An in-depth literature review was carried out to identify the causes of process emission formation, the high-risk areas of typical WWTWs and sludge treatment centres (STCs), the established methods for mitigating these emissions, and the innovative technologies that are being explored. Alongside the final report, assessment tools are available for users to develop tailored recommendations and routemaps for achieving process emission reductions.

What we found:

• Advanced control of activated sludge plants with on-line and in-situ N2O monitoring can significantly reduce N2O emissions at low cost
• Retro-fit technologies that can be easily implemented with low to medium cost to increase capacity and improve efficiency of simultaneous nitrification and denitrification, aeration and denitrification processes should be explored as high priority
• Implementation of robust leak detection and repair schemes has been shown to be the most effective technique for better understanding and mitigating the level of current CH4 leakage from sites 
• Implementation of advanced sludge digestion technologies, although expensive and time consuming, is of clear benefit on a number of fronts, including process emissions reduction
• Sludge de-gassing technologies are clearly of multiple benefits not only to process emissions reduction, but also potentially to operational cost

Ongoing co-ordination between UK & Irish water utilities is core to ensuring progress on process emissions. In light of this, our recommendations are for the industry to pursue a co-ordinated national emissions monitoring plan as a clear priority going forwards.

The lead contractor on this project was Stantec. The UKWIR Programme Lead was Dan Green, and the Project Manager was Linda Hustler. This project sits under our 5th research theme, ‘Achieving net zero carbon.’ To read the report in full, head to:

www.ukwir.org/water-industry-research-reports and search ‘24/CL/01/41’.