City of Lathrop Advanced Wastewater Treatment Facility Expansion

Lathrop, CA

PACE provided project development, studies, design, and bid and construction administration services for three phases of expansion of the City of Lathrop Consolidated Treatment Facility (CTF), an MBR wastewater treatment facility that treats residential and commercial/industrial sewage flows. The Phase 2 expansion took the capacity from 1.0 MGD to 2.5 MGD, and the Phase 3 expansion subsequently brought the facility to 4.0 MGD. Several major provisions designed as part of Phase 3, including a new headworks screening train, bio train process, and a sludge processing and dewatering system. PACE provided a creative approach to the upgrades including a MBR treatment system accessible at grade level with an integrated process mechanical design that minimizes valving and pumping, improving process treatment simplicity and making the unit processes visible to operators. The new treatment system process design is based on the use of the existing chlorine contact basin (CCB), allowing for continued production of Title 22 disinfected tertiary recycled water without having to expand the CCB. This was achieved through a free chlorine contact time revalidation study performed by PACE and approved through the CA DDW.

Phase 4 expansion continues to utilize the MBR treatment process to bring the facility to its full build-out capacity of 6.0 MGD. The designs include the construction of an additional headworks, 2 additional MBR trains, and extending the length of the chlorine contact basins to accommodate the additional treatment volume. Connection mixing pumps, flow-back pipes, and overflow systems are interconnected between the components of the separate Phases. New mechanical equipment is stored in the same rooms as the equipment added in Phases 2 and 3, eliminating any need to construct a separate area and reducing the expansion’s footprint. PACE’s upgrades to the electrical distribution system were designed to support the full buildout capacity of the facility. The expansions included designs for the main switchgear, motor control centers, and a standby generator system to ensure reliable plant operation. Building and lighting systems were developed to comply with California Title 24 energy efficiency requirements.

Key Features:

• Treatment facility expansion from 1.0 MGD to 6.0 MGD
• Consolidation of two treatment facilities into one
• Flexible MBR processing with multiple trains and headworks upgrades
• Allen-Bradley CompactLogix controls
• Instrumentation and controls integration with the existing SCADA system
• Enclosed treatment and odor control systems
• 4000A, 480V electrical distribution system
• Plant-wide control system with a redundant fiber optic ring network
• California Title 24 Compliant Lighting Systems
• Comprehensive short circuit, protective device coordination, and arc flash hazard analysis