Kurdistan University of Medical Sciences Journal of Advances in Environmental Health Research 2676-3478 13 2 2025 04 20 Modeling Greenhouse Gas Emissions in a Full-Scale Activated Sludge Unit Based on Benchmark Simulation Model – A Case Study of Isfahan Wastewater Treatment Plant 96 103 209641 10.34172/jaehr.1386 EN Hamidreza Shiran Department of Environmental Engineering, Aras International Campus, University of Tehran, Jolfa, Iran 0009-0006-5371-6784 Gholamreza Nabi Bidhendi Faculty of Environment, University of Tehran, Tehran, Iran 0000-0001-9406-5195 Nasser Mehrdadi Faculty of Environment, University of Tehran, Tehran, Iran 0000-0002-1608-2405 Journal Article 2024 05 20 <strong>Background:</strong> The objective of this study was to establish a facility-level modeling tool to assess the performance of internal operational strategies and external emissions.<br /><strong>Methods:</strong> The biological process model in Benchmark Simulation Model No. 2<em> </em>(BSM2) was upgraded to include two-stage and four-stage nitrification, as well as denitrification processes, to effectively simulate nitrous oxide (N₂O) production. Emissions of carbon dioxide (CO₂), methane (CH₄), and N₂O were also incorporated, taking into account digestion, cogeneration, and sludge storage processes. The refined model was utilized in a case study at the Isfahan Wastewater Treatment Plant (WWTP) in Iran to assess various operational strategies and explore potential challenges related to emission management.<br /><strong>Results:</strong> The simulation results, based on the model’s structural assumptions, indicate a negative impact on greenhouse gas (GHG) emissions associated with regional energy upgrades in the ventilation system and activated sludge sector. For example, variations in the biogenic and non-biogenic CO₂​ proportions were observed when the total suspended solids (TSS) removal efficiency was altered, decreasing or increasing to 30/70 and 20/80, respectively. While off-site CO₂​ emissions can be mitigated, this reduction is offset by a significant rise in N₂_​O emissions. This is particularly concerning given that N₂​O exhibits a greenhouse effect nearly 300 times greater than that of CO₂​.<br /><strong>Conclusion:</strong> It should be pointed out that numerous studies are needed to evaluate plant-wide control strategies in WWTPs for informed and effective decision-making regarding performance optimization. https://jaehr.muk.ac.ir/article_209641_4d5edd6f2d50315728b7479b7ed16393.pdf