Roughly half of the United States was experiencing drought in March, and climate change is making dry periods hotter and more extreme. More precipitation is arriving in intense bursts that run off hardened ground instead of soaking into soil and aquifers. NASA scientists warn parts of the Southwest and Central Plains could face “megadroughts” after 2050—stretches drier and longer than any seen in the last millennium.
When supplies dwindle, officials often restrict use, raise rates or search for new sources. In many arid regions, however, those options are limited. Bridger Ruyle, an environmental engineer at New York University, points out there is still a demand that must be met in places like Southern California, Arizona and West Texas.
That necessity is renewing interest in wastewater recycling: treating sewage so it can be reused for drinking water, irrigation or to replenish groundwater. The idea has long struggled with a public “yuck factor,” but attitudes are shifting as shortages worsen. A survey of residents in communities under 10,000 found people would pay about $49 a month more to support a local reuse program, with higher willingness among those who have experienced shortages or know about reuse technologies, according to Todd Guilfoos, a water economist at the University of Rhode Island.
How recycling works
Sewage treatment has evolved since the early 20th century. Standard plants use primary treatment to remove solids and secondary biological treatment to break down organic matter; those steps are usually enough to allow safe discharge but not to produce drinking water. Tertiary treatment—processes such as ultrafiltration, reverse osmosis and disinfection with ultraviolet light or chemicals like chlorine—removes pathogens and dissolved contaminants and can produce water suitable for consumption or agricultural use.
Most U.S. treatment plants do not perform full tertiary treatment. The Environmental Protection Agency estimates U.S. plants treat about 33 billion gallons per day but only recover roughly 7% of that for reuse. Closing that gap would require major upgrades to facilities and distribution systems. Samuel Sandoval Solis, a water-resources expert at UC Davis, says recycling treated wastewater can be one of the most cost-effective ways to stretch supplies compared with building new dams or drilling more wells.
Overcoming opposition
Past projects have faltered amid public backlash—San Diego shelved a plan in the 1990s amid “toilet-to-tap” controversy. But scarcity and outreach have changed some minds: San Diego is now building a recycled-water facility expected to deliver about 30 million gallons a day—roughly one-third of the city’s water—by 2035. Similar projects are in progress across drought-prone states including California, Arizona, Texas and Florida.
Experts also note that many people already consume water that was indirectly reused. About half of U.S. drinking-water plants draw from rivers or streams downstream of wastewater discharges, a form of de facto reuse. As Solis puts it, most people are already using recycled water in one way or another.
Costs and tradeoffs
Building reclaimed-water systems is expensive. The first phase of San Diego’s program cost about $1.5 billion, and federal or state funds often help cover those capital expenses. The roughly $49 monthly fee cited in the survey might cover the operating costs and advanced treatment for a household, but not the large upfront investments in new treatment plants, pipes and pumping stations.
There are also environmental and technical tradeoffs. Advanced treatment can require substantial energy—the more stringent the treatment, the higher the power needs. Injecting treated wastewater into aquifers can potentially mobilize heavy metals or other contaminants in soils, creating health and ecological risks. Ruyle cautions that solving one water problem should not create another downstream.
Not a silver bullet
Scientists emphasize that wastewater reuse is not a cure-all. It comes with costs, energy demands and environmental considerations. Still, as climate change diminishes other options, recycling is becoming a practical and sometimes necessary component of water portfolios in many communities. As Ruyle notes, it’s unlikely society can dismiss reuse entirely in the future.
Edited by: Jennifer Collins