ACCIONA Water presents a digital twin for Hong Kong’s Tseung Kwan O seawater desalination plant (130,000 m³/day). Combining real‑time and historical data with dynamic simulation and machine learning, the twin enables scenario testing, optimisation, operator training, and predictive maintenance. The architecture uses AVEVA System Platform for the digital asset model and operator interfaces, a historian connection to the DCS, and AVEVA Dynamic Simulator, with cybersecurity via network isolation and firewalls.