Orange County Sanitation District Treatment Plant

FACILITY BASIC INFORMATION

Plant Names: Reclamation Plant No. 1 (Fountain Valley) & Treatment Plant No. 2 (Huntington Beach)

Location: Fountain Valley and Huntington Beach, Orange County, California

Operating Authority: Orange County Sanitation District (OC San)

Combined Design Capacity: Approx. 372 MGD (Secondary Treatment)

Current Average Flow: 185 MGD

Population Served: 2.6 million residents

Service Area: 479 square miles (Central/Northwest Orange County)

Receiving Water Body: Pacific Ocean (via Ocean Outfall) & Groundwater Basin (via GWRS)

NPDES Permit Number: CA0110604 (Order No. R8-2021-0010)

Read more4D-Printed Smart Materials For Water Treatment

Year Commissioned: 1954 (Plant 1), 1959 (Plant 2)

1. INTRODUCTION

The Orange County Sanitation District (OC San) operates a complex, integrated wastewater treatment system comprised of two primary facilities: Reclamation Plant No. 1 in Fountain Valley and Treatment Plant No. 2 in Huntington Beach. Together, these facilities serve as the backbone of sanitation for 2.6 million residents across 21 cities and unincorporated areas in central and northwest Orange County. Treating an average of 185 million gallons daily (MGD), OC San is a premier example of resource recovery implementation on a massive scale.

Unlike traditional linear treatment systems, OC San is globally renowned for its symbiotic partnership with the Orange County Water District (OCWD) to feed the Groundwater Replenishment System (GWRS)—the world’s largest advanced water purification system for indirect potable reuse. Historically operating under a 301(h) waiver, OC San completed a strategic transition to 100% secondary treatment in 2012, investing billions to meet strict environmental standards. Today, the facility recycles nearly 100% of its reclaimable flow, setting the international benchmark for the “utility of the future” model.

2. FACILITY OVERVIEW

A. Service Area & Coverage

OC San serves a dense, urbanized 479-square-mile area encompassing the residential, commercial, and industrial hubs of Orange County. The collection system includes approximately 396 miles of regional trunk sewers (ranging from 12 to 96 inches in diameter) and 15 major off-plant pump stations. The system is designed to handle flows from a service area that includes Anaheim, Santa Ana, Huntington Beach, and Irvine, effectively managing a mix of domestic wastewater and industrial effluent from the region’s diverse manufacturing sector.

B. Operational Capacity

The system operates as a unified hydraulic entity connected by interplant pipelines.

• Plant No. 1: Located in Fountain Valley, typically handles approximately 130 MGD. It is optimized to produce high-quality secondary effluent specifically for the GWRS advanced purification facility located next door.
• Plant No. 2: Located in Huntington Beach near the coast, handles approximately 55-65 MGD and processes the majority of the system’s biosolids.
• Combined Capacity: The total secondary treatment design capacity exceeds 372 MGD, providing significant redundancy for wet-weather events.

C. Discharge & Compliance

Read moreA Comparison Between Aerobic And Anaerobic Wastewater Treatment Technology

Treated effluent not diverted for recycling is discharged into the Pacific Ocean via an 8.4-mile long outfall system (including land and ocean sections). The primary ocean outfall extends 4.5 miles offshore to a depth of 195 feet, utilizing a multi-port diffuser to ensure rapid dilution. The discharge is regulated under NPDES Permit No. CA0110604, issued by the Santa Ana Regional Water Quality Control Board. The facility has maintained an exemplary compliance record following its transition to full secondary treatment, consistently meeting limits for TSS, BOD, and toxicity.

3. TREATMENT PROCESS

OC San employs distinct process trains at its two facilities, integrated to maximize recycling potential and optimize solids handling.

A. PRELIMINARY TREATMENT

Both plants utilize advanced headworks facilities designed to handle variable flows and aggressive corrosion environments.

• Screening: Mechanically cleaned bar screens (typically 3/8-inch to 1/2-inch openings) remove large debris, rags, and plastics.
• Grit Removal: Aerated grit chambers are utilized to remove sand, gravel, and heavy particulates to protect downstream pumps and digesters.
• Interplant Pumping: Unique to OC San is the ability to divert raw wastewater and sludge between Plant 1 and Plant 2 via large-diameter interplant pipelines, allowing for load balancing and maintenance flexibility.

