Countries and communities require sustainable sources of water for economic growth, sociopolitical stability, and quality of life. However, water scarcity and insecurity are pervasive problems around much of the world. As such, it is important to urgently develop technologies for advanced water reuse that are cost efficient and effective – that may even change the way we use and reuse water.
Nature uses water over and over again, in an endless long cycle of evaporation and precipitation, powered by the sun. Humans, in contrast, tend to use water only once – drawing fresh water from a local source, using it for various purposes, and then discarding the wastewater back into the environment after minimal treatment, often exhausting their limited water resources.
For decades, scientists have been working on new technologies to enable treatment and direct potable reuse of water, but the applications have been largely limited to “out-of-this-world” environments such as water supply systems on the International Space Station.
Colorado Springs Utilities, Colorado School of Mines (Mines), and Carollo Engineers partnered in 2020 to create a “down-to-Earth” version of this technology: a mobile direct potable reuse (DPR) demonstration system (7,000 gpd) that purifies municipal wastewater for potable use. The system is now being tested and demonstrated at the Colorado Springs Utilities’ JD Phillips water reclamation plant, but is due to travel to several other locations in Colorado later this year.
The DPR demonstration lab is the vision of Dr. Tzahi Cath, a Professor of Civil and Environmental Engineering at Mines. “If we can take the water, and instead of just wasting it we could recover it and reuse it again for potable purposes, it will save money and energy, and it will save many problems during drought years” says Cath, “[…] communities must have a wider portfolio of sources of water to make sure that we have drinkable water under any circumstances.”
While there have been previous examples of DPR technology, including units packaged in mobile systems, most of these have relied on reverse osmosis, which leaves behind a waste stream of concentrated contaminants that must be managed and disposed of, also limiting the percent water recovery of the system. In contrast, the Mines mobile DPR lab utilizes advanced treatment technologies such as ozonation, biologically active filtration, ceramic microfiltration, ultraviolet disinfection with advanced oxidation, and granular activated carbon to efficiently destroy pathogens and trap and remove contaminants of emerging concern, purifying close to 100% of the water. The mobile system also has a range of advanced sensors and automated fault detection technologies to ensure that all processes are operating properly and synchronously, and that the water meets drinking water regulations at all times.
The DPR system was recently put to the test, and it passed with flying colors — close to a million gallons of water were successfully treated over the first 6 months of operation. The water met all Colorado’s drinking water quality limits, and a few batches of water from the mobile lab were used to produce beer by several local breweries and soft drinks that were served in public outreach events. Specifically, all emerging contaminants of concern and disinfection by products such as PFAS, 1,4-dioxane, TCEP, TCPP, and NDMA were reduced to much below the regulatory or advisory levels, and microorganisms such as coliforms were completely eliminated from the product water.
Seeing (and Tasting) is Believing
Mines embarked on this technology demonstration project, anticipating that some residents would be nervous about the concept of drinking recycled water. The system is designed to allow visitors to observe the water treatment process directly, and taste the high-quality water produced.
Tourists can visit the PureWater Colorado Mobile Demonstration in Colorado Springs and watch the entire water treatment process in action. Funded by a Colorado Water Conservation Board Grant, with additional support from the National Science Foundation (NSF), and other industry partners, the interactive exhibit shows a scaled model of the carbon-based DPR process.
The mobile DPR demonstrates that advanced water reuse technologies are not as far off as we think, and that you don’t have to be an astronaut to use one. DPR and other advanced water reuse technologies could help communities facing water insecurity and shortages by diversifying water supply and hedging against water risk. DPR could also help to provide clean water quickly and cost-efficiently to people displaced by natural disasters and drought.
On March 8, the project team won the 2022 WateReuse Award for Excellence in Education and Outreach. Award recipients include Colorado Springs Utilities (Kirk Olds, Donene Dillow, Birgit Landin, Shaun Thompson, Jennifer Kemp, Lisa Halcomb), Colorado School of Mines (Tzahi Cath, Mike Veres, James Rosenblum, Tani Cath, Mason Manross, Chris Bellona), and Carollo Engineers (Jason Assouline, Andrew Salveson, Tasie Kade, John Rehring).
DPR, Desalination, and More
Mines is part of the National Alliance for Water Innovation (NAWI), the U.S. Department of Energy’s 5-year research program to lower the cost and energy of desalination and water reuse technologies. NAWI is working to revolutionize the US water supply by enabling the affordable treatment and reuse of non-traditional sources such as wastewater. The operating data generated by the mobile lab will help researchers to develop new control sensors and algorithms to allow such systems to autonomously operate safely, reliably, and inexpensively. The mobile DPR lab is one more step in the shift toward a circular water economy.