Most Americans are familiar by now with the concept of recycled wastewater. We all may not be completely comfortable with the concept of reusing treated sewage, but most of us have at least heard about it, and in some communities we know that it helps parks and street landscaping thrive.

A handful of communities practice what is known as indirect potable reuse, which means using highly refined treated wastewater to recharge groundwater or a reservoir. This water is processed again in a conventional drinking water treatment plant before being delivered to customers.

The next and ultimate step is direct potable reuse, in which wastewater is treated so thoroughly that it meets drinking water standards, and is then plumbed directly into the drinking water distribution system. Texas was apparently the first state to permit this degree of reuse during its long drought in the early 2010s. But this was done on a case-by-case emergency basis, and Texas still does not have comprehensive rules governing the practice.

In January, Arizona became the first state to reach that benchmark, adopting a complete regulatory approach to direct potable reuse. Water Deeply recently spoke with Chuck Graf, principal hydrogeologist at the Arizona Department of Environment Quality, to learn more about the state’s new regulations.

Water Deeply: It’s been a long road getting to this point with recycled water in Arizona, hasn’t it?

Chuck Graf: In Arizona, we’ve been using reclaimed water for a long, long time. In fact, our first rule regarding reuse of reclaimed water was back in 1972. I don’t know if that was a first in the nation, but it was probably in there somewhere.

Actually, we started using reclaimed water back in 1926. And that was at Grand Canyon National Park, when they built a wastewater treatment plant specifically to reuse treated wastewater for steam locomotives and toilet flushing. And they still use it for toilet flushing and landscape irrigation in a much-improved treatment plant.

When they built the first treatment plant in Phoenix in 1931, they actually started distributing that reclaimed water for agricultural irrigation way back then. So it was already being used by the time first rules came into existence in 1972. Then in 2001, we greatly modified our rules for reclaimed water. Arizona probably reuses somewhere above 50 percent, and maybe as much as two-thirds of our treated wastewater.

Water Deeply: What do the new direct potable use regulations allow?

Graf: We started revising the 2001 regulations a few years ago. The first installment of those rules was adopted on January 1 of this year. The big part that’s under this umbrella now is what we call “purified water for potable use.” Now we can issue a permit for a facility that does advanced treatment on reclaimed water, and produces water that’s suitable for putting in a drinking water distribution system.

Our new rule says the source water for this advanced reclaimed water facility would have to go through a multistage, multibarrier treatment process with controls, real-time monitoring, a whole lot of microbial monitoring and chemical monitoring. And the output from that facility is drinking water, and it could be put into a drinking water system.

Water Deeply: What’s the demand for this type of permit?

Graf: We know of no utilities out there that are waiting at the door to come in. The big thing, though, is by having this rule in place now, that utilities and communities can think about maybe this is something we could do in the future and start evaluating this. Because, I think, for any utility to develop a real plan is going to take a couple years with high-level consultant help. By then we should have our final criteria in place, which will probably be early next year, we hope. But if somebody did come in now, we could actually entertain that application.

Water Deeply: Where is Arizona on this compared to other states?

Graf: Texas is taking applications and issuing permits on kind of a case-by-case basis. And they’ve actually issued a couple permits. When they had the big drought there, in Big Spring, Texas, in particular, their reservoir ran dry and they had essentially no water. They had to treat their wastewater and put it in the drinking water system.

The California approach (yet to be finalized) has put in place very detailed specs on what’s involved with doing direct potable reuse. So I think the California approach is at one extreme, where you just have a lot of detail. It’s a very prescriptive approach.

What Arizona wanted was a merging of the two. We don’t want to leave out innovation by making the approach too prescriptive. But we want some detail there.

Water Deeply: In this context, what is the future of indirect potable reuse?

Graf: A number of big cities are doing indirect potable reuse, where they kind of use an environmental barrier: The treated wastewater is mixed with groundwater or surface water, and then you treat that mixture before it goes into the drinking water system. One of the arguments against that is you’ve treated this wastewater to an incredibly high level, and then you’re mixing it with surface water again, which is actually way lower quality. A lot of people are now saying it just makes more sense to start reusing that treated wastewater directly.

Water Deeply: Are consumers ready to start drinking treated wastewater straight from their taps?

Graf: I think once these direct potable reuse plants go in, the technology we’re going to be using is so high that people are going to start demanding some of that technology in normal treatment plants.

People talk about emerging contaminants, and a lot of surface water in the U.S. is influenced in some way by upstream discharges by wastewater treatment plants. You can go to almost any surface water and you can detect some of these chemical constituents – personal care products and pharmaceuticals – at these low levels and I’m sure we’re drinking them now.

The reason we looked at changing the rule is because the technology is here now. We can treat it to any clean standard we want. Also the real-time monitoring technology is there, too, so that you can monitor critical indicators at critical points in the process. That’s important, rather than having to culture a sample and wait 16–18 hours for a report. The combination of those two give us confidence that these plants can be built and operated properly.