Written by Josh DiValentino, MS, MBA
Fondo: The East County water purification treatment project serving the Padre Dam Municipal Water District in southern California was facing aging infrastructure challenges. The upgrade will increase the plants rated capacity to 16 MGD of wastewater for the surrounding community. The project will add 11 MGD of new reclaimed water to the local drinking water supply, a major improvement for a region that has strained water resources. The project, in its final commissioning stages, was delivered via design-build method with AECOM Engineering and W.M. Lyles Construction Joint Venture taking the lead. Schwing Bioset contributed to the success of the project by providing key systems vital to managing the dewatered biosolids from the facility including transfer, storage, and truck loading:
Cake Transfer System: The biosolids cake process begins with two dewatering centrifuges. Directly underneath each centrifuge is where the Schwing Bioset scope begins with a 44’ long inclined shaftless screw, capable of pulling over 300 cubic ft/hr of cake up to the top of the storage bins. These incline conveyors deliver cake to one of two 18” diameter horizontal transfer screws at the top of the cake bins. The horizontal transfer screws span the length of both cake bins, at 58’ long, and with multiple drop points, they evenly fill the cake storage bin below. The system can deliver cake from either centrifuge into either cake bin within minutes, offering full system redundancy. Control of cake transfer is accomplished by custom built slide gates, the project required eighteen (18) gates in total:
Cake Bin Storage: The bins each provide 88 cubic yards of cake storage capacity and are equipped with twin 18” live bottom screws. Three large slide gates spanning the live bottom tub width, with rubber chutes down to the truck bay can meter cake quickly and evenly into trucks below.
Construction Note: The large cake bins were fabricated locally to the jobsite and delivered in a single piece for efficient set-in place installation.
Operation/Control System: The custom-built control system offers the ability to seamlessly deliver dewatered cake from either centrifuge to either cake bin. The loadout control system is also integrated with the truck scales inside the truckload bay. The result is an accurate, repeatable, truck fill in 15 minutes or less.
Access Platforms: A fully integrated deck system built off the cake bin structure was provided. The deck complete with stairways and safety railing provides access to all operational and maintenance points.
Result: Construction was completed in early 2026 with commissioning activities planned for mid-year of 2026. Completing the largest expansion the District has undertaken in decades, Schwing Bioset looks forward to being part of the facilities’ success for many years into the future with long-term support for all our equipment.
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