. Some claim outdated regulations put consumers at risk for contamination.4

President of the World Water Council, Benedito Braga, disagrees: “Standards are stricter because of the novelty of the technology and process….The quality from sewage is very good or better than the tap water in any city in the developed world.”1

Experts agree that the stigma is unwarranted. The chemicals and pathogens found in tap water and recycled water are similar, and sometimes lower in recycled water.2

Dr. Carol Nemeroff of University of South Maine studied public perception of recycled water:

“The disgust comes from intuitive concepts of contagion…if you can see sparkling fresh, clear water, and taste it, that helps to overcome the concept … the contagion type thinking decreases with familiarity…if you’re desperate you’ll override anything for survival.”1

Astronauts Do It

Wastewater recycling is taking place:

  • One of the first systems was put into practice in 1968 in Namibia as an answer to drought and water-borne disease.1
  • Toilet-to-tap is in practice in water-stressed areas such as Australia, California, Israel, Saudi Arabia, and Singapore.5
  • American astronauts have been distilling their urine (and moisture from sweat, breath, and shower water) since 2009.6

How It’s Done

Wastewater goes through a primary treatment:

  • Screens catch and remove large debris from incoming wastewater (influent).
  • Smaller debris is removed in grit tanks.
  • Fats, oils, and other floating debris is skimmed from the top.
  • Small heavy particles sink to the bottom as sludge from which the water is separated. 7

Then wastewater goes through a secondary treatment:

  • The water is mixed with air and living bacteria that break down organic contaminants in the wastewater.
  • Wastewater goes through multiple phases of filtration and quality checks.
  • Decontamination—chlorination, ozone, UV light, and/or peroxide—kills any remaining pathogens.
  • Reverse osmosis forces H2O molecules through pores in a membrane so small that they can only fit molecules through.
  • The outgoing wastewater (effluent) is crystal clear.7,8

Exceeding Regulations

Reclaimed water for both Silicon Valley and Santa Clara County, California, undergo microfiltration, reverse osmosis, intense ultra violet light treatment, a hydrogen peroxide treatment, as well as frequent quality checks. Orange County Water District and Orange County Sanitation District in California officials say their “ultra-purified recycled water exceeds all state and federal quality standards.”5

Wastewater can be recycled for potable use either directly into the water supply or indirectly into an environmental buffer before it is returned to the potable water supply.9 However, because the general population rejects the idea of drinking wastewater, most wastewater is indirectly recycled into natural reservoirs prior to mixing it with natural water sources—a hugely unnecessary step to placate the public. Indirect recycling is actually a counter-intuitive measure that re-contaminates purified water and drives up the cost and the energy required to treat potable water.1

But How Does It Taste?

The ultimate taste test, performed by University of California, Riverside, showed that testers had no preference for bottled water over recycled water. Three types of water tested were groundwater-based tap water, indirectly recycled water, and bottled water. The study compared the personality traits of water testers as either “open to experience” or “anxious” about the experience. Those anxious about the experience preferred bottled and recycled water over the mineral-rich tap water. Those open to the experience liked all three samples the same.10

Non-Potable Reuse

Because the public is so wary about consuming wastewater, it is fortunately being reclaimed for following non-potable uses:

  • Industrial coolingRecycle Water
  • Industrial processing
  • Crop irrigation
  • Landscape irrigation
  • Golf course irrigation
  • Public parks
  • Dust control
  • Toilet flushing
  • Breweries
  • Wineries
  • Construction
  • Concrete mixing
  • Artificial lakes

All Water Is Recycled

One way or another, all water is recycled. Unfortunately, dumping treated wastewater into our oceans won’t solve the global water crisis in the long run. Direct wastewater recycling through a water treatment plant removes the middle (wo)man—Mother Nature—speeding up the water cycle. It is therefore water quality, and not water source, that is of utmost importance.


  1. CNN: From toilet to tap: getting a taste for drinking recycled waste water, Kieron Monks, November 17, 2015.
  2. New York TImes: Wasting the wastewater, Dylan Walsh, January 24, 2012.
  3. NBC Los Angeles: ‘Toilet to tap’ water put to the taste test, by City News Service, June 22, 2017.
  4. From Toilet to Tap, Dr. Mercola, June 13, 2018.
  5. The Mercury News: toilet to tap? some in drought-prone california say it’s time, Devika G. Bansal, July 5, 2017.
  6. How recycled astronaut pee boosts chances for future deep-space travel, Samantha Mathewson, November 16, 2016.
  7. Journey Through the Pipes – What Happens to Wastewater? Angela Lucci, December 4, 2018.
  8. SAMCO: What is a wastewater treatment system and how does it work? December 24, 2016.
  9. Mother Nature Network: How ‘toilet to tap’ water is made. Robin Shreeves, March 21, 2018.
  10. UCR Today: Toilet-to-tap: gross to think about, but how does it taste? J.D. Warren, March 13, 2018.
  11. EPA: Water reuse and recycling: community and environmental benefits,

Bargaining for Clean Water: Why Dean Kamen Invented the Coca-Cola Freestyle

The Coke Freestyle

The technology Kamen used to develop the Freestyle Coca-Cola soda fountain is similar to that in his prescription pumps.1

When Kamen asked Coke for help distributing his water purifier, Coke challenged Kamen to develop a better soda fountain first.

