(The Hill) — Some Californians could find themselves flushing a future drinking water source down their commodes in just a few years — pending the approval of long-awaited, but misnamed, “toilet-to-tap” rules next week. 

The California State Water Resources Control Board will consider a landmark proposal Tuesday to streamline “direct potable reuse” (DPR) — a process by which purified wastewater is discharged right into a public water system or just upstream from a treatment plant. 

“It’s a real important step for just adding to the portfolio that we can use here in the West,” Darrin Polhemus, deputy director of the board’s division of drinking water, told The Hill.

Such capabilities, he explained, could strengthen California’s water resilience, while providing numerous environmental benefits and reducing the need for long-distance water transport.

“We’re not using it one time and dumping it in the ocean,” Polhemus said.  

While these regulations would constitute a giant leap forward in statewide water recycling, California utilities are by no means new to repurposing sewage.

They have for years engaged in “indirect potable reuse,” the injection of treated wastewater into environmental buffers — such as groundwater aquifers, lakes or rivers — before its ultimate release into a municipal system.

Orange County, which has treated sewage in some capacity since the 1970s, now boasts the world’s biggest water purification system for indirect potable reuse. Today, the county claims to be reclaiming 100 percent of its wastewater.

Unlike indirect potable reuse, however, DPR occurs without the use of an underground aquifer or any environmental storage barrier.

Even if the board does approve the rules Tuesday, DPR systems won’t be popping up overnight — and when they do, the wastewater won’t really be flowing right from a toilet to a tap.

The regulations first would have to be accepted by the state’s Office of Administrative Law — which Polhemus said would likely occur by summer or fall of next year. Only after that could utilities begin to build these large and complex projects, most of which would take about six or seven years to complete, he said.

“So no one will be drinking direct potable reuse in the immediate future,” Polhemus added. 

Tapping into an existing system, over and over again

While California is often a national trailblazer when it comes to environmental regulation and legislation, the Golden State would not be the first to adopt rules regarding DPR.

Colorado adopted DPR regulations after updating its drinking water standards in January, though no utilities are making use of these rules thus far. Texas published regulatory guidance for DPR on a case-by-case basis, while Florida and Arizona are now working on related rules.

The California regulations, however, are expected not only to be the most rigorous but would be serving several commercial-scale projects that are already in planning phases.

The proposed regulations stem from the 2017 A.B. 574 bill, which tasked the water resources board with adopting “uniform water recycling criteria for direct potable reuse” on or before Dec. 31, 2023.

Within the regulations are mandates that all source water for DPR projects come from municipal sewage and a ban on building bypasses to circumvent mandatory treatment processes.

The 69-page proposal also provides guidelines for controlling and monitoring chemicals and pathogens, as well as extensive instructions for plant operations, maintenance and compliance. 

Among the expected benefits of the proposed regulations are the provision of a safe, reliable and drought-proof drinking water supply, as well as a streamlined permitting procedure for DPR facilities, according to a statement of reasons issued by the board in July.

As far as the economics are concerned, Polhemus noted that DPR would enable utilities to reduce some of the expensive and disruptive pipeline and infrastructure construction that comes with other types of water recycling efforts.

“DPR does provide this opportunity to tap into the potable water distribution system that exists already,” he said.

Polhemus acknowledged that DPR is expensive but stressed it is far cheaper than desalination. Even when cities develop new natural water sources — which are largely unavailable in California — they confront “phenomenally high” costs for dams and aqueducts, he added.

Getting the public on board

Despite the many potential benefits associated with directly recycling wastewater, California regulators have faced an uphill battle in making this practice a reality.

For example, San Diego launched a campaign to implement DPR in the 1990s, but the plans stalled when a “toilet to tap” misnomer caught on and began to sway public opinion, KPBS reported.

Public opinion on DPR has evolved since the days of the San Diego debacle — both as the science has become clearer and California’s water needs have become more dire.

