Generating energy from wastewater

Giulia Pizzagalli, Innovation Projects Manager at Anglian Water, is overseeing a project to generate energy from wastewater.

In 2019, English and Welsh water companies made a joint pledge to reach the national objective of net-zero carbon emissions by 2030. As part of this commitment, Anglian Water has launched an innovation project integrating wastewater treatment with the generation of green hydrogen and oxygen via electrolysis.

Scheduled for completion in the last quarter of 2024, the project represents a viable strategy to meet the industry’s net-zero ambitions. The initiative has been coined Triple Carbon Reduction because it aims to address climate change-related challenges through a tripartite structure of intervention, including the reduction of nitrous oxide emissions released in the atmosphere; the reduction of energy consumption from wastewater treatment; and the production of green hydrogen to support large-scale decarbonisation efforts.

At its core, the project utilises an electrolyser, a unit wherein the process of electrolysis takes place using electricity to split ultra-pure water into hydrogen and oxygen. Through other traditional operations, the oxygen generated would be vented to the atmosphere and effectively wasted, but with the Triple Carbon Reduction approach, it is instead channelled into a membrane aerated biofilm reactor (MABR).

MABR is a sustainable alternative to traditional wastewater treatment processes that allows for low-energy delivery of oxygen from the carrier side and an increasing treatment capacity by up to 50% within the existing biological tank on-site. 

The Triple Carbon Reduction project aims to offer a viable alternative to conventional water treatment processes that typically exhibit high levels of energy inefficiency. This initiative can significantly lower power requirements, with a calculated prospect of reducing emissions associated with grid electricity usage by up to 85% by adding oxygen into the MABR process air. The use of MABR is key to achieving this. This application already guarantees higher efficiency in both oxygen transfer and aeration system processes, consuming less energy compared to other systems.

The novelty lies in its lower emissions as a direct result of active oxygen and hydrogen production. This is crucial given that wastewater contains common pollutants like nitrogen, which, if not treated properly, can be converted into harmful compounds such as nitrous oxide. MABR has the potential to reduce these greenhouse gas emissions and concentrate them at point source in the off-gas, which could be more significant when oxygen is added. 

Green hydrogen production

Finally, the project seeks to produce a new, low-carbon source of green hydrogen, which can be stored and transported to provide renewable energy. Depending on the scale of production, this could be either used internally or sold to other industries to decarbonise activities that are still reliant on fossil fuels. 

At full capacity, the electrolyser is expected to produce 91 kilograms of H2 and 730 kilograms of O2 per day, with the flexibility to adjust the output based on specific drivers, such as oxygen demand from the MABR or electricity tariffs. The green hydrogen produced holds the potential to fuel approximately 30 hydrogen vehicles and facilitate a faster transition to zero carbon for heavy road vehicles and municipal fleets in the UK.

In Triple Carbon Reduction, we can see how partners from across different industries can come together to create circular solutions. It is exactly this kind of approach that will be needed if we are to provide resilient energy and infrastructure for the future.

For more, visit anglianwater.co.uk

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