The data discussed in this paper is based on one month’s data collection and is shown in Figure 2. It can be concluded that N2O formation is mainly dependent on NH4 loading. During the first 2½ weeks, N2O concentrations were high in both passes, with the highest values in pass 2. This is likely due to an accumulation of nitrites, which coupled with local zones of low oxygen can trigger nitrifier denitrification to produce N2O.
After this period there is a significant drop in the mean ammonium inlet concentration. Subsequently, N2O concentrations in pass 1 are almost negligible, with lower N2O concentrations in pass 2 as well. With a lower load, the ammonium-based aeration controller safely moves the ammonium load toward the second pass. This results in a slower ammonium turnover and reduced nitrite accumulation. This combination leads to a lower N2O production. The load change is also reflected in the effluent ammonium concentrations (Fig. 2).
After analyzing the data, we identified two potential methods for reducing N2O emissions. The first is to improve load balancing where possible, while the second is to distribute NH4 turnover throughout the lane by using aeration cascading that relies on N2O sensor input.
Severn Trent have ambitious plans to be at the forefront of the UK Water Sector’s Net Zero initiative and the circular economy. This includes investments in energy savings and production as well as advanced nutrient recovery – all while reducing the carbon footprint of their operations. With the implementation of real-time N2O monitoring, Severn Trent is now gathering in-depth knowledge and understanding of their sites’ performance and can realize opportunities to reduce greenhouse gases while optimizing the use of energy and resources to the benefit of their customers and the environment.