“Can you imagine a day when you turn on your faucet and no water comes out?”

The hypothetical question, posed by a research team at UNLV, is called a “Day Zero” scenario. It sounds like the plot of a doomsday apocalypse series but it’s not as unimaginable - or as far-fetched - as a Hollywood screenplay might seem.

“A few years ago in Cape Town, South Africa they almost reached this point, where they were about to tell their citizens that they simply had no more water to give them, even though we all know that water is necessary on a daily basis,” said Erica Marti, an associate professor of civil and environmental engineering.

And while the severity of the Southwest water crisis hasn’t reached the “Day Zero” stage, Marti cites recent cuts to Nevada’s Lake Mead water allocation as reason enough to take the possibility seriously. 

She is a member of an interdisciplinary research team that is exploring innovations to keep our water supply from running dry. 

Their solution — while innovative — might bring on the “yuck” factor: reusing wastewater. 

“We often think of wastewater as something just to get rid of, but instead it should be viewed as a resource,” said Marti. “We have the ability to treat it to be able to use it for things like watering our crops, or the ability to be able to drink it again.”

Through a five-year, $450,000 project the research team is developing sustainable water management solutions for rural arid areas in the U.S. and China, focusing on wastewater reuse through solar-powered treatment processes. 

The project is led by Eakalak Khan, professor of civil and environmental engineering at UNLV, and funded by the Cyrus Tang Foundation, which supports projects involving collaboration between U.S. and Chinese universities. This particular project aims to provide low-cost technologies for non-potable — and possibly potable — reuse in rural communities in both countries, addressing water scarcity and quality issues. Rural communities often face challenges with advanced water treatment infrastructure, making innovative and affordable solutions like this project especially valuable for addressing water scarcity and quality concerns.

“With the technology in our project, we’re going to be able to bring this all the way to remote areas and rural regions so that everybody has access to clean water,” said Marti.

Sustainable Solutions to Address Water Scarcity

In Nevada, that community is Cal-Nev-Ari, a small town of about 400 residents located an hour south of Las Vegas. A similarly situated community partner is being cultivated by Northwest Agricultural & Forestry University in China. 

Both areas, Khan said, are experiencing the same water scarcity challenges but also have an abundance of natural resources, like sunlight and agricultural waste. The team’s goal is to develop a device that harvests the abundant resources at the household level to provide a continuous, easy-to-maintain, and cost-effective source of clean water.

“Instead of buying expensive materials — synthetic media — we’re relying on biomass and sustainable technologies,” said Khan. “Instead of having to use electricity, we have solar power as our source of energy to perform the filtration, clean the water at the maximum level, and pump it into your home.”

A key feature of the device — with the prototype to be developed and tested in the next year — is biochar, a charcoal-like substance created in the lab through a process called pyrolysis and made up of biological/agricultural waste, like wheat straw and rice husk, that is capable of removing contaminants from water. 

“The project has gone really well in our first year and is shaping up to have some promising results,” Khan said, adding that the project is especially significant for a community like Cal-Nev-Ari which currently has only one, non-contaminated groundwater well. In a later phase of the project, the U.S. and Chinese research teams will identify additional communities to partner with in their respective countries.  

“We believe our results will have a strong impact on small communities and rural households that have no access to a reliable water supply system.”

But the solution — treated wastewater piped directly to your home tap — has implications for urban environments and for the Las Vegas community in particular. And Los Angeles, for example, announced an ambitious plan to recycle 100% of its wastewater by 2035.

“A project like this is catalyzing other ideas that we have in play right now,” said Edwin Oh, a professor at UNLV’s Kirk Kerkorian School of Medicine and a co-PI on the grant. “And so having this technology — the science of being able to reuse wastewater using solar power — can then be deployed on a greater scale.”

While the “toilet-to-tap” doesn’t seem palatable when you first hear it, communities across the world might not have a choice in the near future.

“They call it the 'yuck factor,'” said Khan. “When people have alternatives, they will say, ‘No, of course, I’m not drinking treated wastewater.’ But no matter if we like it or not, wastewater reuse is going to happen. Southern Nevada is going to have to take a more serious look at this approach because, eventually, Lake Mead is going to dry up. It’s just a matter of time.”

Another reason to get past the yuck: Reused wastewater is also something we’re already consuming, though indirectly.

“Many of us are already drinking wastewater that is cleaned at the treatment plants and then it’s deposited at Lake Mead where it’s further diluted out by the Colorado River. It then gets treated and piped out back to us,” Oh said. “So, we’re already drinking it. But as Lake Mead starts to get lower and lower and lower, the portion that comes back to us is a higher percentage of treated wastewater.”

For now, though, the research team is focused on developing a functional unit in Khan’s lab at the Advanced Engineering Building. It will then be installed in Cal-Nev-Ari. 

“That’s what this whole project is about — it’s about serving rural communities,” Khan said. “The community is desperately in need of water. They’ve seen our proposed treatment schemes and were very excited that we were there to help. Everyone should have access to clean water.”