Measuring Seasonal Variations in Nitrous Oxide Emissions from the Activated Sludge Process: PAPER & PRESENTATION
Wild, R., Carliell-Marquet, C., Srinamasivayam, B., Vale, S., Severn Trent, UK
(free)
Abstract
In Severn Trent we operate water and wastewater services across the midlands region of the UK and
over half of our reported scope 1 emissions come from the activated sludge process. In order to
reduce our scope 1 (direct from operations), 2 (indirect, e.g., electricity consumption) and 3 (supply
chain) emissions to net zero by 2050 we need to start tackling this now.
From the literature, we knew that there was a lot of uncertainty over the level of nitrous oxide (N2O)
emitted. It is important that we understand our true emissions base line, and we realised that we must
measure it, to manage it.
To guide us in developing monitoring and solution trials at full-scale, we generated 48 working
hypotheses about GHG production, spanning wastewater and sludge treatment. These hypotheses
have been used throughout our journey to decide what to monitor, where and how.
We scouted for monitoring options and decided that dissolved N2O monitoring was the most practical
way. We developed a model to convert this to an emissions rate. We have also started rolling out N2O
monitoring at 8 waste water treatment works in order to achieve representative monitoring.
Using data from previous European studies our initial measurements were extrapolated to predict an
annual emission profile. We will discuss the results of our subsequent monitoring against this profile.
Keywords
Activated Sludge Process, ASP, Carbon, Nitrous Oxide, N2O, Process Emissions, Spernal