B. PRIMARY TREATMENT

Primary treatment consists of rectangular clarifiers at both facilities. Ferric chloride and anionic polymers are frequently added to the influent (Chemically Enhanced Primary Treatment – CEPT) to increase the removal efficiency of Total Suspended Solids (TSS) and Biochemical Oxygen Demand (BOD). This chemical addition is critical for reducing the organic loading on the secondary treatment stage.

C. SECONDARY TREATMENT

Secondary treatment is the core of OC San’s compliance strategy, utilizing biological processes to degrade dissolved organics.

• Plant No. 1 (Activated Sludge): Utilizes a conventional air-activated sludge (AS) process. This plant includes older AS basins and newer microprocessor-controlled basins. The focus here is producing effluent with low turbidity suitable for the GWRS microfiltration membranes.
• Plant No. 2 (Pure Oxygen Activated Sludge): Historically, Plant 2 utilized trickling filters. These have been decommissioned and replaced/supplemented with a high-purity oxygen activated sludge (HPOAS) system. The covered reactors use cryogenic oxygen generation plants to supply high concentrations of oxygen, allowing for a smaller footprint and reduced odors—critical for the coastal location.

D. WATER RECLAMATION (The GWRS Link)

While not a treatment stage strictly performed by OC San, the Groundwater Replenishment System (GWRS) is the functional tertiary step. Operated by the Orange County Water District (OCWD) on a site adjacent to Plant No. 1, this facility takes secondary effluent from OC San and treats it via:

1. Microfiltration (MF)
2. Reverse Osmosis (RO)
3. Ultraviolet (UV) Light with Hydrogen Peroxide

With the “GWRS Final Expansion” completed in 2023, OC San now diverts sufficient flow to produce up to 130 MGD of purified water, meaning nearly all recyclable flow from Plant 1 and significant flow from Plant 2 is reused rather than discharged to the ocean.

E. SOLIDS HANDLING

Solids processing is consolidated primarily at Plant No. 2, though Plant 1 has thickening capabilities.

• Thickening: Dissolved Air Flotation (DAF) and centrifuges are used to thicken waste activated sludge (WAS).
• Digestion: Mesophilic anaerobic digesters stabilize the sludge. The system includes over a dozen large digesters operating at approx. 98°F.
• Dewatering: Digested biosolids are dewatered using high-solids centrifuges to achieve a “cake” dryness of roughly 25-28%.
• Disposal/Reuse: The resulting Class B (and increasingly Class A) biosolids are trucked off-site for beneficial reuse in composting and land application in neighboring counties/states.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The combined footprint of the two plants covers hundreds of acres in a high-value real estate zone. Plant No. 1 serves as the administrative hub, housing the new Headquarters Complex, a LEED Platinum certified facility that includes the Emergency Operations Center (EOC) and central laboratory. Plant No. 2 sits adjacent to the Santa Ana River mouth and Huntington State Beach, requiring distinct architectural treatments and berms to minimize visual impact.

B. Energy Systems & Cogen

OC San is a leader in energy self-sufficiency. The Central Generation facility utilizes biogas (methane) produced during the anaerobic digestion process.

• Generation: Internal combustion engines run on scrubbed digester gas to generate electricity and heat.
• Waste Heat Recovery: Heat recovered from the engines is used to heat the digesters, closing the energy loop.
• Efficiency: These systems allow the plants to generate a significant portion (50-70%) of their own power needs, insulating the district from grid volatility.

C. Odor Control

Given the proximity to residential neighborhoods and beaches, odor control is a top priority. OC San utilizes a “hermetically sealed” approach for many process areas. Technologies include:

• Chemical Scrubbers: Two-stage towers utilizing acid and caustic/bleach solutions.
• Biotrickling Filters: Biological scrubbers that use bacteria to oxidize H2S.
• Carbon Adsorption: Polishing stage for difficult odors.

5. RECENT UPGRADES & MAJOR PROJECTS

OC San operates under a robust Capital Improvement Program (CIP). Recent and ongoing projects include:

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

Permitting Evolution: For decades, OC San operated under a 301(h) waiver of the Clean Water Act, allowing for a mix of primary and secondary treated discharge. In 2002, the Board of Directors voted to voluntarily give up this waiver—a monumental decision that triggered over a decade of construction to achieve full secondary treatment standards.

