This past November, Colorado and Texas took key steps toward promoting direct potable reuse (DPR) within their jurisdictions. In effect, the two became the first states in the nation to document their procedures for approving DPR, the sometimes controversial practice in which treated wastewater is further cleansed and then added directly to a drinking water source in the absence of an environmental buffer. 

Eye toward the future

On November 14, Colorado’s Water Quality Control Commission “finalized the approval to implement direct potable reuse into the Colorado Primary Drinking Water Regulations,” which are commonly referred to as Regulation 11, says Kaitlyn Beekman, a spokesperson for the Water Quality Control Division within the Colorado Department of Public Health and Environment. 

“The commission previously voted unanimously to issue preliminary approval for the proposed modifications to Regulation 11,” Beekman says. The DPR rule took effect on January 14 following the new publication of Regulation 11 by the Colorado Secretary of State on December 25.

Development of the DPR rule was crafted with an eye toward the future, rather than a response to an immediate demand for such a regulation. “Water systems [in Colorado] have never been restricted from using direct potable reuse,” Beekman says. However, the state “did not have a robust framework in place to make sure [DPR] could be done safely,” she says. “In preparation for water systems starting direct potable reuse projects, the department proposed this regulation to make sure public health protections are maintained.”

Colorado’s DPR rule spells out requirements pertaining to communications and public outreach, wastewater treatment, treated wastewater characterization, chemical reduction and monitoring, engineered storage, treated total organic carbon, mass balance (total dissolved solids including sodium), operations programs, groundwater environmental buffer, and drinking water treatment for DPR. In tandem with the DPR rule, the CDPHE released a separate document addressing enhanced source control for DPR projects. 

Completion of the DPR rule places Colorado in a unique position when it comes to overseeing the practice. “We believe that Colorado is the first state to move entirely through the regulatory adoption process,” Beekman says.

DPR drivers

Multiple drivers could prompt water providers in Colorado to consider DPR, says Christopher Bellona, an associate professor of civil and environmental engineering at the Colorado School of Mines. For utilities along Colorado’s Front Range that rely in part on water imported across the Continental Divide, part of the appeal of DPR involves “sourcing a local source that you have nearby,” Bellona says. Other factors include “drought conditions, reduced snowpack, and economic considerations,” he says.

That said, at least one large Colorado utility has no current plans for pursuing DPR, despite having conducted extensive research into the process. With funding provided by the Colorado Water Conservation Board in 2020, Colorado Springs Utilities developed a DPR demonstration unit with the Colorado School of Mines and the environmental engineering firm Carollo Engineers. Known as the PureWater Colorado Mobile Demonstration Project, the effort entailed the creation of a mobile treatment unit capable of cleansing treated municipal wastewater such that it attained potable drinking water standards.

Colorado Springs Utilities likely will pursue indirect potable reuse (IPR) before DPR, says Jennifer Jordan, a senior public affairs specialist for the organization. “It will be more beneficial to us and our regional water providers to first implement IPR,” Jordan says. “Our current timeline sets that about 10 years from now. DPR will likely follow at some point after that as our city’s water demand grows. In the meantime, we are reusing 100% of the water we are legally allowed to, primarily through exchanges and our non-potable system.”

DPR in Texas

In 2021, the Texas Legislature passed legislation directing the Texas Commission on Environmental Quality (TCEQ) to develop a regulatory guidance manual detailing how the state regulates DPR and what public water systems must do to receive approval for a DPR project. The resulting staff guidance document, titled Direct Potable Reuse for Public Water Systems, was posted by TCEQ to its website on November 15, 2022. 

The document aims to clarify regulatory requirements for DPR in Texas, which has green-lighted DPR projects previously on essentially an ad hoc basis. TCEQ has “approved several projects under what they call their case-by-case basis approval process, where there isn't a specific regulatory statute or regulation that says, ‘This is how these projects need to be implemented,’” says Eva Steinle-Darling, the water reuse practice director for Carollo. “But they've reviewed them in detail, and then they have what they call an exception authorization process.”

The first such project to receive TCEQ’s blessing was the 1.5 mgd Raw Water Production Facility that is owned and operated by the Colorado River Municipal Water District (CRMWD) in Big Spring. The first of its kind in the nation, the DPR facility began operations in 2013 and uses microfiltration, reverse osmosis, and ultraviolet disinfection to treat reclaimed municipal wastewater. Effluent from the DPR facility enters a raw water pipeline that also accepts water from area lakes. The blended water then undergoes further treatment at one of five different drinking water treatment facilities.

Development of the CRMWD’s DPR facility was spurred by drought conditions, as was a temporary DPR facility operated by Wichita Falls, Texas. Approved conditionally for DPR in July 2014, Wichita Falls “discontinued their project in July 2015 when lake levels returned to normal,” according to a TCEQ spokesperson. Elsewhere in Texas, the City of Brownwood “was given approval to construct their DPR plant but chose not to proceed with the project,” the spokesperson says.

Multiple steps

The 30-page manual from the TCEQ spells out requirements associated with the multiple steps to be followed by applicants seeking approval for a DPR project. The steps include performing wastewater effluent characterization, submitting a pilot-scale study protocol, conducting the pilot-scale study and preparing a report, submitting the report, submitting plans and specifications for the DPR facility, constructing the facility, submitting a disinfection protocol and test parameters to verify membrane performance, submitting a full-scale verification test protocol, starting up the DPR and conducting the full-scale verification test, and submitting the report on the full-scale verification test.

