This document discusses using a co-simulation digital twin approach for managing wastewater treatment operations more efficiently. It describes calibrating a physics-based simulation model in real-time using data from a pilot wastewater treatment plant. This allows the model to provide soft sensing and early detection of issues. Combining the physics model with machine learning techniques could further improve its ability to optimize processes and reduce energy use and costs. The digital twin approach aims to help utilities more sustainably manage increasingly complex wastewater treatment operations.