Lathrop Advanced Wastewater Treatment Facility Expansion

Lathrop, CA


PACE provided project development, studies, design, and bid and construction administration phase services for two phases of expansion of the Lathrop Consolidated Treatment Facility. This membrane bioreactor (MBR) wastewater treatment facility features aesthetic architecture and treats residential and commercial / industrial sewage flows. An administration building on-site allows for public outreach and understanding of the facility’s operations for its visitors. The facility’s capacity was expanded from 1.0 million gallons per day (MGD) to 2.5 MGD in Phase 2 and then to 4.0 MGD in Phase 3, with capacity for future buildout to 6.0 MGD.


PACE provided a creative approach to the upgrade with a new secondary and MBR treatment system accessed at grade level. An integrated process mechanical design minimizes valving and pumping, improves process treatment simplicity, and makes the unit processes visible to operators. The design is straightforward and allows the facility to easily expand. Based on a free chlorine contact time revalidation study performed by PACE and approved through the Division of Drinking Water (DDW), the new treatment system process design uses the existing chlorine contact basin (CCB) so that there is no need to expand the CCB infrastructure for continued production of Title 22 disinfected tertiary recycled water under the new design flow conditions. Additionally, PACE designed a conversion for the existing MBR facility that will be used for aerobic sludge digestion and thickening processes.


The Phase 3 expansion includes provisions for the full buildout of the facilities. A new headworks screening train will provide the full buildout average day flow capacity of 6.0 MGD. A new biotrain process, including anoxic, aerobic, and MBR process tanks and equipment, expands treatment capacity to 4.0 MGD. The aeration equipment and existing electrical room also included provisions for full buildout capacity, such as electrical power and automation controls upgrades. A new sludge processing and dewatering system featuring a screw press, sludge drying beds, and winter dried sludge storage will be included within a new pre-engineered building. An existing basin is being modified to accommodate sludge processing and dewatering and is sized for the facility’s buildout capacity. Upon completion of the 4.0 MGD expansion, the biological tanks and aeration equipment will be the only components needed to treat the future final phase 6.0 MGD buildout capacity.


Key Features:

  • Consolidation of two treatment facility operations (domestic and industrial) into one facility
  • Both new and improvement designs for existing treatment facility
  • Existing CCB improvements
  • Accurate cost estimation and budget creation
  • Major site civil improvements
  • Instrumentation & Controls integration
  • Chlorine contact time re-rating achieved to reduce application and costs
  • Facility maintained full operation during construction
  • Designed and implemented a new Supervisory Controls and Data Acquisition (SCADA) system

City of Lathrop

Communications, Instrumentation & Controls, PLC, Wastewater Treatment