Moulton Niguel Water District

Moulton Niguel Water District
Salinity Management System (SMS) at the Regional Treatment Plant

Integrating UF-RO Treatment to Reduce TDS in Recycled Water
The Moulton Niguel Water District (MNWD) selected our team (WM Lyles, Webb Associates, and AQUA Engineering) through a competitive Progressive Design-Build procurement process to design and deliver a state-of-the-art Salinity Management System (SMS) at the Regional Treatment Plant (RTP) in Laguna Niguel, California. The project targets a critical objective: reduce total dissolved solids (TDS) in the facility’s recycled water by adding a sidestream treatment process that lowers overall effluent TDS while maintaining continuous plant operations.

The core technical challenge was to fit a new ultrafiltration (UF) and reverse osmosis (RO) treatment system and associated processes within a highly constrained area of the operating facility. In coordination with the District, the team identified and selected a compact site, limiting the SMS to a 0.20-acre footprint. To meet these constraints, the design housed most treatment components within a new building.

To confirm the treatment approach, the team sampled influent and conducted pilot testing to characterize solids loading, fouling potential, and membrane flux rates. Using these results, the team sized equipment, defined pretreatment needs, and selected the most efficient UF RO configuration for the available space.

The design also had to meet hydraulic demands, provide chemical dosing capability, and maintain safe access for operations and maintenance. The team evaluated unit spacing, vertical clearances, and piping geometry, then implemented an iterative, two-level building design to maximize usable area and improve process layout efficiency. By grounding the design in measured performance and optimizing the layout around the plant’s physical constraints, the team delivered a sidestream treatment solution that achieves process objectives, integrates cleanly into the existing facility, and minimizes environmental impacts.

Innovations and Value Engineering

Efficient Piping and Site Location: Located facility adjacent to existing recycled water facilities reducing piping connection lengths while allowing for simple process connection when the facility is ready to be integrated into the treatment process.
Early Procurement: Accelerated the schedule by pre-purchasing long-lead equipment.
Energy Optimization: Integrated VFDs and optimized gravity flow alternatives with two-level building layout to reduce pumping requirements and reduce operating costs.

Project Study:

Client	Moulton Niguel Water District
Reference	*Available upon request
Location	Laguna Hills, CA
Features	Progressive Design-Build Delivery TDS Reduction via Sidestream Treatment Integrated UF/RO Treatment System Compact Footprint Design Two Level Building Design to Maximize Space Efficiency Optimized Integration with Existing Operations