Fallbrook Public Utilities District – IM and PFAS

The Fallbrook Public Utility District (FPUD) is integrating a new potable water supply into their portfolio through the Santa Margarita River Conjunctive Use Project (SMRCUP). FPUD constructed an 8 MGD groundwater facility to treat the infiltrated Santa Margarita River water from Marine Corps Base Camp Pendleton (CPEN) wells. CPEN’s groundwater is challenged with elevated TDS, chloride, iron, manganese, and PFAS. As a result, the FPUD groundwater treatment facility includes iron and manganese (IM) treatment, side-stream reverse osmosis (RO), product water stabilization, chlorine disinfection, and granular activated carbon (GAC).

Trussell compiled and analyzed water quality data and guided FPUD through the regulatory framework of recently lowered NLs and response levels to determine if additional treatment at the SMRCUP facilities was needed for PFAS removal and defined the design criteria for the treatment system. Trussell researched and evaluated different treatment options for PFOA and PFOS removals, including GAC, RO, and ion exchange. Each option has advantages and disadvantages, such as capital versus operational costs, ability to treat other contaminants in the water, footprint, energy use, industry experience, operational familiarity, ancillary equipment needs, post-treatment needs, and inhibiting compounds.

After comparing these alternatives, Trussell prepared a conceptual design report for a GAC treatment system on the RO bypass for FPUD’s groundwater treatment facility. Trussell presented the design to DDW and received approval to leverage the results from past studies at other facilities as the basis for design and to proceed without site-specific pilot testing or bench-scale testing, providing significant schedule savings to FPUD.

The lead time for pressure vessels is long, especially amidst the growing demand for PFAS treatment; to ensure that the project schedule was not delayed by this long lead time, Trussell assisted FPUD to pre-purchase the pressure vessels and media. Trussell wrote the pressure vessel specifications for “dual media” vessels to allow FPUD the flexibility to operate with either GAC media or ion exchange resin in the future since the regulatory landscape and science are still evolving.

During construction, Trussell reviewed submittals and RFIs and supported FPUD in preparing the DDW Operations Plan. Trussell is also supporting performance testing, commissioning, operator training, and development of standard operating procedures (SOPs) to prepare for production in Fall 2021. Trussell will continue to support the District after start-up with performance optimization.