Abstract: The COVID-19 pandemic highlighted the urgent need for tools to monitor viral prevalence and incidence. Wastewater-based surveillance (WBS) emerged as a valuable approach after SARS-CoV-2 was found to be stable and detectable in wastewater. This dissertation captures a period of rapid WBS development in Southern California, beginning with sampling optimization at centralized treatment plants in Los Angeles, followed by campuswide monitoring of COVID-19 and influenza at UCI, and concluding with assessments of viral prevalence and removal at wastewater reclamation plants. Overall, this work informs best practices for WBS implementation and contributes to the development of resilient, community-scale public health monitoring systems for pandemic preparedness.