As part of its overview of treatment requirements, the manual addresses pathogen treatment and chemical treatment. “The level of treatment required is determined by the wastewater effluent characterization process, which establishes the starting point for advanced purification,” Steinle-Darling says. “Better quality treated effluent requires less treatment in the downstream advanced purification process.”

When it comes to pathogen treatment, TCEQ has also “set minimum [log removal value] treatment levels for DPR of 5.5-log Cryptosporidium, 6-log Giardia, and 8-log virus,” according to the manual. These minimum treatment levels “are needed even if sampling results from the wastewater characterization suggest lower levels of treatment may be adequate,” the manual states.

Because of concerns regarding potential contaminants that may be present in municipal wastewater, TCEQ will only approve DPR facilities that “include treatment units that remove or degrade a wide range of chemical contaminants, such as reverse osmosis (RO) membranes and ultraviolet light with advanced oxidation,” according to the manual.

“Due to the potentially higher levels of pathogens and chemical contaminants in the WWTP effluent source water, TCEQ looks for at least two physical/removal treatment processes and two inactivation or oxidation treatment processes at each proposed DPR plant,” the manual states.

The guidance manual “is very consistent with the practice that the TCEQ has taken for the last 10 years or more of approving these projects,” Steinle-Darling says. “So, there were no surprises in there based on what we've seen them do before.”

What about water rights?

The DPR-related documents from the two states differ somewhat in terms of their regulatory status. “What was published in Colorado last year were actual formal regulations,” Steinle-Darling says. 

By contrast, the manual for Texas comprises a “published staff guidance document that is still internal to the TCEQ and does not have any regulatory teeth per se,” Steinle-Darling says.

Because they focus exclusively on the issue of water quality, the documents for Colorado and Texas do not address the issue of water rights, other than to note that parties interested in pursuing DPR need to ensure that they have obtained any necessary rights before proceeding.  Given the approaches to water rights in the two states, Colorado entities could face a higher hurdle to DPR projects. 

In Colorado, a potable reuse facility requires “special considerations regarding water rights,” says Wayne Lorenz, the chief engineer and vice president of public works engineering for the water resource, environmental, and civil engineering firm Wright Water Engineers, Inc. “There are some larger systems on the Front Range that have non-tributary groundwater source rights, where most of the water can be reused to extinction,” Lorenz says. “This is an advantage to municipalities that have, or are planning to use, potable reuse systems.”

“On the other hand, many municipal systems use surface water rights that have gone through a change-of-use process,” Lorenz says. “These rights may have historically been used for irrigation purposes and now they are decreed for municipal use. Municipal use may not expand the consumptive use of any water right. Consumptive use is the typical measure of how much water is available for use. Any new municipal consumptive use must not be greater than the established irrigation consumptive use. When reusing that water, any offsetting of the consumptive use water is needed and any consumptive use increase must be replaced. This gets complicated when considering DPR projects.”

The situation is less complicated in the Lone Star State, assuming that the source water for a reuse facility has not been returned to the environment. “If you're keeping [the water] within your control the whole time, there are no water rights restrictions on that,” Steinle-Darling says. In Texas, “when you are allocated rights to a surface water, it is your right to use it to extinction, which means you can use it until nothing's left,” she says. 

Increased interest?

Ultimately, the DPR documents in Colorado and Texas are expected to spur increased interest in the practice in those states. With its “practical and implementable regulations,” Colorado’s regulations can “absolutely facilitate the development of real projects,” Steinle-Darling says.

Now that Texas has guidelines outlining the requirements for DPR, “I think we'll see more of it,” says Robert Mace, the executive director & chief water policy officer for the Meadows Center for Water and the Environment at Texas State University. Previously, some communities might have hesitated to pursue DPR because they did not know what the regulatory process would consist of, Mace says. “But now that there's something in writing, that may make it more enticing for those communities to pursue direct potable reuse in the future.”

The manual from the TCEQ can also help communities realize that they need to begin pursuing DPR well before a severe drought strikes and imperils their existing water supplies, Mace says. “There may be some things that they can do in the meantime to get ready, such as monitoring their wastewater,” he says. “That becomes particularly important if suddenly there's an emergency need for DPR.”

On the other hand, some communities that have been considering the possibility of adopting DPR might rethink the approach after reviewing the TCEQ’s new manual, Mace notes. “One of the potential outcomes from a community looking at that document is they may look at it and say, “This is too much for us, and we may need to go pursue a different source of water than this.”

El Paso’s approach

At least one major DPR project is on the horizon in Texas. El Paso Water “has completed a DPR pilot study and is in the process of pursuing approval for DPR,” according to the TCEQ spokesperson.

Since 2014, El Paso Water has been in the process of developing its Advanced Water Purification Facility, a 10 mgd DPR plant that will accept treated effluent from one of the utility’s wastewater treatment facilities. In 2015 and 2016, the utility conducted a pilot test of the planned facility, which is being designed by Carollo and will employ a treatment process consisting of membrane filtration, membrane desalination, ultraviolet disinfection with advanced oxidation, granular activated carbon filtration, and chlorine disinfection. 

Construction is scheduled to begin in early 2024, says Christina Montoya-Halter, the communications & marketing manager for El Paso Water. “We'll have delivery to customers in 2026,” she says.