Current Compliance:

• NPDES: Adheres to Order No. R8-2021-0010.
• BOD/TSS: The plant consistently achieves >90% removal, often exceeding 95% due to the requirements of the GWRS feed.
• Coastal Impact: Extensive ocean monitoring programs track the health of marine life near the outfall. The shift to full secondary treatment has resulted in measurable improvements in sediment quality and benthic community health in the discharge zone.

7. OPERATIONAL EXCELLENCE

Staffing & Certification: OC San employs approximately 600 staff members. Operations staff are required to hold California State Water Resources Control Board (SWRCB) certifications, with many holding Grade IV and V certifications due to the complexity of the integrated system.

Asset Management: The District utilizes an advanced Enterprise Asset Management (EAM) system (Maximo) to track the lifecycle of over 50,000 distinct assets. Predictive maintenance technologies, including vibration analysis and thermography, are standard protocol.

8. CHALLENGES & FUTURE PLANNING

A. PFAS and Emerging Contaminants

Per- and polyfluoroalkyl substances (PFAS) represent a significant challenge. While OC San is a pass-through entity for these chemicals, the interconnection with GWRS requires rigorous source control and monitoring to ensure the advanced purification process remains effective.

B. Climate Resiliency

Plant No. 2 is located adjacent to the Pacific Ocean. A comprehensive “Climate Resiliency Plan” is in place to address sea-level rise and storm surge risks. This involves hardening perimeter berms, elevating critical electrical infrastructure, and installing flood gates.

C. Infrastructure Renewal

Much of the collection system and Plant 2 infrastructure dates to the 1950s/60s. The “Santa Ana River Interceptor (SARI) Line” relocation and protection project is a prime example of the necessary, expensive work required to protect pipelines from erosion and seismic threats.

9. COMMUNITY & REGIONAL IMPACT

OC San is a critical economic enabler for Orange County. By ensuring reliable wastewater capacity, the District supports the region’s $200B+ economy. Furthermore, the partnership with OCWD provides a drought-proof water supply for 2.6 million people, insulating the local economy from California’s volatile water import market. The District engages the public through its “What Goes Down Comes Around” educational campaign and maintains a transparent Citizens Advisory Committee.

10. TECHNICAL SPECIFICATIONS SUMMARY

11. RELATED FACILITIES

• Groundwater Replenishment System (GWRS): Operated by OCWD, co-located at Plant 1. The largest potable reuse facility in the world.
• Urban Runoff Diversions: OC San operates several diversion structures that route dry-weather urban runoff from flood control channels into the sewer system for treatment, preventing beach pollution.
• Regional Pump Stations: 15 major pump stations lift wastewater from low-lying areas to the treatment plants.

12. FAQ

Technical Questions

Q: Does OC San operate a trickling filter process?
A: Historically, yes. However, Plant No. 2 has phased out trickling filters in favor of Activated Sludge to improve effluent quality for the GWRS connection.

Q: What is the primary difference between Plant 1 and Plant 2?
A: Plant 1 is optimized for water reclamation (feeding GWRS) using conventional activated sludge. Plant 2 handles the bulk of the solids processing/digestion and uses high-purity oxygen activated sludge.

Q: How does OC San handle brine disposal?
A: OC San manages the “Brine Line” (part of the Inland Empire Brine Line system), which conveys salty industrial waste and RO concentrate from GWRS directly to the ocean outfall, bypassing the biological treatment process.

Public Interest Questions

Q: Is the water discharged to the ocean safe?
A: Yes. The water undergoes extensive treatment and is discharged 4.5 miles offshore at a depth of nearly 200 feet. Monitoring shows no adverse effects on public health or marine life.

Q: Does OC San turn toilet water into drinking water?
A: OC San treats the wastewater to a secondary level. It then sends this water to the Orange County Water District (OCWD), which purifies it to drinking water standards. This water is then injected into the ground to replenish the aquifer, which is eventually pumped up for drinking water (Indirect Potable Reuse).

Q: Can I tour the facility?
A: Yes, OC San offers tours for schools, professional groups, and the general public, often in conjunction with OCWD tours of the GWRS.

Disclaimer: This technical profile is for informational purposes for engineering and industry professionals. Data regarding capacity and flows are approximate averages based on available reports as of 2023/2024. For official regulatory documents, please consult the OC San website or the California State Water Resources Control Board.