Sustainable Wastewater Solutions At Robert Mondavi Institute

Improving infrastructure, protecting resources

UC Davis’ Robert Mondavi Institute (RMI) Teaching & Research Winery produces 30,000 gallons of wine annually. RMI promotes public understanding of wine, brewing, and food sciences through events and research within its winery and brewery facilities, as well as its Food Innovation Lab and sensory labs. As the first LEED-platinum-certified winery in the world, sustainability is a high priority for RMI.

Purpose
In October 2024, testing found that UC Davis's wastewater treatment plant (WWTP) exceeded the weekly average limit for 5-day Biochemical Oxygen Demand (BOD), likely due to large volumes of high-organic-strength wastewater entering the system. One source was RMI, which at the time discharged wastewater directly into the sewer system. The WWTP releases treated effluent into the Arboretum Waterway. Because the system can only handle a limited BOD load, excessive levels can reduce dissolved oxygen in the Arboretum Waterway and harm the aquatic ecosystem.

Additionally, high nitrogen content, in the form of nitrates and ammonia, lowers wastewater pH, reducing treatment efficiency and potentially damaging plant equipment. The high BOD levels lead to oxygen depletion at the WWTP, which can kill beneficial bacteria used in the treatment process, resulting in high ammonia levels and potential regulatory fines.

In Spring 2025, Path to Zero Net Energy students Marta Bliemeister, Sean Bernstein, and Ofelia Viloche conducted research and feasibility studies on the most appropriate methods that could mitigate these effects. In May, the project group was awarded a $20,000 grant from The Green Initiative Fund. In collaboration with Alexandra Malm, Facilities Management Engineering Project Manager, James Nelson, Viticulture & Enology Research and Development Engineer, and Leticia Chacon-Rodriguez, Viticulture & Enology Manager, the project has come into fruition and has since been fully designed and installed and is undergoing testing and monitoring.

The Vermifiltration System
After leaving the winery, the wastewater first filters through screens that remove solids. It then flows into the winery sump, which collects the wastewater before it is pumped to a holding tank. In the holding tank, sensors monitor temperature and pH; since low pH can harm the worms and microbes used in the pretreatment system.

The wastewater is then sent to worm tanks containing a vermifiltration substrate made of worms and mulch. Over time, the worms break down waste, aerate the substrate, and encourage aerobic bacteria that efficiently remove BOD. After passing through a rock aeration base, the pretreated wastewater is conveyed to the WWTP, where it can be successfully treated alongside other campus wastewater.

Results
Samples collected between October 2025 and March 2026 show that the vermifiltration system removed 23% to 51% of BOD​​5​​ with 95%​​ confidence.

Impact
This sustainable wastewater filtration system is an efficient and cost-effective treatment approach that supports UC Davis’s sustainability goals. It creates a valuable circular process: spent vermicompost can be reused as vineyard fertilizer, which has been shown to improve grape yields by 22%. The system also serves as a practical, replicable model that other wineries can adopt to reduce waste and improve environmental impact. Additionally, the students involved in the project learned valuable engineering and project management skills.