A digital twin for sewage treatment works

Severn Trent deployed a physics-based digital twin and AI-powered software at its flagship Strongford plant to cut nitrous oxide emissions, reduce energy use and achieve net zero.

Indispensable yet largely invisible, wastewater treatment runs 24/7, consuming considerable energy and creating a significant share of greenhouse gas emissions. In the UK, decades of underinvestment, rising demand and climate change have pushed aging facilities to their limits and placed green infrastructure firmly at the top of the industry agenda.

At Strongford, with support from the Ofwat Innovation Fund, Severn Trent is transforming its wastewater treatment plant into a flagship blueprint for the sector, demonstrating process emissions can be tackled through practical innovation. The company is integrating and retrofitting a suite of physical low-carbon technologies alongside a high-fidelity Digital Twin into the facility to reduce environmental impact and support its journey towards net-zero emissions.

Digital model + real-world data + physics-based rules = less N₂O

Nitrous oxide (N₂O) is 273 times more potent than CO₂ and can account for up to half of a plant’s total carbon footprint. To reduce this potent gas, Severn Trent explores both physical and digital technologies. Apart from trialing advanced N₂O destroying technology, the Strongford Net Zero Hub project also looks into a breakthrough solution - the first model of nitrous oxide that uses a virtual replica driven by real data and physics - with our technology.

The Digital Twin and the AI-powered software solution work together to provide real-time insight into wastewater processes that are traditionally difficult to assess. They draw on 60,000 dynamic and static data points and 29,000 different equations to model the complex biological, chemical and physical processes that take place from the moment the water enters to when it exists the plant.

AI-powered software solution provides real-time monitoring

“What the SIWA Treatment Optimizer does is provide operators with recommended control setpoints so they can run their processes in a way that minimizes these emissions,” explains Adam Cartwright, who previously led our water and wastewater software strategy.

Beyond the Strongford project, AI-powered SIWA applications such as SIWA Leak Finder and SIWA Blockage Predictor also use live and historical data to distinguish normal from abnormal conditions across water networks.

Digitalization drives ecological and energy efficiency

Software-based models, or soft sensors, estimate key variables - such as biological oxygen demand and nitrous oxide emissions - using available data, even where direct measurement is not possible. This gives operators deeper insight into performance and supports regulatory compliance.

Combined with real-time water quality monitoring, SIWA applications enable operators to fine-tune aeration and chlorine dosing, among others, reducing uncertainty as well as energy and chemical consumption.

“What we really wanted to do is to give that simulation capability to allow our operational team to balance all of the competing drivers that they have today.“ says Jess Alce, Strategic Innovation Lead at Severn Trent.

Modernizing infrastructure while providing continuous service is no easy task. Approximately 400,000 people in Newcastle-under-Lyme and Stoke-on-Trent depend on the Strongford water treatment. We were proud to bring our decades of process experience to this project, helping deliver cleaner, more sustainable operations and raising the bar for an industry we care deeply about.

Severn Trent is a UK-based water and wastewater company, supplying 4.6 million households and 220,00 businesses in the English midlands and parts of Wales.

Severn Trent Water