Dean Kamen, Inventor of Medical Technology

The inventor of the Segway, Dean Kamen is known in the scientific community for developing medical equipment. His inventions include a wearable prescription pump for insulin and chemotherapy, a microdosing prescription pump for infants, and a home dialysis machine.When Kamen realized his dialysis machine required too much distilled water and energy for home use, he developed a system to purify tap water that would run on less power than a hairdryer.

And that’s not all it does. Kamen’s water purifier can take any water source and return water safe even for infants to drink.2

How it works

  • Kamen’s water purifier uses vapor compression distillation system.
  • It uses less than one kilowatt of electricity per hour (less electricity than a hairdryer).
  • The purifier uses any water source, no matter how polluted—laundry water, groundwater, seawater, even sewage.
  • It boils and evaporates the source water then condenses and collects clean drinking water.
  • One system purifies up to 850 liters per day, which can provide safe drinking water for around 300 people.2, 3

Water Purification for the World

While he was developing it, Kamen realized his water purifier had world-wide benefits. It could supply clean water for disaster relief and to areas with polluted or low water supply.2

Waterborne Disease: #1 Killer

Kamen believes that 50% of the world’s medical issues can be solved with clean water. He says children are at the highest risk.4 The World Health Organization (WHO) agrees. Water-borne disease kills more than 3.4 million people, mostly children, every year, making it the world’s largest killer.5

This is the result of more than 2 billion people across the world using contaminated water. Approximately 844 million people lack a potable water source, including 159 million people who use surface water for their daily needs. WHO estimates that half the globe will be water-stressed by the year 2025.6

Goliath, Meet Slingshot

Kamen named his water purifier Slingshot as the appropriate weapon for the global water crisis, which he calls Goliath.4

Kamen’s goal to mass distribute Slingshots to thousands of water-polluted/water-stressed rural locations has been slowed by his lack of resources. Unfortunately, his medical connections were little help delivering water purifying systems to rural areas—medical technology is distributed in wealthy areas. So, he turned to Coke for assistance in mass distributing his invention.3

Bargaining: The Freestyle

Coke’s counter-proposal: first build a better soda fountain. This is how the inventor of medical supplies came to develop the Freestyle Coca-Cola soda fountain.2

Expanding the Handshake Deal

By the time Kamen’s soda fountain, the Coca-Cola Freestyle, was put in production, Coke had a new CEO. But Muhtar Kent didn’t drop Kamen’s handshake deal. He expanded on the informal agreement to mass-produce and distribute the water purifier. To get the water purifiers to rural areas, Coke is distributing Slingshots within their Ekocenter.2

Ekocenter Modular Community Market

Coke’s Ekocenter is a solar-powered shipping container that provides low-income rural communities with safe water, internet access, non-perishables, first-aid supplies, and more. Coca-Cola calls their Ekocenter a “modular community market.” It is an opportunity for local (usually female) entrepreneurs, who are trained by Coke.6

Going Far Together

To distribute the Ekocenters, Coke is following the proverb, “If you want to go fast, go alone. If you want to go far, go together.” Coke has pooled resources with 10 other companies to greater impact the world. By December 2017, 150 solar powered Ekocenters had been placed in 8 low-income countries. These Ekocenters can distribute 78.1 million total liters of potable drinking water per year.6

Kamen’s Vision and Future Use

Kamen’s vision involves the distribution of 2,000 units to low-income rural areas.2 Is his vision of clean water distribution different than Coke’s vision? Is the need more immediate? In America, water-polluted urban areas like Reno and Las Vegas; Pittsburg; Milwaukee; Flint, Michigan; Brady, Texas; to name a few, and the water-stressed state of California, which is researching ways to recycle wastewater for potable use, might look into using the Slingshot. Comment below and let us know what future use(s) you envision for Kamen’s Slingshot.

Tune in next week to read Toilet-to-Tap—Taking the Ick Out of Wastewater Recycling.

  1. Coca-Cola Freestyle: The Soda Machine of the Future (+ the Past), By Elina Shatkin, March 1, 2012.
  2. Popular Science, Pure Genius: How Dean Kamen’s Invention Could Bring Clean Water to Millions, by Tom Foster, June 16, 2014.
  3. Coca-Cola Journey™: Sustainability, EKOCENTER & Slingshot Clean Water Partnerships.
  4. WHO Drinking-water Key Facts, February 7, 2018,
  5. Dean Kamen Inventor – Slingshot Water Purifier, By Datun Center, April 17, 2015.
  6. WHO: Waterborne Disease is World’s Leading Killer, by Jessica Berman, October 29, 2009.
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