Reclaimed water is wastewater that has been treated and purified so it can be used again. Most commonly, it comes from household and commercial sewage that goes through multiple rounds of filtration, disinfection, and chemical treatment before being redistributed for irrigation, industrial cooling, groundwater recharge, or even drinking water. In water-stressed regions across the U.S. and worldwide, reclaimed water has become a critical tool for stretching limited freshwater supplies.
How Wastewater Becomes Reusable
Turning sewage into safe, reusable water involves several distinct stages. First, a wastewater treatment plant removes trash, solids, and many harmful germs through physical screening and biological processes. This produces what’s called secondary-treated water, which is clean enough for some limited uses but still contains contaminants.
For higher-quality applications, the water moves to an advanced treatment plant that removes additional germs, chemical residues, and microscopic particles through processes like membrane filtration, ultraviolet disinfection, and reverse osmosis. If the water is destined for drinking, it then passes through a drinking water treatment plant for final disinfection and testing against federal and state standards before it reaches any tap.
The level of treatment determines what the water can be used for. California’s regulations, which serve as a model for many other states, distinguish between “disinfected tertiary” water and “disinfected secondary-23” water. Tertiary-treated water must meet stricter bacteria limits and demonstrate a 5-log removal of viruses, meaning it eliminates 99.999% of target viruses. This higher grade is required whenever the water might become airborne, such as in cooling towers or misting systems, or when workers could come into direct contact with it. Secondary-23 water, held to a somewhat looser bacterial standard, is permitted for enclosed industrial uses like boiler feed water where human contact is minimal.
Non-Potable Uses
The vast majority of reclaimed water in the U.S. goes toward non-potable purposes, meaning it’s not intended for drinking. Landscape irrigation is the most visible application. Golf courses, public parks, highway medians, and residential common areas in many cities across Florida, California, Texas, and Arizona run on reclaimed water. Agricultural irrigation is another major use, particularly for crops that undergo processing before consumption.
Industrial facilities are increasingly large consumers. Data centers use reclaimed water for cooling systems, and car manufacturing plants use it in production processes. Power plants, refineries, and concrete mixing operations also rely on it. These industrial applications reduce pressure on drinking water supplies while giving communities a productive use for treated wastewater that would otherwise be discharged into rivers or the ocean.
The Purple Pipe System
If you’ve ever noticed purple pipes, sprinkler heads, or valve boxes in a park or commercial property, you’ve seen reclaimed water infrastructure. The purple color coding is a regulatory requirement designed to prevent anyone from accidentally connecting reclaimed water lines to the drinking water system. In Texas, for example, all irrigation pipelines carrying reclaimed water must be purple (specifically Pantone 521 or 525), and all irrigation valves must sit inside purple locking boxes.
Above-ground faucets and quick-connect couplers on reclaimed water lines must be enclosed in lockable devices. Warning signs on a purple background with white or yellow lettering, in both English and Spanish, must clearly state: “Do not drink irrigation water.” These cross-connection prevention rules exist in virtually every state that permits water reuse, though the specific requirements vary.
Reclaimed Water for Drinking
Using reclaimed water as a drinking water source is growing rapidly, and it comes in two forms. Indirect potable reuse sends highly treated water into an environmental buffer, like a lake, river, or underground aquifer, where it blends with natural water before being drawn out and treated again at a conventional drinking water plant. This approach has been in use for decades. Orange County, California, has operated one of the world’s largest indirect potable reuse systems since the 1970s, injecting purified recycled water into groundwater basins that supply drinking wells.
Direct potable reuse skips the environmental buffer entirely. The treated water goes straight from the advanced purification facility into the drinking water distribution system. This approach requires even more rigorous real-time monitoring but eliminates the need for a natural water body as an intermediary. It’s newer and less common, but several communities in Texas and other states have adopted it or are actively planning systems.
Both approaches put the water through the same gauntlet: wastewater treatment, advanced purification (typically reverse osmosis and UV disinfection with hydrogen peroxide), and then conventional drinking water treatment. Staff test the finished water to confirm it meets federal and state drinking water regulations before distribution.
What About Contaminants?
The concern most people have about reclaimed water involves contaminants of emerging concern: pharmaceuticals, hormones, PFAS (sometimes called “forever chemicals”), and microplastics. These substances pass through conventional wastewater treatment largely intact, which is why advanced treatment stages matter so much.
Modern purification technology is effective against most of these compounds. Advanced oxidation processes combined with ozone can degrade 90 to 92% of pharmaceutical micropollutants in real-world effluent containing 20 or more different compounds. Specialized membrane systems have achieved over 90% degradation of specific hormone disruptors and common painkillers. For antibiotics like ciprofloxacin, newer extraction methods have reached 99.5% removal from hospital wastewater.
PFAS remains the trickiest category because these compounds resist breakdown by design. Research on farmland irrigated with river water that contained treated wastewater found very low PFAS concentrations in crops (under 1 nanogram per gram in mint and alfalfa), with some plants showing no uptake at all. Reverse osmosis, the backbone of most potable reuse systems, is currently the most reliable method for removing PFAS from water.
Environmental Benefits
Reclaimed water addresses two environmental problems simultaneously. First, it reduces the volume of treated wastewater discharged into rivers, streams, and lakes. Those discharges carry nutrients like nitrogen and phosphorus that fuel algal blooms and degrade aquatic ecosystems. Every gallon of wastewater that gets reclaimed instead of discharged is a gallon of pollution kept out of surface waters.
Second, reclaimed water helps recharge depleted underground aquifers. Many regions across the American West and Southeast are drawing groundwater faster than rain can replenish it. Injecting or percolating highly treated reclaimed water into these aquifers slows that depletion and, in some cases, creates a barrier against saltwater intrusion in coastal areas. Microsoft’s data center operations in Washington State, for instance, reuse water in a way that supports local groundwater supply.
How It’s Regulated
There is no single federal law governing water reuse in the United States. The EPA published Guidelines for Water Reuse in 2012, which remain the current federal reference document, but these are guidelines rather than enforceable regulations. Individual states set their own rules, and the strictness varies considerably. California, Florida, Texas, and Arizona have the most developed regulatory frameworks because they’ve been practicing water reuse the longest.
State regulations typically specify treatment requirements, water quality limits (particularly for bacteria and turbidity), approved uses for each quality tier, monitoring frequency, and infrastructure standards like purple pipe coding. For potable reuse systems, states layer additional requirements on top, including continuous online monitoring, multiple treatment barriers, and mandatory response protocols if any quality parameter falls outside its target range.