There is no question that water scarcity is a major issue around the world. With ongoing droughts and dwindling water supplies, certain regions will have to turn to a previously underused resource: sewage water.

What is ‘toilet to tap’?

Toilet to tap is pretty much what it sounds like. It is the process of recycling wastewater to the point that it is clean and safe enough to be classified as potable (drinkable) water. Cities around the world, including some in Singapore, South Africa, Belgium, and the United States, have already taken strides to invest in this necessary technology. 

Why is it necessary?

Climate change, as well as increasing demands on water supplies due to a growing population, has led to a global water scarcity issue. By the end of the 21st century, the amount of people impacted by extreme droughts is likely to double. This will have significant effects not only on people’s health, but also on water-heavy industries including agriculture and manufacturing.

Parts of the United States, including California, have experienced severe droughts over the last several years. These droughts cause major water depletion. According to the U.S. Forest Service, this level of drought could lead to half of the country’s freshwater basins being unable to fulfill the monthly water demand of its users by the year 2071. 

So, many cities have turned to water recycling, including the recycling of wastewater, as a way to provide enough potable water to their residents. 

How does water recycling work?

When water goes down your toilet (or your sink, shower, clothes washer, etc.), it goes into a sewer line that connects your home (and others in your area) to a municipal water treatment plant. The treatment plant takes the “used” water and cleans it through a multi-stage process. 

During this water treatment process, the following occurs:

• Chemicals are added to the water to reduce odor. 
• Water moves through screens that separate out larger solids. 
• Water sits in settling tanks, which further separates out solids as they sink to the bottom of the tanks.
• Water is stirred to help release trapped gases, while air is pumped in to aid in the decay of organic matter. 
• Solids are removed as they settle to the bottom of tanks.
• Water is moved through sand to filter out more bacteria, odors, and other solids. 
• The remaining water is treated with bacteria-killing chlorine. 

After water goes through this treatment process, it is typically used for watering crops or is returned to the environment (in streams, rivers, and lakes). Some places, including Northern  Virginia, Phoenix, and Southern California, go further with wastewater and purify it to the point that it can be used as drinking water.  

El Paso’s closed-loop water recycling system

El Paso (TX) is working on taking things a step further by creating a closed-loop water recycling system. This system will be able to purify wastewater and return it to the potable water supply right away.

El Paso receives an average of nine inches of rain per year. The Rio Grande, which previously was able to supply half of El Paso’s water supply, is drying up. 

El Paso currently discharges clean wastewater into a local aquifer, a process that takes years for the recycled water to reenter the drinking water supply. A closed-loop system would significantly speed this up by adding additional purification stages to the water treatment process. Once the water goes through these additional steps, and is deemed safe by El Paso water technicians, the treated water will reenter the drinking water supply immediately.

Gaining support for ‘toilet to tap’

Although this advanced process of recycling and treating wastewater provides water that is both clean and safe enough to drink, it is not always received well. According to a 2015 survey of 2,000 U.S. residents, 13% of adult Americans sampled would never try recycled water, 49% are willing to try it, and 38% are uncertain whether or not they would try it.

Many of those sampled were concerned about contamination and other issues. While recycling sewage water is unpopular with a lot of people now, it may be more well received as people learn about the extensive treatment process that produces this water. 

El Paso, for example, is working on being transparent and proactive about educating residents on the closed-loop water recycling system. As of 2016, almost 90 percent of residents supported the idea of using the closed-loop system to produce more drinking water.