Drinking toilet water: The science (and psychology) of wastewater recycling

Would you drink water that came from a toilet? The imagery isn’t appealing. Even knowing that the water, once treated, may be cleaner than what comes out of most faucets, many people are disgusted by the idea. But in places like Singapore and Namibia, limited supplies of freshwater are being augmented by adding highly treated wastewater to their drinking water. As climate change and population growth strain freshwater resources, such strategies are likely to become more common around the world, and in the United States.

A Limited Resource

Freshwater is a more precious commodity than many people in the developed world recognize. More than 97 percent of Earth’s water is saline, unfit for drinking. Of the remainder, more than two-thirds is frozen in glaciers and icecaps, leaving just 1 percent of all the water on our planet fresh. About one one-hundredth of that 1 percent resides in lakes, rivers and other waterways; the rest is in aquifers beneath the surface or trapped in soil. It’s a wonder that so many of us take limitless, on-demand clean water for granted.

Pressure on this invaluable resource is growing. Over the last several decades, regional and local water shortages are becoming increasingly common. Australia saw the worst droughts in its settled history between 1995 and 2009. Droughts across the U.S. last summer crippled farm crops. And people are adding to that burden: Los Angeles, Las Vegas and Phoenix are located in some of the driest parts of the U.S.; they are also among the metro regions experiencing the highest rates of population growth.

Control of water resources is also a point of friction along already-contentious borders between Israel and Jordan, India and Pakistan, and Turkey and Syria, for example. And some experts think that water may supplant oil as a major spark of future conflicts.

“Water is becoming a geopolitical conflict,” says David Feldman, a political scientist at the University of California at Irvine. “When we talk about reclaimed wastewater, we’re not talking about something that’s simply at the level of convenience. We’re really dealing with an issue that is going to be affecting every country, every society.” Avoiding future clashes over water, he says, will mean having to drink treated wastewater.

With only a finite amount of water on the planet, chances are good that the water you drink passed through a person or animal at some point. More directly, many cities use rivers like the Colorado, Mississippi and Thames as their source for drinking water, while at the same time other cities upriver are discharging treated waste into them.

Down the Drain

Understanding the process of water treatment can help to make wastewater recycling more palatable, say scientists and activists working to promote its adoption. In most Western cities, when a person flushes a toilet, waste is carried by sewers to a municipal wastewater plant. There, large solid material is separated from liquid with grates or screens. In a settling tank, smaller solids fall out of solution while oils rise to the surface and are skimmed off. The wastewater next moves to an aeration tank, where microbes feed on the waste and break it down. After a final settling step, the clarified water is treated with ultraviolet light, chemicals like chlorine, or other processes to kill any remaining germs before the water is released back into the environment. Many of these steps are then repeated when water for consumption is drawn from the same river, lake or reservoir where the treated wastewater was released.

In essence, advocates of recycling wastewater for human consumption merely want to shorten this pathway, by reintroducing highly treated wastewater into water supplies without first depositing it in an intervening lake or river. Several cities around the world are already showing that it’s possible.
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The 10 Most Important Water Stories in 2014

1. The California Drought Becomes an Emergency
California’s multi-year drought grew dire enough in 2014 to prompt Governor Jerry Brown to declare a drought emergency in January. By the end of the year, California had experienced the driest and hottest 36 months in its 119-year instrumental record. Some researchers described the drought as 1) the worst in over 1200 years and 2) evidence of rising temperatures globally as climate changes accelerate. As of mid-January, the drought is continuing.

2. Tigris and Euphrates River Dams Influence Islamic State Expansion
Conflicts over water have a long history. In 2014, a new analysis described the links between drought, climate change, water management, and the Syrian civil war. By the end of the year, the region’s major dams were targeted for control by the Islamic State (IS) and used as weapons to flood parts of Iraq and to divert water away from some communities for political purposes. IS forces near these dams were also targets of allied air strikes because of the dams’ strategic importance.

3. U.S.-China Climate Agreement Includes Water-Energy Provisions
On November 12, 2014, the President of the United States reached a momentous accord with the President of China to cap greenhouse gas emissions and do a whole lot more for Mother Earth and its human inhabitants. The agreement encourages collaboration between the world’s two largest economies to much more quickly put into place new tools, practices, and especially markets to contend with radically different ecological and economic conditions. The agreement includes two provisions to secure freshwater supplies in energy production. The two nations are 1) investing in research to improve efficiency and conservation in water supply for energy generation and 2) developing a carbon-sequestration demonstration project in China to put to good use the water that is displaced from deep beneath the surface during CO2 storage.

4. The U.S. Safe Drinking Water Act Turns 40 Amid Mounting Safety Lapses
In the year that the U.S. Safe Drinking Water Act turned 40, Toledo, Ohio, Charleston, West Virginia, and towns along North Carolina’s Dan River were the victims of pollution incidents that highlighted the continued challenges in safeguarding water supplies and protecting public health. Toledo shut down its water supply after poisonous algae toxins developed in Lake Erie. Charleston’s water supply was fouled by a chemical spill that prompted the Justice Department to indict the plant’s owners for water-quality violations and obstruction of justice. In North Carolina, a storage basin failure at a Duke Energy power plant sent more than 35,000 metric tons of coal ash, a noxious waste product, flowing into the Dan River, a drinking water source.

5. Evidence of the Link between Climate Change and Extreme Hydrologic Events Grows Stronger
The evidence of the links between climate change and extreme hydrologic events grew more powerful in 2014. A series of scientific reports addressed heat waves in Europe, coastal damages in the Eastern United States during extreme tides and storms, flooding in the UK from more intense rain storms, drastic loss of Arctic ice, and droughts in Australia and the Southwestern United States. Lloyd’s of Londonconcluded in May that the influence of rising sea levels increased the damages from Hurricane Sandy by $US 8 billion in New York alone. Sao Paulo, Brazil’s largest city and located close to the water-rich Amazon Basin, suffered its worst drought.

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