Is Potable Reuse the future of water and energy abundance in California?
“Water is too precious to use only once.”
At the December 2024 ACWA conference, Ali Chehrehsaz, CEO of TerraVerde Energy, hosted a panel with leaders in the California water industry to discuss their views and insights on water reuse.
The session, “Balancing the Water-Energy Nexus of Direct Potable Reuse” featured panelists: Dennis D. LaMoreaux, General Manager of Palmdale Water District; Marco Tule, President of Inland Empire Utilities Agency; and Stephen Dopudja, President of Dopudja & Wells Consulting.
Water reuse projects utilizing reverse osmosis technology are setting the stage for new water supply in California. Projects leveraging reverse osmosis (RO) including Direct Potable Reuse (DPR) and Indirect Potable Reuse (IPR) facilities come with significantly increased electricity demand.
How much electricity is needed? Is the substantial increase in energy consumption material to existing operations of water and wastewater facilities?
Let’s dig in.
The Energy Context
Ali opened the panel by sharing reference calculations based on the energy needs of an operating DPR project: ACWA Member, Monterey One Water’s “toilet to tap” facility in Monterey, California.
Based on the electricity usage forecast provided by Monterey One, the facility will consume about 15.9 gigawatt hours of electricity when operating at seven million gallons per day (MGD) production.
This is a 138% increase in annual usage at Monterey One.
By comparison, the energy use intensity (EUI) of this advanced water purification facilities is about 500 times that of an AI data center.
While EUI is a notable metric, the gross electricity usage for reverse osmosis (RO) technologies is the notable issue that needs to be addressed.
Leveraging solutions like on-site electricity generation from hybrid renewables, covered further in this blog post, provides options to water agencies and municipalities to mitigate the electricity expense while building redundancy to more reliably operate these facilities.
With the energy context in mind, the conversation kicked off with a discussion on the policy landscape.
The Policy Landscape
Stephen of Dopudja & Wells Consulting noted, “Agencies are wrestling with how to use wastewater efficiently and effectively. With climate change, they’re now looking at it as their most reliable source of water. It’s really changing policy and economic decisions statewide as to how to reuse it, and how many times they can reuse it, rather than relying on importing water.”
In October 2024, regulations went into effect which allow public water agencies to obtain permits to develop DPR projects. IEUA is pursuing a program called the Chino Basin Program, with the plan being to inject water into the ground and extract it later. As a State Water Project dependent area, the development of local supplies is essential for IEUA and its customer agencies.
“But now regulations are in place to consider DPR,” said Marco of IEUA, “we can look at the possible opportunity of serving treated water directly to our residents, which just wasn’t a possibility before October. Being able to take advantage of DPR also puts our region in a position to be good neighbors and establish reliable partnerships for these kinds of projects going forward.”
Digging deeper, Ali asked, “At the water agency level, what is the cost of business-as-usual a.k.a. doing nothing?”
Dennis of Palmdale Water District explained, “Our district has local surface water, and we are in an adjudicated groundwater basin. But we’re also in the north end of LA county and our boundaries include a lot of the undeveloped land left in the county. So, more growth and more water demand are going to happen, and it’s our job to try and accommodate that. The cost of doing nothing would be catastrophic to the economic development of the city.”
Ali drew a parallel between water and electricity needs in the state: “On the energy side, electrification of buildings and transportation is increasing demand for electricity. But we are facing an increasingly unreliable power grid to provide the supply of electricity needed. That story mirrors what water agencies are going through on the water supply side.”
Water Reuse Projects & Solutions for Water Agencies
The conversation then went into the various solution sets, with panelists outlining the water reuse projects they are currently are developing.
Dennis kicked off the conversation by helping the audience understand the geographic context of the Palmdale region driving the unique needs of the district.
The Pure Water Antelope Valley Project by Palmdale Water
The city of Palmdale sits in Antelope Valley, 70 miles north of Los Angeles in a closed basin with no outflow, brine lines or access to the ocean. Because of their wastewater disposal problem, the area has historically used wastewater for agriculture. For a while, they tried different iterations of blending with state water for their supply, but after securing a contract with the Palmdale Sanitary District in 2016, Palmdale Water District has now pivoted to advanced water treatment to fill that supply gap locally, a solution that benefits both agencies and the wider public.
The Pure Water Antelope Valley project will use state-of-the-art technology to purify wastewater that has already been cleaned extensively in order to help meet the water needs of their community. The project will produce a new, locally controlled drought-resilient water supply to help replenish Antelope Valley’s groundwater basin.
Worth noting is the project’s partnership with a company called Capture 6, which takes brine through a chemical process to capture carbon from the air while also putting water back into the treatment plant. Dennis says it costs less to work with Capture 6 than to do more passes of RO, treat the land for evaporation, or some other mechanical way of dealing with the brine.
“We looked at purchasing additional groundwater rights,” Dennis said, “but the going price would have been ten times more expensive than doing this kind of a project. It’s good fit for us because we’re in a closed basin and the sanitary district has an interest in helping us as a way of relieving their disposal problems. It could certainly be a solution in other areas of the state as well.”
