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34 | MARCH 2022 | UTILITY WEEK Analysis Modelling London's 25km super sewer Thames Tideway's Peter Vale explains how the company has harnessed existing technology to digitalise and automate wastewater network systems during wholesale upgrades to London's ageing sewer infrastructure. W hile Peter Vale, engineering infor- mation manager at Thames Tide- way, acknowledges the description of wastewater as a "dumb" asset by some industry colleagues, he explains that efforts to manage it are anything but. Discussing the incorporation of smart water systems and digitalisation to better manage the 25km Tideway Tunnel currently under construction beneath London at the Utility Week WWT Wastewater 2022 confer- ence, Vale outlined a variety of modeling approaches to support the creation of a com- plex system. The "supersewer" Tideway project har- nesses technology to digitalise and auto- mate wastewater network systems, which are being put in place to reduce pollution of the River Thames. This entails upgrad- ing a sewer network built in the late 1800s and still in use despite London's population growing from two million to eight million in that time. As such, London's current sewer sys- tem is hampered by overloaded treatment works – in which the quality of treated discharge deteriorates during heavy rain- fall – and an overloaded network that is frequently discharging untreated sewage into the tidal Thames via Combined Sewer Overflows (CSOs). In a typical year, around 40 million sq m of untreated sewage is dumped into the tidal Thames across more than 50 occasions – almost once a week on average. Modelling challenge The project to upgrade sewage treatment works and create an additional 1.6 million cubic metres of additional storage across the 25km-long Tideway Tunnel and the 7km Lee Tunnel (pictured) was initially recommended off the back of studies started in 2000. However, project leaders were faced with a range of design challenges such as vari- able ground conditions and a vast number of interfaces with existing, ageing, infrastruc- ture – spanning not only existing sewers, but the London underground networks, piers, bridges – and the need to minimise the num- ber of work sites across the capital, accord- ing to Vale. He says that in order to deliver a 120-year design life, the Thames Tideway has to pro- vide mechanical ventilation and air treat- ment to reduce risk of odour complaints and accommodate large flows and huge drops in the sewage system. To tackle this series of complex prob- lems – and ultimately create a sewer that prevented frequent pollution of the Thames and changed the relationship between Lon- don, Londoners and the river – Vale explains that Thames Tideway is required to harness a broad variety of different models, spanning catchment, pneumatics and transients, com- putational fluid dynamics, physical and air movement and dispersion models. This system largely reflects one already developed by Thames Water, Vale adds, with the company charged with serving 15 million customers across London and the Thames Valley benefitting from a comprehensive dig- ital footprint. Such modelling shaped Tideway's CSO