Utility Week

40 | JANUARY 2022 | UTILITY WEEK Case study Cold AD could be emissions game-changer for water A major collaborative project led by Thames Water is striving to slash energy consumption in wastewater treatment through the pioneering application of cold anaerobic processes. I n September, a Thames Water-led project – whose members included the University of South Wales, Welsh Water, South West Water, United Utilities, Scottish Water, York- shire Water and Northumbrian Water – net- ted more than £6 million from Ofwat's first Water Breakthrough Challenge to collabo- ratively test two cold anaerobic wastewater treatment processes in a bid to decarbonise wastewater treatment and boost resource recovery. According to Thames Water statistics, the water industry consumes between 2% and 3% of the electricity consumed in the UK – the same as two million households – with roughly 55% of that accounted for by sewage processing plants. While anaerobic digestion is heralded as a low cost waste and wastewater treatment method, it's usually conducted at tempera- tures between 20 to 45C to support bacte- ria which thrive in moderate temperatures. Functioning in this range requires energy to heat, meaning that cold processes poten- tially offer both cost and environmentally friendly alternatives. As such, the seven-strong consortium will test a membrane-free cold process which maximises biogas generation, removes nitro- gen and phosphorus, and will be deployed as a mobile unit at multiple sewage treatment works to test different wastewater concentra- tions. This will then inform its deployment at a larger demonstration plant. The second process treats crude sewage at a larger scale by combining existing technol- ogy with alternative nutrient removal appa- ratus at laboratory-scale. Micro pollutant removal and pathogen antimicrobial resist- ance will also be tested at all trials. Leaving a legacy Thames, which serves 15 million custom- ers across London and the Thames Valley, believes that such cold processes have the potential to transform wastewater treatment by eliminating energy usage from conven- tional methods, reducing nitrous oxide emis- sions and thereby the sector's carbon output, as well as yielding phosphorus and nitrogen in forms that can be readily recovered. "I'm passionate about leaving a legacy for future generations, just like the Victori- ans did for us," says Sarah Bentley, Thames Water CEO. "I'm delighted that we've won this award, which will allow us to change our approach to the wastewater treatment process in a way that will reduce our carbon footprint. "It's fantastic to be able to work along- side seven great organisations who share our drive to innovate and shape the future." Professor Sandra Esteves, project lead at the University of South Wales, adds: "The funding will enable the team to drive the novel concept integration and evaluate its impact in reducing society's wastewater treatment energy footprint and in promoting sustainable resource recovery." Adapting to ambient temperatures Andrea Gysin, Thames' head of innova- tion partnerships, dives deeper into the cold anaerobic processes at the heart of the award-winning collaboration. "Conventional wastewater treatment pro- cesses rely on bacteria to break down organic material in the presence of oxygen, which causes carbon dioxide and nitrous oxide to be emitted to atmosphere," she explains. "In the absence of air or oxygen – anaero- bic conditions – different types of bacteria will thrive. When these bacteria break down organic material, they produce a mixture of

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