Jennifer West, managing director at the NGO WateReuse California, said she believes DPR has become more palatable to Californians as they have begun to understand the value of water amid multiple decades of drought.

“Using water one time and discharging it — we can do better than that,” she told The Hill.

West said she has seen a shift in “the collective consciousness” of Californians, noting that residents now complain when their cities aren’t reclaiming enough wastewater.

Polhemus likewise attributed the increasing public acceptance to the fact that water recycling — at least in indirect form — has now been occurring for a long time.

“For decades, we’ve learned from all of the activities we’ve done for recycling — from irrigation to indirect potable reuse,” he added, describing DPR as “the final step.”

If the regulations are approved, they would also require engagement with members of the public prior to the establishment of any DPR facility, according to Polhemus.

“We want the public to be brought along, to be explained what’s going on and be part of that decision-making process,” he said.

Emphasizing that “we’re not imposing this on anybody,” Polhemus reiterated that the board is simply providing utilities with a framework if they so choose to build a facility.

One long-standing issue that he and others identified as a barrier toward getting the public on board has been a discomfort linked to the potential presence of both chemicals and infectious diseases in wastewater.

Polhemus stressed, however, that the proposed regulations included “triple redundancy” to ensure the elimination of biological contaminants.

To identify an acceptable pathogen threshold and treatment protocol, researchers relied upon both the Giardia and Cryptosporidium parasites and on norovirus, the most common cause of acute gastroenteritis, according to the July statement of reasons.

They determined that regulating bacteria levels was unnecessary, as the treatment for handling “the hardier pathogen types” could “easily deal with the bacteria threat,” the document stated.

“The regulations are extremely protective of public health, and it’s going to be the cleanest water around,” West added.

On the chemical side, Polhemus touted an effective combination of reverse osmosis, advanced oxidation and granulated activated carbon.

That redundancy, he contended, gives regulators “the confidence that we’ll be able to treat for things we don’t even know are there.”

‘A community’s always going to produce wastewater’

If the DPR regulations receive an official stamp of approval, there are several Southern California projects prepared to embark on a multi-year planning and construction journey.

Among these projects is Pure Water San Diego, a multi-phased program to provide nearly half of San Diego’s water from local sources by the end of 2035. 

Although the first phase of Pure Water San Diego will use a reservoir for indirect potable reuse, the city is considering incorporating DPR into the next phase, according to the plans.

The Metropolitan Water District of Southern California, meanwhile, is partnering with Los Angeles County Sanitation Districts on a two-phased initiative, Pure Water Southern California, which plans to include DPR from the get-go.

The first phase is expected to involve a mix of indirect potable use and a type of DPR called “raw water augmentation,” in which treated wastewater would be blended with imported Colorado River water and state resources.

This process still qualifies as DPR because the mix would go directly into a drinking water treatment plant and on to customers, rather than first spending time in an environmental buffer.

“Our plan is to have Pure Water Southern California online and using DPR by 2032,” Rebecca Kimitch, press office manager for Metropolitan Water District, told The Hill.

As far as the second phase is concerned, project officials said they have yet to decide whether the DPR technology will again involve raw water augmentation or another approach.

“DPR is a vital component of our Pure Water Southern California program as well as to California’s water management strategy as a whole,” Kimitch said.

“But DPR will allow us to take this stream of purified water and incorporate it into our system right away, regardless of what the conditions in nature are,” she added.

Because Southern California lacks the natural resources to quench the thirst of its residents, the region has been relying on bringing in water from the Colorado River and from the northern parts of the state, Kimitch noted.

“We want to just use it as much as we can,” she continued. “Using it once and then sending it to the ocean — that’s not being as efficient and as sustainable as we can be.”

Polhemus echoed many of these sentiments, noting that as utilities consider how to bolster its resilience amid drought, adding DPR to their portfolios simply “makes a lot of sense.”

“A community’s always going to produce wastewater,” he said.