Increasing Nitrogen Supply and Reducing Greenhouse Gas Emissions through Active Management of Wastewater Treatment Plants

Abstract

To increase nitrogen supply and reduce GHG (greenhouse gas) emissions through active management at sewage treatment plants, the power self-sufficiency rate and CO₂ offset rate were evaluated using the sewage treatment plant performance evaluation system (PES) for a treatment plant with a treatment capacity of 74,400 m³ day^₋1. In active management, the nitrogen supply concentration in January was the highest at 21.2 mg L^₋1, but the increase in concentration was limited to 2.6 mg L^₋1. On the other hand, the effect of reducing the aeration air volume by nitrification-suppression operation was large, and the aeration ratio decreased by nearly 50% to 3.2 times, leading to a reduction in power consumption by nearly 20%. The power self-sufficiency rate was calculated to be 54% with the introduction of digestion gas power generation and increased by 4 points to 58% with active management, and the power self-sufficiency rate increased to 81% when nitrogen was recovered as biomass. The CO₂ offset rate was calculated to be 45% with the introduction of digestion gas power generation, was 49% when active management was applied, and increased to 55% when nitrogen was recovered as biomass. With the additional measures, it was expected that the CO₂ offset rate would be increased to 96%, confirming the high potential of the sewage treatment plant.