LAGUNA NIGUEL, CA: SOCWA REGIONAL TREATMENT PLANT

Project Background & Challenges

The South Orange County Wastewater Authority (SOCWA) has three primary treatment facilities to treat approximately 26 million gallons of wastewater per day. SOCWA must manage these plants to keep the infrastructure working to create both recycled water and treated effluent. The Laguna Niguel Regional Treatment Plant under SOCWA was built in 1982. This plant has a capacity to treat 12 Millions Gallons of liquid waste per day, with an average capacity of 7.3 million gallons used per day. The existing panel diffuser aeration system had exceeded its useful lifespan. Many existing diffusers were broken or did not function properly, resulting in poor plant performance and reduced capacity and efficiency. In addition, the plant needed to prepare for future plant flows and future goals to improve effluent quality. A total of six existing aeration basins needed upgrades.

The EDI Solution

SOCWA’s engineer and EDI worked to design a plant that would offer robust, reliable aeration and meet the range of design requirements the plant experiences. The new aeration system needed to be designed to increase the capacity, allowing the plant to accommodate the community’s growing population while maintaining and even improving high standards of effluent quality.

EDI designed the new aeration system to meet the increased future demand using a total of 11,940 units of 9” FlexAir Pro EPDM Membrane Disc diffusers to be installed in six aeration basins. It was designed for both current and future operating modes. For the plant’s current operation, the aeration system only needed to have the capacity to remove BOD, but in the future the plant will need to operate for nitrification. For start-up and low flow scenarios, the diffusers needed to provide uniform mixing in each aeration basin even when oxygen demands were low.

Site Construction with Reliable Fine Bubble Diffusers

The new aeration system’s drop pipes matched the old drop locations; thus, it was possible to re-use the existing basin infrastructure and piping. Each aeration basin had four zones and each zone was fed by one drop pipe. The FlexAir® Pro disc diffuser offers saddle-mounted disc diffusers for maximum diffuser and pipe strength and reliability. EDI’s FlexAir Pro glass filled polypropylene diffuser holders are suitable for high temperatures and are less brittle at low temperatures compared to industry standard PVC diffuser holders.

The piping provided by EDI is iron pipe size (IPS) piping which means it is commercially available at local hardware stores in case the owner ever needs to make modifications to the aeration system piping. FlexAir Pro 9” discs provide efficient oxygen transfer and the high quantity of diffusers installed matches the high future oxygen demand scenarios.

Since EDI’s FlexAir Pro aeration piping is custom configured, it was designed to fit perfectly into the footprint of the existing aeration tanks. The aeration zones are tapered with more diffusers at the influent end of each basin where oxygen demand is highest.

Upgraded System Performance

The result of the upgrade has been significant. The plant can now operate with fewer tanks in operation during the dry season, reducing the energy required to maintain the wastewater treatment process. The dissolved oxygen levels in the wastewater are now at the desired level, and the effluent quality is better than ever. The plant’s goals of low life cycle cost and reliability have been achieved with the upgrade, making it a successful and cost-effective solution for the growing city.

In conclusion, the aeration technology upgrade at SOCWA’s Regional Treatment Plant has been a success, delivering improved effluent quality and increased capacity to accommodate the growing population. The use of fine bubble aeration has proven to be a reliable and efficient solution for wastewater treatment, achieving the plant’s goals of low life cycle cost and reliability.