Stephen added, “I think agencies are looking at all solutions. The way that re-use has fundamentally changed the market, whether it’s a public partnership or a public-private partnership, I think all options are on the table.”
The City of Rialto & Inland Empire Utilities Agency Partnership
This project started about 10 years ago, when we started to see the trend: waste is becoming a resource.
The City of Rialto is in a unique geographic, political, and economic location. The City is oriented on a slope that flows north to south with the City’s wastewater treatment plant on the south end of town, at the lowest elevation. Interestingly, as the project was getting started, the new development was occurring in the northern part of town.
City of Rialto is in the San Bernadino Valley Municipal Water District’s service area. Just to the west is the Inland Empire Utilities Agency (IEUA) which is a member agency of the Metropolitan Water District of Southern California.
The way these two agencies cover their costs is fundamentally different. Metropolitan uses an all-in cost model. While for San Bernadino Valley, the capital costs are put on the property tax bill and the variable cost is paid by the City of Rialto. Knowing the low variable cost of ~ $150 per acre foot, it did not make much economic sense to move water from the south end of town to the north end. As such, implementing a water reuse project within its own service area was not justifiable.
However, knowing that IEUA is to the south of the City, we started to wonder: is there an opportunity that could benefit both agencies given that IEUA’s variable cost is about $1,000 per acre foot?”
The project that emerged is a pump station built at Rialto’s wastewater treatment plant and an 11-mile pipeline that conveys treated wastewater for six months out of the year to IEUA’s water recycling plant in Rancho Cucamonga for advanced water purification treatment. With Rialto producing 7 million gallons of wastewater a day, the two agencies structured the project collaboratively to come up with a cost that made sense for everyone. Incorporating a “base” and “optional” water supply and taking into consideration the fixed cost of capital to build the project, they were able to keep O&M and energy costs low. IEUA owns the facility and established a lower rate in its base-supply in exchange for capacity rights.
There is also a water storage facility being developed in conjunction with the project for the six months of the year when water will not be sent to IEUA. While the initial plan was to discharge excess water into the Santa Ana River, environmental considerations led to a storage facility that can periodically drain river channels to prevent the proliferation of invasive fish species. Dopudja says, “there really are holistic, layered benefits to this project.”
Energy & Funding Solutions
So, what does all this mean in terms of energy?
With a 50-year agreement between the City of Rialto and IEUA, the two agencies are anticipating spikes in energy use and costs over time. Built into their contract are indexed rates based on the Consumer Price Index (CPI) for the base-supply and whichever rate between CPI and Metropolitan Water District is larger for their optional supply. This gives IEUA the reassurance that prices won’t rise above what they’d normally see as customers of Metropolitan Water District. This also benefits Rialto. Because Rialto is not a Metropolitan customer, they are able to rely on that cost increase over time.
If energy costs eventually grow beyond the threshold of CPI prices? Stephen says, “the city wasn’t looking for the highest price it could get, it was looking for a partner. When you’re in a long-term partnership, if your partner does well, you do well. So, we have certain resets written into our contract to allow us to sit down and revisit our options when necessary.”
The City of Rialto is considering a solar, battery, and biogas powered CHP microgrid to power their wastewater treatment plant. The challenge is that the new DPR project only operates six months out of the year and the City doesn’t want to tether this new project to the microgrid. However, discussions remain open around possible future expansion. “The key is to give ourselves flexibility, and to leverage the partnership we’ve built to solve issues as they arise,” Stephen says.
In Palmdale, Dennis says the energy crisis caused them to consider all options when it comes to energy. They have developed both a wind project that they are now considering replacing with a solar project, as well as micro-hydro-power project. They have worked with federal agencies to secure funding and also established rate schedules that have supported past projects. With the growing demands of the region, the city will have to get creative about implementing more cost-saving and resilient energy solutions.
Marco says IEUA foresees their energy portfolio tripling over the next decade. “We’ll have to have conversations with our partners including Southern California Edison and consider forming JPAs to develop new energy sources. This will also be crucial as we are required to electrify our fleets.” IEUA currently deploys solar, wind, batteries and backup generators that were dispatched when needed through an SCE program. With 50 MGD at their combined facilities, IEUA’s 6 MW of independent generation and 4 MW of battery storage will need to grow significantly. Marco is confident though that they’ll be able to meet the challenges ahead through the strength of the coalitions they are building at the local level.
Imagining the future
With large-scale data center operators like Google using hybrid renewables, Ali affirms, “water agencies can adopt similar approaches with on-site generation and microgrids.” As mentioned by all the panelists, building strong local and regional partnerships is crucial to developing projects that meet the energy demands of the future.
Stephen closed out the panel by emphasizing that the larger narrative around water abundance in the state must evolve as cities and public agencies plan these projects.
“There’s this undertone that if we talk about abundance, we have failed to conserve which is a false narrative,” he says. “When it comes to the State, that understanding is starting to change. And it is incumbent on policymakers to communicate on the global stage, at the level of this State’s economy, that we do have water and energy abundance in California.”
As collaborative water reuse projects combine with on-site hybrid renewable infrastructure to increase energy supply, Stephen’s assertion rings true.