Design of Yorba Linda Water District’s
New 19 MGD PFAS Treatment Plant
A Report on OCWA’s February 2021 Webinar
By Tim Hogan
Recent years have witnessed the emergence of PFAS in our nation’s groundwaters. A family of man-made compounds, PFAS pose multiple health risks. Developed in the 1940s for their unique oil- and water-repellent properties, as well as their resistance to degradation, the very characteristics that made them so useful have made them hard to breakdown and remove, especially from water. For this, they’ve been dubbed “forever chemicals.”
Because PFAS were prized as stain-resistant treatments for clothing and carpeting, as well as non-stick coatings for cookware, they found widespread industrial and manufacturing use. Unfortunately, this led to widespread environmental contamination in soil, air, and water. Despite two individual “long-chain” PFAS — perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) — being phased out of production in the US and EU over concerns about their effects on human health, the full impact of their use has only recently begun to emerge.
Locally, the Yorba Linda Water District (YLWD) has been especially hard hit. To learn more about what the District has planned to deal with the issue, OCWA was pleased to host Rosanne Weston, the YLWD Engineering Manager, for the second of our monthly Industry Insight webinars for 2021. Her presentation was underwritten, in part, by three of our Corporate Sponsors for 2021, Tetra Tech, Carollo Engineers, and Richard C. Slade & Associates. A record 198 people signed up to view the presentation, strong testament to the importance of this topic to the Orange County water community.
As Ms. Weston explained, all of YLWD’s ten (10) wells have been negatively impacted by PFOA and PFOS and test above the State’s Response Levels. Where ordinarily YLWD pulls 75% of its source water from local groundwater and 25% imported water from Metropolitan Water District of Southern California, YLWD has switched to 100% imported water until its PFAS Treatment Plant is in operation. As a result, the District has seen its cost of water more than double, an increase of approximately $27,000 per day.
After extensive consultation with Orange County Water District (OCWD), the authorized guardian of all the County’s groundwater, YLWD entered an agreement with OCWD to design and construct a treatment plant, the largest plant of its kind in the nation.
Since their agreement in early 2020, OCWD has worked closely with YLWD to fast-track the design of the project. Carollo Engineers were brought in to complete the initial planning study, Tetra Tech was hired to provide design and construction management services, and Pacific Hydrotech was recently awarded the construction contract. If all goes as expected, the treatment plant should be in operation by the end of October 2021.
YLWD researched the many different technologies to treat PFAS. The research included attending tours and meetings with industry PFAS specialists. The tours educated YLWD on what worked, what didn’t, what to expect, and how to avoid pitfalls from those who operated PFAS treatment plants.
YLWD set up a pilot test to simulate a full-scale PFAS treatment plant to test the performance of Granulated Activated Carbon and several Ion Exchange resins using groundwater from one of its wells. The pilot test was run for about five (5) months, and provided excellent information that helped YLWD design its treatment plant.
In the end, the decision was made to design an Ion Exchange (IX) plant. YLWD received great results using resins in the pilot test, and as a well-established treatment technology, they knew it would be acceptable to the State. It was also the least costly option, requiring fewer vessels and thus less resin. It would also have a smaller footprint, which was important, since they’d decided to build the plant on their headquarters site.
The decision to build on their headquarters site was both straightforward and cost effective. Since it was on land the District owned, there were fewer permitting requirements, especially since they’re in an industrial area and not a residential neighborhood. Capital and operating costs would be reduced, as well, since they wouldn’t need as many backup vessels. This would mean less resin would be needed, too. And since it will be on site, operators can quickly handle any issues.
As can be seen in the rendering above, the plant will consist of six pre-filter vessels, then 22 resin vessels coupled in pairs for a total of 11 trains. The pre-filters, which will remove contaminants before the water is sent through the resin, are there to help extend the life of the resin as much as possible, since it is very expensive. The pre-filters can process 2900 gallons per minute.
The coupled resin vessels permit water flow in either direction, which will maximize the life of the resin. Each vessel is 12 feet in diameter and some 16.5 feet tall. At a working capacity of 1600 gallons per minute per train, collectively they can process up to 25 million gallons a day. However, the plant is rated, and will be run, at 19 million gallons per day.
The system is designed to remove all PFOA and PFOS.
To fully tout the ease of operation for the plant, and put everyone’s mind at ease about what it will look like, Tetra Tech set up a virtual reality tour, using Occulus headsets, so a good number of the District’s employees could get an up-front look at the system — how close the vessels will be to each other and the placement of the valves. Ms. Weston shared a video of the experience so the webinar participants could get a good perspective of the project.
For such a critical project, the timeline from conception to completion is relatively quick. It took eight months to plan and design, and construction should take eight to nine months to complete. Total cost for the project is not yet known, but construction — which includes replacement of a chlorination facility and installation of a new generator — should run around $17.3 million.
• • •
OCWA was pleased to host this timely presentation by Rosanne Weston. For those interested, a PDF of Ms Weston’s PowerPoint presentation is available for download by OCWA’s members only. Yet another great reason to consider becoming a member if you aren’t one already.
The March Industry Insight webinar promises to be equally enlightening. Eros Yong, Engineering Manager for the Planning Division, Orange County Sanitation District, will provide a look at The Role of Asset Management in Support of OC Sanitation’s Mission. She will show us the approach the District took to develop its program, share details on the process, and give valuable insight on how it is used on a daily basis.
Register Now to Ensure You Don’t Forget!
OCWA Members: Free. Non Members: $10.00
So join us, March 17, to learn how to use your assets wisely while you protect their useful life.